What Is a Thyroid Ultrasound?
The thyroid gland is a small and butterfly-shaped gland located in front of the neck. It is a crucial gland, as the hormones secreted by them regulate the entire body's metabolism. It is also considered one of the chief organs responsible for the whole of the body's functioning and development. The incidence of thyroid diseases is increasing and is seen most frequently in females. Thyroid diseases consist of many thyroid anomalies, including benign and malignant tumors. Thyroid cancer is one of the most common endocrine malignancies, and similar to thyroid diseases, thyroid cancer also sees a female predominance. Advanced diagnostic aids are crucial ways to diagnose thyroid disorders. Though thyroid hormone tests and radioactive scans are preliminary tests for a thyroid disorder, ultrasonography goes hand in hand with these tests to support and confirm a diagnosis.
A thyroid ultrasound is a non-invasive imaging test used to view the thyroid gland and its adjacent structures. It is considered a safe procedure as it uses sound waves to create pictures of the thyroid gland. In addition, a thyroid ultrasound can detect abnormalities such as cysts, benign tumors, nodules, thyroid diseases, or malignant tumors. The only drawback with thyroid ultrasound is that it cannot determine the functioning ability of the thyroid; hence along with the ultrasound, thyroid function tests are always recommended to support the diagnosis.
What Are the Uses of a Thyroid Ultrasound?
The following conditions are the most common indications for thyroid ultrasound:
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Primarily to detect and confirm the presence of nodules.
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To characterize the nodule and differentiate benign from malignant tumors based on the sonographic changes.
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To aid in biopsy (ultrasound-guided biopsy).
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It is a valuable tool to screen high-risk patients (patients with familial history of thyroid cancers or genetic syndromes) as they have an increased predisposition to thyroid cancer.
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Ultrasound-guided ethanol injection reduces the nodule size in thyroid adenomas.
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Periodic ultrasound in thyroidectomy patients is vital to check for the recurrence of thyroid carcinoma.
How Should Patients Prepare for Thyroid Ultrasound Procedures?
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This procedure does not require any special preparations. It is a simple test carried out on an outpatient basis.
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The patient should wear comfortable, loose clothes.
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They should remove any jewelry and accessories, especially necklaces and chains.
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No dietary restrictions are required.
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Patients can continue taking their prescription medicines as before.
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Patients on thyroid hormone replacement should inform the doctor before the procedure.
What Is the Principle of Ultrasonography?
Ultrasound examination uses sound waves to assess the organs and capture them in pictorial form. Ultrasonography does not use any radiation; hence it is a relatively safe procedure. The ultrasound unit comprises a transducer, a computer, and a screen. The transducer is a small microphone-like device that discharges high-frequency sound waves into the body. These sound waves are inaudible to the human ear. The sound waves strike any structure within the body and bounce back, again captured by the transducers. The computer processes the images based on the frequency, amplitude, and time these sound waves take to bounce back. These images appear as real-time images on the monitor.
How Is the Procedure Done?
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The patient will be advised to change into a hospital gown and should lie down flat on their back.
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Their neck will be supported by a pillow so that the neck extends slightly.
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The radiologist will apply a clear gel on the front part of the throat. The ultrasound transducer will be moved back and forth over the skin in the area. Slight pressure may be applied but will not be painful.
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The gel helps obtain a secure contact of the transducer with the skin and eliminates any air pockets that may hinder the sound waves.
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The transducer emits sound waves into the body, which are then processed into images by the computer. These images appear on the monitor.
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Once the radiologist confirms all the obtained images, the patient can wipe off the gel and wait in the recovery room.
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The entire procedure takes about 30 minutes.
What Are the Instructions After the Procedure?
Ultrasonography is a simple procedure; hence there are no restrictions after the procedure. The patient can continue their normal activities as before.
How Are the Results Interpreted?
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The radiologist interprets the result after analyzing the images.
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A normal result usually indicates no abnormalities in the thyroid gland's structure, size, shape, and location.
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An abnormal result could be due to any growth, cysts, or tumors. Ultrasound can help detect the size of these growths if there are more than one tumor or nodule, location, boundaries, and even the blood supply within the tumor.
The following table gives the ultrasound features of certain common thyroid anomalies:
Hyperechoic: When too many sound waves bounce back. They appear light gray in USG. They usually contain air, fluid, or some fat, but they are not solid masses.
Hypoechoic: When there are decreased sound waves bouncing back. They appear dark gray in USG, and most of them are dense solid lesions.
Isoechoic: When the echo produced by the bounced-off sound wave is similar to the surrounding tissues and organs.)
What Are the Benefits of This Procedure?
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Ultrasound is a non-invasive procedure.
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It is painless, fast, and accessible.
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Cost-effective.
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Widely available and well tolerated by the patients.
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It is incredibly safe as there is no radiation issue.
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Superior to X-rays in providing precision images.
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The possibility of viewing the images while examining makes ultrasound a beneficial tool for minimal procedures such as biopsy and for aspirating the fluids (fine needle aspiration cytology).
What Are the Risks Associated With This Procedure?
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An ultrasound procedure has no known risks.
What Are the Limitations of This Procedure?
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An ultrasound cannot determine the thyroid function (whether the thyroid is normal or with increased or decreased activity). Therefore, a thyroid function test or radioiodine scan may be required to establish thyroid functions.
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Ultrasound has low specificity in differentiating a few benign and malignant tumors due to overlapping features. Hence, it may lead to further ancillary tests to confirm the diagnosis.
What Are the Recent Advances in Thyroid Ultrasound?
Ultrasound Elastography
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Elastography is a specialized ultrasound technique that determines mechanical properties such as tissue elasticity or stiffness to differentiate benign from malignant tumors.
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The elasticity of the tissue is measured based on the amount of distortion that has occurred under external pressure.
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This procedure uses external compression along with some low-frequency vibrations. Ultrasound detects the speed with which these vibrations travel to and from the tissues, then uses a computer to assess these to create a visual map of the tissue elasticity.
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Benign tumors are soft and easily deformed with external compression, whereas malignant tumors are more rigid and resist deformation. Therefore, it is easy to differentiate malignant tumors from their benign counterparts based on this principle.
Conclusion:
Ultrasound is considered a vital tool in evaluating and diagnosing various thyroid diseases. The possibility of concurrent diagnosis and therapeutic intervention makes ultrasound a prime diagnostic aid in thyroid disorders. In addition, the novel advances in thyroid sonography have enhanced diagnostic accuracy and made it more viable. An ultrasound is also the preferred diagnostic aid in pregnant ladies and kids, considering its no radiation protocol.
