ESTRO 2024 - Abstract Book

S3967

Physics - Image acquisition and processing

ESTRO 2024

• 5 radiotherapy dosimetrists: discussions here focused on anatomy variances between the different scans, and how to present data meaningfully. This group also raised the importance of training, competence and confidence in dealing with PET-CT.

Results:

Local guidelines were created accounting for the following:

Radiologist recommendations:

• Selection of an appropriate PET dataset that has had SUV calculated (avoidance of “NAC” datasets) in post processing to visualise the scan as per radiology report. • Selection of appropriate SUV thresholds (suggesting SUV max 7 or 10 for FDG PET, 15+ for PSMA). • Importance of being able to set and fix the SUV threshold when viewing and relate this to the PET-CT imaging report. • Highlighted the relevance of the functional imaging relating to the anatomy at the time of PET-CT acquisition. • Highlighted limitations of PET-CT resolution. • Noted that patient position and couch top varies between PET-CT and CT Planning Scan, especially with anatomical variations (such as intentional bladder fill for radiotherapy).

Clinical Oncologist recommendations:

• Easy navigation and safe visualisation of the secondary datasets to limit confusion. • To be able to view the PET-CT scan simultaneously with the planning CT to appreciate the differences between the datasets where they exist. • Consideration of peer review by a radiologist for complex cases. • Selection of the most appropriate PET-CT Dataset(s) to assist with delineation. For example, a lymphoma specialist recommended the dataset of “worst disease burden”.

Radiotherapy recommendations (physics and dosimetry):

• Ensure appropriate training for use of PET-CT in planning. • Use software that has dedicated support for the use of PET-CT if possible such as MIM Maestro. • Staff should feel competent in using the datasets per radiologist and oncologist recommendations. • Image match should be prioritised to the area of anatomical interest. • Suggest avoiding overlaying the PET functional data on the planning CT so that variances in anatomy between scans can be adequately appreciated and corrected for. • Have access to nuclear medicine specialists to ask for help if required.

Conclusion:

Using PET-CT in radiotherapy treatment planning is complex but can be done safely especially when partnering with radiology professionals to guide practice. Recommendations from radiology should be considered and coupled with requirements from the prescribing clinical oncologist to optimise utilisation.