DMS 202: Anatomy Chapt 7

When a solid mass appears isosonic to the organ parenchyma it is part of, the

Mass is only distinguishable by its walls. This border differentiation may be the only clue to the presence of an isosonic mass or masses

A localized change in the normal appearance of parenchyma represents

Mass or multiple masses, which are circumscribed to a specific area.

Case presentation is the

Method of presenting the images and related details of an ultrasound study to the interpreting physician

Isogenic Isosonic Isoechoic

Same echogenicity

Every internal body structure visualized with ultrasound has a typical normal appearance of its

Shape, size, contour, and position within the body and for soft tissue structures the parenchymal texture as well

Solid tissue masses are characterized sonographically in the same manner as

Soft tissue organs, with the terms homogeneous, heterogeneous, isosonic, hyperechoic and hypoechoic

A mass may be described as

Solid, cystic or complex according to its composition

Image quality is directly proportional to the

Technical proficiency and scanning expertise of the sonographer

Clinical correlation

The images you take should be the best representation of the ultrasound findings; they should provide data necessary for a physician to render a diagnosis

The scanning planes used in sonography are the same as anatomic body planes but their interpretations depend on

The location of the transducer and the sound wave approach (where the sound waves enter the body)

To be considered a simple or true cyst

The mass in question must meet 3 sonographic criteria

If one of the three simple cyst criteria is not met,

The mass is not a true cyst. A mass that meets only or two of these criteria is said to be cystic in nature.

Because the abdominal aorta is retroperitoneal and one of the deepest structures of the body,

The transducer of choice is usually 3.0 or 3.5 MHz

Body structures are accurately identified on ultrasound images by

Their location - not by their sonographic appearance, since it may be altered by pathology or other factors

Septations are

Thin, membranous inclusions found in some cystic masses.

The classic anatomic body planes are:

Transverse Sagittarius Coronal

Imaging criteria

• Begin with a transducer best suited to the structure(s) of interest. Use real-time transabdominal or endocavital scanners with sector or curved linear transducers. • Use a coupling agent such as gel to remove the air between the transducer and the surface of the patient's skin. • Patient comfort and the amount of transducer pressure exerted on the patient are important considerations. Experiment by using different amounts of transducer pressure on your own skin surface. • Perform comprehensive scanning surveys. A survey is a detailed assessment and inclusive observation. All ultrasound examinations should begin with a longitudinal and axial survey of either all abdominal structures or the area of interest and immediate adjacent structures. • No images are taken during a survey. This is a time to fine-tune technique, establish the optimal patient position(s) and breathing technique(s), thoroughly and methodically investigate the area(s) of interest, and rule out normal variants or abnormalities. • Adjust field size to best view the area of interest. • Focus near and far gain settings to enhance visualization of the area of interest. • Adjust contrast to help differentiate structures from one another. • Adjust gain settings so that the margins of structures are well defined. • Power settings should be low. Compensate with adjusted TGC (time-gain compensation) slope (see Table 7-2). • Avoid areas of fade-out on an image whenever possible. Try increasing or adjusting the TGC slope, or switch to a more powerful transducer. • Follow a scanning protocol—this ensures standardization and is essential for comparing studies.

Extraorgan features include:

• Displacement of other organs and structures • Obstruction of other organs or structures from view • Internal invagination of organ capsules • Discontinuity of organ capsules

Intraorgan features include:

• Disruption of the normal internal architecture • External bulging of organ capsules • Displacement or shift of adjacent body structures

Transverse plane:

• Divides the body into unequal superior and inferior sections. • Perpendicular to the long axis of the body.

All abnormalities or pathology can be evaluated and documented the same way:

• First, during the survey determine the number—how many? Then the origin of the abnormality—which organ(s) or structure(s) is (are) primarily involved? Which of the adjacent structures, if any, are involved? • Second, determine the composition of the abnormality. Is it solid, cystic, complex (solid and cystic), or septated? (Discussed in greater detail later in this chapter.) • Third, pathology images are documented following the standard protocol images and include the size of the abnormality(ies) with volume measurement(s) (greatest dimensions in at least two scanning planes) and high and low gain images (gain range helps to resolve composition) in at least two scanning planes.

