Minimizing Motion In SPECT/CT Images from Maa Mapping and Y-90 Post Injection
Abstract
Purpose
The NRC reported that between 2015 to 2024 nearly 50% of Medical Events were Y-90 related. In our institution we started using SPECT/CT 3D images from 99mTc-MAA mappings to determine target delineation, and extrahepatic shunting to the lung/gastrointestinal tract. We found that a large percentage of the images were clearly mis-registered by up to 3cm primarily attributable to the patient motion between the CT scan and the slower SPECT scan time (0.5 vs 20 minutes respectively). We speculate that some of these NRC Medical Events may be caused by this misregistration. Although misregistered scans can be manually corrected using special fusion software, this is prone to operator error. The purpose of this research was to eliminate any patient motion.
Methods
Patients undergoing MMA mapping or post Y-90 treatment were imaged on a GE Discovery NM/CT 670 scanner. Initial motion correction of the raw data was done on the GE Xeleris 3 workstation. These images were then exported to our MIM system v7.4.1 software. Upon review of the images in 3D with MIM software, it was obvious there was misalignment between the SPECT/CT images. The MIM software allowed us to manually correct the registration.
Results
After requiring the physicist attend an actual SPECT/CT session, they noticed that the default CT Protocol the announced “Breath in and hold it”. This has continued for several years before it was noticed. Images of 10 patients before and after stopping the auto announcement were analyzed. The studies indicated that the required post correction was reduced upon utilization of free breathing during the data acquisition.
Conclusion
Have a Physicist attend the CT scan to ensure it does not say “Breath in and hold it”. Confirm patient can lay still for 30 minutes e.g. knees raised. Perform MAA mapping and post Y-90 injection dosimetry.