Thieme Clinical Companions: Ultrasound E-Book

Gunter Schmidt

• Herausgeber: Thieme
• Kategorie: Fachliteratur
• Serie: Clinical Companions
• Sprache: Englisch
• Veröffentlichungsjahr: 2006

Seitenzahl: 562

Beschreibung

A handy, portable guide to managing problems in the everyday setting

This compact book provides radiologists, ultrasonographers, residents, and trainees with a handy, portable guide to managing problems in the everyday setting. The first section of the book provides a thorough review of basic physical and technical principles and examination techniques. In the second section of the book, the author helps the clinician answer such questions as:

• What differential diagnoses should be considered for specific signs and symptoms?
• When can ultrasound advance the diagnosis?
• What are the typical sonographic signs that suggest a diagnosis?

The book describes systematic approaches to the ultrasound examination of specific organs and organ systems, postoperative ultrasound, with emphasis on scanning protocols, normal findings, and possible abnormal findings and their significance. Color-coded sections aid rapid reference to topics of interest.

Leseprobe

Thieme Clinical Companions

Ultrasound

Günter Schmidt, MD

Formerly Evangelisches Krankenhaus Kredenbach Kreuztal, Germany

With contributions by

B. Beuscher-Willems, L. Brügmann, C. Görg, T. Grebe, L. Greiner

1091 illustrations

Georg Thieme VerlagStuttgart • New York

Library of Congress Cataloging-in-Publication Data is available from the publisher.

This book is an authorized and revised translation of the 3rd German edition published and copyrighted 2005 by Georg Thieme Verlag, Stuttgart, Germany. Title of the German edition: Checkliste: Sonographie

1st German edition 19972nd German edition 1999

Translator: Terry Telger, Translations for the Health Sciences, Fort Worth, TX, USA

Important note: Medicine is an ever-chan ging science undergoing continual development. Research and clinical experience are continually expanding our knowledge, in particular our knowledge of proper treatment and drug therapy. Insofar as this book mentions any dosage or application, readers may rest assured that the authors, editors, and publishers have made every effort to ensure that such references are in accordance with the state of knowledge at the time of production of the book.

Nevertheless, this does not involve, imply, or express any guarantee or responsibility on the part of the publishers in respect to any dosage instructions and forms of applications stated in the book. Every user is requested to examine carefully the manufacturers’ leaflets accompanying each drug and to check, if necessary in consultation with a physician or specialist, whether the dosage schedules mentioned therein or the contraindications stated by the manufacturers differ from the statements made in the present book. Such examination is particularly important with drugs that are either rarely used or have been newly released on the market. Every dosage schedule or every form of application used is entirely at the user's own risk and responsibility. The authors and publishers request every user to report to the publishers any discrepancies or inaccuracies noticed. If errors in this work are found after publication, errata will be posted at www.thieme.com on the product description page.

Some of the product names, patents, and registered designs referred to in this book are in fact registered trademarks or proprietary names even though specific reference to this fact is not always made in the text. Therefore, the appearance of a name without designation as proprietary is not to be construed as a representation by the publisher that it is in the public domain.

This book, including all parts thereof, is legally protected by copyright. Any use, exploitation, or commercialization outside the narrow limits set by copyright legislation, without the publish-er's consent, is illegal and liable to prosecution. This applies in particular to photostat reproduction, copying, mimeographing, preparation of microfilms, and electronic data processing and storage.

© 2007 Georg Thieme Verlag,Rüdigerstrasse 14, 70469 Stuttgart, Germany

http://www.thieme.de

Thieme New York, 333 Seventh Avenue,New York, NY 10001, USA

http://www.thieme.com

Cover design: Thieme MarketingTypesetting by Hagedorn Kommunikation, ViernheimPrinted in Germany by Druckhaus Götz, Ludwigsburg

10-ISBN 3-13-142711-6 (GTV)13-ISBN 978-3-13-142711-3 (GTV)10-ISBN 1-58890-552-7 (TNY)13-ISBN 978-1-58890-552-9 (TNY)                                  1 2 3 4 5 6

Preface

Rapid advances in ultrasound imaging have resulted not only from continual improvements in equipment and new technologies, but also from expanded diagnostic capabilities. Color Doppler sonography and ultrasound contrast agents, combined with advances in standardizing diagnostic criteria and defining guidelines, have led to dramatic progress in sonographic diagnosis.

For example, it is now possible to use contrast-enhancing agents in nearly all areas of ultrasonography, although the examiner's experience and equipment availability continue to limit these applications. For those who are still learning how to use ultrasound, however, it is first necessary to acquire a sound basic knowledge of this modality in order to take advantage of these new and expanded methods.

This book presents a comprehensive collection of B-mode scans, but also a quantitiy of color Doppler images, as well as several examples of the uses of contrast-enhanced sonography. For ease of use in different situations, it is divided into three parts (gray: Basic Principles, green: Ultrasound Investigation of Principal Signs and Symptoms, blue: Ultrasound of Specific Organs and Organ Systems).

The editor and two other authors (Prof. Dr. Ch. Görg, Prof. Dr. L. Greiner) are regular leaders of seminars run by the German Society for Ultrasound in Medicine (DEGUM) and co-authors of three German editions of a similar text, and of other books on sonography. Each of them has an area of interest and expertise in their daily experience and on courses on ultrasound from which the current imaging approaches have been developed.

I extend special thanks to the staff at Thieme Medical Publishers, particularly Ms. Stefanie Langner, Dr. Christiane Brill-Schmid, Ms. Anja Dessauvagie, Ms. Elisabeth Kurz, and Mr. Stephan Konnry. They worked with the authors tirelessly and patiently (and at times, with gentle insistence) to bring this book to completion. A number of other men and women at Thieme Medical Publishers helped with the artwork, image reproductions, and production of the book, and their help is gratefully acknowledged. To all those who read this book, delve deeply into its contents, and use it as a practical reference, I wish much success in their dealings with ultrasonography.

