Diagnosis
Computed Tomography and Magnetic Resonance Imaging
Î Ultrasound has certain limitations related to the underlying technology,
particularly in the imaging of deep structures and those acoustically
shielded by air or bone.
• For this reason, cross-sectional imaging with CT or MRI may play a supplemental role
in preoperative imaging for thyroid cancer in a minority of cases. (See Table 3)
Î CT imaging of the neck is optimized by iodinated intravenous contrast.
Notes:
▶ This advantage must be balanced against the impact the iodine load will have in
causing what is usually a minor delay in subsequent postoperative radioactive iodine
ablation. Thus, preoperative communication between the surgeon and endocrinologist
is important.
▶ After the administration of iodinated contrast, a waiting period of at least one month is
recommended to allow urinary iodine levels to return to baseline levels before moving
forward with radioactive iodine ablation. At present, there is no evidence to suggest
that delays of this scale adversely affect thyroid cancer outcomes.
Î MRI with gadolinium contrast is an alternative axial scanning modality
that avoids the use of iodine but may be less informative to surgeons as
compared to CT in the central compartment due to motion artifact arising
from swallowing and respiration.
Table 3. Findings That May Prompt Axial Imaging
Hoarseness with vocal cord paresis/paralysis
Progressive dysphagia or odynophagia
Mass fixation to surrounding structures
Respiratory symptoms, hemoptysis, stridor, or positional dyspnea
Large size of tumor or mediastinal extension, incompletely imaged on ultrasound
Rapid progression/enlargement
Sonographic suspicion for significant extrathyroidal invasion (cT4)
Bulky, posteriorly located, or inferiorly located lymph nodes incompletely imaged by
ultrasound
Ultrasound expertise not available
