AbstractObjective To compare the leaf open time (LOT) parameters and γ passing rates between the 4.0.4 and 4.2.3 helix Tomotherapy planning systems and evaluate the improvement. Methods Retrospective comparison of the treatment plans of 345 cases selected by 4.0.4 and 4.2.3 versions was performed. The Machine Specific Sinogram of each plan was extracted from the archived plan file to calculate the LOT. The evaluated LOT parameters included the projection time, the maximum LOT, the mean non-zeros time, the time difference between the projection time and the maximum LOT, the relative count of leaves with LOT greater than maximum LOT minus 5ms, the relative count of leaves with LOT lower than 100ms and the beam on time. The γ passing rate (criteria:3mm/3%, 10% threshold and global error) and the LOT parameters between two version systems were evaluated with the independent t-test. The relationship between the LOT parameters and γ passing rate was analyzed by the multiple linear regression method. Results The γ passing rate of the Ver 4.0.4 system was 97.86%, significantly lower than 98.6% of the Ver 4.2.3 system (P<0.001). The time gap between the projection time and the maximum LOT of the Ver 4.2.3 system was significantly less than that of the Ver 4.0.4 system (1 ms vs. 11 ms, P<0.001). For the Ver 4.0.4 system, the multiple linear regression method showed that the maximum LOT ratio and the beam on time were negatively correlated with the γ passing rate (both P<0.001). However, for the Ver 4.2.3 system, only the beam on time showed a negative correlation with the γ passing rate (P<0.001). Conclusion The γ passing rate of the Ver 4.2.3 system is significantly higher than that of the Ver 4.0.4 system. The decrease of γ passing rate caused by the leaves near the maximum LOT is properly resolved in the new version system.
Yue Qi,Duan Jimei,Wang Zhiwei et al. Comparison of validation results and leaf open time before and after upgrading of helix tomotherapy planning system[J]. Chinese Journal of Radiation Oncology, 2021, 30(4): 382-386.
Yue Qi,Duan Jimei,Wang Zhiwei et al. Comparison of validation results and leaf open time before and after upgrading of helix tomotherapy planning system[J]. Chinese Journal of Radiation Oncology, 2021, 30(4): 382-386.
[1] Mackie TR, Holmes T, Swerdloff S, et al. Tomotherapy:a new concept for the delivery of dynamic conformal radiotherapy[J]. Med Phys, 1993, 20(6):1709-1719. DOI:10.1118/1.596958. [2] Fenwick JD, Tomé WA, Jaradat HA, et al. Quality assurance of a helical tomotherapy machine[J]. Phys Med Biol, 2004, 49(13):2933-2953. DOI:10.1088/0031-9155/49/13/012. [3] Thomas SD, Mackenzie M, Field GC, et al. Patient specific treatment verifications for helical tomotherapy treatment plans[J]. Med Phys, 2005, 32(12):3793-3800. DOI:10.1118/1.2134929. [4] Langen KM, Papanikolaou N, Balog J, et al. QA for helical tomotherapy:report of the AAPM Task Group 148[J]. Med Phys, 2010, 37(9):4817-4853. DOI:10.1118/1.3462971. [5] Neilson C, Klein M, Barnett R, et al. Delivery quality assurance with ArcCHECK[J]. Med Dosim, 2013, 38(1):77-80. DOI:10.1016/j.meddos.2012.07.004. [6] Low DA, Harms WB, Mutic S, et al. A technique for the quantitative evaluation of dose distributions[J]. Med Phys, 1998, 25(5):656-661. DOI:10.1118/1.598248. [7] Templeton AK, Chu JC, Turian JV. The sensitivity of ArcCHECK-based gamma analysis to manufactured errors in helical tomotherapy radiation delivery[J]. J Appl Clin Med Phys, 2015, 16(1):4814. DOI:10.1120/jacmp.v16i1.4814. [8] Westerly DC, Soisson E, Chen Q, et al. Treatment planning to improve delivery accuracy and patient throughput in helical tomotherapy[J]. Int J Radiat Oncol Biol Phys, 2009, 74(4):1290-1297. DOI:10.1016/j.ijrobp.2009.02.004. [9] Sevillano D, Minguez C, Sanchez A, et al. Measurement and correction of leaf open times in helical tomotherapy[J]. Med Phys, 2012, 39(11):6972-6980. DOI:10.1118/1.4762565. [10] Chen Q, Westerly D, Fang Z, et al. TomoTherapy MLC verification using exit detector data[J]. Med Phys, 2012, 39(1):143-151. DOI:10.1118/1.3666762. [11] Ezzell GA, Burmeister JW, Dogan N, et al. IMRT commissioning:multiple institution planning and dosimetry comparisons, a report from AAPM task group 119[J]. Med Phys, 2009, 36(11):5359-5373. DOI:10.1118/1.3238104. [12] Binny D, Lancaster CM, Harris S, et al. Effects of changing modulation and pitch parameters on tomotherapy delivery quality assurance plans[J]. J Appl Clin Med Phys, 2015, 16(1):87-105. DOI:10.1120/jacmp.v16i5.5282. [13] Smilowitz JB, Dunkerley D, Hill PM, et al. Long-term dosimetric stability of multiple TomoTherapy delivery systems[J]. J Appl Clin Med Phys, 2017, 18(3):137-143. DOI:10.1002/acm2.12085.