MELODY PRESENTATION

Menofia University Faculty of Applied Medical Science

Principles of Ultrasound Technique

Radiological Sciences and Medical Imaging Technology Department

Fall 2020-2021

Supervised By: DR: Dalia Aggour

List of content :

Basic terminology

1. Brightness Mode (B-mode) • The standard ultrasound mode for all clinical imaging • Converts ultrasound waves into a grayscale image [1] • Figure 1.1—B-mode imaging 2. (b) Motion Mode (M-mode) • Evaluates the movement of structures within the body [2] • Records movement of a structure over time • A vertical line is placed through the structure of interest. • The machine then converts ultrasound echoes measured at this line onto the vertical axis of a graph with time on the horizontal axis [2]. • Figure 1.2—M-mode imaging 3. (c) Frequency • The number of sound waves per unit time. • For clinical imaging, this typically ranges from 2 megahertz (MHz) to 15 MHz [1]. • Higher-frequency transducers have less tissue penetration but provide more detailed image resolution. • Lower-frequency transducers have greater tissue penetration but sacrifice image resolution.

4. (d) Gain • Controls amplification of returning ultrasound waves [2]. • This translates to brightness of the ultrasound image [2]. • Gain can be manually controlled by the sonographer and should be optimized for image clarity. • If the gain is too high, the image will be bright. • Figure 1.3—High gain • If the gain is too low, the image will be dark. • Figure 1.4—Low gain 5. (e) Depth • Refers to how far sound travels prior to returning to the transducer, typically reported in centimeters. • If depth is increased, the ultrasound machine listens for returning echoes for a longer period of time to collect data [2] necessary to create an image. • If depth is decreased, the machine will listen for a shorter period of time. • This can be manually controlled by the sonographer. • Depth should be optimized so that the structure of interest is imaged within the center of the screen.

• Figure 1.5—High depth • Figure 1.6—Shallow depth • Figure 1.7—Ideal depth 6. (f)Doppler• Measures frequency shift • Doppler shift is defined as a change in frequency that occurs when sound reflects off a moving structure [2]. • Calculates blood velocity • An increase in velocity causes an increase in Doppler shift. • Color Doppler • Shifts in velocity are color coded according to direction of flow in relationship to the transducer. • Flow away from the transducer will appear blue. • Flow toward the transducer will appear red. • This can be remembered as “BART,” Blue Away Red Toward. • Figure 1.8—Color Doppler

• Power Doppler • Displays a signal in color if there is any motion detected at all • Does not indicate velocity or direction • Higher sensitivity than color Doppler allowing for imaging slower flow [2] • Good for low-flow applications such as the testicle and ovary • Figure 1.9—Power Doppler 7. (g) Transducer • Contains piezoelectric crystals that have the unique ability to translate electrical signal into sound waves. • Sound waves are sent to tissues then reflected back to the transducer. • Reflected sound waves are translated into electric signals by the same piezoelectric crystals. • Computer software processes these signals into an ultrasound image. 8. (h) ALARA • “As low as reasonably achievable” [1, 2] • Ultrasound principle to use the least amount of ultrasound possible on each patient

Figure 1.1 B-mode imaging: Brightness mode imaging of the heart. Brightness mode or B-mode is the standard ultrasound mode for all clinical imaging

Figure 1.2 M-mode imaging: Motion mode imaging of the heart. Motion mode or M-mode cardiac evaluates the movement of structures within the body. This image demonstrates the utilization of M-mode to evaluate movement of the left ventricle over time

Figure 1.3 High gain: This image demonstrates the parasternal long view of a heart with high gain. Gain is related to brightness of the image. When the gain is too high, the image will be bright and details are lost

Figure 1.5 High depth: This image demonstrates the parasternal long view of a heart with the depth set too deep. The structure of interest should be centered in the screen

Figure 1.4 Low gain: This image demonstrates the parasternal long view of a heart with low gain. Gain is related to brightness of the image. When the gain is too low, the image will be dark and details are lost

Figure 1.6 Shallow depth: This image demonstrates the parasternal long view of a heart with the depth set too low. The structure of interest should be centered in the screen

Figure 1.7 Ideal depth: This image demonstrates the parasternal long view of a heart with ideal depth and gain settings to properly vision the entire structure of interest as well as the appropriate level of detail

Figure 1.8 Color Doppler: Color Doppler measures shifts in velocity which are color coded according to direction of flow in relationship to the transducer; flow away from the transducer will appear blue, and flow toward the transducer will appear red. Note that it does not relate to venous and arterial flow. In this image, the testicles are being assessed for vascular flow with color Doppler

Figure 1.9 Power Doppler: Power Doppler will display a signal in color if there is any motion at all. It does not indicate velocity or direction. In this image, the testicles are being assessed for vascular flow with power Doppler

List of abbreviations

Abstract

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Ultrasound is a high-frequency sound wave. It can be bounced off tissues by using special devices. The echoes are then converted into a picture called a sonogram. Ultrasound imaging allows an inside view of soft tissues and body cavities without the use of invasive techniques.(3) Ultrasound (US) remains an excellent first line investigation of the gallbladder and for indicating diagnosis and defining levels of extrahepatic biliary obstruction and screening for liver metastases.(4) With the high prevalence of diffuse liver disease there is a strong clinical need for noninvasive detection and grading of fibrosis and steatosis as well as detection of complications .B-mode ultrasound supplemented by portal system Doppler.Ultrasound grading of hepatic steatosis.(5) Diffuse liver disease is becoming more prevalent and there is a strong clinical need for noninvasive detection.

Introduction

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Ultrasound was originally developed during World War I to track submarines as SONAR technology (Sound, Navigation And Ranging). Ultrasound was first used medically in the 1950s, with very early applications in fetal biometry; nowadays, it is used in just about every field of medicine.[1] Ultrasound (US) is an imaging technology that uses high-frequency sound waves to characterize tissue. It is a useful and flexible modality in medical imaging, and often provides an additional or unique characterization of tissues, compared with other modalities such as conventional radiography or CT. Ultrasound relies on properties of acoustic physics (compression/rarefaction, reflection, impedance, etc.) to localize and characterize different tissue types. The frequency of the sound waves used in medical ultrasound is in the range of millions of cycles per second (megahertz, MHz). In contrast, the upper range of audible frequencies for human is around 20 thousand cycles per second (20 kHz).

An ultrasound transducer sends an ultrasound pulse into tissue and then receives echoes back. The echoes contain spatial and contrast information. The concept is analogous to sonar used in nautical applications, but the technique in medical ultrasound is more sophisticated, gathering enough data to form a rapidly moving two-dimensional grayscale image. Some characteristics of returning echoes from tissue can be selected out to provide additional information beyond a grayscale image. Doppler ultrasound, for instance, can detect a frequency shift in echoes, and determine whether the tissue is moving toward or away from the transducer. This is invaluable for evaluation of some structures such as blood vessels or the heart (echocardiography). Ultrasound continues to evolve additional functions, including 3D ultrasound imaging, elastography, and contrast-enhanced ultrasound using microbubbles. [2]

General principles of US

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Physical Properties: Sound is a wave of energy that, unlike x-rays, must be transmitted through a medium. Sound waves can be described by their frequency, wavelength, and velocity. The frequency is the number of cycles or waves that are completed every second, and the wavelength is the distance needed to complete one wave cycle. The frequency of the sound waves used in ultrasonography is well above the limit of the human ear (20,000 kHz) — usually in the range of 2 to 12 MHz (2 to 12 million Hz). An inverse relationship exists between the frequency and the wavelength of a sound wave: the higher the frequency, the shorter the wavelength.

This relationship affects the choice of frequency used in each patient undergoing ultrasonography. Higher-frequency ultrasound waves create higher-resolution images, but their shorter wavelength makes them unable to penetrate deeper tissues. Lower-frequency waves have better penetrating power, but because of their longer wavelengths, their resolution is lower. Weighing the need for higher resolution versus more penetrating power is always a consideration when selecting a transducer frequency. (8,9)

The velocity of an ultrasound wave is independent of the frequency. However, it changes depending on the medium through which the wave is traveling. For example, the velocity of sound is 331 m/sec in air and 4,080 m/sec in bone.2 Within the soft tissues of the body, it is considered to be steady at about 1,540 m/sec.3 This medium-dependent variation affects the ultrasound image produced (discussed below).

