2. Imaging of thyroid disease - AAES GUIDELINES
Ultrasound is the primary imaging modality for thyroid disease and a high quality ultrasound, including the cervical lymph nodes should be performed on all patients. The aim of an ultrasound is to assess the presence, size and possible suspicious features of any thyroid nodules, as well as to determine the presence of cervical lymph node metastases in patients with thyroid cancer. If a nodule is suspicious a fine needle biopsy will be performed with ultrasound guidance. A number of grading systems are used to determine the need for fine needle biopsy.
CT AND MRI SCANS
Cross-sectional imaging is primarily used as an adjunct to ultrasound in patents with thyroid cancer in order to assess the extent of disease including local invasion of the windpipe or oesophagus. It is also used to assess the extent of a retrosternal goitre which has grown into the chest.
PET scanning has no role in the initial diagnosis of thyroid disease. It may however pick ups a suspicious incidental thyroid nodule when used for follow-up of a patients with other malignancies.
THYROID NUCLEAR MEDICINE SCANS
Although these were once the mainstay of thyroid investigation, the role of technetium nuclear medicine scanning is limited to the assessment of the overactive thyroid or the follow-up of thyroid cancer after radioiodine ablation therapy
Recommendation 4: A diagnostic US should be performed in all patients with a suspected thyroid nodule
Every patient with thyroid disease should have an initial high quality thyroid ultrasound including the cervical lymph nodes. My preference in the Australian setting is for this to be performed in a high volume radiology practice by an experienced ultrasonographer with access to latest technology as I find the "office ultrasound" performed on basic equipment can miss important findings. The most common grading system used in Australia to determine whether a nodule should have a fine needle biopsy is the TI-RADS system developed by the American College of Radiology. This is based on a combination of ultrasound characteristics (eg calcification, irregular edge etc) and size with a TI-RADS 1 lesion being benign and a TI-RADS 5 nodule being highly suspicious warranting needle biopsy.