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Thyroidologists should seek training in ultrasound to better understand echogenic foci
Echogenic foci are commonly identified on thyroid ultrasound. Some echogenic foci such as microcalcifications are associated with increased risk for malignancy, whereas others such as comet tail artifact are associated with low risk.
Microcalcifications are tiny and without posterior shadowing. They are often more readily seen while performing ultrasound in real time and often less obvious on still images. As the ultrasound probe is moved back and forth, microcalcifications come in and out of view. Some have called this the “starry sky at night” because of this twinkling appearance. Macrocalcification can be distinguished from microcalcifications and comet tail artifact because they are larger and there is posterior shadowing.
Thomas B. Repas
Comet tail artifact appears as a bright echogenic line with an echogenic triangle or lines reverberating posterior to it (See image). In a study by Beland and colleagues, no thyroid nodules with bright echogenic linear foci with or without comet tail were malignant. In contrast, the risk for malignancy when a nodule had macrocalcification was 4%, whereas the risk when there was microcalcification was 31%.
Because the presence of such findings may raise or lower one’s concern for possible cancer, it is essential for the presence of these to be noted on ultrasound reports. Sometimes, those who are unfamiliar with thyroid ultrasonography misinterpret what type of echogenic foci a patient has. I have frequently seen echogenic foci with comet tail artifact incorrectly called “microcalcifications.”
Comet tail artifact appears as a bright echogenic line with an echogenic triangle or lines reverberating posterior to it.
Source: Thomas B. Repas, DO, FACP, FACE, CDE
To avoid this error, thyroid ultrasound should be performed and interpreted by clinicians who are not only skilled in ultrasound technique and knowledgeable about thyroid disease but who are also familiar with the unique history and presentation of each patient. The results of ultrasound are dependent on both the operator and the interpreter.
I strongly encourage any thyroidologists who are not already performing their own ultrasounds but are interested in doing so to seek further experience and training. The American Association of Clinical Endocrinologists offers basic and advanced courses, as well as a certification program, in endocrine neck ultrasound.
For more information:
- American Association of Clinical Endocrinologists. Endocrine Certification in Neck Ultrasound Program. Available at: www.aace.com/ecnu.
- Beland MD. J Ultrasound Med. 2011;30:753-760.
- Thomas B. Repas, DO, FACP, FACE, CDE, is an endocrinologist, lipidologist and physician nutrition specialist in clinical practice at the Regional Medical Clinic Endocrinology and Diabetes Education Center in Rapid City, S.D. Repas is the former chairman of the professional diabetes advisory committees of the Wyoming and the Wisconsin Diabetes Prevention and Control Programs.