The following equation demonstrates the relationship between frequency, wavelength, and velocity: Velocity (m/sec) = Frequency (cycles/sec) x Wavelength (m)

Image Production:

Two basic principles need to be understood regarding how ultrasound is generated and an image is formed. The first is the piezoelectric effect, which explains how ultrasound is generated from ceramic crystals in the transducer. An electric current passes through a cable to the transducer and is applied to the crystals, causing them to deform and vibrate. This vibration produces the ultrasound beam. The frequency of the ultrasound waves produced is predetermined by the crystals in the transducer. The second key principle is the pulse-echo principle, which explains how the image is generated. Ultrasound waves are produced in pulses, not continuously, because the same crystals are used to generate and receive sound waves, and they cannot do both at the same time. In the time between the pulses, the ultrasound beam enters the patient and is bounced or reflected back to the transducer. These reflected sound waves, or echoes, cause the crystals in the transducer to deform again and produce an electrical signal that is then converted into an image displayed on the monitor. The transducer generally emits ultrasound only 1% of the time; the rest of the time is spent receiving the returning echoes. (10)

Interaction with Tissue:Ultrasound produced by the transducer interacts with different tissues in a variety of ways that may help or hinder image formation. Attenuation and refraction are the two major types of tissue interaction. Attenuation: is the gradual weakening of the ultrasound beam as it passes through tissue. Attenuation can be caused by reflection, scattering, or absorption of the sound waves and is compensated for by use of specific controls, discussed below. (12) Reflection: takes place when ultrasound waves are bounced back to the transducer for image generation. The portion of the ultrasound beam that is reflected is determined by the difference in acoustic impedance between adjacent structures. Acoustic impedance is the product of a tissue's density and the velocity of the sound waves passing through it; therefore, the denser the tissue, the greater the acoustic impedance. The large differences in density and sound velocity between air, bone, and soft tissue create a correspondingly large difference in acoustic impedance, causing almost all of the sound waves to be reflected at soft tissue-bone and soft tissue-air interfaces. On the other hand, because there is little difference in acoustic impedance between soft tissue structures, relatively few echoes are reflected to the transducer from these areas. (11,12)

Scattering:refers to the redirection of ultrasound waves as they interact with small, rough, or uneven structures.5 This tissue interaction occurs in the parenchyma of organs, where there is little difference in acoustic impedance, and is responsible for producing the texture of the organ seen on the monitor. Scattering increases with higher-frequency transducers, thus providing better detail or resolution. (12) Absorption: occurs when the energy of the ultrasound beam is converted to heat. This occurs at the molecular level as the beam passes through the tissues. (11) Refraction: occurs when the ultrasound beam hits a structure at an oblique angle. The change in tissue density produces a change in velocity, and this change in velocity causes the beam to bend, or refract.2,5 This type of tissue interaction can also cause artifacts that need to be recognized by the sonographer. (11)

Display Modes:

Information generated from an ultrasound examination can be displayed in a variety of ways, called modes. The mode used for display depends on the type of ultrasound unit used, the information to be obtained, and the organ being examined.

A (Amplitude) Mode In A mode, the returning echoes are displayed on the monitor as spikes originating from a single vertical or horizontal baseline.5 The depth of the echo is determined by the position of the spike on the axis, with the top or left side of the monitor being the most superficial and the bottom or right side being farther away. The height of the spike correlates to the amplitude of the echo. This mode is not frequently used other than in ophthalmology. (10)

B (Brightness) Mode In B mode, echoes are represented by dots on a line that form the basis of a two-dimensional image. 5 The brightness of each dot indicates the amplitude of the returning echo. Its location relative to the transducer is displayed along the vertical axis of the monitor, with the top of the monitor representing the transducer. The returning echo's location along the axis is based on the amount of time it takes for the ultrasound wave to be transmitted from the transducer and reflected back. Echoes arising from structures in the near field (close to the transducer) take less time than those coming from the far field (farther away from the transducer) because they travel a shorter distance. (10)

Real-time B mode ultrasonography allows a complete, two-dimensional, cross-sectional image to be generated by using multiple B-mode lines.5 In real-time B mode, the transducer sweeps the ultrasound beam through the patient many times a second. With each pass of the ultrasound beam, multiple lines of dots are generated on the monitor, producing a complete image. These B-mode lines remain on the monitor until the next sweep of the ultrasound beam. Because several beam sweeps are performed per second, a moving, changing, "real-time" image is generated. This is the mode most commonly used in veterinary practice. (11,12)

M (Motion) Mode:

M mode is used in echocardiography and allows the sonographer to measure the heart to assess cardiac function and chamber size. M mode uses a single B-mode line, with the amplitude of the echoes indicated by the brightness of the displayed dots. The difference is that the information obtained from that single line is constantly swept across the monitor so that the motion of the body part being investigated is displayed along the horizontal axis. (11,12)

Tranceducer Types

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-An ultrasonic transducer , also referred to as a probe : is a system that generates sound waves that bounce off body tissues and echoes . -The transducer also receives the echoes and sends them to a computer using them to create a sonogram image . -The ultrasonic transducer is a very important component of the ultrasonic system and a key part of the image restoration signal transmission chain . This is also the key determinant of image quality . - A piezoelectric crystal is the critical element of each ultrasonic transducer , It both generates and receives ultrasonic waves . Ultrasound transducers can be found in different : shapes , sizes , and with various features . That's because different requirements are required to maintain image quality across different parts of your body . Either transducers can be passed across the surface of the body ( external transducers ) , or they can be placed into an orifice , such as the rectum or vagina ( internal transducers ) . (13,14)

In construction, the ultrasonic transducers vary on the basis of : 1. Arrangement of a piezoelectric crystal . 2. aperture (footprint) . 3. frequency

Ultrasound Transducer Types :

1.Linear transducers : The piezoelectric crystal arrangement is linear , the beam form is rectangular and the near-field resolution is strong . The aperture , frequency and linear transducer applications depend on whether the product is for 2D or 3D imagery . This appears to be high frequency and has a low footprint, making it a good choice for certain peripheral nerve blocks where the surface area is reduced and the nerves are not deep inside the tissue. .The linear 2D imaging transducer has : a large footprint , and its central frequency is 2.5Mhz – 12 Mhz .

This transducer can be used for different applications such as : 1.Vascular inspection .2.Venipuncture, visualization of the blood vessels . 3.Breast , Thyroid and tendon . The linear transducer for 3D imagery has : a large footprint and a 7.5Mhz-11Mhz central frequency . This transducer may be used for a range of uses such as : 1.Breast . 2.Thyroid . 3.artery carotis . Lung imaging using the straight linear array probe . Note the rectangular shape produced by the probe . R: rib , P: pleural line , S: rib shadow .

2. The convex ultrasound transducer :

is also called the curved transducer because it is curvilinear in the piezoelectric crystal arrangement . - Are low frequency transducers requiring a wide field. Since these transducers are low frequency, they provide strong penetration of depth. Since they are curved, however, the width of the scan lines decreases as depth increases which decreases the image resolution. The shape of the beam is convex . I. The convex transducer has : a large footprint for 2D imaging and its central frequency is 2.5MHz -7.5MHz . This transducer can be used for a number of uses such as: 1.abdominal checks . 2.transvaginal and trDiagnosis of organs . 3.ansrectal checks . II. The convex 3D imaging transducer has : a wide field of view and a 3.5MHz - 6.5MHz central frequency . They can be used for abdominal exams .

so it can usually be used by physicians in neonatal so pediatric applications .Scan of a left frontal cystic metastasis of a non–small cell pulmonary carcinoma , C:tumor cyst

Ultrasound scan of a normal lung using convex probe .

There is a subtype called micro convex , as well as the convex transducers . It has a much smaller footprint ,

3.phased array transducer :

This transducer is named after the piezoelectric crystal arrangement called the phased array and is the most commonly used crystal phased array transducer with a small footprint and low frequency , its central frequency is 2Mhz – 7.5Mhz . Produce a fan-like image that's narrow as the transducer leaves and increases with depth. It is ideal for imaging through small "windows" like in the temple's cranial window, or between the ribs. We are widely used in cardiac and trans-cranial imaging. Such transducers provide good penetration in depth, but have very low near field resolution.

The point of the beam is not wide but it extends according to the frequency applied . The beam shape is also nearly triangular , and the near-field resolution is poor .We can use this transducer for a variety of applications :such as:1.cardiac exams . 2.Abdominal exams 3.brain exams .

4. Pencil transducers :

also known as CW Doppler probe , are used for : 1.measuring blood flow . 2.blood sound speed . This has a low footprint and uses low frequency ( usually 2Mhz – 8Mhz ) .

5. Endocavitary transducers :

These probes give you the ability to conduct the patient's internal examinations . Thus they are designed to fit into specific orifices of the body . The endocavitary transducers include transducer of endovaginal , endorectal , and endocavity . They typically have small footprints, and the frequency varies between ( 3.5Mhz - 11.5Mhz ) .

6. Trans -esophageal (TEE) transducers : It has a small footprint and is used for internal exams . The obtaining of a better image of the heart through the oesophagus is often used in cardiology . The frequency is middle , between ( 3Mhz - 10Mhz ) .

7. 4D transducer : 3D imaging allows fetal structures and internal anatomy to be visualized as static 3D images . Nevertheless , 4D ultrasound allows us to add live streaming video of the images , showing the motion of the fetal heart wall or valves , or blood flow through different vessels . Thus , in live motion , it is 3D ultrasonic . It uses either a 2D transducer which rapidly acquires 20 - 30 volumes or a matrix array 3D transducer is used . -4D ultrasound has the same advantages as 3D , while also allowing us to study the movement of different moving body organs . Its clinical applications are still under investigation . -It is actually often used to provide fetal keepsake images , a use that most medical watchdog sites are prohibited from . (13.14)

Some tips to keep in mind when selecting any type of probes :

.Frequency : The frequency spectrum can have a major impact on the picture you are making , so always remember the bottom line higher frequency equals higher resolution , lower frequency equals better penetration . .Depth : The depth of penetration is closely related to Frequency . If you are imaging the abdomen of a horse , you will need significantly greater depth than you would if you were imaging superficial nerves and tendons in a dog, for example . You'll need a lower frequency transducer to maximize depth to achieve this . Find the depth you need first , then adjust the frequency to maximize the resolution while keeping the penetration going . (13,14) .

