Room: Exhibit Hall | Forum 7
Purpose: To investigate dosimetric and radiobiological impact of residual setup errors on the carcinoma cervix IIB patients treated with VMAT using in-house DVH Analyzer.
Methods: A cohort of 16 carcinoma cervix (stage IIB) patients were selected for this study. Plans were generated on Eclipse TPS (version 13.6) with different uncertainties ranging from -10 mm to 10 mm in all directions, namely lateral (X), longitudinal (Y) and Vertical (Z) in an interval of 1 mm. MATLAB based in-house program "DVH Analyzer" was written to analyze bulk DVHs generated from uncertainty module of TPS with known uncertainties. "DVH Analyzer" was tested and validated on Dell Precision T5610 CPU with 32GB of RAM. DVHs of plans were analyzed using "DVH Analyzer" for different dosimetric parameters of organs at risk (OARs) (Bladder, Rectum) and TCP of PTV.
Results: D2cc, D15% of bladder in X, Y and Z directions varies (in percentage) from minimum to maximum as (-0.14 to 0.18, -0.56 to 0.36), (-0.08 to 0.36,-0.05 to 0.49), and (-.2.45 to 1.18, -9.70 to 1.59) respectively. Similarly, D2cc and V50Gy of rectum in X, Y and Z directions varies (in percentage) from minimum to maximum as (-0.01 to 0.58, -0.01 to 3.46), (-0.76 to 1.06,-2.48 to 9.02) and (-21.56 to 3.38, -12.90 to 32.51) respectively. Maximum deviation (in percentage) observed in TCP of PTV as 22.12, 97.62 and 99.99 in X, Y and Z directions respectively.
Conclusion: Our study concludes that patient setup errors are more sensitive for PTV and OARs in Y and Z directions as compared to X direction. TCP is greatly affected with the errors beyond 5 mm in all directions. The in-house "DVH Analyzer" is very efficient in processing and analyzing bulk DVHs data.
Dose Volume Histograms, Setup Errors, Rotational Therapy
TH- External beam- photons: treatment planning/virtual clinical studies