Data visualization technique was applied to analyze the daily QA results of photon and electron beams. Special attention was paid to any trend the beams might display. A Varian Trilogy Linac equipped with dual photon ...Data visualization technique was applied to analyze the daily QA results of photon and electron beams. Special attention was paid to any trend the beams might display. A Varian Trilogy Linac equipped with dual photon energies and five electron energies was commissioned in early 2010. Daily Linac QA tests including the output constancy, beam flatness and symmetry (radial and transverse directions) were performed with an ionization chamber array device (QA Beam Checker Plus, Standard Imaging). The data of five years were collected and analyzed. For each energy, the measured data were exported and processed for visual trending using an in-house Matlab program. These daily data were cross-correlated with the monthly QA and annual QA results, as well as the preventive maintenance records. Majority of the output were within 1% of variation, with a consistent positive/upward drift for all seven energies (^+0.25% per month). The baseline of daily device is reset annually right after the TG-51 calibration. This results in a sudden drop of the output. On the other hand, the large amount of data using the same baseline exhibits a sinusoidal behavior (period = 12 months;amplitude = 0.8%, 0.5% for photons, electrons, respectively) on symmetry and flatness when normalization of baselines is accounted for. The well known phenomenon of new Linac output drift was clearly displayed. This output drift was a result of the air leakage of the over-pressurized sealed monitor chambers for the specific vendor. Data visualization is a new trend in the era of big data in radiation oncology research. It allows the data to be displayed visually and therefore more intuitive. Based on the visual display from the past, the physicist might predict the trend of the Linac and take actions proactively. It also makes comparisons, alerts failures, and potentially identifies causalities.展开更多
This study is to investigate three common potential setup uncertainties during Linac commissioning and annual QA and to evaluate how these uncertainties propagate into the quality of beam profiles and patient dosimetr...This study is to investigate three common potential setup uncertainties during Linac commissioning and annual QA and to evaluate how these uncertainties propagate into the quality of beam profiles and patient dosimetry using gamma analysis. Three uncertainty scenarios were purposely introduced for gantry position tilted from 0˚- 3˚(scenario 1), isocenter position misaligned from 0 - 6 mm (scenario 2) and SAD changed from 99.5 - 103 cm (scenario 3). A 60 × 60 × 60 cm<sup>3</sup> water phantom cube was created to replicate a 3D water tank in VarianEclipse (V.11) treatment planning system (Varian Medical Systems, Palo Alto, CA). For each scenario, beam data profiles (crossline and diagonal) and PDD curves were calculated at different field sizes and depths for three energies: 6 MV, 6 MV-FFF and 10 MV-FFF. Gamma analysis method was used to compare a total of 263 profiles to baseline using a 1%/1mm parameter with 90% gamma passing rate criteria. For scenario 1, a ≥90% gamma passing rate and ≤1% dose difference were seen on both crossline and diagonal profiles, and PDD curves for gantry tilted up to 2˚. For 3˚degree tilt, the gamma passing rate decreased to ≤90% at depth of ≥20 cm for 6MV/6MV-FFF and depth of ≥12 cm for 10MV-FFF. For scenario 2, a ≤90% gamma passing rate and ≥1% dose difference were seen at depths from d<sub>max</sub> to 20 cm for all energies. For depths ≥20 cm, mostly ≥90% gamma passing rate and ≤1% dose difference were seen. For scenario 3, a ≥90% gamma passing rate and ≤1% dose difference were seen on ≤4 mm isocenter misalignments for all energies. In summary, gamma analysis of the beam profiles is a very sensitive test for SAD deviation scenarios and can reveal issues of sub millimeter setup uncertainty. However, it is not as sensitive for isocenter misalignment scenarios. The test is also more sensitive for FFF beams than flattening filter beams.展开更多
Objective To test a quality assurance(QA)DVS solution-DVS based on a linac electronic field imaging device(EPID)and evaluate its accuracy and ease of use.Methods All of the QA items that do not require the dedicated Q...Objective To test a quality assurance(QA)DVS solution-DVS based on a linac electronic field imaging device(EPID)and evaluate its accuracy and ease of use.Methods All of the QA items that do not require the dedicated QA phantom in the DVS solution were tested.Test methods were chosen based on the test items:for the collimator rotation center,the coincidence of the radiation and mechanical,mechanical flatness/symmetry and MLC transmission were compared with the existing QA solution;for the leaf position accuracy and repeatability,the original preset beam fields and fields adjusted by 1 mm were compared.Results The collimator rotation center by the DVS solution is similar to the existing solution.For coincidence of radiation and mechanical,the DVS solution provides more data,including 3D distance.For the flatness/symmetry property,the DVS solution can display more graphics,but the overall data is less than the ion-chamber matrix solution.The DVS solution can directly obtain the MLC transmission value and quickly and intuitively measure the position accuracy of the MLC.However,the repeatability is slightly worse.Conclusion The DVS solution can improve the QA work efficiency and reduce workload,and there are more opportunities for improvement.展开更多