Array shape : The array is the part of the probe that is in contact with the patient . Arrays can be flat or curved (convex), and array shape will determine the shape of the picture you see. A flat array creates a square or rectangular image , and a curved array creates a wedge- or pie-form image .a convex probe , you can interpret this as a wider field of view , but it also means that in the far field , where sound beams spread as they get further from the probe , you may see some distortion or loss of resolution . The tighter the radius (the deeper the array curvature) , the greater that effect you will see . We tend to use linear probes for small , superficial structures such as tendons , nerves and vessels . In body cavities such as the abdomen and thorax use convex probe . .length of array : A longer array would accommodate more anatomy below it , making it more suitable for larger or deeper structures . For smaller structures a short sequence is sufficient to make them appear larger on the screen relative to the probe . For example , this is one reason why a linear rectal probe is not the best option for equine distal limb examinations ; within the longer array the transverse parts of the tendons appear relatively small .(13.14)

Doppler

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What is doppler US?! A Doppler ultrasound is a noninvasive test that can be used to estimate the blood flow through your blood vessels by bouncing high-frequency sound waves (ultrasound) off circulating red blood cells.

A regular ultrasound uses sound waves to produce images, but can't show blood flow. [15,16,17,18]

Fig (I.16): (Left) Image of Hepatic Vein using Color Doppler; (Right): Image using color mode of SMI (cSMI) showing the detail resolution and numerous micro vessels of the liver at high frame rates.

Types of Doppler ultrasound:

1) Color Doppler The use of color flow Doppler (CFD) or color Doppler imaging (CDI) sonography allows the visualization of flow direction and velocity within a user defined area.

A region of interest is defined by the sonographer, and the Doppler shifts of returning ultrasound waves within are color-coded based on average velocity and direction. [19]

Fig (I.17): Ultrasound Images-Hepatic vein, color Doppler.

2) Power Doppler

Power Doppler is a technique that uses the amplitude of Doppler signal to detect moving matter. Power Doppler: • Is independent of velocity and direction of flow, so there is no possibility of signal aliasing

• Is independent of angle, allowing detection of smaller velocities than color Doppler, facilitating examinations in certain technically challenging clinical setting • Has higher sensitivity than color Doppler, which makes a trade-off with flash artefacts. [20].

Fig (I.18): Ultrasound images, Fig (I.19): Power Doppler Hepatic veins, power Doppler. Ultrasound scan of blood flow in a normal liver.

3) Duplex Doppler

Duplex imaging gathers both the B-mode and pulsed signal wave Doppler (spectral Doppler). The probe is identical to a B-mode imaging probe but with a little group of the probe elements applied to send and discover pulsed Doppler signals. The residual elements utilize the B-mode imaging. This mechanism lets the blood vessel to be scanned and the depth of sample is adjusted by an option on monitor screen cursor called the “Doppler gate.” The Doppler gate width can be changed to alter the depth range. A second mark (cursor) on screen monitor is referred to the “angle.” The Doppler gate with this angle can be aligned with the direction of the vessel to produce a calculation of the insonation angle with the blood flow thus that speed of blood flow can also be calculated through applying the Doppler formula.

Duplex Doppler scanning technique also helps to measure the volume flow which is performed through measuring the lumen diameter on the B-mode image, the highest flow in systole stage, and calculation of the cross-sectional region. [21]

Fig (I.20): Showing duplex Doppler (Spectral Doppler).

What is it used for? “Indication”

A Doppler ultrasound may help diagnose many conditions, including: • Blood clots • Poorly functioning valves in your leg veins, which can cause blood or other fluids to pool in your legs (venous insufficiency) • Heart valve defects and congenital heart disease • A blocked artery (arterial occlusion) • Decreased blood circulation into your legs (peripheral artery disease) • Bulging arteries (aneurysms) • Narrowing of an artery, such as in your neck (carotid artery stenosis)

A Doppler ultrasound can estimate how fast blood flows by measuring the rate of change in its pitch (frequency). During a Doppler ultrasound, a technician trained in ultrasound imaging (sonographer) presses a small hand-held device (transducer), about the size of a bar of soap, against your skin over the area of your body being examined, moving from one area to another as necessary.This test may be done as an alternative to more-invasive procedures, such as angiography, which involves injecting dye into the blood vessels so that they show up clearly on X-ray images. A Doppler ultrasound test may also help your doctor check for injuries to your arteries or to monitor certain treatments to your veins and arteries. [15,16,17,18]

General indications(uses)of ultrasound in general

Ultrasound examinations can help to diagnose a variety of conditions and to assess organ damage following illness. and also is used to help physicians to evaluate symptoms such as: pain - swelling -infection Ultrasound is a useful way of examining many of the body's internal organs, including but not limited to the heart and blood vessels, including the abdominal aorta and its major branches : liver , gallbladder , spleen , pancreas , kidneys , bladder , uterus, ovaries, and unborn child (fetus) in pregnant: eyes , thyroid and parathyroid glands , scrotum (testicles) , brain in infants , hips in infants , spine in infants

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Ultrasound is also used to guide procedures such as needle biopsies, in which needles are used to sample cells from an abnormal area for laboratory testing.-image the breasts and guide biopsy of breast cancer..-diagnose a variety of heart conditions, including valve problems and congestive heart failure, and to assess damage after a heart attack. Ultrasound of the heart is commonly called an "echocardiogram" or "echo" for short. -Doppler ultrasound images can help the physician to see evaluate: -blockages to blood flow (such as clots)

-narrowing of vessels -tumors and congenital vascular malformations -reduced or absent blood flow to various organs, such as the testes or ovary -increased blood flow, which may be a sign of infection With knowledge about the speed and volume of blood flow gained from a Doppler ultrasound image, -the physician can often determine whether a patient is a good candidate for a procedure like angioplasty. -Ultrasound has many different uses that help a physician evaluate, diagnose, and treat various medical conditions. -…One of the best known uses for ultrasound imaging is fetal ultrasound, which is used to examine a baby during pregnancy. It’s also used to view the ovaries and uterus during pregnancy. -An abdominal ultrasound examines abdominal tissues and organs. -Bone sonometry is a type of ultrasound imaging that examines bone density and assesses risk for osteoporosis. -Breast ultrasound screening can help detect breast cancer in women with dense breasts.

-An echocardiogram, an ultrasound of the heart, allows assessment of the overall function of the heart. Echocardiograms are often combined with Doppler ultrasound, which visualizes blood flow through blood vessels and organs. -Ultrasound may be used to assist with biopsies. -Opthalmic ultrasound examines the structures of the eye. -Ultrasound can help assess joint inflammation. -Ultrasound imaging can help diagnose causes of pain, swelling, and infection inside the body. -Physicians use ultrasound imaging to examine the structures of internal organs for damage after illness. -Ultrasound can help detect genital and prostate pproblems Doctors commonly use ultrasound for procedures such as: 1)abdominal scans – may be used to investigate abdominal pain, nausea, vomiting, abnormal sounds and lumps. Structures to be examined may include the gallbladder, bile ducts, liver, pancreas, spleen, kidneys and large blood vessels. Structures that contain air (such as the stomach and bowels) can’t be examined easily by ultrasound because air prevents the transfer of the sound waves .

2) pelvic scans – may be performed if a woman is suffering pelvic pain or has abnormal periods, fibroids, cysts or other conditions associated with the female reproductive system 3) pregnency scans – used to check for fetal abnormalities (such as spina bifida), check the age and position of a fetus, and monitor fetal growth and development. Undergoing an ultrasound scan is now considered routine for pregnant women in Australia 4) other uses – musculoskeletal scans (to check regions like a shoulder, hip or elbow), breast scans (for example, to further investigate an abnormality picked up by physical examination or mammogram) and a scan of a person’s eye (to check its internal structures). A special type of ultrasound scan, called a Doppler ultrasound, is used to detect the speed and direction of blood flow in certain regions of the body, for example, neck arteries and leg veins.(22-23-24-25-26-27)

General Ultrasound Preparation

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-Ultrasound imaging, also called ultrasound scanning or sonography, involves exposing part of the body to high-frequency sound waves to produce pictures of the inside of the body. An ultrasound carries minimal risks. Unlike X-rays or CT scans, ultrasounds use no radiation. For this reason, they are the preferred method for examining a developing fetus during pregnancy. The steps you will take to prepare for an ultrasound will depend on the area or organ that is being examined.