Günter Schmidt

Contributors

B. Beuscher-Wilhelms, MDMedizinische KlinikKrankenhaus BethsedaFreudenbergGermany

L. Brügmann, MDEvangelisches KrankenhausBernhard-Weiss-KlinikKreuztal-KredenbachGermany

C. Görg, MDProfessorMedizinische KlinikKlinikum der UniversitätDepartment of Hematology/OncologyMarburgGermany

T. Grebe, MDEvangelisches KrankenhausBernhard-Weiss-KlinikKreuztal-KredenbachGermany

L. Greiner, MDProfessorKlinikum BarmenMedizinische Klinik AWuppertalGermany

Contents

Gray Part: Basic Principles

1Basic Physical and Technical Principles

1.1 Physics of Ultrasound

1.2 Ultrasound Techniques

1.3 Color Duplex Sonography (CDS)

1.4 Imaging Artifacts

2The Ultrasound Examination

2.1 Abdominal Sonography

2.2 Ultrasound Imaging of Joints (Arthrosonography)

3Documentation and Reporting

3.1 Requirements for Documentation

3.2 Guideline-Oriented Documentation

3.3 Sonographic Nomenclature

4Function Studies

4.1 Basic Principles

4.2 Sonographic Measurements

5Interventional Ultrasound

5.1 Fine-Needle Aspiration Biopsy (FNAB)

5.2 Therapeutic Aspiration and Drainage

Green Part: Ultrasound Investigation of Specific Signs and Symptoms

6Principal Signs and Symptoms

6.1 Upper Abdominal Pain

6.2 Lower Abdominal Pain

6.3 Diffuse Abdominal Pain

6.4 Diarrhea and Constipation

6.5 Unexplained Fever

6.6 Palpable Masses

6.7 Enlarged Lymph Nodes

6.8 Edema

6.9 Renal Insufficiency and Acute Renal Failure

6.10 Jaundice

6.11 Hepatosplenomegaly

6.12 Ascites

6.13 Joint Pain and Swelling

6.14 Goiter, Hyper- and Hypothyroidism

Blue Part: Ultrasonography of Specific Organs and Organ Systems, Postoperative Ultrasound, and the Search for Occult Tumors

7Arteries and Veins

7.1 Examination

7.2 Aorta and Arteries

7.3 Vena Cava and Peripheral Veins

8Cervical Vessels

8.1 Examination

8.2 Abnormal Findings

9Liver

9.1 Examination

9.2 Diffuse Changes

9.3 Circumscribed Changes

9.4 Changes in the Portal Venous System

10Kidney and Adrenal Gland

10.1 Examination

10.2 Diffuse Renal Changes

10.3 Circumscribed Changes in the Renal Parenchyma

10.4 Circumscribed Changes in the Renal Pelvis and Renal Sinus

10.5 Evaluation and Further Testing

10.6 Perirenal Masses and Adrenal Tumors

11Pancreas

11.1 Examination

11.2 Diffuse Changes

11.3 Circumscribed Changes

12Spleen

12.1 Examination

12.2 Sonographic Findings

13Bile Ducts

13.1 Examination

13.2 Intrahepatic Ductal Changes

13.3 Extrahepatic Ductal Changes

13.4 Evaluation and Further Testing

14Gallbladder

14.1 Examination

14.2 Changes in Size, Shape, and Location

14.3 Wall Changes

14.4 Intraluminal Changes

14.5 Evaluation and Further Testing

15Gastrointestinal Tract

15.1 Examination

15.2 Stomach

15.3 Small Intestine

15.4 Large Intestine

16Urogenital Tract

16.1 Examination

16.2 Renal Pelvis, Ureter, and Bladder

16.3 Male Genital Tract

16.4 Female Genital Tract

17Thorax

17.1 Examination

17.2 Chest Wall

17.3 Pleura

17.4 Lung Parenchyma

18Thyroid Gland

18.1 Examination

18.2 Diffuse Changes

18.3 Circumscribed Changes

19Major Salivary Glands

19.1 Examination

19.2 Abnormal Findings

20Postoperative Ultrasound

20.1 Normal Postoperative Changes

20.2 Postoperative Complications

21Search for Occult Tumors

21.1 Principal Signs and Symptoms

21.2 Sonographic Criteria for Malignancy

21.3 Evaluation and Further Testing

Subject Index

Sources of Illustrations

1 Basic Physical and Technical Principles

1.1 Physics of Ultrasound

Properties of Sound Waves

Propagation characteristics: Sound waves have several essential properties:

• Propagation of ultrasound waves: Sound waves travel through air, fluids, and human tissue almost exclusively as longitudinal waves. These are zones in which the molecules that make up the medium are alternately rarefied and condensed. Thus, sound waves must propagate through matter and cannot exist in a vacuum.

• Propagation speed: The speed of sound is relatively slow in all materials (in tissue about 1540 m/s). Consequently, its transit time can be accurately determined by electronic measurements and correlated with the distance traveled by applying the time–distance principle.

• Reflection (partial or complete) of sound waves at interfaces: The degree of reflection of incident sound waves at an interface depends on the acoustic resistance (“impedance”) of the medium:

Doppler effect: The Doppler effect states that the frequency of the returning (received) sound waves changes when the source of the sound is moving toward or away from the receiver. According to the time–distance law, the product of time and velocity equals the distance traveled. Thus, the frequency changes in the sound waves reflected from moving red blood cells can be analyzed to determine the direction and velocity of blood flowing through vessels and in the heart.

Resolution

Ultrasound frequency: The quality of an ultrasound examination depends on two criteria relating to the properties of the sound waves:

• The highest possible resolution (high transducer frequency).

• An adequate depth of sound penetration (low transducer frequency).

• Rule: Shorter wavelengths improve resolution but decrease the penetration depth of the ultrasound beam.

• Tradeoff: The optimum frequency range for diagnostic ultrasound is 1–10 MHz. The optimum range of wavelengths is 0.15–1.5 mm (Table 1).

Fig. 1 Ultrasound beam shape and electronic focusing (after Röthlin, Bouillon, and Klotter)

Velocity of sound propagation: This depends on the density of the medium (approximately 1500–1600 m/s in soft tissues and fluids, 331 m/s in air, and 3500 m/s in bone). Ultrasound instruments are calibrated to a mean sound velocity of 1540 m/s.

Axial resolution: A sound pulse composed preferably of two (or three) wavelengths is emitted in the longitudinal (axial) direction. The maximum ability to resolve two separate points in the longitudinal direction is equal to one-half the pulse length, or approximately one wavelength. For example, the resolution at an operating frequency of 3.5 MHz is approximately equal to 0.5(–1) mm.

Lateral resolution: The ultrasound beam initially converges with increasing depth, and then widens out again with decreasing intensity and resolution. The focal zone (“waist”) of the beam is 3–4 wavelengths wide and is the area where lateral resolution is highest (Fig. 1). The lateral resolution at a frequency of 3.5 MHz is approximately 2 mm, meaning that two adjacent points can be distinguished as separate points when they are at least 2 mm apart.

