The utility of the interpretation of PET-MR simultaneously versus independently of each other in patients with well-differentiated thyroid cancer

Abstract

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Objectives: Magnetic resonance imaging scans (MR) and positron emission tomography scans (PET) with 18-fluoro-deoxyglucose (FDG) are valuable diagnostic imaging modalities in the management of patients with suspected recurrent or metastatic well-differentiated thyroid cancer (WDTC). However, frequently the MRs and FDG PETs are interpreted independently of each other. The objective of this study was to evaluate the results of the interpretation of MR and FDG PET simultaneously relative to the interpretation of each independently. Methods: A retrospective review was performed from May 2004 to Oct 2005 at Wash Hosp Ctr of all patients who (1) were suspected to have recurrent WDTC, (2) had a FDG PET that included the neck area, and (3) a MR of the neck within 30 days of the PET. The MR and PET were graded blindly and independently by an expert (am and ea, respectively) without knowledge of the results and/or images of the other scan as 1=normal/benign, 2=most likely normal/benign, 3=indeterminate, 4=most likely malignant, or 5=malignant. Later, the two experts together interpreted the FDG PET and MR simultaneously using the same grading scale. Statistical analysis was performed using the Student T test. Results: Thirty patients (19 female, 11 male) had a mean age of 39 y.o.(range 15-65), and the results are shown below. Of the 13 patients whose grade changed from 1, 2 or 3 on either PET or MR to Grade 4 or 5 on combined PETs-MRs, WDTC has been confirmed in 5 (38%) patients by either fine needle aspiration or surgery. Only 1 MR with grade of either 4 or 5 was changed to a grade of 3 on combined PET-MR, and no PET with a grade of 4 or 5 was changed to a grade of 1, 2 or 3. Conclusions: In patients with WDTC, the simultaneous interpretation of PETs and MRs reduced significantly the number of normal and/or benign interpretations on either MR or PET interpreted independently of each other.

Results