Patient Safety Tips Prior to a Diagnostic Exam in Radiology

• Please let us know if you have any allergies or adverse reactions to medications. • Please leave your valuables at home or in your room in the hospital. • Please let us now if you need interpreting services, this can be arranged for you. • Late arrival policy: If you are more than 10 minutes late for your appointment there is a possibility you may not be seen for your examination. Being seen for your appointment will be left to the discretion of your provider based on the nature of your concern and the schedule of the provider.

Preparation for the Exam : • The technologist will verify your identification and exam requested. • The preparation for this test will depend on the type of ultrasound procedure your doctor has ordered. Some preparations include drinking a quart of water before the test to obtain better images. Your doctor will instruct you. • If you are having a biopsy, you will be asked to not eat or drink anything past midnight the night before the exam. Your doctor will instruct you. During the Exam • The duration of the exam will vary, but the average is about 30-60 minutes. • The technologist will position you on the exam table, and give you instructions. • You will have the opportunity to ask the technologists questions. • A small amount of water-soluble gel is applied to the skin over the area to be examined. • A hand-held instrument is placed against the gel on your body. This instrument will be moved across the area being examined.

After the Exam

• If you are going home, you may resume normal activities. • Most ultrasound procedures do not require advance preparation. The exceptions are listed below: For any study, if your doctor gave you an order, please bring it with you. Abdominal Ultrasound and Abdominal Ultrasound with Doppler (Liver, spleen, gallbladder, kidneys, pancreas, abdominal aorta, biliary system) • (Exam time: 30 min; visit time about 1-1/2 hours) • Adults: Do not eat or drink eight hours before exam. • Children: Do not eat or drink four hours before study or skip one meal. • Take medications with a small sip of water. • If you are diabetic, please take your insulin. Pelvic Ultrasound (Uterus, ovaries, fallopian tubes, urinary bladder) • (Exam time: 30 min; visit time about 1-1/2 hours) • Our protocol is to include transvaginal ultrasound for females.

• Eat normally. • One hour before your exam, drink 32 ounces of water. • Do not empty your bladder before your exam. Bladder Ultrasound • For both male and female patients, one hour before your exam, drink 32 ounces of water. Prostate-Transrectal Ultrasound • Two hours before your exam, do a cleansing with a Fleet enema #1. • Follow preparations for prostate ultrasound Transvaginal Ultrasound • Drink 32 ounces of any liquid one hour before the exam. Do not urinate before the exam so you arrive for at the exam with a full bladder.

Hysterosonogram • No unprotected sexual relations during the first 10 days of your menstrual cycle. Ultrasound-Guided Biopsies Ultrasound breast biopsy • You must be off aspirin, blood thinners and vitamin E for seven days prior to your biopsy. Liver biopsy / paracentesis / thoracentesis / prostate biopsy • Do not eat or drink after midnight the day before your biopsy. • You must be off aspirin, blood thinners and vitamin E for seven days before your biopsy.

If there are hairy in the place of examination ,remove it because it is block the sound from the body.

How do I prepare for an ultrasound of the liver? This procedure requires little to no special preparation. Your doctor will instruct you on how to prepare, including whether you should refrain from eating or drinking beforehand. Your doctor may tell you to fast for eight to 12 hours before your ultrasound, especially if your abdomen is being examined. Undigested food can block the sound waves, making it difficult for the technician to get a clear picture.

For an examination of the gallbladder, liver, pancreas, or spleen, you may be told to eat a fat-free meal the evening before your test and then to fast until the procedure.

However, you can continue to drink water and take any medications as instructed. For other examinations, you may be asked to drink a lot of water and to hold your urine so that your bladder is full and better visualized. Be sure to tell your doctor about any prescription drugs, over-the-counter medications, or herbal supplements that you take before the exam. It’s important to follow your doctor’s instructions and ask any questions you may have before the procedure.

How do I prepare for a vascular ultrasound of the liver? -You will be given instructions before the exam. -You may be asked to not eat or drink anything 8 hours before the exam. However, you may still take your medicine with sips of water. -You should wear comfortable, loose-fitting clothes for your exam. Leave valuables, such as jewelry and credit cards at home. -You may be asked to wear a gown during the exam. (28-29-30-31-32-33)

Ultrasound artifacts

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are commonly encountered and familiarity is necessary to avoid false diagnoses. They are not to be confused with ultrasound probe defects, which represent hardware failure.

Artifacts :1- acoustic enhancement : Acoustic enhancement is a localized increase of echo amplitude distal to a structure of low attenuation, seen as an area of increased brightness. When sound waves pass through a poorly attenuating structure that allows them easy passage, there is less tissue reflection and an area of artifactual increased echogenicity is produced right under the structure because more sound waves are present in this area compared with tissues at the same depth around. It is typically seen with fluid-filled structures in a soft tissue background (e.g. gallbladder, liver cyst). Acoustic enhancement can help differentiate fluid-filled structures from solid, hypoechoic masses.

2- Acoustic shadowing: The phenomenon of acoustic shadowing (sometimes, somewhat tautologically, called posterior acoustic shadowing) on an ultrasound image is characterized by a signal void behind structures that strongly absorb or reflect ultrasonic waves. It is a form of imaging artifact. This happens most frequently with solid structures, as sound conducts most rapidly in areas where molecules are closely packed, such as in bone or stones. 3-Aliasing : is a phenomenon inherent to Doppler modalities which utilize intermittent sampling in which an insufficient sampling rate results in an inability to record direction and velocity accurately.

The second image shows the same vessel after the PRF has been increased (5.15 kHz). The cine loop shows how aliasing gradually disappears as the PRF is adjusted (Note: the frame rate has been reduced to increase visual clarity).

The first image and shows the CCA scanned with an inappropriately low PRF (1.4 kHz) for the high velocity arterial flow. As a result flow above the upper threshold of is displayed with blue hues, during the systolic peak.

4- Anisotropy : is the most significant and commonly encountered artifact (potential pitfall / imaging mistake) with the superficial structures in musculoskeletal ultrasound and it is particularly potentially problematic when using linear transducers. It refers to the property of tissue to differentially conduct or reflect sound waves back to the transducer based on the angle of incidence of the sound waves. The anisotropic artifact refers to a

darkening and loss of resolution of the image which occurs when the approach of the sound waves is less than perpendicular (ie, angle of incidence greater than 0 degrees). Therefore, the sonographer should attempt to keep the direction of the beam as close to perpendicular as possible.

Anisotropy is still one of the main challenges for sonographers who are developing their learning curve on a certain level. Being aware of the potential presence of anisotropy is important in qualitative scanning and pathology recognition. In SonoSkills courses we pay a lot of attention in the recognition and prevention of anisotropy. 5- Beam width artifact: Ultrasound beam width artifact occurs when a reflective object located beyond the widened ultrasound beam, after the focal zone, creates false detectable echoes that are displayed as overlapping the structure of interest. To understand this artifact, it is important to remember that the ultrasound beam is not uniform with depth, the main beam leaves the transducer with the same width as it, then narrows as it approaches the focal zone and widens again distal to this zone 1.

Usually, it occurs when scanning an anechoic structure and some peripheral echoes are identified, i.e. gas bubbles in the duodenum simulating small gallstones and peripheric echoes in the bladder. It is possible to avoid this artifact adjusting the focal zone to the depth level of interest and by placing the transducer at the center of the object being studied.

6- Blooming or color bleed artifact occurs when the color signal indicating blood flow extends beyond its true boundaries, spreading into adjacent regions with no actual flow.

This artifact mainly affects the portion of the image distal to the vessel and the transducers. It is somewhat similar to its MRI namesake as both phenomena denote something that seemingly appears larger than its true physical limits.

Blooming occurs because the spatial resolution of color Doppler is lower than greyscale ultrasound . It can be exaggerated by inappropriately high color gain. It is important to be aware of as it may obscure partial occlusions such as thrombi resulting in misdiagnosis. It can be avoided by lowering the color gain until the bleed of signal outside of the vessel disappears .

7- Color bruit artifact The color bruit or tissue vibration artifact is a type of color Doppler ultrasound artifact which results in color signal overflowing to the perivascular tissues most often caused by stenosis, AV fistulas, or shunts. Thus, this artifact is useful by pinpointing areas of potentially pathological blood flow.

8- Color flash artifact: The color flash artifact is a commonly encountered artifact on color Doppler ultrasound, representing spurious flow signal arising due to tissue/transducer motion

9- Comet-tail artifact The comet-tail artifact is a grey-scale ultrasound finding seen when small calcific / crystalline / highly reflective objects are interrogated and is believed to be a special form of reverberation artifact. It is similar to the color comet-tail artifact and is seen in similar situations, although is in general less sensitive than the latter. √small renal or ureteric calculi √small common bile duct stones √adenomyomatosis of the gallbladder √pancreatic calcifications of chronic pancreatitis √testicular microlithiasis (sometimes) √thyroid colloid nodules √identification of foreign bodies -surgical clips -catheter tips -debris / glass / metal

10- Double aorta artifact (ultrasound) The double aorta artifact is a relatively common ultrasound artifact, which can appear both on standard B-mode and color Doppler imaging, resulting in an artifactually duplicated abdominal aorta in the transverse plane. Knowledge of this artifact is paramount as potential differential diagnoses include life threatening conditions (e.g. aortic dissection).