Focusing: The purpose of beam focusing in sonography is to achieve maximum resolution and improve the ability to recognize fine details.

• Technical options:

– Make the transducer face concave to produce a convergent beam (concave mirror effect).

– Use a collecting lens.

• Mechanical focusing: This creates a fixed focal zone that cannot be moved (fixed-focus system), although it can be modified somewhat by scanning through a fluid offset.

• Electronic focusing: With this option, the focal zone can be set to any desired depth (Fig. 1). For example, the focal zone can be positioned to give a sharp image of the gallbladder, or it can be extended over the full depth of the image field.

• Adjusting the focus during an ultrasound examination: This is the hallmark of a proficient examiner. One feature of a high-quality ultrasound system is that a definite change in resolution is seen as the focal zone is moved.

Propagation Characteristics of Sound Waves

The propagation of ultrasound waves obeys the laws of wave physics. The following terms have been adopted from radiation optics and wave optics.

Reflection: Sound waves are partially reflected and partially transmitted in biological tissues. An image of an organ is generated from the returning echo signals by analyzing the impedance differences at acoustic interfaces. The higher the acoustic impedance, the greater the degree of reflection, with total reflection occurring at interfaces with a very high impedance mismatch (e.g., between soft tissue and bone, calcium, or air, producing a high-amplitude echo). Interfaces with a high acoustic impedance (e.g., gallstones) reflect all of the incident sound and cast an acoustic shadow.

Scattering: This consists of randomly directed reflections that occur at tissue interfaces and rough surfaces. The echoes generated by scattering centers contribute significantly to medical imaging (e.g., the imaging of rounded organ contours).

Refraction: This phenomenon is most pronounced at smooth interfaces with a high acoustic impedance. The sound waves are deflected at an oblique angle relative to the direction of the main beam.

Absorption and attenuation: These describe the “loss” of sound waves due to their spatial distribution in the tissue and the conversion of sound energy to heat. According to the findings of a WHO commission, the conversion of sound energy to heat is within safe limits at the low energy levels used in diagnostic ultrasound. Even so, it is prudent to use the lowest possible ultrasound energy when scanning children and pregnant women. Sound waves are also attenuated in tissues as a result of reflection, scattering, and refraction. This leads to a significant energy loss, which is offset by adjusting the time gain compensation (TGC) on the scanner.

1.2 Ultrasound Techniques

A-Mode, B-Mode, and M-Mode Scanning

A-mode scanning (Fig. 2a): In this technique the amplitudes (A-mode) of the echo signals returned from tissue interfaces are displayed as a series of amplitude deflections along a horizontal axis, as on an oscilloscope.

B-mode scanning (brightness mode, Fig. 2b):

• Principle: Reflected ultrasound pulses are displayed on the monitor as spots of varying brightness in proportion to their intensity. The sound waves are transmitted into the tissue in a parallel scan or a fan-shaped beam, and the echoes are reflected back to the transducer and assembled line-by-line according to their arrival time.

• Signal display and image reconstruction: Approximately 120 image lines are assembled to make a two-dimensional sectional image. The various echo intensities are converted by electronic processing into image spots of varying density or shades of gray (gray-scale display, brightness modulation).

M-mode scanning (time–motion): This technique generates a time–motion trace that records the motion of acoustic reflectors such as heart valves and myocardial walls over time.

Doppler and Duplex Sonography

Continuous-wave (CW) Doppler:

• Principle: Two piezoelectric crystals are used, one for the continuous transmission of ultrasound pulses (continuous wave) and one for the reception of reflected ultrasound signals.

• Signal display: The frequency spectra of returning echoes are displayed acoustically and also visually if desired. The frequency shifts can be used to calculate the direction and velocity of blood flow. This technique does not, however, provide information on the depth or range of the echo source.

Pulsed Doppler:

• Principle: This technique employs one piezoelectric crystal that functions alternately as a transmitter and receiver (pulsed wave).

• Signal display: Echo signals are recorded from a designated sample volume during the receiving phase of the scan. This makes it possible to determine the depth and width of the sample volume and investigate blood flow within a circumscribed area.

Duplex sonography:

• Principle: CW or pulsed Doppler is combined with B-mode imaging, providing visual feedback for positioning the Doppler beam and the sample volume.

Power Doppler: This technique demonstrates the spatial distribution of blood flow but cannot determine flow direction. It is most useful in establishing the presence or absence of vascularity and evaluating the quantity of blood flow. Power Doppler is excellent for detecting increased vascularity due to inflammation, for example.

Spectral Doppler: The spectral analysis of blood flow patterns is used to determine the time course and velocity distribution of the flow, i.e., its mean and maximum velocities. This is of key importance in the diagnosis of vascular stenosis.

Ultrasound Transducers

Linear scanner: This type of transducer consists of a linear array of up to 512 piezoelectric elements that are electronically activated in groups. Parallel beam scanning creates a geometrically true image, but the large footprint may be a problem (e.g., in the presence of bowel gas). A linear array is best for imaging superficial structures.

Convex scanner: The piezoelectric elements are the same as those used in a linear array, but they are arranged along a curved surface, resulting in a fan-shaped beam.

Sector scanner: This may be mechanical or electronic. In a mechanical sector scanner, the elements are mechanically rotated to produce a radial-format scan. With an electronic sector scanner, the crystals are pulsed in phases (phased array) to produce a sectoral, pie-shaped scan. The advantage of a sector scanner is its small footprint, which makes it easier to scan around obstructions such as ribs and bowel gas. It is particularly useful for imaging deeper structures.

Signal Processing

Preprocessing: Electronic enhancement of signal quality and resolution at the time the echoes are received.

Postprocessing: Improving the contrast between weak signals (soft tissues) and strong signals (calcified or bony structures) by amplifying or suppressing certain gray-scale ranges.

Time gain compensation (TGC): Signals arriving later (from greater depths) are amplified more than earlier signals to compensate for the attenuating effect of tissues (e.g., the attenuation of deeper echoes in a fatty liver).

Transmitted power: The maximum power output set on the machine, designated as 0. To avoid swamping or washing out the gray-scale image, the power should be set as low as possible, e.g., 3–9% below the maximum setting (this also avoids potential adverse effects in children and pregnant women).

