Thyroid ultrasound technique is performed for diagnostic and therapeutic purposes. Patients do not need to prepare and get special treatment before the examination.
Examination is usually fast and the patient is in a supine position so that patient comfort is maintained. After thyroid ultrasound examination, the patient should do follow-up again according to the disease.
Thyroid ultrasound does not require any special preparation. The patient does not require medication or anesthesia. Thyroid stimulating hormone (TSH) suppressive therapy does not need to be discontinued for this test.
Informed consent needs to be obtained from the patient after explaining the diagnosis, purpose of the procedure, procedure for action, other alternative actions, risks, complications, prognosis of action and follow-up. Physical examination of the thyroid by palpation of the thyroid gland and cervical lymph nodes can be performed to provide an overview of the number, size, consistency, motility of thyroid nodules, and lymphadenopathy.[1,6,7]
The equipment needed for a thyroid ultrasound examination is an ultrasound machine, which includes:
Pulser/transmitter that produces waves,
A transducer that converts electrical energy into acoustic energy and vice versa
A receiver that detects, compresses, and amplifies the signal returning to the transducer
Screen for displaying signals in the form of B-mode, motion M-mode, Doppler,
Memory for storing stationary data and videos
Due to the presence of an air gap that cannot conduct ultrasonic waves, a liquid or gel medium is needed. The type of probe used for thyroid ultrasound examination is linear with a frequency of 6–15 Hz. This frequency was chosen because of its penetration depth and spatial resolution which is suitable for the thyroid gland
Thyroid Ultrasound Imaging Method
The following are some of the thyroid ultrasound imaging methods.
Ultrasonography in Grayscale (Grayscale Ultrasonography):
This method is the most commonly used method. Ultrasonography in grayscale uses intermittent pulses of sound energy generation and reception of echoes to produce images of tissue structures through which sound travels.
This technology produces high-resolution thyroid images with sound frequencies between 5–13 MHz and penetrating to a depth of 5 cm (the thyroid gland is in this range in the majority of patients). Modern transducers can produce high resolutions as small as 2 mm, provided the ecodensities of the structures are different or separated by two different tissues.
Three-Dimensional Ultrasonography (Three-Dimensional Ultrasonography):
This technique can assist in the analysis of anatomical structures and tumors in relation to surrounding structures.
Color Doppler Ultrasound:
This method is used to describe the blood vessels of the thyroid gland and its surroundings. This method is based on changing the frequency of the wave, where when the wave (transducer) approaches something, the sound will enlarge and vice versa.
Doppler imaging provides information about blood flow which when superimposed on a real time grayscale ultrasound image will describe the direction and velocity of blood flow.
B-flow imaging is a non-Doppler technology that depicts movement within anatomical structures. The advantage of this method is that it can avoid artifacts in Doppler imaging.
The way this imaging works is that ultrasonic waves separated by a certain distance are transmitted, then the reflected signal (separated by a predetermined and shorter distance) will be detected. Then, the overlapping signals are combined and processed into an image on the screen. The resulting information relates to the movement of blood flow in the thyroid.
Ultrasound with Contrast Material:
In recent see website developments, ultrasound can use experimental materials, such as air-filled microbubbles with a diameter smaller than red blood cells, and Levovist (an agent consisting of granules containing 99.9% galactose and 0.1% palmitic acid). ). The advantage of this material is that it will increase the echogenicity of blood and increase the ratio of signal to noise (noise) when injected intravenously.
Elastography aims to assess the level of stiffness of a tissue related to the consistency of the anatomical structure. Tissue deformation can be seen by observing changes in the Doppler signal. These changes occur in response to external pressure and vibration or the propagation of wave shifts.
By assessing the level of flexibility of an organ or tissue, it can be determined whether the disease condition is benign or malignant. A malignant thyroid nodule has low flexibility or stiffness. Elastography is useful for the assessment of noncystic and noncalcified thyroid nodules.
Thyroid ultrasound is also used for invasive diagnostic purposes, such as in ultrasound-guided fine-needle aspiration biopsies. The use of ultrasound helped reduce the number of nondiagnostic samples to 7% from the original 16% when using palpation techniques for biopsy samples.