E-Book, Englisch, 480 Seiten, ePub
Reihe: Clinical Companions
Schmidt Thieme Clinical Companions: Ultrasound
1. Auflage 2006
ISBN: 978-3-13-258136-4
Verlag: Thieme
Format: EPUB
Kopierschutz: 6 - ePub Watermark
E-Book, Englisch, 480 Seiten, ePub
Reihe: Clinical Companions
ISBN: 978-3-13-258136-4
Verlag: Thieme
Format: EPUB
Kopierschutz: 6 - ePub Watermark
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.
Zielgruppe
Ärzte
Autoren/Hrsg.
Fachgebiete
Weitere Infos & Material
Gray Part: Basic Principles
1 Basic Physical and Technical Principles
1.1 Physics of Ultrasound
1.2 Ultrasound Techniques
1.3 Color Duplex Sonography
1.4 Imaging Artifacts
2 The Ultrasound Examination
2.1 Abdominal Ultrasound
2.2 Ultrasound Imaging of Joints (Arthrosonography)
3 Ultrasound Documentation and Reporting
3.1 Requirements for Documentation
3.2 Guideline-Oriented Documentation
3.3 Sonographic Nomenclature
4 Function Studies
4.1 Basic Principles
4.2 Sonographic Measurements
5 Interventional Ultrasound
5.1 Fine-Needle Aspiration Biopsy (FNAB)
5.2 Therapeutic Aspiration and Drainage
Green Part: Ultrasound Investigation of Specific Signs and Symptoms
6 Principal 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
7 Arteries and Veins
7.1 Examination
7.2 Aorta and Arteries
7.3 Vena Cava and Peripheral Veins
8 Cervical Vessels
8.1 Examination
8.2 Abnormal Findings
9 Liver
9.1 Examination
9.2 Diffuse Changes
9.3 Circumscribed Changes
9.4 Changes in the Portal Venous System
10 Kidney 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
11 Pancreas
11.1 Examination
11.2 Diffuse Changes
11.3 Circumscribed Changes
12 Spleen
12.1 Examination
12.2 Sonographic Findings
13 Bile Ducts
13.1 Examination
13.2 Intrahepatic Ductal Changes
13.3 Extrahepatic Ductal Changes
13.4 Evaluation and Further Testing
14 Gallbladder
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
15 Gastrointestinal Tract
15.1 Examination
15.2 Stomach
15.3 Small Intestine
15.4 Large Intestine
16 Urogenital Tract
16.1 Examination
16.2 Renal Pelvis, Ureter, and Bladder
16.3 Male Genital Tract
16.4 Female Genital Tract
17 Thorax
17.1 Examination
17.2 Chest Wall
17.3 Pleura
17.4 Lung Parenchyma
18 Thyroid Gland
18.1 Examination
18.2 Diffuse Changes
18.3 Circumscribed Changes
19 Major Salivary Glands
19.1 Examination
19.2 Abnormal Findings
20 Postoperative Ultrasound
20.1 Normal Postoperative Changes
20.2 Postoperative Complications
21 Search for Occult Tumors
21.1 Principal Signs and Symptoms
21.2 Sonographic Criteria for Malignancy
21.3 Evaluation and Further Testing
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: – Impedance = the ratio of the incident sound intensity to the portion that is transmitted. – Acoustic resistance = the product of the density times the speed of sound. 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. Fig. 2a, b A-mode and B-mode scans, illustrated for the maxillary sinus. a A-mode signal. b B-mode display: echo amplitudes are converted to spots of varying brightness. E = entry echoes (bone), E' = entry echo (bony ridge or polyp), M1 = mucosa, M2 = thickened mucosa, F = fluid, EE = exit echo 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...