文摘Data visualization technique was applied to analyze the daily QA results of photon and electron beams. Special attention was paid to any trend the beams might display. A Varian Trilogy Linac equipped with dual photon energies and five electron energies was commissioned in early 2010. Daily Linac QA tests including the output constancy, beam flatness and symmetry (radial and transverse directions) were performed with an ionization chamber array device (QA Beam Checker Plus, Standard Imaging). The data of five years were collected and analyzed. For each energy, the measured data were exported and processed for visual trending using an in-house Matlab program. These daily data were cross-correlated with the monthly QA and annual QA results, as well as the preventive maintenance records. Majority of the output were within 1% of variation, with a consistent positive/upward drift for all seven energies (^+0.25% per month). The baseline of daily device is reset annually right after the TG-51 calibration. This results in a sudden drop of the output. On the other hand, the large amount of data using the same baseline exhibits a sinusoidal behavior (period = 12 months;amplitude = 0.8%, 0.5% for photons, electrons, respectively) on symmetry and flatness when normalization of baselines is accounted for. The well known phenomenon of new Linac output drift was clearly displayed. This output drift was a result of the air leakage of the over-pressurized sealed monitor chambers for the specific vendor. Data visualization is a new trend in the era of big data in radiation oncology research. It allows the data to be displayed visually and therefore more intuitive. Based on the visual display from the past, the physicist might predict the trend of the Linac and take actions proactively. It also makes comparisons, alerts failures, and potentially identifies causalities.
文摘This study is to investigate three common potential setup uncertainties during Linac commissioning and annual QA and to evaluate how these uncertainties propagate into the quality of beam profiles and patient dosimetry using gamma analysis. Three uncertainty scenarios were purposely introduced for gantry position tilted from 0˚- 3˚(scenario 1), isocenter position misaligned from 0 - 6 mm (scenario 2) and SAD changed from 99.5 - 103 cm (scenario 3). A 60 × 60 × 60 cm<sup>3</sup> water phantom cube was created to replicate a 3D water tank in VarianEclipse (V.11) treatment planning system (Varian Medical Systems, Palo Alto, CA). For each scenario, beam data profiles (crossline and diagonal) and PDD curves were calculated at different field sizes and depths for three energies: 6 MV, 6 MV-FFF and 10 MV-FFF. Gamma analysis method was used to compare a total of 263 profiles to baseline using a 1%/1mm parameter with 90% gamma passing rate criteria. For scenario 1, a ≥90% gamma passing rate and ≤1% dose difference were seen on both crossline and diagonal profiles, and PDD curves for gantry tilted up to 2˚. For 3˚degree tilt, the gamma passing rate decreased to ≤90% at depth of ≥20 cm for 6MV/6MV-FFF and depth of ≥12 cm for 10MV-FFF. For scenario 2, a ≤90% gamma passing rate and ≥1% dose difference were seen at depths from d<sub>max</sub> to 20 cm for all energies. For depths ≥20 cm, mostly ≥90% gamma passing rate and ≤1% dose difference were seen. For scenario 3, a ≥90% gamma passing rate and ≤1% dose difference were seen on ≤4 mm isocenter misalignments for all energies. In summary, gamma analysis of the beam profiles is a very sensitive test for SAD deviation scenarios and can reveal issues of sub millimeter setup uncertainty. However, it is not as sensitive for isocenter misalignment scenarios. The test is also more sensitive for FFF beams than flattening filter beams.
文摘Objective To test a quality assurance(QA)DVS solution-DVS based on a linac electronic field imaging device(EPID)and evaluate its accuracy and ease of use.Methods All of the QA items that do not require the dedicated QA phantom in the DVS solution were tested.Test methods were chosen based on the test items:for the collimator rotation center,the coincidence of the radiation and mechanical,mechanical flatness/symmetry and MLC transmission were compared with the existing QA solution;for the leaf position accuracy and repeatability,the original preset beam fields and fields adjusted by 1 mm were compared.Results The collimator rotation center by the DVS solution is similar to the existing solution.For coincidence of radiation and mechanical,the DVS solution provides more data,including 3D distance.For the flatness/symmetry property,the DVS solution can display more graphics,but the overall data is less than the ion-chamber matrix solution.The DVS solution can directly obtain the MLC transmission value and quickly and intuitively measure the position accuracy of the MLC.However,the repeatability is slightly worse.Conclusion The DVS solution can improve the QA work efficiency and reduce workload,and there are more opportunities for improvement.