Overall gain: Amplifies the returning signals. The gain setting should be matched to the transmitted power (the power emitted by the transducer).

Digital Image Processing

Increasingly, conventional imaging is being augmented by digital signal processing with powerful computers that can carry out several billion operations per second. This trend has been supported by advances in transducer technology from single-line arrays to multiline (matrix) arrays and broadband arrays in which the transmitted and received frequencies can be selected and used over a broad spectrum. Combined with digital signal processing and a high sampling rate of the echo signals, these developments make it possible to obtain ultrasound images with high contrast and high resolution, and even study the dynamics of slow blood flow in small vessels.

Contrast harmonic imaging (CHI) and tissue harmonic imaging (THI): Nonhomogeneous tissues give rise to echo signals that contain harmonic echo frequencies in addition to the fundamental frequency of the transmitted pulse.

• THI combines special transmitted pulse sequences with a broadband reception technique, using the harmonic frequency components to create ultrasound images that have high contrast, high spatial resolution, and low noise.

• CHI employs echo-enhancing contrast agents that increase the harmonic frequency component to improve the discrimination between blood-flow echoes and tissue echoes.

Photopic ultrasound imaging: This technique can be used to optimize image contrast. By the conversion of gray levels to monochromatic color values, very subtle structural differences can be appreciated.

3D sonography: Large sets of image data can be stored in great numbers by means of high-speed digital signal processing. A position sensor is not required. Local echo information from contiguous image slices is used to reconstruct 3D data sets with an isotopic voxel size. Data acquisition can be done freehand with standard transducers, or matrix transducers can be used that allow electronic beam steering. The B-mode images and Doppler scans are acquired separately and may be displayed separately or in a combined format.

Contrast-Enhanced Sonography

Technique and development: Lesions as small as 4 mm in diameter can be detected with the ultrasound technology currently available. However, because of patient-related factors (obesity, overlying bowel gas, inability to take deep breaths) and the acoustic properties of some tumors, which are isoechoic to surrounding tissue, certain masses can be difficult to detect. In these cases ultrasound contrast agents (echogenic microparticles injected intravenously) can be used to locate and even characterize masses based on the Doppler effect.

Applications:

• Gastroenterology, hepatic ultrasound: The use of echo-enhancing agents has been investigated in many studies in recent years and may be considered the standard for “high-end ultrasound,” especially in the discrimination of focal hepatic lesions.

• Neurological ultrasound: In the field of neurology as well, contrast-enhanced sonography is widely practiced in specialized ultrasound laboratories, where the use of echo-enhancing agents can significantly improve the diagnostic yield because of the difficulty of scanning through the skull.

• There are other areas, such as the investigation of myocardial perfusion, where contrast-enhanced sonography has not yet come into broad clinical use.

Equipment Settings

Note: An accurate sonographic diagnosis relies on the experience and diligence of the examiner but also requires optimum equipment settings. The settings on the ultrasound scanner should be continually adjusted from patient to patient and from organ to organ.

Monitor settings:

• Brightness: First, adjust the brightness control so that structures are clearly outlined in relation to the background brightness.

• Contrast: Next, adjust the contrast control until the full range of gray levels can be identified on the gray-scale bar.

Basic settings on the ultrasound scanner:

• Power setting: Set to the lowest possible level.

• Overall gain: Lower the gain if the image appears washed out.

• Time gain compensation: Adjust the TGC to obtain a homogeneous sonodensity and uniform image brightness.

Common errors of adjustment:

• Gain set too high or too low

• Faulty adjustment of the TGC

• Washed-out appearance of the near field, far field, or both

Note: The goal of optimum monitor and scanner settings is to avoid errors of image interpretation.

1.3 Color Duplex Sonography (CDS)

Method, Diagnostic Information

Synonyms: CDS, color flow imaging (CFI), color flow mapping (CFM), color velocity imaging (CVI).

Principle: CDS combines conventional gray-scale imaging with Doppler flow sampling. Doppler sample volumes are positioned within a B-mode image sector or over the entire B-mode image, and Doppler frequency shifts are registered and electronically color-coded. By general convention, flow toward the transducer is encoded in red and flow away from the transducer is encoded in blue.

Goals and capabilities:

• Mapping: Moving particles in organs are scanned over a broad imaging area.

• Motion detection (e.g., of blood cells) based on frequency changes stemming from the Doppler effect.

• Visualization of blood vessels: The sampling cursor (the sample volume in pulsed Doppler) is positioned in the vessel of interest, and color pixels are electronically displayed within the vessel lumen.

• Measurement of maximum flow velocities (with CW Doppler): Stenoses and/or flow direction can be detected on the basis of spectral waveform analysis, color changes, and mixed (turbulent) color patterns.

Signal Processing, Equipment Settings

Equipment settings:

• The penetration depth and detectable flow velocity depend on the type of transducer used and its operating frequency.

• The power setting (expressed as a percentage of the maximum power output or in decibels) should be kept as low as possible, both for safety reasons and to prevent color-encoding artifacts such as artificial turbulence and extraluminal color bleed.

• The overall gain (receiver gain) and TGC should be set at the upper end of the range.

Wall filter:

• The wall filter limits signal acquisition to designated frequency ranges (e.g., to detect low flow velocities).

• It also filters out unwanted frequencies.

Doppler frequency:

• The maximum measurable Doppler frequency is adjusted with a dial or toggle switch. The maximum frequency or velocity is displayed above and below the color scale at the edge of the screen.

• The velocity setting is based on the anticipated frequency spectrum. Parenchymal vessels, for example, would be expected to have lower frequencies and velocities than resistance-type vessels.

• The maximum detectable frequency depends on the pulse repetition frequency (PRF), which depends in turn on the transducer frequency and penetration depth.

• The PRF setting should be twice as high as the maximum detectable velocity. If the PRF is set too low, it may cause an apparent flow reversal called aliasing.

Shifting the baseline: The measured frequencies or velocities are displayed on a scale with a central baseline and plus/minus ranges. If the range of detectable frequencies is insufficient at high velocities, the baseline can be shifted up or down to expand the range of interest.

Beam angle:

• As in pulsed and CW Doppler, the detectable frequency shift depends on the incidence angle of the ultrasound beam. For a given velocity, the frequency change (Doppler shift) will increase as the beam angle is decreased.

• The measurement error decreases as the beam angle approaches 0°.

• A Doppler frequency shift can be accurately converted to velocity only if the incidence angle of the beam is known. For the scanner to make this conversion automatically, the beam angle must be indicated by marking the flow direction in the blood vessel with an angle cursor.