•Physics The artifact is caused by the differential refraction of the ultrasound beam while passing through the relatively echogenic rectus abdominis muscles, and the comparatively hypoechoic fatty tissue underneath. The interface between these tissues creates an acoustic prism effect. The artifact primarily affects curvilinear transducers 1.

•Radiographic features Partially, or less commonly completely duplicated, "double barrel" appearance of the abdominal aorta in the transverse plane is characteristic, which also affects color Doppler imaging. Adjacent structures (e.g. anterior vertebral echo) are duplicated too, but this is usually harder to appreciate. •Practical points The artifact can be diminished by changing the angle of insonation in a way that the beam no longer passes through the "acoustic prism" formed by the rectus abdominis muscles and the fatty tissue beneath the linea alba. Rotating the probe into the sagittal plane has a similar result. Note that pulsed wave Doppler ultrasound curves are not affected by this artifact, and will display normal spectral waveform, which also differentiates this phenomenon from its mimickers. The artifact is more common in younger, athletic patients, and the duplication is usually incomplete .

11- Electrical interference artifact (ultrasound): Electrical interference artifact is an ultrasound artifact usually caused by the ultrasound machine being too close to the unshielded electrical equipment. The disturbance appears as arc-like moving bands in the ultrasound image. While the presence of electrical equipment (e.g unshielded ventilators) near the ultrasound machine may cause this artifact because of external electronic signals, the artifact can also occur when the ultrasound probe malfunctions.

12- hardware-related artifacts * Transducer-related artifact Artifacts in ultrasound imaging may result from faults in the transducer itself or in the transducer cable.

13- Mirror Image Artifact * Mirror image artifact in sonography is seen when there is a highly reflective surface (e.g. diaphragm) in the path of the primary beam. The primary beam reflects from such a surface (e.g. diaphragm) but instead of directly being received by the transducer, it encounters another structure (e.g. a nodular lesion) in its path and is reflected back to the highly reflective surface (e.g. diaphragm). It then again reflects back towards the transducer.

The ultrasound machine makes a false assumption that the returning echo has been reflected once and hence the delayed echoes are judged as if being returned from a deeper structure, thus giving a mirror artifact on the other side of the reflective surface. It is a friendly artifact that allows the sonographer to exclude pleural effusion by the reflection of the liver image through the diaphragm.

Examples: -reflection of a liver lesion into the thorax (the commonest example) -reflection of abdominal ascites mimicking pleural effusion -duplication of gestational sac (either ghost twin or heterotopic pregnancy) 3 -duplication of the uterus To avoid this artifact, change the position and angle of scanning to change the angel of insonation of the primary ultrasound beam.

14- Multipath Artifact *. A multipath artifact is an ultrasound beam artefact in which the primary beam reflects off anatomy at an angle, resulting in a portion of the beam returning to the transducer, whilst another portion takes a longer duration as it reflects a second structure. This phenomenon results in a propagation path error in which the transducer will interpret a structured to be deeper than it is. What assumption: A pulse travels directly to a reflector and then back to the transducer is invalid. Reflections are produced by structures located in the main axis of the beam is invalid. Description of Artifact: Created when sound pulses glance off a second structure on the way to or from the primary reflector. Resulting in the transmit path length differing from the return path length. USA: Image appears deeper or misplaced. How to prevent: Change the angle of the beam and change the depth you are working with.

15- Reverberation artifact *Reverberation artifact occurs when an ultrasound beam encounters two strong parallel reflectors. When the ultrasound beam reflects back and forth between the reflectors ("reverberates"), the ultrasound transducer interprets the sound waves returning as deeper structures since it took longer for the wave to return to the transducer. Reverberation artifacts can be improved by changing the angle of insonation so that reverberation between strong parallel reflectors cannot occur.

comet-tail artifact is a specific type of reverberation artifact. This results a short train of reverberations from an echogenic focus which has strong parallel reflectors within it (e.g. cholesterol crystals in adenomyomatosis). With comet tail artifact, the space between the two strong parallel reflectors may be less than 1/2 the space pulse length, causing the echoes to be displayed as triangular lines (the later echoes get attenuated and have a decreased amplitude, manifesting on the display as decreased width). The appearance of the reverberation artefact depends on: • The size of the two reflective surfaces • The distance between the two reflective surfaces (long vs short path reverberation artefacts) • And how much ultrasound energy is lost – dissipated or attenuated, between each re-reflection.

16- Refraction artifact: Refraction artifact can occur when a transmitted ultrasound pulse strikes an interface at a non-perpendicular angle. The difference in propagation speeds between the two tissues can cause refraction to occur. Should the refracted incident sound wave strike a reflector and cause an echo to return to the transducer, this may be displayed at an incorrect location as the transducer assumes all echoes have traveled along a direct path. Refraction artifact should resolve if the transducer is moved such that the incident pulse is perpendicular to the interface.

*Refraction represents a change in the transmitted ultrasound pulse direction at a boundary with nonperpendicular incidence when the two adjacent tissues support a different speed of sound. Misplaced anatomy can occur in the image from the beam redirection as the echoes propagate back to the transducer over a similar return path. The sonographer must be aware of objects appearing and disappearing with slight differences in orientation of the transducer array.

At the edges of smooth-rounded organs, refraction of the beam at nonnormal incidence can redirect the beam away from the edge, creating a shadow of reduced intensity beyond the edge and resulting in an edge artifact. In many situations, the cause of the refraction artifact can be traced back to anatomic structures.

17- Ring down artifact*"Ring-down" is an ultrasound artifact that appears as a solid streak or a series of parallel bands radiating away from abdominal gas collections. Using an in vitro system of bubbles in water or gelatin, it was found that the ring-down artifact originated from the center of a cluster of four bubbles (bubble tetrahedron), three on top and one nestled beneath. Entrapped between the bubbles is a horn- or bugle-shaped fluid collection that we theorize emits a continuous sound wave back to the transducer when struck by an ultrasound pulse. Electronic processing by the scanner converts this continuous sound wave into the series of bands seen in the ring-down artifact. *Ring down artifact is a special type of resonance artifact. Its appearance is similar to the ladder-like reverberation of comet-tail artifact, but it is produced by a completely different mechanism.

The artifact is only associated with gas bubbles, and occurs when an ultrasound pulse encounters a "horn" or "bugle" shaped fluid collection that is trapped between an inverted tetrahedron of 4 bubbles (3 on top and 1 nestled deep to them). The trapped fluid resonates, emitting a continuous signal back to the transducer. Whereas the transducer pulse is broad spectrum, the returning signal consists of one or more discrete (resonant) frequencies. "Beats" between these frequencies produce the variable appearance of the ring down. There is no "reverberation" ( i.e. multiple reflectances).

*This artifact can be eliminated by angling the ultrasound probe.

18- Side lobe artifact *Side lobe artifacts occur where side lobes reflect sound from a strong reflector that is outside of the central beam, and where the echoes are displayed as if they originated from within the central beam. Ultrasound transducer crystals expand and contract to produce primary ultrasound beams in the direction of expansion and contraction. Secondary beams occur because the crystals also expand and contract radially. These radial beams are called side lobe beams. Side lobe beams are low-intensity beams that surround the central beam. Side lobe artifacts are echogenic, linear or curvilinear artifacts. Strong reflectors include bowel gas adjacent to the gallbladder or urinary bladder.

Transducer side lobes consist of multiple low-intensity sound beams located outside of the main ultrasound beam. Although the echoes generated by side lobes originate outside of the main beam, they appear as specular or diffuse artifactual echoes within the beam. They are visible with both static and real-time equipment.

Transducer side lobes consist of multiple low-intensity sound beams located outside of the main ultrasound beam. Although the echoes generated by side lobes originate outside of the main beam, they appear as specular or diffuse artifactual echoes within the beam. They are visible with both static and real-time equipment.

19- Speckle artifact *Speckle artifact may be encountered in ultrasound. It is caused by the scattering of waves from the surface of small structures within a certain tissue. The artifact produces a textured appearance. *Speckle patterns in ultrasound images may move in a way which bears no simple relationship to the motion of the corresponding tissues. In some instances the speckle motion replicates the underlying tissue motion, in others it does not.

The authors name "speckle motion artifact" the difference between the speckle and the underlying tissue motion. An echographic image formation model is used to study the motion artifact produced by a rotating phantom and observed by a linear scan imaging system with a Gaussian beam.

The authors propose that when the tissue is modeled as a random array of small and numerous scatterers, such motion aberration be accounted for by the 2D phase characteristics of the imaging system. An analytic prediction of this motion artifact in relation to the imaging system characteristics (beam width, transducer frequency, pulse duration) is presented. It is shown that the artifact results from the curvature of the system point spread function, which in turn determines the curvature of the 2D phase characteristics. To the authors' knowledge, it is the first time a comprehensive model of ultrasonic speckle motion artifact is presented. The model has been developed to study rotation-induced artifact; the method is however quite general and can be extended to study the effects of other tissue motion, in particular deformation and shear.

