Clearer Guidance on Necessary Use of Imaging for Thyroid Disease

ACR/ATA recommendations clarify the occasions in which thyroid imaging is advisable and when it is not to optimize patient management.

with Victor Bernet, MD, and Jenny K. Hoang, MBBS    

  • Is there ever a time when a patient with hypothyroidism should have an imaging study done?
  • Should patients with palpable nodules have a CT scan or MRI as first-line diagnostics?
  • Should iodinated contrast be avoided in any patient with thyroid cancer?

These topics reflect some of the common occasions addressed by the American College of Radiologists’ (ACR) working group in devising criteria on the most effective use of imaging in the diagnosis of eight thyroid conditions with input from the American Thyroid Association.1

ACR guidelines refine when and for whom thyroid imaging is warranted.

This isn’t about over-utilization as much as it’s about optimization, said lead author Jenny K. Hoang, MBBS, an associate professor of medicine at Duke University School of Medicine in Durham, North Carolina. Doing too many scans may not be harmful to a patient but it does unnecessarily waste resources.

Revised Center for Medicare & Medicaid Services rules will require physicians to rely on guidelines such as these to support procedure decisions, Dr. Hoang said. The “Appropriate Use Criteria” are currently under voluntary reporting until 2020 when penalties for noncompliance will be instituted following an unspecified period mandating education in the application of imaging criteria.1

“The recommendations were developed from consensus among the panel members, and have been highly welcomed,” Dr. Hoang said, particularly with regard to guidance when variations occur in specific conditions, such as tumor assessment.

Thyroid Imaging Guidelines Provide More Targeted Use of Diagnostic Resources 

Among the key recommendations identified as common misconceptions, see how many are as you already practice:1

  • There is no need to order imaging tests for patient who are hypothyroid cases.
  • No need to worry that iodinated contrast will cause delays in efficacy of radioiodine ablation therapy (RAI) or whole-body scans after imaging. Iodinated contrast usually clears the body within 8 weeks, and most patients getting radioiodine therapy can start treatment after a month. Contrast media is often avoided to avoid precipitating hyper- or hypothyroidism; however, the evidence doesn’t support this concern, rather contract  should be “judiciously used” in all cases.
  • Often, functional magnetic resonance imaging (MRI) may be substituted for computerized tomography (CT) scans so long as the interference caused by compromised swallowing and breathing are not a concern.
  • Thyroid function testing should be done to guide which type of imaging test should be selected in evaluating neck nodules. For patients who are euthyroid, start with ultrasound. Similarly, to determine size and scope of a goiter, start with ultrasound. If there is any concern about impact on the trachea or a need to know how deep the goiter resides, then CT without contrast is indicated.
  • In cases of possible thyrotoxicosis, the selection of ultrasound (ie, Doppler may be helpful), or radionuclide uptake and scan are indicated.
  • Ultrasound should be employed in patients with preoperative differentiated thyroid cancer to aid in staging; CT with iodine contrast  may be considered for patients with advanced cancer.
  • Following cancer surgery, all patients should receive ultrasound at six to 12 months followup. Here there was not agreement regarding the use of CT with contrast of the neck or whole body scintigraphy was beneficial, as the literature was too limited. The recommendation indicates that this approach is “controversial but may be appropriate.”
  • When recurrence of differentiated thyroid cancer is suspected, ultrasound of the thyroid and whole body scintigraphy is recommended. Use of CT with contrast, or MRI with or without contrast should be used as second line testing. PET scans may be useful only for certain subsets of patients.  
  • In the presence of elevated blood markers raising suspicion of a recurrence of medullary thyroid cancer, ultrasound imaging should be ordered. CT of the neck may be beneficial in cases requiring deeper investigation of cervical nodes. Chest and abdominal CTs are warranted with higher calcitonin levels. Bone mass may be identified with either bone scans or MRI of the spine.

Order Thyroid Imaging Studies When and Only When It Is Efficacious 

While over reliance of scans wasn’t the focus driving the development of this guidance, there are some providers who will certainly benefit from learning when not to order imaging, said Victor Bernet, MD, the chief operating officer of the American Thyroid Association, and associate professor of medicine at the Mayo Clinic College of Medicine in Jacksonville, Florida.

Dr. Bernet said these criteria will be particularly invaluable for primary care physicians. “In that, particularly with more complicated cases, I believe there is room for clinicians to be making more optimal choices,” he told EndocrineWeb.

The danger in ordering imaging studies may come in spending time and money on tests that won’t provide the patient or physician with any added insight regarding disease management. “You can use thyroid ultrasound to look at the structure of the gland, but not how well it is functioning,” said Dr. Bernet. “Meanwhile, thyroid lab testing can tell you about the status of the gland but little about structure.”

As is often the case, more testing may raise findings that appear worrisome but need not be. For instance, if a patient receives an ultrasound without specific indication and small nodules are found, further imaging may be ordered to rule out cancer for masses that prove to be benign.

Clarifying Common Practices to Focus Assessment of Thyroid Diseases

Dr. Bernet said he is pleased with how well-balanced the recommendations are, and that the working group had addressed some of the common myths that have driven reliance on imaging without sufficient basis, such as the dangers of using of contrast in imaging for patients with hyperthyroidism and how quickly that contrast clears from a patient’s system. “It turns out that it clears fairly quickly. The old beliefs and methods of practice used to be doctrine.”

This working group will review and reevaluate the criteria for employing imaging regularly, according to Dr. Hoang. Dr. Bernet added that he expects the criteria to be refined even further as the science advances.

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