Color Artifacts

Note: Many color artifacts can adversely affect or distort the interpretation of CDS findings. Some are unavoidable and can actually be used to enhance the accuracy and sensitivity of the diagnosis.

Noise: Causes may include setting the color gain too high. It is a troublesome artifact, but in some cases it should be provoked as a means of detecting slow flow.

Motion artifacts: Motion artifacts (color flash) are also troublesome. Their possible causes include transmitted cardiac pulsations (e.g., when examining vascularized masses in the left lobe of the liver) and transmitted aortic pulsations.

Aliasing: This becomes a problem when, for diagnostic reasons, the color scale of the instrument has been set to a certain velocity range (PRF) that does not match the flow velocity in all of the sampled vessels. This results in unwanted zones of color reversal.

Confetti artifact: Appearing as multiple small color pixels, this is an important sign of an abnormality, such as turbulent flow past a stenosis.

Twinkling artifact: This has major diagnostic significance. It occurs when confetti pixels or color bands (red and blue pixels) are produced by a very strong acoustic reflector (stone, cholesterol polyp) lying in an acoustic shadow. Twinkling is caused by a vibration of the reflector induced by the impinging sound waves. It may be helpful in the diagnosis of kidney stones and other lesions.

1.4 Imaging Artifacts

Basic Principles

Definition: In ultrasound, artifacts are acoustic images that do not correlate with an anatomical structure. They result from the fact that not all physical phenomena are taken into account in the imaging process.

Significance: Artifacts can have varying significance in the interpretation of sonographic images. Some, such as slice-thickness artifact, can interfere with image interpretation whereas others, such as acoustic shadowing, are diagnostically useful.

Overview: See Tables 2 and 3.

Table 2.

Overview of imaging artifacts

Important artifacts

Less important artifacts

Side-lobe artifact (p. 9)

Motion artifact

Noise (p. 10)

Double image artifact

Acoustic shadowing (p. 11)

Transit-time artifact

Acoustic enhancement (p. 11)

Slice-thickness artifact (p. 12)

Mirror image artifact (p. 13)

Reverberations (p. 14)

Edge shadowing (p. 15)

Table 3.

Classification of artifacts by echogenicity

Hyperechoic

Isoechoic

Anechoic

Side-lobe artifact

Motion artifact

Acoustic shadowing

Noise

Double images

Mirror image artifact

Acoustic enhancement

Transit-time artifact

Edge shadowing

Mirror image artifact

Mirror image artifact

Beam-width artifact

Reverberations

Side-Lobe Artifact (Figs. 3 and 4)

Definition: An object is improperly represented in the display as a result of echoes generated by side lobes that accompany the main beam.

Description: A side-lobe artifact appears as a curved line in an anechoic structure.

Significance: They may be mistaken for internal echoes in cystic organs (septa, sediment).

Differentiation from a real object: The artifact is easily eliminated by angling the transducer or changing the scan plane.

Fig. 4 Side-lobe artifact: The arrows indicate a side-lobe artifact in a stone-free gallbladder (GB). The artifact is caused by gas in the adjacent duodenum (DUO)

Noise (Figs. 5 and 6)

Definition: Extremely fine echoes caused by voltage fluctuations in the imaging electronics.

Description: Noise appears as multiple tiny echoes in the near portion of anechoic structures (“ground glass” appearance in cystic structures).

Significance: The fine spurious echoes in cystic structures may be mistaken for sludge or gravel. Small cysts may even appear solid.

Differentiation from a real object: Noise can be eliminated by lowering the gain setting and/or changing the focus.

Fig. 6 Noise in a hepatic cyst (C). Multiple fine echoes appear in the anterior part of the cyst

Acoustic Shadowing (Figs. 7 and 8)

Definition: An absence of echoes behind structures that are strong reflectors or absorbers of ultrasound.

Description: The shadow appears as an anechoic band posterior to a high-amplitude echo (from a strong reflector such as calcium, air, or bone).

Significance:

• Helpful in the diagnosis of stones and cysts (edge shadowing).

• Troublesome in abdominal ultrasound (bowel gas and rib shadows).

• Acoustic shadows are cast not only by strong reflectors but also by connective tissue that is struck tangentially by the beam (ligamentum teres, connective tissue in the porta hepatis).

• Small stones will cast an acoustic shadow only if they are directly within the focal zone of the transducer.

Fig. 8 Typical acoustic shadow (S) associated with a gallstone

Acoustic Enhancement (Figs. 9 and 10)

Definition: A relative increase in echogenicity caused by a lack of sound attenuation.

Description: Structures located behind cysts, abscesses, or necrotic metastases appear more echogenic than adjacent tissues at the same depth.

Significance:

• Helpful in the diagnosis of cysts and other anechoic structures.

• Troublesome in evaluating areas behind cysts and other liquid structures.

Fig. 10 Posterior acoustic enhancement. An area of increased echogenicity (arrows) appears behind the gallbladder (GB)

Slice-thickness Artifact (Figs. 11 and 12)

Definition: Artifact occurring at curved interfaces between anechoic and hyperechoic structures, caused by the beam thickness.

Description: Appears as fine echoes layered along the inner wall of a fluid-filled structure, causing the wall to appear thickened and indistinct.

Significance: May be mistaken for debris, sludge, gravel, or clotted blood.

Fig. 12 Beam-width artifact: Transverse scan through the bladder (B) shows partial thickening and lack of sharpness of the bladder wall, especially on the far side (arrow)

Differentiation from a real object:

• Reposition the patient

• Improve the focus

• Change the scan plane

Mirror Image Artifact (Figs. 13 and 14)

Definition: “Ghost images” may appear behind strong reflectors because the reflection alters the path of the beam and doubles its transit time.

Description: Liver tissue located below the strong reflector of the diaphragm is projected to a supradiaphragmatic location in the basal lung zone (“pseudoecho”).

Significance: Minimal, since awareness of the artifact should preclude errors of interpretation.

Differentiation from a real object: The normal parenchyma of the liver and spleen can mimic a pleural effusion, but doubts can be resolved by examining the patient in a sitting position and scanning from the posterior side.