Image documentation criteria:

• Labeling should be confined to the margins surrounding the images. Labels should not cover any part of an image being submitted for diagnostic interpretation because it could potentially cover information pertinent to the diagnosis. If labeling or measurement calipers are used on an image, it is standard practice to document that same image with the labels or calipers removed. • Use up-to-date, calibrated ultrasound machinery. • Documented areas of interest or required images must be represented in at least two scanning planes that are perpendicular to each other to give a more dimensional and therefore more accurate representation. Single plane representation of a structure is not enough confirmation. • Required images must be documented in a logical sequence. Follow a scanning protocol. • In most institutions, abnormal ultrasound findings are documented after a scanning protocol's sequence of required images. Otherwise, the documentation becomes confusing for the interpreting physician. • Abnormal ultrasound findings are also documented in at least two scanning planes that are perpendicular to each other to give a more dimensional and accurate representation and to calculate volume measurements.

Coronal plane:

• Midcoronal plane runs along the midaxillary line and divides the body into equal anterior and posterior halves. • All other coronal plane sections divide the body into unequal anterior and posterior sections. • Perpendicular to sagittal planes and parallel to the long axis of the body.

Sagittal plane:

• Midsagittal plane divides the body into equal right and left halves. • Parasagittal planes divide the body into unequal right and left sections. • Parallel to the long axis of the body.

The following must be done for case presentation

• State the type of examination and reason for it. • Present patient history. • Relate patient's lab data and any other known correlative information such as reports and films from other imaging modality studies. • Present documentation in the sequence it was taken. • Be capable of justifying your technique and procedures. • Be able to describe the ultrasound findings using appropriate sonographic terminology (see How To Describe Ultrasound Findings, below).

Whether you are in a classroom or clinical setting, certain professional and clinical standards should be followed:

• Wear appropriate attire. • Wear a personal identification badge. • Introduce yourself to patients; put them at ease and make them as comfortable as possible. • Practice courteous and respectful interactions with patients and staff. • Conversations with patients should be proper and professional. Never discuss the sonographic findings or offer your opinion of the study results. Only physicians can legally render a diagnosis. • Check every patient's identification bracelet (or patient number) against the patient's chart; make very sure you have the correct patient. • Briefly explain the examination process to the patient. • Inquire about the patient's symptoms and history of illness or surgeries. • Instruct the patient in a slow, clear, and appropriate manner. • When required, help the patient to dress in an examination gown. • Assist patients with any medical equipment that may be attached to them, such as an oxygen tank. • Before helping the patient onto the examination table or stretcher, check that the brakes are set to ensure that the table or stretcher cannot move. Have a handled step stool available to assist shorter patients onto the table. • Drape patients properly and explain to them why it is necessary to do so. • Be familiar with your institution's isolation policies. • Be familiar with sterile techniques. • Be familiar with procedures to assist physicians with special studies. • Most transabdominal pelvic studies require the patient to have a full urinary bladder. Because this can cause the patient discomfort, scan prudently to complete the examination in a timely manner. • Most institutions require patients to sign a consent form prior to endocavital studies. Further, it is recommended that the examination should be witnessed by 95another sonographer or appropriate health care professional. The sonographer's and a witness's initials should be part of the permanent record. • Know how to handle all ultrasound equipment. Practice attaching and detaching transducers from the machine. • Be comfortable operating the image documenting system.

The level of echogenicity and appearance of tissue texture depend on:

• What type of localized disease is present • The degree of its density • Its effect on internal architecture

It is standard practice to measure the long axis, greatest width and greatest depth of a mass in order to calculate a volume measurement

(LxWxAP)=V

Accomplished scanning techniques are a result of a practice & knowledge of the following:

1. Location of anatomy 2. Sonographic appearance of normal body structures & the terms used to describe their appearances 3. Body planes, directional terms & how to interpret ultrasound scanning planes 4. Imaging criteria 5. Sonographic characterization of ultrasound findings and the terms used to describe them

The 3 sonographic criteria for simple or true cysts are

1. Mass must appear anechoic with no internal echoes. 2. Mass walls must be well defined, thin, and smooth. 3. Mass must exhibit posterior through transmission or increased echo amplitude visualized posterior to a structure that does not attenuate (decrease, stop, or absorb) the sound beam. There are 2 situations in which the posterior through transmission criterion may be difficult to meet: (1) A cyst located deep in the body beyond the focal zone of the transducer, which means not enough sound waves are being generated to pass through the fluid to create the enhancement effect; and (2) A cyst located directly anterior to a bony structure, which absorbs the sound waves, preventing through transmission.

