Simultaneous positron emission tomography and MRI (PET/MRI) is a technology that combines the anatomic and quantitative strengths of MR imaging with physiologic information obtained from PET. PET and computed tomography (PET/CT) performed in a single scanning session is an established technology already in widespread and accepted use worldwide. Given the higher cost and complexity of operating and interpreting the studies obtained on a PET/MRI system, there has been question as to which patients would benefit most from imaging with PET/MRI versus PET/CT. In this article, we compare PET/MRI with PET/CT, detail the applications for which PET/MRI has shown promise and discuss impediments to future adoption. It is our hope that future work will prove the benefit of PET/MRI to specific groups of patients, initially those in which PET/CT and MRI are already performed, leveraging simultaneity and allowing for greater degrees of multiparametric evaluation.

Level of evidence

5 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2017;46:1247-1262.

The purpose of this prospective study was to determine the correct localization rate (CLR) of ¹⁸F-fluorocholine PET for the detection of parathyroid adenomas in comparison to ^99mTc-sestamibi imaging. Methods: This was a single-arm prospective trial. Ninety-eight patients with biochemical evidence of primary hyperparathyroidism were imaged before parathyroidectomy using ¹⁸F-fluorocholine PET/MRI. ^99mTc-sestamibi imaging performed separately from the study was evaluated for comparison. The primary endpoint of the study was the CLR on a patient level. Each imaging study was interpreted by 3 masked readers on a per-region basis. Lesions were validated by histopathologic analysis of surgical specimens. Results: Of the 98 patients who underwent ¹⁸F-fluorocholine PET, 77 subsequently underwent parathyroidectomy and 60 of those had ^99mTc-sestamibi imaging. For ¹⁸F-fluorocholine PET in patients who underwent parathyroidectomy, the CLR based on the masked reader consensus was 75% (95% CI, 0.63-0.82). In patients who underwent surgery and had an available ^99mTc-sestamibi study, the CLR increased from 17% (95% CI, 0.10-0.27) for ^99mTc-sestamibi imaging to 70% (95% CI, 0.59-0.79) for ¹⁸F-fluorocholine PET. Conclusion: In this prospective study using masked readers, the CLR for ¹⁸F-fluorocholine PET was 75%. In patients with a paired ^99mTc-sestamibi study, the use of ¹⁸F-fluorocholine PET increased the CLR from 17% to 70%. ¹⁸F-fluorocholine PET is a superior imaging modality for the localization of parathyroid adenomas.