Fig. 14 Mirror image artifact: Right subcostal oblique scan demonstrates the liver (L), the diaphragm (D, or lung entry echo), a subphrenic hepatic hemangioma, and the reflected hemangioma imaged at a supraphrenic location (arrows)

Reverberations (Figs. 15 and 16)

Definition: Linear artifacts caused by multiple reflections between two highly reflective interfaces. The computer of the ultrasound system interprets the time delays as increasing distance from the transducer.

Description: Appear as a series of echogenic lines that are parallel to one another and to the transducer face and whose amplitudes diminish at greater depths

Special forms:

• Comet-tail artifact

• Ring-down artifact

Significance: Reverberations are consistently present in cystic organs but may also occur in solid structures. They are always troublesome and rarely helpful. They can be eliminated by changing the direction of the beam.

Edge Shadowing (Figs. 17 and 18)

Definition: Lateral acoustic shadows caused by a tangential beam angle, scattering, refraction, attenuation, and extinction of the ultrasound beam at cyst walls

Description: Narrow hypoechoic bands or shadows at the edges of cystic structures, often showing a divergent pattern.

Significance: Edge shadowing is a useful criterion for diagnosing cysts.

Differentiation from a real object:

• Edge shadows can mimic stones, especially in the gallbladder fundus and cystic duct.

• Double-check the finding in a second scan plane.

Fig. 18 Edge shadowing. The refraction and attenuation of sound at cyst margins produces a divergent or convergent pattern of acoustic shadowing. Sound attenuation by the echogenic walls of cystic structures is not the only cause of this artifact, which may also result from deviation of the beam due to scattering and refraction. This explains the divergent pattern of edge shadowing that may be seen.

2 The Ultrasound Examination

2.1 Abdominal Sonography

Examination Conditions

Prerequisites: The patient should be examined in a darkened room with a quiet atmosphere and comfortable ambient temperature. It is essential to select the proper transducer (depending on the organ of interest) and use the correct monitor and scanner settings (p. 6). Other important keys to a successful examination:

• Address the clinical problem.

• Premedication with simeticone is rarely needed. When indicated, a high dose should be administered in liquid form.

• Use sufficient coupling gel between the skin and transducer, eliminating all air bubbles. Use a sterile film on fresh wounds (a cheaper option is a disposable glove without talcum).

• Reschedule if the examination conditions are poor.

Positioning: Most organs are scanned with the patient supine. Less common positions are right or left lateral decubitus, sitting, standing, and the semiupright position (see also scanning tips). The examination couch should not be too soft. Bedside examinations are difficult.

Classification of Scan Planes

Introductory notes:

• The organs are displayed in “thin slices” as defined by the geometry of the beam (see Fig. 19).

• Standard ultrasound scan planes basically consist of longitudinal and transverse planes

• During the examination, the transducer should be oriented in a defined way referring to a special topographic anatomy (Figs. 21,22,35,37,38). This is important for anatomical orientation in the displayed image.

• The transducer position can be checked in the moving image to confirm right– left orientation. The image lines should be generated from right to left on the monitor when the transducer is moved to the left, and an acoustic shadow should appear on the left side when the examiner slips a finger beneath the left side of the probe.

Transverse scan: In a transverse (axial) scan, the right side of the image should correspond to the anatomical left side, and the left side of the image to the anatomical right side. Structures that are closer to the transducer should appear at the top of the image, and structures farther from the transducer should appear at the bottom.

Longitudinal scan: In a longitudinal scan, the left side of the image should be cranial (superior) and the right side caudal (inferior). Structures closer to the transducer should appear at the top of the image, and structures farther from the transducer should appear at the bottom (as in a transverse scan).

Overview: See Table 4.

Fig. 19 Schematic representation of a body slice

Table 4.

Overview of standard ultrasound scan planes

Standard scan planes

Organs imaged

Transverse scans

Upper abdominal transverse scan

Liver, stomach, pancreas, vessels (Fig. 23)

Right subcostal oblique scan

Liver, gallbladder (Figs. 24,30,33)

Left subcostal oblique scan

Left lobe of liver, stomach, spleen (Fig. 34)

Lower abdominal transverse scan

Bladder, rectum, uterus, fallopian tubes, prostate (Fig. 39)

Longitudinal scans

Intercostal scan (porta hepatis scan, shoulder–umbilicus scan)

Liver, porta hepatis, gallbladder, bile ducts (Figs. 25–27)

Right flank scan

Liver, kidney (Fig. 29)

Left flank scan

Spleen, kidney (Figs. 31,32)

Upper abdominal longitudinal scan

Liver, stomach, pancreas, vessels (Figs. 28,36)

Lower abdominal longitudinal scan

Bladder, rectum, uterus, prostate (Fig. 40)

Scanning Protocol

Beginners in particular should follow a systematic protocol in routine ultrasound examinations to ensure complete coverage. The scan planes shown in Fig. 20 can be imaged in the sequence indicated.

The examination proceeds in a counterclockwise direction. Longitudinal and transverse scans are carried out continuously along the vessels, working from the upper abdomen to the lower abdomen.

Possible sequence of standard scan planes:

• Upper abdominal transverse scan

• Right subcostal oblique scan

• Right intercostal scan

• Extended right intercostal scan

• Longitudinal paramedian scan

• Right flank scan Right midabdominal transverse scan

• High left intercostal scan (high left flank scan)

• Left flank scan

• Left midabdominal transverse scan

• Left subcostal oblique scan

• Upper abdominal longitudinal scan

• Lower abdominal longitudinal scan

• Lower abdominal transverse scan

Fig. 20 Standard and supplemental scan planes

Classification of Scan Planes, Sonographic Topography

Relationship of the gallbladder to adjacent organs:

Fig. 21a, b a The gallbladder fundus extends past the inferior border of the liver. It lies to the right of the C-shaped duodenal loop and cranial to the right colic flexure. b Visceral surface: The caudate lobe is bounded by the superior border of the liver, falciform ligament, gallbladder, and vena cava. The quadrate lobe is bounded by the inferior border of the liver, falciform ligament, gallbladder, and portal vein

Topographic anatomy of the pancreas and bile ducts:

Fig. 22a, b a The splenic artery runs posteriorly and superiorly, the splenic vein posteriorly and inferiorly. The tail of the pancreas extends toward the hilum of the spleen, and the head of the pancreas lies within the C-shaped loop of the duodenum. The left lobe of the liver is anterior to the pancreas, and the aorta is posterior. b Topographic anatomy of the bile ducts

Upper abdominal transverse scan:

Fig. 23 The upper abdominal transverse scan displays the following structures from anterior to posterior: liver (L), splenic vein (SV), pancreas (P), aorta (AO)

Anatomical guidelines for scanning the liver:

• The right and left lobes of the liver are separated by the falciform ligament. The ligament appears sonographically as an echogenic band (see Fig. 359), p. 252; scans through the right and left lobes).

