A cervical Magnetic Resonance Imaging (MRI) scan does show the thyroid gland. While a cervical MRI is primarily ordered to evaluate the cervical spine (C-spine), spinal cord, and surrounding soft tissues, the thyroid often falls within the standard imaging area. Because the gland’s anatomical location is in the lower front of the neck, it is frequently captured in the field of view (FOV). The inclusion of the thyroid is incidental to the main purpose of the spinal examination, but it can provide important health information.
Anatomy and Field of View of a Cervical MRI
A cervical MRI is designed to create detailed images of the bony vertebrae, intervertebral discs, nerve roots, and the spinal cord. The scan focuses on the posterior and central neck structures to diagnose conditions like herniated discs or spinal stenosis. However, the standard imaging protocol requires a field of view that extends anteriorly to ensure full coverage of the targeted spinal structures.
The thyroid gland sits just below the voice box, wrapping around the trachea in the lower part of the neck. Due to this anterior position relative to the lower cervical vertebrae, the gland is often included in the C-spine MRI’s coverage margins. While the scan is optimized for bone and nerve tissue, the thyroid’s general appearance is visible to the radiologist reviewing the images.
Recognizing Incidental Thyroid Abnormalities
Since the thyroid is visible on the images, radiologists are trained to look for and report any abnormalities, even though they are outside the scan’s primary target. These unexpected findings are termed “incidentalomas” and can include a variety of thyroid conditions. The most common incidental finding is the presence of one or more thyroid nodules.
Studies show that incidental thyroid abnormalities are detected in a significant percentage of cervical MRI scans, with reported prevalence ranging widely from about 5% to nearly 50%. Thyroid nodules were the most frequent abnormality, followed by generalized enlargement of the gland, known as a goiter. Less common, but more serious, findings like thyroid cancer have also been identified incidentally on these scans. A radiologist’s report will flag these findings, often describing the size, number, and basic appearance of any visible nodules or changes.
Limitations Compared to Dedicated Thyroid Imaging
Despite its ability to detect thyroid abnormalities, a cervical MRI is not a replacement for dedicated thyroid imaging. The MRI is not optimized for thyroid tissue, meaning its resolution is lower compared to high-resolution ultrasound. Ultrasound is superior for visualizing small nodules, especially those under 5 millimeters, which a cervical MRI may miss entirely.
A dedicated thyroid ultrasound also offers specialized capabilities that an MRI lacks, such as the ability to assess blood flow (vascularity) within a nodule using Doppler technology. Ultrasound provides a clear view of specific features—like microcalcifications, irregular margins, or a taller-than-wide shape—that help differentiate a benign nodule from one that may be malignant. The incidental finding on a cervical MRI serves as an alert that necessitates a follow-up examination with a focused thyroid ultrasound for definitive characterization and diagnosis. The specialized ultrasound allows doctors to apply established risk-stratification systems to determine if a biopsy is required.