20- Speed displacement artifact *Speed displacement artifact, also known as propagation velocity artifact, is a gray scale ultrasound finding that can be identified as an area of focal discontinuity and displacement of an echo deeper than that its actual position in an imaged structure. Depth determination by an ultrasound machine is based on the principle that the average propagation velocity of sound in human tissue is 1540 m/s, and as such the time between broadcasting and detecting the returned sound wave to the transducer is multiplied by this number and halved to determine distance, regardless of tissue type 1. As a result, if the true propagation velocity of a tissue falls significantly below or above 1540 m/s, such as fat or bone, then the distance calculated by the machine will be false, displaying an inaccurate depth measurement. By this same principle, if there is differential variation in tissue composition of the tissues under the same ultrasound beam, then different return times to the transducer will be processed as different depths of tissue as opposed to differences in propagation velocity between the tissues.

This may result in discontinuity in the displayed ultrasound image, and as such is referred to as a propagation velocity misrepresentation. A commonly encountered scenario is speed displacement artifact due to slowing of the ultrasound beam by focal fat, such as in focal fatty sparing in case of hepatic steatosis.

21- Twinkling artifact *Twinkling artifact is seen with color flow Doppler ultrasound. It occurs as a focus of alternating colors on Doppler signal behind a reflective object (such as a calculus), which gives the appearance of turbulent blood flow.

It appears with or without an associated color comet-tail artifact. The underlying mechanism of this artifact is thought to be a result of inherent noise within the ultrasound scanner, specifically phase (a.k.a. clock) jitter within the Doppler electronics.

Twinkling artifact is more sensitive for detection of small stones (e.g. urolithiasis, cholelithiasis) than is acoustic shadowing. It is most pronounced when the reflecting surface is rough and highly dependent on machine setting: • when the focal zone is located below a rough reflecting surface, the twinkling artifact becomes more obvious than when it is above it decreased pulse repetition frequency facilitates better visualization of the artifact. • The presence of renal twinkling artifact on sonography has a high positive predictive value (78%) for the presence of nephrolithiasis at unenhanced CT. (34-35-36-37)

Anatomy of liver

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The liver in general: is the largest organ, accounting for approximately 2% to 3% of average body weight. The liver has 2 lobes typically described in two ways, by morphologic anatomy and by functional anatomy (as illustrated in Fig. 1).1 Located in the right upper quadrant of the abdominal cavity beneath the right hemidiaphragm, it is protected by the rib cage and maintains its position through peritoneal reflections, referred to as ligamentous attachments (Fig. 2). Although not true ligaments, these attachments are avascular and are in continuity with the Glisson capsule or the equivalent of the visceral peritoneum of the liver .

The Ligaments of the Liver: 1-The Falciform ligament of liver. 2- The Ligamentum teres hepatis. 3- The coronary ligament. 4- The right triangular ligament. 5- The left triangular ligament. 6- The Hepatogastric ligament. 7- The hepatoduodenal ligament. 8- The Ligamentum Venomous.

fig.2 the ligaments of liver

Segmental anatomy: The gross anatomical division of the liver into its right and left lobes is useful in gross description but is without morphological significance. The areas of supply of the right and left hepatic arteries, with accompanying portal vein and bile duct branches, can be demarcated by a line passing through the inferior vena cava and the fossa of the gall bladder, i.e. into roughly equal functional right and left lobes. These can be subdivided into a further eight segments, four to each functional lobe (Figure 3), each segment with its individual blood supply and biliary drainage. This arrangement allows the surgeon to carry out segmental hepatic resections.

Liver segment nomenclature : In a clockwise fashion starting with caudate lobe as segment I , left posterolateral segment is number II, left anterolateral segment III, left superomedial segment IVa, left inferomedial segment IVb, right anteroinferior segment V, right posteroinferior segment VI, right posterosuperior segment VII, and right anterosuperior segment VIII. After all, this looks more complicated than it is Right liver lobe.

(Figuer3) The segmental anatomy of the liver with the tributaries of the portal vein

The major functions of the liver include: The liver is classed as a gland and associated with many functions. It is difficult to give a precise number, as the organ is still being explored, but it is thought that the liver carries out 500 distinct roles. • Bile production: Bile helps the small intestine break down and absorb fats, cholesterol, and some vitamins. Bile consists of bile salts, cholesterol, bilirubin, electrolytes, and water. • Absorbing and metabolizing bilirubin: Bilirubin is formed by the breakdown of hemoglobin. The iron released from hemoglobin is stored in the liver or bone marrow and used to make the next generation of blood cells.

• Supporting blood clots: Vitamin K is necessary for the creation of certain coagulants that help clot the blood. Bile is essential for vitamin K absorption and is created in the liver. If the liver does not produce enough bile, clotting factors cannot be produced. • Metabolizing carbohydrates: where they are broken down into glucose and siphoned into the bloodstream to maintain normal glucose levels. • Filters the blood • Immunological function: (Kupffer cell) • Production of albumin: Albumin is the most common protein in blood serum. It transports fatty acids and steroid hormones to help maintain the correct pressure and prevent the leaking of blood vessels.

Blood supply of the liver: • Proper hepatic artery the right and left hepatic arteries enter the porta hepatis. • The right hepatic artery usually gives off the cystic artery, which runs to the neck of the gallbladder. • The blood vessels conveying blood to the liver are the hepatic artery (30%) and portal vein (70%). • The hepatic artery brings oxygenated blood to the liver, and the portal vein brings venous blood rich in the products of digestion, which have been absorbed from the gastrointestinal tract. • The arterial and venous blood is conducted to the central vein of each liver lobule by the liver sinusoids.

• The central veins drain into the right and left hepatic veins, and these leave the posterior surface of the liver and open directly into the inferior vena cava.(38-39-40)

Fig .(4 ) Showing blood supply of the liver.

‏Ultrasound Technique of liver

* * *

Scanning technique : Scanning should be in sagittal , transverse and oblique planes , including scans through the intercostal and subcostal spaces . Scanning should be done with a slow rocking movement of the transducer in all planes to obtain the best visualization of the whole liver , Always clear 2-3cm beyond the margin of any organ to avoid exophytic or adjacent masses .(41)

• Technique of liver scan : Longitudinal sections : The transducer is placed in the midline just under the xiphistemum. Then angle the transducer up & down if necessary to can view the diaphragm & the inferior border. Angling the transducer to slowly as far left as possible to out of the left lobe. Search for the left lobe & left hepatic vein. Return back slowly to the midline, see the p middle hepatic vein and portal vein. Angle slightly to the right to see as much of right lobe as possible, angling again up & down. Look for the IVC and aorta in longitudinal sections. Move the transducer towards the right, and still in the longitudinal position , then look for the portal vein , right hepatic vein & bile ducts. Angle upwards below the ribs to can see the liver. Look for right kidney & compare its texture with the liver once. After that start to hit colonic gas.

To avoid this ask your patient to breathe in deeply to push & force the liver down more under ribs or, better, try to turn the patient into the LLD position. Before tuming the patient, look for if any free fluid may be lying on surface of the liver or in the sub-hepatic space or lateral to it. If little can be seen subcostally , so you will need to scan intercostally. Then position the footprint of transducer against the intercostal space in axillary line so the plane of the scan is lieing parallel to the intercostal space. If it doesn't lie parallel, shadows from ribs will be apparent. Patients can raise their arms above their heads to increase intercostal space (the inspiration will raise the ribs. Bucket handle effect). These sections will be longitudinal coronal views. The scans should be also made from different intercostal spaces. The intercostal scanning will demonstrate the lateral aspect of liver better. You will probably have to scan with a higher intercostal space than you think; but not too high though. You should remember that the diaphragm curves are down laterally & will come between the transducer & the liver.

Transverse sections : the transducer is placed transversely in the subxiphisternal area. Angle it to right & left as far as can be seen to show in order left & right lobes. Angle the transducer to the head t see the diaphragm, As much of the both lobes as possible, as much texture as possible & confluence of the 3 hepatic veins into the IVC. Then identify the ligamentum teres between the left and right lobes.(41) Oblique sections : Scanning with long axis of ultrasound beam at rightangles to lower costal margin. This in theory should give the largest slice area of the liver. Look carefully at the vessels and the porta hepatis entering the liver. Start by scanning the liver when the patient is supine, gas will often be displaced & better images obtained by turning patient into the LLD or LPO positions. The relationship of transducer to the body surface is nearly the same as when the patient is ling supine. LPO position Turn the patient 45° to the left side & provide support so that the patient will be comfortable. Raise the right arm so that will help to raise the ribs. Liver should fall slightly inferiorly to permit better access &the gas in large intestine should rise up & away from the midportion of the abdomen.

LLD POSITION: Turn your patient a further 45° to left so that they are lying on thier left side with hips & knees are flexed slightly to provide more stability in this position. This is could be an altemative to the LPO position & allows an obese abdomen to fall far away from the area of interest. It is expected that the flexibility of technique & thought for the patient's condition will decide whether to turn the patient or not . (41)

1. Liver sagittal Lt Lobe

Fig (II.78) Showing probe with sagittal plane.