• The separation of the two anatomical halves of the liver by the falciform ligament is most clearly appreciated when viewed from the posteroinferior direction.

• Based on the segmental anatomy of the liver, a line drawn from the gallbladder to the vena cava, marked by the interlobar fissure, separates the physiological right and left lobes of the liver.

• The gallbladder lies against the inferior surface of the right lobe of the liver.

• To locate the caudate and quadrate lobes more easily, imagine the letter H drawn on the visceral surface of the liver. One limb of the H is formed by a line connecting the gallbladder and vena cava (which lie in grooves in the liver); the other limb is formed by the falciform ligament. The crossbar is formed by the porta hepatis where the portal vein divides into its right and left main branches. The open areas of the H are occupied superiorly by the caudate lobe and inferiorly by the quadrate lobe (see Fig. 319), p. 231; visceral surface of the liver).

Right subcostal oblique scan:

Right intercostal scan:

Fig. 25 The intercostal scan is placed on an imaginary line between the right shoulder and the umbilicus. From this point the beam can be swept across the liver (L) in a fan-shaped pattern. The kidney (K) is posterior

Extended right intercostal scan:

Fig. 26 The extrahepatic bile ducts are defined in the porta hepatis scan by sliding the probe toward the umbilicus. The probe can be slightly angled and rotated to demonstrate the bile duct (BD), vena cava (Vc), and portal vein (Vp) in approximate longitudinal sections. These structures are easier to define in left lateral decubitus at full inspiration

Extended right intercostal scan:

Right longitudinal paramedian scan:

Fig. 28 The probe is oriented longitudinally and is placed lateral to the midline in an intercostal space or below the costal arch. The liver (L) is displayed in longitudinal section, and the shape of the (normally acute) inferior hepatic angle can be evaluated. The fundus of the gallbladder (Gb) projects past the inferior border of the liver. The vena cava (Vc) is displayed in longitudinal section and is posterior to the liver. Vena cava filling can be evaluated in this plane

Right flank scan:

Fig. 29 The flank scan is obtained by moving the probe laterally from the paramedian position. It is used to evaluate the pleural angle distal to the diaphragm (D) and displays a longitudinal section of the kidney (K) posterior to the liver (L)

Right midabdominal transverse scan:

Fig. 30 While viewing the kidney in longitudinal section, the examiner rotates the probe to a midabdominal transverse position and slides it toward the midline. The kidney (K) is displayed in cross-section posterior to the liver (L). The vascular pedicle with the renal vein (Vr) and renal artery (Ar) can be identified from anterior to posterior at the level of the renal hilum, and the ureter may also be seen. In thin patients, one section may display the termination of the renal vein at the vena cava (Vc), the origin of the renal artery from the aorta (Ao), and the gallbladder (Gb) at the inferior border of the liver

High lateral intercostal scan (high left flank scan):

Fig. 31 The probe is placed in an intercostal space cranial to the left flank and is angled cephalad and medially to demonstrate the spleen (S) in longitudinal section. The upper pole of the spleen appears on the left side of the image, the lower pole on the right side. The probe is rotated, slid, and angled until the longest diameter is visualized. The length of the spleen and its thickness at the level of the splenic hilum are measured

Left flank scan:

Fig. 32 As the probe is moved caudad from the high flank scan, the kidney (K) appears in longitudinal section posterior to the spleen (S). The orientation of the kidney, its posteriorly placed upper pole, and its anteriorly directed lower pole can be clearly identified

Left midabdominal transverse scan:

Left subcostal oblique scan:

Fig. 34 From the midabdominal transverse scan, the probe is slid to a position below the left costal arch to obtain a left subcostal oblique scan. The liver (L) is visible on the left side of the image. The spleen (S) appears posterolaterally on the right side of the image, displaying its true width and a foreshortened longitudinal diameter

Diagram of the major abdominal vessels:

Fig. 35 Diagram of the arterial vessels arising from the aorta and the tributaries of the vena cava. These vessels can be distinguished sonographically and can provide useful landmarks for intra-abdominal scanning

Upper abdominal longitudinal scan:

Fig. 36 The following structures can be identified from anterior to posterior: liver (L), pancreas (P), superior mesenteric vein (Vms), celiac trunk (Tc), and superior mesenteric artery (Ams), the latter two arising from the aorta (AO). The spinal column (Sc) is visible posteriorly

Diagram of the female genital organs:

Fig. 37 Relationships of the lower abdominal organs in the female. This diagram aids in understanding how the ultrasound probe should be directed during the examination. The uterus lies posterior and superior to the bladder. The following structures appear in sagittal section from anterior to posterior: pubic symphysis (sound does not penetrate bone, so the probe must be placed above the symphysis), bladder, uterus, and rectum. The probe can be angled downward to demonstrate the vagina

Diagram of the male genital organs:

Fig. 38 The male pelvis has a similar structure. It is important to note that the prostate is inferior to the bladder, and the seminal vesicles are posteroinferior

Lower abdominal transverse scan:

Fig. 39 The following structures are defined from anterior to posterior: abdominal wall, bladder (B), and uterus (U), which is flanked by the fallopian tubes (T)

Lower abdominal longitudinal scan:

Fig. 40 From anterior to posterior: abdominal wall, bladder (B), and uterus (U), which is bounded by the fundus above and the vagina (V) below

Examination of Specific Organs: See Blue Part

Arteries and veins, p. 188; cervical vessels, p. 214; liver, p. 231; kidney, p. 262; adrenal glands, p. 292; pancreas, p. 293; spleen, p. 312; bile ducts, p. 322; gallbladder, p. 334; gastrointestinal tract, p. 352; urogenital organs, p. 375; pleura and lung, p. 400; thyroid gland, p. 412; salivary glands, p. 425.

2.2 Ultrasound Imaging of Joints (Arthrosonography)

Basic Principles

Clinical importance: In recent years, ultrasonography of the musculoskeletal system has developed into a recognized and clinically important imaging modality. For investigations in rheumatology, ultrasound imaging is the next step in the diagnostic algorithm following the history and physical examination. The intraand periarticular soft-tissue changes that are typical of inflammatory joint diseases can be detected much earlier by sonography than by physical examination or radiography. Sonography can make an important contribution to diagnosis (e.g., detecting clinically asymptomatic synovitis) as well as management (e.g., the prompt initiation of basic treatment for early destructive joint changes).

