Plan Quality Comparison between C-Arm and PET-Linac on Pancreatic Cases to Consider Known Abdominal Imaging Advantages
Abstract
Purpose
The RefleXion linear accelerator utilizes a 6 MV FFF beam with a binary multi-leaf collimator and a pair of Y- jaws with clinical openings of 1 cm and 2 cm. The machine is equipped with a 16-slice on-board fan-beam CT and an on- board PET detector system. For non-PET cases, the machine offers superior diagnostic quality images compared to cone- beam CTs on C-arm linacs. This makes localization of abdominal cases more robust. The purpose of this work is to evaluate plan quality of the RefleXion system to that of C-arm linacs for conventional pancreatic treatments. through DVH statistics, for patients treated for pancreatic cancer.
Methods
Five pancreatic treatment plans delivered on the RefleXion linac were re-planned on either a Novalis TX or a TrueBeam C-arm linac. Each plan consisted of 2-3 treatment arcs delivering a total of 5040 cGy in 28 fractions. PTV coverage and tolerances for Organs-at-Risk (OARs) such as the liver, small and large bowel, left and right kidneys, stomach, and spinal canal were evaluated.
Results
RefleXion plans compared with C-arm linear accelerator plans showed an average decrease (standard deviation) in PTV V100% by 2.0% (5.8%). Liver mean dose increased by 125 cGy (55 cGy), small and large bowel maximum doses increased by by 84 cGy (186 cGy) and 24 cGy (56 cGy), respectively, stomach maximum dose increased by 5 cGy (61 cGy), and left and right kidney mean dose by 102 cGy (286 cGy) and 141 cGy (154 cGy), respectively.
Conclusion
This work showed a DVH comparisons for pancreatic plans generated with a RefleXion and with C-arm linear accelerator. RefleXion plans showed decreased PTV coverage and increased OAR maximum and mean doses. However, all RefleXion plans met DVH planning criteria and the improved abdominal visualization can be considered for certain cases.