ESTRO 2024 - Abstract Book

S5519

RTT - Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO 2024

The result showed that setup of stream 1 had a significant larger translational deviation in R-L (p<0.001), TVE (p<0.001)for both femoral heads. A significant larger rotation deviation in pitch (p=0.03) was also shown compared to stream 2 and 3. The incidence rate of translational deviation (R-L, S-I and A-P) exceeding 5mm was 7%, 1%, 6% for right femur (RF) and 7%,3%,11% for left femur (LF) in stream 1; 0%, 1%, 13% for RF and 0%, 9%, 13% for LF in stream 2; 0%, 3%, 0% for RF and 0%, 2%, 1% for LF in stream 3. Moreover, the incidence rate of rotation deviation (pitch, roll and yaw) more than 2° was 14%, 16%, 6% for RF and 21%,26%,4% for LF in stream 1, 1%, 6%, 0% for RF and 9%, 11%, 1% for LF in stream 2, 9%, 5%, 2% for RF and 11%, 5%, 2% for LF in stream 3.

Conclusion:

In comparison to the reproducibility of prostate, seminal vesicle, bladder and rectum, femurs usually have the least importance in image-guided prostate radiotherapy because of their high dose tolerance. This study showed that there were cases with translation more than 5mm and rotation more than 2° on both femurs, which didn’t affect the treatment as long as the target and the high dose volume of bladder and rectum were in place. However, in proton therapy, the reproducibility of femoral heads, which located in the routine lateral opposing beam path for prostate proton therapy, becomes crucial as it directly affects the dose and range uncertainty.

Among our various setups, stream 1 exhibited the most significant translational offset. Technically, these resulting uncertainties can be compensated by using calculated robustness in proton therapy treatment plan, typically set at