PET/MRI: a new era in multimodality molecular imaging

Abstract

Hybrid PET/MR imaging has long been considered an impossible combination due to the difficulty of ensuring the functioning of PET detectors within the magnetic field of an MR scanner, and the artifacts from the electronics of the PET scanner, which can affect MR images. Recent advances in technology have brought to the market hybrid devices in which the two modalities are set side by side along a single bed or in which solid-state detector rings are integrated into the MRI gantry. While the clinical and added value of such hybrid devices is still to be demonstrated, the ability to acquire perfectly registered images from both modalities in a single imaging session offers tangible advantages to patients needing to undergo both examinations as part of their clinical workup. Such cases include patients with head and neck cancers, prostate cancers, patients undergoing staging, and monitoring of extensive and high-risk breast cancers and gynecological cancers, and pediatric oncology cases where repeated studies are required and the reduction of radiation exposure by replacing the CT component of PET/CT scans with MRI is particularly important. It is anticipated that wider adoption of PET/MR imaging will occur once the added value and improvement in diagnostic accuracy have been demonstrated in prospective clinical studies. The introduction of new PET tracers is also likely to lead to wider clinical use of PET/MR. One example is the recent introduction of 18F-labeled NaF for bone metastases that makes PET in combination with MR imaging ideal for the characterization of bone lesions. The development of other new tracers may extend the use of PET/MR to domains other than oncology, such as cardiology and neurology.