ESTRO 2021 Abstract Book

S1264

ESTRO 2021

PreciseRTx software and first predicted plans (FPPs) were created. Dose and volume changes in PTV and OARs were compared with the original plan and treatment was initiated. After the daily treatment, another CT image (PostCT) was taken from the patients, and second predicted plans (SPPs) were created transferring the original plans and structures to the PostCT with PreciseRTx. Dose and volume differences in OAR and PTV were examined and compared with FPPs. Results Ten patients were included in the analysis. No clinically significant differences were observed between the original plans and the FPPs about PTV coverage and the maximum point doses within the PTV (95,8% vs. 96,4% and 41,3Gy vs. 41.3Gy respectively). When the FPPs and SPPs were compared, there were no clinical differences for PTVs. The bladder volumes in the original CTs were not statistically different from their volume in PreCT (p=0.08) and there was no statistically significant difference for bladder dose criteria (all p>0.05). However average bladder volumes increased from 171,4cc to 393,9cc after the treatment and this was statistically significant (p<0,001). This increase in volume caused a decrease in bladder doses between FPPs and SPPs (V50%: 25,8% vs. 24,3%; V100%: 3,02% vs. 1,7%). In terms of rectum volumes and doses, statistically significant differences were not found between the original CTs and PreCT, and between the PreCT and PostCT (p>0.05). Conclusion As long as there is a strict preparation for OARs and accurate tracking for prostate SBRT, daily adaptation might not be feasible and necessary. PO-1540 Wireless Device for Adaptive Planning Based upon Thermoacoustic Range Estimates-Benchtop Validation S. Patch 1,2 , M. Naranaswamy 3 1 UW-Milwaukee, Physics, Milwaukee, USA; 2 Acoustic Range Estimates, All, Milwaukee, USA; 3 Swamy Enterprises, All, Milwaukee, USA Purpose or Objective Transitioning thermoacoustic range verification from benchtop experiments with cumbersome research equipment to clinical practice is the purpose of our work. A wireless device for thermoacoustic range verification with correlation to online ultrasound images has been developed for initial application to adaptive planning (Fig a). Materials and Methods A custom detector with dimensions 7 x 5.5 x 3.5 cm (NucSafe) requiring 5V power supply replaces the 0.5 m long prompt gamma detector that required -2 kV. The new detector provides both analog and digital signals to quantify proton pulse shape and serve as a trigger. Oscilloscopes are replaced by a wireless data acquisition board (DAQ) with vertical resolution of 38 uV. 4-6 acoustic channels are amplified, whereas compact gamma detector signal is not amplified. Data is acquired continuously for up to 30 minutes and stored on a secure data card for retrieval via a serial port after the exam. Two different types of transducers provide broadband response in a compact form factor. Results A custom receive chain provides improved 10-18 dB greater sensitivity over the relevant frequency band (10- 100 kHz, Fig b). Transducers positioned to either side of the ultrasound imaging array are up to 8 dB more sensitive to low frequencies (Fig c). The new DAQ provides 10 dB greater amplification. A wireless ultrasound imaging array (Clarius P4-1) provides greater imaging depth, 30 cm vs 7 cm, and smaller footprint (Fig. d).