If the patient is very thin, a

5.0 MHz transducer may be the best choice

Complex masses

A mass containing both fluid and tissue components; may be primarily cystic or primarily solid

Localized disease

A mass or multiple masses circumscribed to a specific area

Differentiating

Abnormal echo patterns from normal echo patterns

Sonographer's

Acquire, assess, modify, analyze, document and describe the ultrasound findings using ultrasound terminology in an oral or written technical observation

Remember that: Differentiating Documenting Describing

Afford the interpreting physician with the comprehensive sonographic details of a study on which the diagnosis is based

If disrupted or changed by disease the parenchyma typically assumes

An irregular, or heterogeneous, echo pattern

Cystic noise

Anterior reverberation within a simple cyst; that is, low-level echoes may be located near the anterior wall.

Describing

Any difference in echo pattern appearance using sonographic terminology

Documenting

Any differences in echo pattern appearance

It is very important to convey the

Appearance of mass borders to the interpreting physician. This means describing the borders as smooth or irregular, thin or thick and including whether they appear uniform or uneven throughout.

An understanding of the normal sonographic appearance provides the

Baseline against which to recognize abnormalities

Changes caused by infiltrative diffuse disease are

Changes in size, shape, and position of an organ; May be subtle and unrecognizable or they may be immediately obvious.

Hypoechoic

Decreased echogenicity compared to an adjacent structure(s)

When diffuse disease causes enlargement of an organ, the sonographer must

Determine the extent of increase and describe whether any adjacent structures have been compromised; All or just a portion of an organ may extend far beyond its normal boundaries, possibly displacing other organs and structures from their normal positions or blocking them entirely from view

Anechoic

Echo free

A solid mass appears as

Echogenic shades of gray representing its tissue composition on an ultrasound image

Lower-number megahertz transducers are best for

Evaluating deep structures

Deep exhalation does the opposite

Everything moves upward

The sonographic appearance of the walls of complex masses varies

From well defined and smooth to poorly defined and irregular

Normal organ parenchyma (soft tissue) is described sonographically as

Homogenous, or uniform in texture

The higher-number megahertz (MHz) transducers are best for

Imaging superficial structures

Deep inspiration forces the diaphragm and everything below it

In the abdomen to move down

Hyperechoic

Increased echogenicity compared to an adjacent structure(s)

Diffuse disease

Infiltrative; spreads throughout an entire organ

When describing the origin of pathology it is routine to classify localized disease as

Intraorgan (originates within an organ) Extraorgan (originates outside an organ)

Heterogenous

Irregular or mixed echo pattersn

Refraction shadows

Is a change in direction of sound as it passes through a boundary. They can occur at edge margins, especially on round structures

The survey of the aorta usually begins

Longitudinally (sagittal) from an anterior (transabdominal) approach in the sagittal scanning plane.

All pathology visualized with ultrasound disrupts in some way the normal sonographic appearance of the structure involved. It does this by changing

One, some or all of the characteristics of the structures typical normal appearance

Mass descriptions should include

Origin (location) Size Composition Number Any associated complications with adjacent structures

Even if a sonographer doesn't know what is causing the change or deviation in the normal echo pattern,

Recognizing it as a deviation is what is most important

The patient should fast for at least 8 hours before the aorta study; this should help

Reduce the amount of gas in the overlying bowel, which can obscure visualization of portions of the abdominal aorta. In the instance a patient has recently eaten, still attempt the study on the chance that you may be able to visualize the aorta.

