Utility of PET/neck MRI digital fusion images in the management of recurrent or persistent thyroid cancer.

BACKGROUND Approximately 30% of thyroid cancer patients present with reappearing disease within 40 years of initial diagnosis. Hence, sensitive postsurgical monitoring techniques are imperative to successful long-term care. The objective of this study was to assess the added clinical utility of a combined positron emission tomography/magnetic resonance imaging (PET/MRI) of the neck in conjunction with standard imaging in the detection of recurrent thyroid carcinoma. We define standard imaging as a neck sonogram, 131I scan, computed tomography, and MRI. METHODS This study included 34 patients treated for thyroid cancer at Washington Hospital Center. All patients had previously undergone near-total or total thyroidectomy, standard follow-up imaging studies, and laboratory studies. Twenty-nine of thirty-four patients had received at least one 131I treatment prior to the study. Each patient received a PET and MRI scan, and these images were subsequently digitally fused. RESULTS Individually and blinded, four endocrinologists retrospectively reviewed all information in patient charts prior to PET and PET/MRI coregistration. A clinical assessment and treatment plan were devised with these data. Following the initial assessment, the endocrinologists were provided results from the PET and PET/MRI fusion studies and asked to make a revised assessment and treatment plan. For each patient, the physicians categorized PET/MRI fusion results as providing new information that altered the initial treatment plan, providing new information that confirmed the initial treatment plan, or providing no additional information. On average, PET/MRI coregistration provided additional information that altered the treatment plan in 46% of the cases, provided additional information that confirmed the treatment plan in 36% of cases, and did not provide any additional information in 18% of cases. CONCLUSION The combination of structural and functional data that PET/neck MRI fusion offers provided further information in an overwhelming majority of thyroid cancer patients in this study. Thus PET/MRI can be a useful tool in surgical planning, radioactive iodine therapy decisions, and determining the level of follow-up necessary for each patient.