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SU‐E‐T‐505: Inter‐Comparison of Clinical Plans Created On Truebeam with Trilogy and Clinac
Author(s) -
Sharma M,
Wu Y,
Kim S
Publication year - 2015
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4924867
Subject(s) - truebeam , trilogy , medicine , nuclear medicine , dosimetry , linear particle accelerator , computer science , beam (structure) , physics , artificial intelligence , optics
Purpose The purpose of this study is to investigate the dosimetric differences in clinical treatment plans when machine parameters are switched from Varian Truebeam to older Varian models and vice‐versa. This is used to determine the clinically‐safe limits to directly transfer patients from Truebeam to Trilogy or Clinac. Methods Thirty‐two patients with cancer of different treatment sites such as lung, head‐and‐neck, prostate and breast were studied. The clinically approved IMRT, VMAT or 3D conformal treatment plans were delivered either on Truebeam or Clinac/Trilogy. Keeping the monitor units, fraction size and other machine parameters the same, the plans were recomputed on a different Varian linear accelerator (e.g., Truebeam plans were recomputed on Trilogy and vice‐versa). The plans comparison was done using the target D98 and normal organ D2, D10, D20, D30, D50 and D70 dose metrics. Results The perfraction dose‐difference in the PTV‐D98 for all 32 patients varied from 0.01 to −0.06 Gy with median being −0.04 Gy. For a 2Gy/fraction treatment course, this would be maximum PTV‐D98 dose‐difference of 6 cGy/fraction or 30 cGy/5fractions. For organs‐at‐risks the maximum per‐fraction dosedifference in D2, D5, D10, D20, D30, D50 and D70 between Truebeam and Trilogy/Clinac plans varied from 0.06 to −0.07 Gy with median being with — 0.02 Gy. The 3D‐CRT plans had relatively lower dose‐difference in comparison to IMRT and VMAT plans. The dose computed on Truebeam was systematically lower than the dose computed on Trilogy/ Clinac. Conclusions for conventional fractionation schedules, assuming the maximum uncertainty of <2%, it is clinically safe to switch the treatment machine for 5 fractions. For hypo‐fractionated treatments with higher dose per‐fraction, plans may need to be revisited before switching the linear accelerator from Truebeam to Clinac/Trilogy or vice‐versa.