Quantification of residual dose estimation error on log file-based patient dose calculation.

PURPOSE The log file-based patient dose estimation includes a residual dose estimation error caused by leaf miscalibration, which cannot be reflected on the estimated dose. The purpose of this study is to determine this residual dose estimation error. METHODS AND MATERIALS Modified log files for seven head-and-neck and prostate volumetric modulated arc therapy (VMAT) plans simulating leaf miscalibration were generated by shifting both leaf banks (systematic leaf gap errors: ±2.0, ±1.0, and ±0.5mm in opposite directions and systematic leaf shifts: ±1.0mm in the same direction) using MATLAB-based (MathWorks, Natick, MA) in-house software. The generated modified and non-modified log files were imported back into the treatment planning system and recalculated. Subsequently, the generalized equivalent uniform dose (gEUD) was quantified for the definition of the planning target volume (PTV) and organs at risks. RESULTS For MLC leaves calibrated within ±0.5mm, the quantified residual dose estimation errors that obtained from the slope of the linear regression of gEUD changes between non- and modified log file doses per leaf gap are in head-and-neck plans 1.32±0.27% and 0.82±0.17Gy for PTV and spinal cord, respectively, and in prostate plans 1.22±0.36%, 0.95±0.14Gy, and 0.45±0.08Gy for PTV, rectum, and bladder, respectively. CONCLUSIONS In this work, we determine the residual dose estimation errors for VMAT delivery using the log file-based patient dose calculation according to the MLC calibration accuracy.

[1]  Uulke A van der Heide,et al.  An accurate calibration method of the multileaf collimator valid for conformal and intensity modulated radiation treatments. , 2004, Physics in medicine and biology.

[2]  C. Fiorino,et al.  Accuracy of dose calculation algorithms for static and rotational IMRT of lung cancer: A phantom study. , 2015, Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics.

[3]  Tony Teke,et al.  A Varian DynaLog file-based procedure for patient dose-volume histogram-based IMRT QA. , 2014, Journal of applied clinical medical physics.

[4]  Benjamin E Nelms,et al.  Per-beam, planar IMRT QA passing rates do not predict clinically relevant patient dose errors. , 2011, Medical physics.

[5]  A Agnew,et al.  Monitoring daily MLC positional errors using trajectory log files and EPID measurements for IMRT and VMAT deliveries , 2014, Physics in medicine and biology.

[6]  L Kumaraswamy,et al.  Using an EPID for patient-specific VMAT quality assurance. , 2011, Medical physics.

[7]  A. Niemierko.  Reporting and analyzing dose distributions: a concept of equivalent uniform dose. , 1997, Medical physics.

[8]  An MLC calibration method using a detector array. , 2009, Medical physics.

[9]  Cinzia Talamonti,et al.  GafChromic(®) EBT3 films for patient specific IMRT QA using a multichannel approach. , 2015, Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics.

[10]  M K Jørgensen,et al.  Tolerance levels of EPID-based quality control for volumetric modulated arc therapy. , 2011, Medical physics.

[11]  J. Dempsey,et al.  Evaluation of the gamma dose distribution comparison method. , 2003, Medical physics.

[12]  I. Kawrakow,et al.  Investigation of variance reduction techniques for Monte Carlo photon dose calculation using XVMC , 2000, Physics in medicine and biology.

[13]  Quan Chen,et al.  Phantomless patient-specific TomoTherapy QA via delivery performance monitoring and a secondary Monte Carlo dose calculation. , 2014, Medical physics.

[14]  C. Ling,et al.  Physical and dosimetric aspects of a multileaf collimation system used in the dynamic mode for implementing intensity modulated radiotherapy. , 1998, Medical physics.

[15]  Alejandra Rangel,et al.  The sensitivity of patient specific IMRT QC to systematic MLC leaf bank offset errors. , 2010, Medical physics.

[16]  Jan-Jakob Sonke,et al.  3D Dosimetric verification of volumetric-modulated arc therapy by portal dosimetry. , 2010, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[17]  Geoffrey G. Zhang,et al.  VMAT QA: Measurement-guided 4D dose reconstruction on a patient. , 2012, Medical physics.

[18]  K. Bush,et al.  Clinical significance of multi-leaf collimator positional errors for volumetric modulated arc therapy. , 2010, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[19]  G. Kopanitsa,et al.  Efficiency of biological versus physical optimization for single‐arc VMAT for prostate and head and neck cases , 2014, Journal of applied clinical medical physics.

[20]  Mike Oliver,et al.  Understanding the impact of RapidArc therapy delivery errors for prostate cancer , 2011, Journal of applied clinical medical physics.

[21]  Fang-Fang Yin,et al.  Task Group 142 report: quality assurance of medical accelerators. , 2009, Medical physics.

[22]  T. Losasso,et al.  IMRT delivery performance with a varian multileaf collimator. , 2008, International journal of radiation oncology, biology, physics.

[23]  X. Franceries,et al.  2D EPID dose calibration for pretreatment quality control of conformal and IMRT fields: A simple and fast convolution approach. , 2016, Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics.

[24]  Iori Sumida,et al.  Quality assurance of MLC leaf position accuracy and relative dose effect at the MLC abutment region using an electronic portal imaging device , 2012, Journal of radiation research.