Schmidt / Kurjak Color Doppler Sonography in Gynecology and Obstetrics

1. Auflage 2004
ISBN: 978-3-13-257822-7
Verlag: Thieme
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 410 Seiten, ePub

This beautifully illustrated and formatted book covers all of the established and developing indications for the use of color Doppler ultrasound in gynecology and obstetrics. In gynecology the modality is used to measure blood flow in benign changes of the endometrium as well as malignant tumors of the uterus; screening for ovarian carcinoma, including 3D-power doppler for the assessment of angiogenesis of ovarian tumors; and as an adjunct examination in assessing tumors of the breast. In obstetrics, the imaging method is useful in screening for gestosis and placental insufficiency in early pregnancy; evaluating the umbilical cord; fetal echocardiography and much more. More recent developments show the modality to be helpful in infertility diagnosis and reproductive medicine, providing information on the patency of the fallopian tubes, the quality of the vascularization of the uterus and more. With almost 600 illustrations and 90 useful tables, as well as a text that is highly structured for efficient reading, this text provides practitioners with technical and methodological basics as well as advanced tips for experienced users.

Werner Schmidt, Asim Kurjak

Zielgruppe

Ärzte

Autoren/Hrsg.

Schmidt, Werner O.

Kurjak, Asim

Fachgebiete

• Medizin | Veterinärmedizin Medizin | Public Health | Pharmazie | Zahnmedizin Klinische und Innere Medizin Gynäkologie, Geburtshilfe
• Medizin | Veterinärmedizin Medizin | Public Health | Pharmazie | Zahnmedizin Medizinische Fachgebiete Bildgebende Verfahren, Nuklearmedizin, Strahlentherapie Sonographie, Ultraschall

Inhaltsverzeichnis

Physical and Technical Principles
1 Physical and Technical Principles of Color Doppler Sonography
2 Safety Aspects of Doppler and Color Doppler Sonography
Infertility Evaluation and Assisted Reproduction
3 Uterine Blood Flow in Fertile and Infertile Women
4 Uterine Causes of Infertility
5 Changes in Uterine and Ovarian Perfusion with the Onset of Menopause
6 Color Doppler Sonography for the Optimization of Assisted Reproduction
7 Pulsed Doppler and Color Duplex Sonography in the Assessment of Tubal Patency
8 Abnormalities of Corpus luteum Function
9 Interventional Ultrasound in Reproductive Medicine
Obstetric Ultrasound
10 Doppler Ultrasound Examinations from Folliculogenesis to Early Pregnancy
11 Evaluation of Early Placentation and the Embryonic Circulation with Doppler Ultrasound
12 Color Doppler Sonography in Ectopic Pregnancy
13 Physiology of Doppler Flow in Maternal Vessels during Pregnancy
14 Color Doppler Sonography of the Uterine Arteries in Early Pregnancy to Screen for Preeclampsia and Uteroplacental Insufficiency
15 Normal Fetomaternal Doppler Indices in the Second and Third Trimesters of Pregnancy
16 Venous Doppler Sonography
Specific Obstetric Problems
17 Color Doppler Sonography in the Diagnosis of Nuchal Cord
18 Chronic Placental Insufficiency
19 Severely Abnormal Doppler Findings and Perinatal Abnormalities
20 Fetal Doppler Findings in Late Pregnancy
21 Intrapartum Fetal Heart Rate Changes and Doppler Sonography
22 Color Doppler Ultrasound in Fetal Echocardiography
23 Use of Color Doppler in Echocardiography
24 Structure of the Human Placenta and Pathomorphological Changes in Placental Insufficiency
25 Morphological and Morphometric Studies of the Placenta with Doppler Abnormalities of the Fetal Umbilical Arteries
Gynecologic Ultrasound
26 Sonographic and Doppler Sonographic Examination of Uterine Anomalies
27 Doppler Examination of the Normal Endometrium and Benign Endometrial Changes
28 Transvaginal Color Doppler and Pulsed Doppler Diagnosis of Benign Changes in the Uterine Myometrium
29 Use of Color Doppler in the Evaluation of Suspicious Endometrial Findings
30 Malignant Uterine Tumors
31 Blood Flow Changes in Cervical Carcinoma Treated by Primary Chemotherapy
32 Color Doppler Imaging of Benign Adnexal Masses—A Spectrum of Findings
33 Malignant Adnexal Tumors
34 Three-Dimensional Power Doppler Sonography in Evaluating the Angiogenesis of Ovarian Tumors
35 Ovarian Cancer Screening
36 General Aspects of the Ultrasound Investigation of Blood Flow in Breast Tumors
37 Color Doppler Sonography in the Diagnosis of Breast Cancer
38 Usefulness of the Minimum Resistance Index in the Benign–Malignant Discrimination of Breast Tumors
39 Effect of Menopausal Status and Hormone Replacement on Therapy Resistance Indices and Blood Flow Velocities in Breast Tumors
40 Benign–Malignant Tumor Discrimination and Prognostic Evaluation of Breast Tumors with Color Doppler Sonography

Leseproben

1 Physical and Technical Principles of Color Doppler Sonography

R. Kubale and G. Hetzel

Historical Development

Duplex sonography and its offshoot, color duplex sonography, are relatively new methods that combine the pulsed echo technique of sectional image formation with the Doppler evaluation of blood flow. It is based on B-mode ultrasound, which permits an accurate morphological description of gynecological and obstetric findings as a result of increasingly higher resolution and faster frame rates. The first attempts to measure blood flow date back to Satomura12. It was not until the early 1970s that Pourcelot11 was able to use continuous wave (CW) Doppler to investigate cerebrovascular diseases. Since 1977, authors have described Doppler ultrasound applications in the abdomen and especially in obstetrics and gynecology3,13,16. During the past 15 years, these applications have become widely adopted and established through the use of color-flow techniques and ongoing refinements in instrumentation10.

Below we shall explore the physical and technical principles that are essential for optimally utilizing and interpreting B-mode and color Doppler sonography and avoiding misinterpretations.

B-Mode Sonography

Physical Principles of Echo Production

The ultrasound wave is a density and pressure wave that propagates through a medium, its behavior essentially conforming to the laws of sound and optics. Sound attenuation, sound reflection, and resonance phenomena can be utilized as means of identifying defects in the insonated medium. The pulse-echo principle is most commonly used in medicine and will be discussed below in greater detail.

Acoustic impedance. The echoes that are displayed in an ultrasound image are based on reflections that occur when the sound wave travels through media of different acoustic impedance. Acoustic impedance () is a material-dependent (i.e. tissue-dependent) quantity that is the product of the density of the material (?) and the velocity of sound in it (). For the time being, we shall assume that this velocity is a material- and tissue-independent constant (equation 1) (see New Technical Processes and Approaches, p. 25).

Because the sound wave consists of alternating high and low pressure peaks, the tissue that transmits the wave is transiently compressed, and the sound velocity changes: the “peaks” at a higher pressure move faster than the “valleys” at a low pressure. This phase-dependent change in sound velocity distorts and steepens the original sine wave, analogously to a water wave breaking on the shore. As a result, the reflected wave acquires a component that is a multiple of the emitted basic frequency (harmonic energy). These frequencies, which create unwanted signals in the conventional B-mode image (see Principle of Echo Detection and Scanning Techniques, p. 3), can be utilized for specific “harmonic” imaging. This technique, called tissue harmonic imaging (THI), makes it possible to examine even patients who are technically difficult to scan (see New Techniques of Signal Acquisition and Processing, p. 25).

The acoustic impedance of tissues has a value similar to that of water. The exact value varies with the composition of the tissue (Table 1.1). Note that the acoustic impedances of soft tissues are markedly different from the impedances of air and bone.

Reflection. Reflection occurs at every interface between two media that have different acoustic impedances. The reflected portion of the ultrasound wave (the echo) increases with the magnitude of the acoustic impedance difference. The amount of reflection that occurs at the interface between two different tissues with impedances tissue1 and tissue2 is described by the reflection factor (Table 1.1) as given by equation (2):

If the impedance mismatch between the tissues is small, the transmitted ultrasound wave will retain enough energy to produce additional echoes in deeper tissue layers. But when a large impedance mismatch exists, such as tissue–air or tissue–bone interfaces, almost all of the incident sound energy is reflected. Objects located behind such an interface cannot be visualized with ultrasound.

Refraction. Reflection is strongly angle-dependent and is subject to the same laws as optical refraction. If the sound strikes the interface between different tissues at a perpendicular angle, most of the reflected wave will return to the transducer. But if the sound strikes the interface at an oblique angle, only part of the reflected wave will reach the transducer, and the wave will deviate from its original direction as it continues on through the second medium (refraction).

Scattering. If the sound beam encounters a rough surface or small reflectors whose diameters are significantly smaller than the wavelength of the sound, the beam will be reflected or “scattered” in various directions. This occurs not just at interfaces but everywhere in the tissue. Because of scattering, homogeneous soft tissue is depicted as an interference pattern with a coarse or fine texture, depending on the transducer frequency (Speckle).

Absorption and attenuation. In addition to losses due to reflection and scattering, some of the ultrasound energy is absorbed in a frequency-dependent fashion as it overcomes cohesion and relaxation forces in the medium. The amplitude of the sound pressure declines exponentially with the thickness of the medium traversed—i.e., it is attenuated. Attenuation refers to the relationship of the initial sound pressure to its pressure after the sound has propagated for a given distance. It depends on the distance traveled by the sound pulse, the frequency of the transducer, and a material-specific constant. The following simplified formula (equation 3) is valid for soft tissues and for frequencies from 0.2 MHz to 100 MHz:

Principles of Ultrasound Instrumentation

Principle of Echo Detection and Scanning Techniques

Ultrasound pulses are generated and processed by means of piezoelectric elements that are assembled into a transducer. In principle, a transducer is both a transmitter and a receiver of sound. An electric pulse (pulse length 0.5–2 wave trains of 1 µs duration) excites the active elements of the transducer. The resulting mechanical vibration propagates through the tissue. The mechanical vibration is reflected from a target object, and the returning sound wave induces the transducer elements to generate an electric signal. The time (t) between the emission of the pulse and the reception of the echo is a measure of the distance (z) of the transducer elements from the reflecting object (pulse-echo principle) (equation 4):

where is the velocity of sound and is the time from pulse transmission to echo reception.

B-mode image. A two-dimensional sectional image is produced when a number of adjacent ultrasound beams are transmitted and received in the same plane. In the B-mode technique (for “brightness mode”), the echoes are displayed at a brightness that is proportional to their amplitude. The brightness-modulated signals that are received (ultrasound lines) are temporarily stored in a matrix. The contents of this matrix are transferred to a monitor at correlative sites and assembled into a geometrically correct ultrasound sectional image (Fig. 1.1).

Fig. 1.1 Production of an ultrasound image, illustrated for a linear array transducer. Transverse abdominal scan through the liver, kidneys, pancreas, and spine. When a pulse is transmitted, portions of the ultrasound energy are reflected from the organ surfaces and from interfaces within the organ parenchyma. These echoes are assigned to specific locations based on the transit time for a known sound velocity. The sum of the brightness-modulated points yields a sectional image in which the liver, aorta, pancreas, and kidneys can be evaluated.

The first ultrasound imagers were based on the manual movement of a single transducer over the patient (compound scan). These were initially replaced by mechanical transducers in which an element was rotated to produce a fan-shaped beam pattern.

Transducer arrays. Most scanners today employ transducer arrays consisting of individual elements arranged in a closely spaced row. Each array has a certain number of elements, in some cases more than 196. The elements are fired (excited) in groups, each of which transmits and receives an ultrasound line. Starting on one side of the array, the edge line is acquired first. Adding an element on one side of the group and turning off an element on the other side, the active group is shifted across the array. As the next group transmits and receives, the tissue is scanned in a sequential fashion. As this process is continued, a sectional image is produced. If the elements in the array are arranged in a straight row, the transducer is classified as a linear array. If the elements are arranged along a curve, the unit is called a curved or convex array (Fig. 1.2).

Fig. 1.2 Functional principles of different transducer types.

a In a linear array, the elements are fired in offset groups at times A and B, producing a rectangular beam...

Über Autor(innen)

Werner Schmidt, Asim Kurjak