Fig (II-79) Showing left lobe of the liver.

Fig (II.80) Showing probe with sagittal plane In the patient with tilt the transducer to the left.

Fig (II.81) Showing liver and IVC (sagittal plane).

The probe is in the epigastric region just below the sternum. It is angled cephalad to view the left lobe in its entirety. The probe may need to be angled towards the left side to see the most medial edge of the left lobe

Fig (II.82) Showing Scan Plane Left Lobe of Liver.

Fig (II.83) Showing Normal Anatomy seen in the Transverse View of the Left Lobe.

Fig (II.84) Showing probe with transverse Plane with tilt and move the transducer Inferiorly and superiorly.

Fig (II.85) Showing liver and IVC and SMA in transverse plane.

Through the entire left lobe, caudate lobe, then right lobe and out of the right lobe in the sagittal plane This is done initially from a subcostal approach.

Fig (II.87) Showing Left lobe/caudate lobe in sagittal, with IVC.

Fig (II.86) Showing Probe Move more middle.

Fig (II.88) Showing IVC, Left hepatic vein using Doppler ultrasound.

Fig (II.90) Showing Transverse image of the porta hepatus.

Fig (II.89) Showing position of Probe to detect Portal vein.

Fig (II.91) Showing Color Doppler sonogram of the porta hepatis showing the main portal vein (arrow, MPV), branching into the left portal vein (arrow, LPV) and right portal vein (arrow, RPV), as well as bifurcation of the right portal vein into anterior (arrow, RAPV) and posterior (arrow, RPPV) branches. (39,41,42)

2. Liver sagittal Rt lobe:

Fig (II.92) Showing probe with sagittal plane in the patient with moving the transducer to the right.

Fig (II.93) Showing GB and duodenum shadows in sagittal plane.

Fig (II.95) Showing GB and liver in sagittal plane .

Fig (II.94) Showing GB and liver in sagittal plane in the patient with moving the transducer to the right and put more deep.

Fig (II.96) Showing probe with sagittal plane in the patient with moving the transducer to the right.

Fig (II.97) Showing liver and RT kidney in sagittal plane.

Fig (II.98) Showing probe with sagittal plane in the patient with tilt the transducer to the left and use enough deep to see diaphragm.

Fig (II.99) Showing liver dome in sagittal plane.

Fig (II.100) Showing parasagittal scan plane of liver.

Fig (II.101) Showing parasagittal scan of liver and right kidney.

Fig (II.103) Showing hepatic veins and IVC in transverse plane.

Fig (II.102) Showing probe with transverse plane with orient the transducer parallel to the right shoulder and tilt inferiorly.

Fig (II.104) Showing probe with transverse plane with move the transducer to the right below the ribs and tilt inferiorly and use less deep.

Fig (II.105) Showing CBD and portal vein in transverse plane.

Fig (II.106) Showing probe with transverse plane with move transducer to the right and use more deep.

Fig (II.107) Showing liver and Rt kidney in transverse plane.

Fig (II.108) Showing intercostal scan plane.

Fig (II.109) Showing the middle and Rt hepatic vein are visualized in this view.

Fig (II.110) Showing subcostal scan plane. The probe is angled cephalad under the ribs to avoid any bowel or ribs shadowing over the liver.

Fig (II.111) Showing Rt portal vein is shown coursing transversely in this view.

Normal liver on ultrasound

* * *

Abdominal ultrasound is an accurate method for estimating liver size, which should be determined at the midclavicular line and in normal conditions is less than 16 cm [42]. The liver parenchyma should be evaluated for focal and/or diffuse abnormalities. The normal liver appears as homogeneous with an echogenic texture. In normal conditions, liver echogenicity equals or slightly exceeds that of the renal cortex. This comparison heavily relies on the visual perception of the observer and on the presence (or absence) of disease processes in the renal cortex [43]. The right and left lobes, as well as the caudate lobe can be identified with the use of an ultrasound [3]. Other structures that should be identified are the main lobal fissure, which separates the left and right lobes and appears as an echogenic line that extends to the gallbladder fossa; the falciform ligament, which divides the left lobe into the medial and the lateral segments and appears as an echogenic area in the left lobe; and the ligamentum venosum, which separates the caudate from the left lobe and appears as an echogenic line anterior to the caudate lobe [44].

The liver is a large, pyramidal shaped organ and liver sectional anatomy may be best described imaged and defined using by real time ultrasound. Conventional real time ultrasound, produces images of thin slices of the liver on the screen, and so it is essential that the operator scans the entire organ systematically/ritually, in at least two anatomical planes, to be entirely convinced that the entire volume of the liver tissue and structures has been imaged. The operator must then synthesise this 2 dimensional information in their brain to develop a 3 dimensional map of the individual patient`s liver anatomy and pathology. This requires good hand-eye-brain coordination.

Figure 1 shows how a normal liver appears in an abdominal ultrasound.

For orientation, three levels of the central portion of the liver can be differentiated: • Level of the cConfluences of the liver veins [Figure 1]. • Level of the Pars umbilicalis of the (left) portal vein branch [Figure 2]. • Level of the gall bladder [Figure 3].

Figure 1:

Confluences of the liver veins. This “junction” level is the first one in ultrasound examination of the right liver lobe by subcostal scanning sections steeply “looking” upwards, preferably in deep inspiration [video]. VCI: inferior vena cava. LLV: Left liver vein. MLV: Middle liver vein. C: Confluens of the LLV and MLV. RLV: Right liver vein. The RLV often separately joins the inferior vena cava, whereas the LLV and MLV often reveal a common trunk (“C”).

Figure 2:

“Pars umbilicalis” of the portal vein – scanning planes display the left and right liver lobes in a more downwards orientated view into the right liver lobe as compared to the level of the confluens of the liver veins [video]. PA: Portal vein. PU: pars umbilicalis of the portal vein. VCI: Inferior vena cava.

Figure 3:

Gallbladder level as the most caudate scanning plane [video]. GB: Gallbladder. LTH: LLigamentum teres hepatis. S4: Segment IV of the liver (quadrate lobe).

Analysing the ultrasound examination, these levels mean the access for a number of (more or less) parallel scanning sections, which in there summary in the examiner`s brain form an real time three dimensional (“4D”) copy of the given patient`s individual anatomy and pathology. Standardised scanning in a ritualized sequence of probe- and patient positions and of scanning planes is mandatory to cover all segments and the complete liver surface [see videos].

The patient should be examined from sub- and intercostally in the decubitus position as well in modified slightly oblique positions with the right arm above the head and the right leg stretched during all respiration cycles to identify the best approach and to avoid artefacts caused by the thorax. Examination in the standing position is additionally helpful due to its weight, the liver moves caudally by gravity, and scanning from sub- or intercostal probe positions – according to the individual anatomy - avoides the interposed lung which is mainly true for the right posterolateral (superficial) parts of the liver using the intercostal approach. Other examination techniques have also been described but are not mentioned here in detail which might be additionally used. A great number of variants of the normal has to be encountered – e.g. with respect to accessory lobules, vascular branching, shape and configuration.

Examination criteriaAn acronym has shown to be didactically helpful [“SSOTM”]: • S = size • S = shape • O = outline • T = texture • M = measurement Size The size of the liver has been measured by many methods, including 3D-reconstructions. Liver size measurement has no impact in daily routine because there is no reliable and reproducible ultrasound method established so far [Sienz M et al., submitted].

Shape: Normally described as pyramidal.

Outline : The normal liver surface should be smooth with no lumps protruding or indentations. The inferior liver border in the normal patient should have an acute angled edge. Liver surface border delineation and other ultrasound criteria: Other ultrasound criteria are described in the respective chapters.

Texture, echogenicity: The normal liver parenchyma is of medium homogenous echogenicity, usually slightly darker than the spleen and slightly brighter than the renal cortex independently of the age except in childhood [(32)]. It is essential when comparing the liver with the spleen and renal cortex that the comparison is done at the same depth. Liver surface and vessels borders are smooth and vascular architecture with its classic dichotomy in branching is percepted as an harmonic and detailed aspect. The image of the normal parenchyma varies very little among individuals. An abdominal ultrasound can also identify the major hepatic and perihepatic vessels, including the inferior vena cava (IVC), the hepatic veins, the main portal vein, and the right and left branches of the portal vein [44].

The main portal vein is characterized by thick and echogenic walls and enters the liver at the hilum. It divides into the right and left portal branches, and the left branch then divides into medial and lateral branches. The hepatic veins, which drain in the inferior vena cava, have thinner walls in comparison to the portal vein [3]. In addition, abdominal ultrasound is a reliable method for a first-line evaluation of portal vein abnormalities suggestive of portal hypertension [45]. It is also very useful to evaluate the biliary tree and to detect ascitic fluid, and it can also be used to guide the performance of a paracentesis [44]. Doppler evaluation should be used to document blood flow characteristics and blood flow direction, which is crucial in the diagnosis of portal hypertension [46]. In addition, Doppler evaluation can distinguish nodular lesions that are suggestive of hemangiomas, of hepatocellular carcinoma, or of liver metastases [47].

