Clinical Research Review of Scheduled vs. Completed PET/MRI Scans

Objectives Simultaneous PET/MRI scanners are still new to the research and clinical settings. It can be informative to investigate the total scheduled scans vs. the total scans that are completed due to issues unique to PET/MRI hybrid technology. Claustrophobia, MRI safety screening failures, and unforeseen hardware or software malfunctions can be enough to necessitate premature termination of a PET/MRI scan. We evaluated clinical research studies conducted at our institution over 19 months using the GE SIGNA PET/MRI scanner and insight into reducing the overall number of scan failures and cancellations is discussed.

Methods All consented participants from 13 different IRB-approved protocols were reviewed. They are categorized into the following groups: participants who consented and successfully completed the study, participants who consented but either did not schedule or cancelled scan appointments, participants seen for the scan appointment but not injected with radiotracer and participants injected with radiotracer but unable to complete the imaging procedure.

Results A total of 238 participants were consented between May 2014 and January 2016. A total of 210 participants (88.2%) were injected and completed the study, while 28 (11.8%) did not. From the latter group, 8 participants (3.4%) were either no longer eligible at time of scan or declined to participate, 9 participants (3.8%) could not be injected with radiotracer, usually due to safety screening or equipment failure, and 11 participants (4.6%) were injected but did not complete imaging, mainly due to equipment failure or claustrophobia. Of note, 10 of these 28 participants (4.2%) did not complete the study due to scanner malfunctions. Discussion: Participants were unable to be injected with radiotracer for various reasons including safety screening failure, claustrophobia, and scanner mechanical or software malfunctions. These issues can be prevented with proper prescreening before arrival, premedication for claustrophobia and allowing enough time at the start of the day for PET and MRI quality assurance testing and additional calibrations/repairs as needed. The worst-case scenario of injecting a participant with radiotracer yet not completing the PET/MRI scan is more difficult to avoid. Reasons for this include insurmountable scanner malfunctions (due to either PET, MRI, or software component issues), unexpected claustrophobia, power loss due to a lightning strike to the building, and one subject experiencing too much pain to remain still for scanning. Many of these issues are unique to PET/MRI compared to PET/CT hybrid imaging or MRI alone. Claustrophobia may not be an issue in a wider bore PET/CT scanner or a dedicated MRI scanner with minimal coil coverage but a more significant issue for whole body PET/MRI with additional coils, longer scan times and a smaller bore size. As these hybrid scanners are still relatively new, there can be more hardware and software issues coupled with fewer experienced engineers available for diagnostics and increased down time for repairs. An important factor to consider is the number of scans rescheduled due to scanner down time. Conclusions: -