Calculi are distinguished sonographically by the fact that they

Reflect and impede or stop sound waves. As a result, their surface appears highly echogenic and bright and posteriorly they cast shadows

A fourth "soft" simple cyst criterion is the

Refractive edge shadows that emanate from the edge margins of rounded structures. Simple cysts are generally round and therefore may also exhibit refractive shadowing

Alternative patient positions for viewing the abdominal aorta include

Right or left lateral decubitus Right or left posterior oblique Sitting semierect to erect

Homogenous

Uniform or similar echo patterns

Necrosis

Usually means that a solid mass has begun to liquefy and thereby assume a more complex sonographic appearance

The best patient position is determined by

What will produce optimal views of areas of interest

Bones, fat, air, fissures, ligaments, tendons, & the diaphragm

▪ Appear echogenic and vary in brightness depending on the density of the structure, its distance from the sound beam, and the angle at which the beam strikes the structure. ▪ Because these structures either reflect or attenuate the sound beam, they appear hyperechoic or brighter compared with adjacent structures; they may cast a posterior shadow.

Nerves

▪ Appearance is generally described in comparison with adjacent structures: hyperechoic or brighter when compared with the appearance of muscle; hypoechoic or less echogenic when compared with the appearance of tendons. ▪ Peripheral nerve fibers present as very low gray or echo-poor with a distinctive internal echo pattern that appears stippled in axial sections and honey-combed in longitudinal sections.

Placenta

▪ Echo texture changes throughout a pregnancy, from homogeneous or uniform with moderate to high echogenicity to heterogeneous or mixed echo pattern, when interrupted by multiple vascular components. ▪ Normally hyperechoic or brighter appearance relative to uterine myometrium.

Tissue

▪ Echo texture is homogeneous or uniform and moderately echogenic. ▪ Margins appear very bright or hyperechoic compared with adjacent structures.

Muscle

▪ Homogeneous or uniform echo texture with low echogenicity. ▪ Muscles typically appear hypoechoic or less echogenic relative to the organ(s) or body structure(s) they are adjacent to. ▪ Skeletal muscle bundles are distinctly separated by bright symmetric bands of fibroadipose septate that appear hyperechoic or more echogenic compared with the low gray appearance of the muscle.

Organ parenchyma

▪ Homogeneous or uniform echo texture with ranges in echogenicity. ▪ Liver parenchyma, for example, could be described as homogeneous and moderately echogenic.

Fluid-filled structures: Blood vessels Ducts Umbilical cord Amniotic sac Brain ventricles Ovarian follicles Renal calyces Urine-filled urinary bladder Bile-filled gallbladder Bursa

▪ Lumens appear anechoic (black; echo-free). ▪ Walls appear bright; highly echogenic or hyperechoic compared with adjacent structures. ▪ May exhibit bright posterior through transmission, making them easy to distinguish sonographically.

Gastrointestinal (GI) tract

▪ Walls are thin and generally appear hypoechoic or less echogenic compared with adjacent structures; however, they can appear very bright if they are surrounded by an extensive amount of fat. ▪ The appearance of the GI tract lumen varies depending on its contents. ▪ A fluid-filled lumen appears anechoic. ▪ A gas- or air-filled lumen will appear bright, highly echogenic, and generally hyperechoic relative to adjacent structures. ▪ The lumen can also have a complex or mixed appearance, displaying anechoic portions from fluid, along with echogenic portions that vary in brightness depending on their composition (partially digested food, indigestible material, gas, air). ▪ All or individual sections of the GI tract may cast a posterior shadow where air or gas is present in the lumen. ▪ Empty, collapsed bowel has a distinctive "bull's eye" appearance due to the contrast between the very bright, collapsed lumen and hypoechoic walls.

For legal purposes and standardization, the following information MUST be included on image documentation:

✓ Patient name and identification number ✓ Date and time ✓ Scanning site (name of hospital, private office, etc.) ✓ Name or initials of person performing the study ✓ Name or initials of endocavital studies witness ✓ Transducer megahertz ✓ Patient position ✓ Scanning plane ✓ Area of interest: general (i.e., aorta) and specific (i.e., proximal, mid, or distal)