Thyroid ultrasonography (synonyms: ultrasound of the thyroid gland; thyroid ultrasound) is a noninvasive (not penetrating into the body) diagnostic procedure of radiology, which is currently the most important examination method for the clarification of abnormal thyroid findings and for control examinations of the thyroid gland. The sensitivity (percentage of diseased patients in whom the disease is detected by the application of the procedure, i.e. a positive finding occurs) of the procedure can be rated as very good. Due to the fact that the thyroid gland is a very superficial organ, it can be optimally visualized and evaluated with the help of sonographic measures. Furthermore, the use of thyroid sonography allows for an adequate selection of further examination procedures with regard to their usefulness when pathologic findings occur in the area of the thyroid gland.
Indications (areas of application)
- Hypothyroidism (underactive thyroid gland).
- Hyperthyroidism – hyperthyroidism represents a pathological process, which must necessarily be diagnostically clarified with thyroid sonography. The detection of nodules in the sonography may indicate an autonomic process here.
- Thyroiditis (inflammation of the thyroid gland) – Pain in the area of the thyroid gland can indicate thyroiditis. Attention should be paid to possible bleeding.
- Clinical complaints that may indicate thyroid disease – typical for an anatomical changes or functional changes of the thyroid gland are dysphagia or globus sensation (lump feeling: foreign body sensation in the throat or. Throat that is independent of food intake), tachycardia (too fast heartbeat: > 100 beats per minute) or bradycardia (too slow heartbeat: < 60 beats per minute), weight loss or weight gain, heat or cold feelings and restlessness or lack of drive.
- Tumor follow-up – the procedure plays an important role in the follow-up of tumor diseases, since possible metastases (scattered tumor foci) or recurrences (recurrence of tumors) can be well detected with sonography.
Note: The German Society of Endocrinology (DGE) indicates that ultrasound screening for thyroid changes should not be performed in the elderly. For the reasons for the decision, see in the literature cited below.
The procedure
In contrast to palpation (tactile findings), thyroid sonography provides a reliable and accurate tool for monitoring the thyroid gland and its function. Thus, the procedure can also detect pathological changes that are not accompanied by any symptoms. In addition, the method ensures that neoplastic changes (tumor diseases) of both the thyroid gland and the surrounding structures can be detected. However, to confirm a finding involving a functional change of the thyroid gland, thyroid scintigraphy should be performed in addition to thyroid sonography. Examination Technique
- Normally, sonographic examination is performed with the patient lying down, because in this position it is easier to tilt the neck toward the scapulae. A pillow should be placed in the patient’s neck for support.
- First, the examiner should calculate the volume of the thyroid gland to make a statement about a possible enlargement of the thyroid gland. For this purpose, as an orienting volume calculation, a formula is used to calculate the determination of the size dimensions of an ellipsoid of revolution. The formula for the volume of the thyroid gland is length × width × depth × 0.5. However, it should be noted that when this formula is used, the volume of the thyroid gland is often overestimated. The thyroid volume is up to 18 ml in women and up to 25 ml in men.
- Furthermore, it must be noted that in order to produce meaningful examination results, the images must be created in two planes and here the anatomical reference points must be documented. It is also indispensable that the respective findings include detailed data on the thyroid volume separately for right and left side.
- In addition, an assessment of the position and shape of the thyroid gland is also important for the significance of thyroid sonography.The focus here is the detection of a thyroid gland, if necessary, partially retrosternal (located behind the sternum).
- For the functional assessment, the observation of the thyroid tissue is of great importance, as this can be used to draw a conclusion about a possible pathological process. However, it should be noted that most diseases of the thyroid gland present variably with existing examination methods. For example, a thyroid adenoma may be associated with functional impairment of the thyroid gland.
- The use of thyroid sonography is also indicated when a neoplastic process (tumor) is suspected. Three criteria determine the pros or cons of biopsy: microcalcifications, size greater than 1-1.5 cm, completely solid consistency (= echo-poor) – these three sonographic criteria are associated with the risk of malignancy of a thyroid nodule. Purely cystic and/or spongiform nodules can usually be observed conservatively. In order not to miss tumor foci, the cervical neighboring organs (organs in the neck region) must also be assessed. In addition, if malignancy (malignant finding) or inflammation is suspected, a statement about the local lymph node status should be included in the findings.
In addition to the direct diagnostic function of the procedure, sonography in thyroid diagnostics is also used in fine needle aspiration of the thyroid gland. The use of thyroid sonography significantly improves the accuracy of the puncture, so that nonpalpable nodules that initially escaped puncture can now be safely punctured.