A publication of the American Thyroid Association

Summaries for Patients from Clinical Thyroidology by Ernest Mazzaferri, MD MACP
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Abbreviations & Definitions

PET Positron Emission Tomography is a scanning technique used in conjunction with small amounts of radiolabeled glucose to visualize the anatomy and function of tumors, including information on blood flow, glucose metabolism and tumor location.

PET/CT PET scans alone often do not identify the precise anatomical location of a tumor. To fix this, radiologists digitally fuse the PET scan and a Computed tomography (CT) into one image which provides both functional and anatomical information about a tumor. Other imaging devices can also be fused with PET scans.

MRI/PET MRI is magnetic resonance imaging, a procedure in which radio waves and a powerful magnet linked to a computer are used to create detailed images of areas inside the body. MRI produces better images of organs and soft tissue than many other scanning techniques, such as computed tomography (CT) or x-ray. MRI is especially useful for imaging the brain, spine, and soft tissue of joints, and the inside of bones. The National Cancer Institute website has considerable information on these imaging devices.

Web links provide further information:

What is the study about? PET/MRI fusion studies in patients with differentiated thyroid cancer.

The full article title: “Utility of PET/neck MRI digital fusion images in the management of recurrent or persistent thyroid cancer” It is in the February 2008 issue of Thyroid (Volume 18, Issue 2, pages 103-11. The authors are L Seiboth, D Van Nostrand, L Wartofsky, L., Y Ousman, J Jonklaas, C Butler,F Atkins, and K Burman. The abstract can be obtained from:

What is known about the problem being studied? Serum thyroglobulin levels and neck ultrasound examinations are the mainstay of diagnostic follow-up studies in patients who clinically appear free of disease. Patients with more serious disease usually require a variety of imaging studies to identify the site and extent of metastatic tumor. One such study is PET scanning that is being increasingly utilized with CT or MRI to produce images that provide both anatomic and metabolic information.

What was the aim of the study? To assess the clinical utility of coregistered (fused images) of PET and MRI in patients with thyroid cancer

Who was studied? The study subjects were 34 patients with thyroid cancer who had undergone PET and MRI imaging for thyroid cancer at some point during their follow-up. Of this group, 31 (91%) had papillary thyroid cancer and one had medullary thyroid cancer. All were initially treated with total or near-total thyroidectomy.

How was the study done? Four endocrinologists who did not know the results of the fusion studies each reviewed the patient charts to make a clinical assessment and theoretical treatment plan. After this was accomplished, each endocrinologist was individually provided the results of the PET/MRI studies. With these new images, each endocrinologist made a revised clinical assessment and treatment plan and then categorized the PET/MRI information into three groups: (1) new information that altered the treatment plan, (2) new information that confirmed the initial proposed treatment plan, or (3) no new information.

What were the results of the study? The PET/MRI fusion studies provided additional information that altered the treatment plan in 46% of the patients, and confirmed the proposed treatment plan in 36% patients and provided no additional information in 18% of the patients.

How does this compare with other studies? There no similar studies with which to compare this study.

What are the Limitations of this study? The main limitation is that PET/MRI was not compared with PET/CT, the most commonly used digitally fused PET studies.

What are the implications of this study? This study provides important information that may change decisions regarding surgical therapy for patients with thyroid cancer. This requires further study.

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