Purpose: Patient-specific QA (PSQA) measurements for carbon ion radiotherapy (CIRT) are critical components of processes designed to identify discrepancies between calculated and delivered doses. We report t...Purpose: Patient-specific QA (PSQA) measurements for carbon ion radiotherapy (CIRT) are critical components of processes designed to identify discrepancies between calculated and delivered doses. We report the results of PSQA conducted at the QST Hospital during the period from September 2017 to March 2018. Methods: We analyzed PSQA results for 1448 fields for 10 disease sites with various target volumes, target depths and number of energy layers. For the PSQA, all the planned beams were recalculated on a water phantom with treatment planning software. The recalculated dose distributions were compared with the measured distributions using a 2D ionization chamber array at three depths, including 95% of the area of the prescription dose. These recalculated dose distributions were evaluated using the 3%/3mm gamma index with a passing threshold of 90%. Results: The passing rates for prostate, head and neck, and bone and soft tissue were 96.8%, 99.3%, and 91.7%, respectively. Additionally, 94.7% of lung plans with low energy beams passed. Overall, the CIRT in the QST Hospital reached a high passing rate of more than 95%. Although the remaining 5% failed to pass, there was no dependence between measurement depth and disease sites in these failures. Conclusion: Using PSQA measurements, we confirmed consistency between the planned and delivered doses for CIRT using the full energy scanning method.展开更多
Using quadrupole mass spectrometer,calibration gas PFTBA was turned on in constant flow to get the signal intensity,and off to get the noise value.Different scan time and dwell time was used separately for full scan m...Using quadrupole mass spectrometer,calibration gas PFTBA was turned on in constant flow to get the signal intensity,and off to get the noise value.Different scan time and dwell time was used separately for full scan mode and SIM to find out the effect of scan rate on signal intensity and noise.展开更多
文摘Purpose: Patient-specific QA (PSQA) measurements for carbon ion radiotherapy (CIRT) are critical components of processes designed to identify discrepancies between calculated and delivered doses. We report the results of PSQA conducted at the QST Hospital during the period from September 2017 to March 2018. Methods: We analyzed PSQA results for 1448 fields for 10 disease sites with various target volumes, target depths and number of energy layers. For the PSQA, all the planned beams were recalculated on a water phantom with treatment planning software. The recalculated dose distributions were compared with the measured distributions using a 2D ionization chamber array at three depths, including 95% of the area of the prescription dose. These recalculated dose distributions were evaluated using the 3%/3mm gamma index with a passing threshold of 90%. Results: The passing rates for prostate, head and neck, and bone and soft tissue were 96.8%, 99.3%, and 91.7%, respectively. Additionally, 94.7% of lung plans with low energy beams passed. Overall, the CIRT in the QST Hospital reached a high passing rate of more than 95%. Although the remaining 5% failed to pass, there was no dependence between measurement depth and disease sites in these failures. Conclusion: Using PSQA measurements, we confirmed consistency between the planned and delivered doses for CIRT using the full energy scanning method.
文摘Using quadrupole mass spectrometer,calibration gas PFTBA was turned on in constant flow to get the signal intensity,and off to get the noise value.Different scan time and dwell time was used separately for full scan mode and SIM to find out the effect of scan rate on signal intensity and noise.