Liver veins: The three liver veins are positioned in between the liver segments. Their course - additionally to the Glisson`s triad - is helpful in defining liver lobes and liver segments. Number and course of liver veins is somewhat variable [Figure 1]. Portal vein: Formed by the confluens of the splenic and superior mesenteric vein, the portal vein can be sonographically displayed using scans more or less perpendicular to the lower costal margin (orientation might be achieved referring from the right shoulder to the umbilicus), preferably in a left decubitus position and in variably deep inspiration. Intrahepatically, the portal vein bifurcates into a main left and right branch. The first (right) portal vein branch splits into an anterior and into a posterior branch, which itself leads to the segments V – VIII.

The latter (left) main portal branch bifurcates into segments II and III and, additionally, into the left medial branches for segments I (caudate lobe), IVa and Ivb [Figure 2]. Hepatic artery : The common hepatic artery has its source from the celiac axis, branching into the gastroduodenal artery and into the proper hepatic artery (arteria hepatica propria). Anatomical variations are frequent (in up to 50 %), e.g. the origin of the left proper hepatic artery out of the left gastric artery as well as the variable arterial supply of the liver by superior mesenteric artery branches. The hepatic artery runs with the portal vein, the right main arterial branch frequently meandering around the portal vein sonographically displayed in short segments medially (or less often laterally) of the portal vein. The normal and pathological flow patterns are described below in the Doppler chapter.

Bile ducts: Bile ducts accompany the portal vein and hepatic artery branches from the liver hilum into the liver lobules, intrahepatically forming the ductus principalis dexter and the ductus principalis sinister, which join as common bile duct (CBD). The extrahepatic course of the CBD is cranially (pre-pancreatic) often ventral to the portal vein and caudally (intrapancreatic) more dorsolateral. The respective course of the hepatic artery is more variable [Figure 4]. Figure 4 Common bile duct (CBD). The CBD, and therefore, the liver hilum, is often best examined in a left lateral decubitus position using a subcostal approach in slight inspiration [video]. In the typical view CBD (in between markers), portal vein (PV), hepatic artery (HA), inferior vena cava (IVC) and right renal artery (RRA) (and sometimes also the aorta [AO]) can be seen; the papilla region (PAP) is indicated.

Perihepatic lymph nodes: Perihepatic lymph nodes in the hepatoduodenal ligament (LK) can be commonly found next to the cystic duct, so called cystic duct lymph node [Figure 5].

Figure 5: Perihepatic lymph nodes. Perihepatic lymph nodes in the hepatoduodenal ligament (LK) can be commonly found next to the cystic duct, so called cystic duct lymph node, as shown in the portmortem examination by ultrasound (a) and macroscopically (b). VCI: Vena cava inferior.

Indication of liver in to ultrasound

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To asses and detect the size and location of the liver and to detect any abnormalities 1-Blockage in blood vessels

a. Hepatic vein thrombosis (HVT): Blocks drainage System in your liver, Impeding blood flow back to your heart, your liver stops getting the Fresh oxygen it needs to function

b- Portal vein thrombosis (PVT) lead to increased pressure in Portal Vein System, reduced blood supply to liver

Right hepatic vein thrombosis

Portal vein thrombosis

3-Suspected liver masses Called benign mass or tumor, liver lesions. That lead to fever, weight loss, no sea, vomiting Peeling of fullness, bloating Swelling or belly Pain

2-Liver metastasis (secondary liver cancer) cancerous tumor that spread to the liver started in another place or organ in the body (48-49)

Metastatic liver cancer

Hyperechoic lesions

5- Jaundice Condition in which skin, whites of eyes and mucous membranes turn yellow Caused by high level of bilirubin

4-Suspected liver abscess Mass filled with pus inside the Liver Caused by appendicitis, diverticulitis and Complication of Liver injury

Liver abscess

Extrahepatic jaundice

7-Ascites : Abnormal build-up fluid in the caused by liver cirrhosis , cancer , blockage of hepatic vein.

6- Enlarged liver (hepatomegaly) Caused by heart failure, Cancer and alcohol Consumption, liver appears Swollen beyond its normal Size

8- Abdominal trauma, abdominal pain, tenderness and rigidity (48-49)

Advantages of Ultrasound

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• They are generally painless and do not require needles, injections, or incisions. • Patients aren't exposed to ionizing radiation, making the procedure safer than diagnostic techniques such as X-rays and CT scans. In fact, there are no known harmful effects when used as directed by your health care provider. • Ultrasound captures images of soft tissues that don't show up well on X-rays. • Ultrasounds are widely accessible and less expensive than other methods • Can detect lesions in women with dense breasts when mammograms cannot. • Can help identify the nature of a lesion that is unclear from a mammogram • Widely available, and less expensive than a mammogram. • The only way to tell the difference between a cyst and a solid mass without using a needle to draw out fluid (non-invasive). • Patient is never exposed to radiation during an ultrasound, allowing pregnant women to use this imaging technique. • Can use ultrasound to detect blood flow through vessels.

• Ultrasounds do not cause any health problems, and there are no known harmful effects to humans • Simple • Real time imaging • Portable machine • Can repeat and easy to store ➨Ultrasound sensors are useful to detect objects which are greater than 1 meter away. ➨Ultrasound frequencies are unaffected by direct sunlight, fluorescent tubes and other sources of light which can interfere with infrared devices. ➨Ultrasound devices are more accurate which are capable of placing objects within 5 mm of distance.

➨Ultrasound devices are capable to measure distance to liquids and other transparent onjects which are not possible to be detected using infrared waves ➨It does not use any ionizing radiation during working operation . ➨It provides clear image of soft tissues which do not show up in X-Ray images. ➨Preferred method to diagnose complications of unborn babies. (50-51-52)

Advantage of contrast-enhanced ultrasound

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the main reasons you would have a contrast-enhanced ultrasound are:  To get better-quality images of an abnormality seen on a regular ultrasound, CT scan, or MRI  To monitor a known abnormality for changes in size or appearance  To image organs after trauma, infection, or suspected masses  To monitor the liver for hepatocellular carcinoma (a type of liver cancer) in patients with cirrhosis (scarring of the liver)  To image the liver or urinary system in patients who are allergic to the contrast used in CT or MRI  To check how open a blood vessel is, or to look for clots in a vein  To differentiate a gallbladder tumor from benign sludge

 4 Key Advantages:  Safety  No radiation  Safe for patients with CT or MRI contrast allergy  Safe in patients with poor renal function  Ease  Takes 30 minutes or less  No enclosed spaces or loud noises  No prior lab testing for renal or liver function  Accuracy  Clear view of organs that don’t show well on x-ray  Faster diagnosis than CT or MRI  Affordability  Generally more affordable than MRI or CT scans (50-51-52)

Disadvantages of ultrasound

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• Ultrasound results may identify a potential area of concern that is not malignant. These false-positive results could lead to more procedures, including biopsies, that are not necessary . Preliminary data from a trial being conducted showed that there was a higher rate of false-positive results with ultrasounds than with mammography (2.4%-12.9% for ultrasound and 0.7%-6% for mammography). • Although ultrasound is often used in an attempt to prevent an invasive measure for diagnosis, sometimes it is unable to determine whether or not a mass is malignant, and a biopsy will be recommended. • Many cancers cannot be detected via an ultrasound. • Calcifications that are visible on mammograms are typically not visible on ultrasound scans. This may prevent early diagnosis of a portion of breast cancers that begin with calcifications. • Ultrasounds are not available everywhere, and not all insurance plans cover them.

• An ultrasound requires a highly experienced and skilled operator to detect a malignant lump, as well as good equipment. If the cancerous tissue is not detected at the time of the scan, it will not be caught as early as possible. The ACR-accredited facilities database is a good way to determine the expertise of a facility in ultrasound imaging• Operator and equipment dependant • Hard tissue cannot be imaged • Deep structures cannot be visualized ➨It has poor penetration through bone or air. Moreover it has limited penetration in obese patients. These are the disadvantages in imaging domain. ➨The quality of results and use of equipment depend on skills of operator. ➨MRI scan has long imaging times and relatively higher in cost ➨Images can be difficult to interpret and requires experienced operators or radiologists. ➨Image resolution is less compare to CT and MRI scan. ➨Air or bowel gas prevents visualization of structures. (50-51-52)

Disadvantage of contrast-enhanced ultrasound

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• The contrast agents used in abdominal CEUS carry a very small risk of an allergic reaction. This risk is low—similar to the risk of an allergy from many antibiotics—and is lower than the risk of allergic reactions to contrast agents used in CT and MRI scans. (50-51-52)

Conclusion

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In conclusion, ultrasound imaging is highly focused on the acoustic impedances of various mediums. (Acoustic impedance = Density*Velocity) The waves of sound that are reflected back to the detector in the transductor are converted in to graphs and then to a clear 2D image. With this technology it is possible to examine the human body without the need for surgery or other procedures. (53)

References

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