Capabilities of arthrosonography:

• Detection of exudative or proliferative articular synovitis

• Detection of exudative or proliferative tenosynovitis

• Detection of synovial cysts

• Early detection of erosive defects in bone and joint margins

• Detection of degenerative articular and soft-tissue changes such as marginal osteophytes, bursitis, periarticular ossification, and tendon lesions

Limitations of arthrosonography:

• Limited ability to image superficial joint structures, depending on individual anatomy

• Poor visualization of deeper joint structures, with an inability to evaluate intraarticular or subchondral lesions

• Limited ability to discriminate synovitis (“inflammatory substrates”) in the B-mode image

Normal findings (Table 5):

Table 5.

Normal sonographic findings

Structure

Sonographic appearance

Synovial membrane

Echogenic, normally difficult to delineate from connective tissue

Cartilage

Anechoic, parallel to bone surface

Bone

Very echogenic with an associated acoustic shadow

Tendons

Echogenic when scanned at a perpendicular angle, but may appear hypoechoic (Fig. 41) when scanned at certain angles (acoustic anisotropism; compare with muscle)

Muscle

Hypoechoic; typical pennate pattern in longitudinal section; mottled echo pattern in transverse section

Fig. 41a, b Anterior transverse scan of the shoulder. a When the long biceps tendon is perpendicular to the beam, it appears as a bright round echo (→). b When the long biceps tendon is scanned at a different angle, the sound waves are not reflected and the tendon groove (→) appears empty.Caution: Do not interpret this as a tendon rupture

Typical abnormal findings (Table 6):

Table 6.

Typical abnormal findings

Structure

Sonographic appearance

Joint effusion

Anechoic or hypoechoic (Fig. 42)

“True” bone erosion

Constant surface discontinuity with echoes from the base of the erosion (Fig. 43)

Pseudoerosion

Apparent defect caused by beam obliquity relative to the bone surface; no base echoes

Pannus

Erosive changes in articular surfaces with infiltration of tendons (Fig. 44)

Synovitis (“inflammatory substrate”)

B-mode image: hypoechoic thickening of the joint capsule (the proliferative and exudative components cannot be positively distinguished in most cases)

Color or power Doppler: increased vascularity (Fig. 45)

Tenosynovitis

Anechoic or hypoechoic margin surrounding an echogenic tendon(Fig. 46)

Fig. 42a, b Anechoic effusion in exudative coxitis. Ultrasound demonstrates convex widening of the joint capsule. a Longitudinal scan,b transverse scan

Fig. 43 Echogenic base of an erosion: circumscribed erosive defect at the base of the first proximal phalanx (arrow) in erosive psoriatic arthritis

Fig. 44a–d Pannus. a, b Hypoechoic infiltration of the tendon by pannus tissue (arrows) due to pannous flexor tenosynovitis in a patient with chronic rheumatoid arthritis. a Survey image,b zoom image. c, d Fifth MTP joint with pannus in the right foot (c); compare with the same joint without pannus in the left foot (d)

Fig. 45a–c Synovitis in an arthritic knee.a Transverse B-mode image.b CDS demonstrates areas of boggy synovial thickening with increased vascularity.c Doppler spectrum shows a typical increase in diastolic flow

Fig. 46a, b Tendovaginitis appears as a hypoechoic rim around the tendon of the extensor carpi ulnaris. a Transverse scan,b longitudinal scan over the distal ulna

General Scanning Guidelines

Transducers:

• High-frequency linear transducer (7.5–15 MHz): Used for examining superficial structures (e.g., tendons and ligaments) and small joints in the hands or feet.

• Low-frequency linear transducer (5 MHz): Used for scanning deeper joints (e.g., the hip and shoulder joints).

• Convex 3.5 MHz transducer: Necessary only in rare cases, as in very obese patients.

Scanning tips:

• Use standard anatomical landmarks for orientation.

• Locate the static transverse and longitudinal scan planes.

• Use the RES function on the machine to zoom selected regions of interest while maintaining high resolution.

• For dynamic scanning, move the transducer continuously during active or passive motion of the scanned structures. Joint motion is often necessary in order to detect subtle abnormalities (e.g., mild degrees of exudation).

• Always compare the findings with the contralateral joint.

Sonography of the Shoulder

The patient is examined in a sitting position with the arm hanging at the side, the elbow flexed 90°, and the forearm supinated. Dynamic scans are obtained with internal/external rotation and abduction of the shoulder joint.

Scan planes:

• Anterior longitudinal scan:

Fig. 47a, b Sonography of the shoulder: anterior longitudinal scan. a Scan plane, b normal findings. The humerus appears below the long biceps tendon, and above that is the deltoid muscle

• Anterior transverse scan:

• Posterior longitudinal scan:

• Posterior transverse scan:

Fig. 50a, b Sonography of the shoulder: posterior transverse scan. a Scan plane, b normal findings. The humerus appears on the right side of the image. To the left of it is the scapular border, and above that is the infraspinatus. The deltoid muscle is visible above the humerus

• Lateral longitudinal scan:

Fig. 51a, b Lateral longitudinal scan of the rotator cuff. a Scan plane,b normal findings. The image in this place resembles a bird's head and beak. The acromion is on the left, the humerus is at lower right. Between them is the supraspinatus muscle, and above that is the deltoid

• Lateral transverse scan:

Fig. 52a, b Lateral transverse scan of the rotator cuff. a Scan plane,b normal findings. The image in this plane resembles a tire on a wheel. The humerus appears at the bottom of the image, with the rotator cuff above it. Above the rotator cuff are the deltoid muscle and subcutaneous tissue

• Axillary longitudinal scan (Fig. 53): Can detect small effusions.

Caution: Do not press too hard with the transducer, as this could mask small effusion volumes.

Fig. 53a, b Axillary longitudinal scan. a demonstrates the axillary recess of the joint capsule, which is concave and parallel to the neck of the humerus. b Major vascular structures (axillary artery) appear hypoechoic on CDS

Sonography of the Elbow

The patient is examined in a standing position.

Scan planes: Posterior scans with the elbow flexed, anterior scans with the elbow extended.

• Anterior humeroradial scan:

•Anterior humeroulnar scan:

• Posterior longitudinal scan: