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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5793_Библиотеки_им_академика_М_И_Перельмана.pdf
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E. I. Peniaeva et al.
a
b
Fig. 13.2 Difculties in differential diagnosis of neck lymph nodes and parathyroid lesions.
Grayscale US. (a) Reactive lymph nodes adjacent to the inferior pole of the thyroid lobe. (b)
Adenoma of the left inferior parathyroid gland adjacent to the inferior pole of the thyroid lobe
The same can be said about esophageal diverticulum. In most cases, sonographers have a mental image of “typical” thyroid nodules based on their own experience, so any lesion differing from this typical image should be interpreted with extra
caution.
Congenital anomalies of the thyroid gland and surrounding organs may also
cause difculties. The beginning sonographer may experience certain doubts, for
example, with aplasia/agenesis, severe thyroid hypoplasia, right-sided location of
the esophagus, etc.
13 Main Challenges andPitfalls inThyroid Ultrasound
247
Special opportunities for differential diagnosis are provided by auxiliary methods, such as turning the patient’s head, compression of the neck tissues with ngers,
swallowing, and others. Modern equipment permits accurate US visualization of
solid thyroid nodules larger than 2–3mm in size. The presence of smaller lesions is
preferably reported without the term “nodule.” Drawing a conclusion about the
lesion is expedient only when it can be clearly visualized in at least two mutually
perpendicular scans.
It is important to adhere to the correct examination technique. Thyroid structure
including small parts can be estimated only with linear probes at frequencies of
7.5MHz and higher. Convex abdominal probes may be used to measure the lengths
of thyroid lobes or for large thyroids. The use of a convex probe alone for thyroid
examination results in multiple severe errors and discredits the eld of
sonography.
Imaging of the thyroid diseases may be accompanied with US artifacts that are
common not only of the thyroid gland. The main ones are listed below:
• Acoustic shadowing is typical for calcications (e.g., in thyroid cancer, coarse,
and egg-shell calcication in benign nodules).
• Reverberation “comet’s tail” artifact appears in colloid lesions, inclusive of
macrofollicles.
• Marginal artifact of lateral acoustic shadows is characteristic of some types of
solid nodules and can be combined with “hallo” sign, for example, in thyroid
adenoma.
• Posterior echo enhancement is typical of uid collections.
Similarly, some artifacts arise in color-coded modes. It is important to set optimal parameters in CDI, PDI, and PW Doppler to ensure the quality of obtained data.
Visualization of blood ow with incorrect settings, particularly low velocity threshold, is accompanied with an aliasing artifact in both color and spectral Doppler
(Fig.13.3). Here, the velocity exceeds the Nyquist Limit, and the image displayed
would suggest ow is heading in the opposite direction.
When utilizing ultrasound elastography technologies, it is extremely important
to adhere the technique. Differences in technology, measurements, and ways of
interpretation of tissue strain on scanners of different manufacturers lead to high
number of uncertain conclusions. Quantitative data of tissue rigidity/elasticity supply some objective data, but different units of measurement (kPa, m/s, etc.) make
the studies hard to compare. Compression ultrasound elastography can also be
accompanied with some artifacts [3, 4], such as listed below:
• “Maltese cross”—the emergence of shadows around a hard formation, which
entrains soft tissues adjacent to its boundaries in the process of compression. The
latter are shown more rigid than they are in fact.
• Edge enhancement of hard lesion due to the involvement and displacement of the
surrounding tissues during compression.
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E. I. Peniaeva et al.
a
b
Fig. 13.3 Aliasing artifact in under-sampling in CDI assessment of blood ow
• Artifacts of incorrect compression (excessively strong or weak). Too much pres-
sure applied to the tissues can reduce the clarity of the boundaries of the lesion
and sometimes causes lateral displacement of the tissues.
• Artifacts of large liquid collections. When tissue is compressed, random character of
uid movement can also generate artifacts that mimic the solid structure of the lesion.
Differential diagnosis of thyroid tumors does not always depend on radiologist
or clinician. Despite all the advances in ultrasound imaging, innovation, and
13 Main Challenges andPitfalls inThyroid Ultrasound
249
progress, more than 4% of malignant thyroid tumors have atypical ultrasound features [1] (Fig.13.4).
The result of an ultrasound study should be presented as a clear conclusion. It
inuences the choice of further diagnostic and treatment. It helps a surgeon to determine the volume and type of operation, an endocrinologist to assign therapy, and a
radiologist to plan follow-up.
The conclusion is a clear summary of the descriptive part and regarding the
thyroid gland, in our opinion, should necessarily contain the following four
aspects:
a
b
Fig. 13.4 Thyroid cancer. Sonograms. Benign ultrasound signs with (a) grayscale US and (b)
PDI.Malignant hard pattern with (c) compression USE and (d) shear wave elastography
250
E. I. Peniaeva et al.
c
d
Fig. 13.4 (continued)
1. Data of echovolumetry (thyroid enlargement)
2. The condition of the thyroid parenchyma (e.g., diffuse changes of the paren-
chyma characteristic of AIT)
3. Summary on the detected lesions (e.g., nodule of the right thyroid lobe)
4. Specication of thyroid lesions according to the TIRADS (e.g., TIRADS 2)
13 Main Challenges andPitfalls inThyroid Ultrasound
251
An important component of echography is digital archive of the obtained data.
Almost all ultrasound devices can store and transmit digital information in universal
DICOM format. It facilitates follow-up and further diagnosis and provides easy,
convenient, and efcient communication between various medical equipment, clinics, and networks. Some advantages, like fusion technology, are already utilized in
everyday practice; the prospects are obvious.
References
1. Sencha AN. Ultrasound diagnostics. Surface-located organs. Moscow: Vidar M Publishing
House; 2015. (Book in Russian).
2. Bataeva RS, Mitkov VV, Mitkova MD.Evaluation of the reproducibility of the results of
ultrasound volumetry of the thyroid gland. Ultrazvukovaya i Funkcionalnaya Diagnostica.
2006;1:37–43. (Article in Russian).
3. Bamber J, Cosgrove D, Dietrich CF, et al. EFSUMB guidelines and recommendations on the
clinical use of ultrasound elastography. Part 1: basic principles and technology. Ultraschall
Med. 2013;34(2):169–84.
4. Osipov LV. Ultrasound diagnostic devices. Modes, methods and techniques. Moscow: Izomed;
2011 (Book in Russian).