PET/MR Oncologic Whole Body Workflow Optimization

Objectives Simultaneous PET/MRI scanners can combine the functional information from PET with the soft tissue definition of MRI beyond what PET/CT hybrid systems offer currently. The time required to screen patients for MR safety, position the MR coils and scan with patient tailored whole body (WB) and organ specific MR sequences can add significantly to total exam time. Overall workflow optimization is discussed for WB time-of-flight (TOF) oncologic imaging on the GE Signa PET/MRI scanner.

Methods Efficient workflow is essential for minimizing technologist radiation exposure. Due to the added steps of placing coils, respiratory bellows, ear protection, etc., the patient is positioned 45 min post injection for a targeted PET emission acquisition starting approx. 60min post injection. The procedure is reviewed and the patient is screened for MR safety. While the patient changes into MR compatible clothes, the exam is set up at the console. The exam begins with MR Ax, Sag and Cor localizer scans over 4 MR stations. Stations are pasted together to resemble a CT localizer scan and used for both PET bed positioning and prescribing of MR sequences. The PET scan is prescribed first and sets the region for MR scans within each PET bed. A WB scan is 6-8 beds with 3-4 repeating MR sequences confined to each PET bed, lasting 3-4min each. These include the attenuation correction scan, Ax DWI, Cor DWI, and Cor SSFSE. MR slice thickness and field of view are maintained for every PET bed to allow for pasting of images for WB PET/MR image fusion. Breath holds are utilized For MR sequences over the chest and abdomen. Upon PET completion, MR contrast injection and WB Ax LAVA-Flex sequences complete the scan.

Results WB oncologic PET/MR procedure times have been reduced from >120min to 45-60min and will continue to improve as sequence optimization is established.

Conclusions Issues being assessed include determining ideal sequence selection while minimizing MR artifacts, allowing for dedicated scanning tailored to patient history including higher resolution, organ specific imaging, reduction of scan time, and minimizing image artifacts.