Three-dimensional gamma analysis of dose distributions in individual structures for IMRT dose verification

Our purpose in this study was to implement three-dimensional (3D) gamma analysis for structures of interest such as the planning target volume (PTV) or clinical target volume (CTV), and organs at risk (OARs) for intensity-modulated radiation therapy (IMRT) dose verification. IMRT dose distributions for prostate and head and neck (HN) cancer patients were calculated with an analytical anisotropic algorithm in an Eclipse (Varian Medical Systems) treatment planning system (TPS) and by Monte Carlo (MC) simulation. The MC dose distributions were calculated with EGSnrc/BEAMnrc and DOSXYZnrc user codes under conditions identical to those for the TPS. The prescribed doses were 76 Gy/38 fractions with five-field IMRT for the prostate and 33 Gy/17 fractions with seven-field IMRT for the HN. TPS dose distributions were verified by the gamma passing rates for the whole calculated volume, PTV or CTV, and OARs by use of 3D gamma analysis with reference to MC dose distributions. The acceptance criteria for the 3D gamma analysis were 3/3 and 2 %/2 mm for a dose difference and a distance to agreement. The gamma passing rates in PTV and OARs for the prostate IMRT plan were close to 100 %. For the HN IMRT plan, the passing rates of 2 %/2 mm in CTV and OARs were substantially lower because inhomogeneous tissues such as bone and air in the HN are included in the calculation area. 3D gamma analysis for individual structures is useful for IMRT dose verification.

[1]  M. Alber,et al.  A revision of the γ-evaluation concept for the comparison of dose distributions , 2003 .

[2]  R. Mohan,et al.  A Monte Carlo study of radiation transport through multileaf collimators. , 2001, Medical physics.

[3]  M. Stock,et al.  Interpretation and evaluation of the gamma index and the gamma index angle for the verification of IMRT hybrid plans. , 2005, Physics in medicine and biology.

[4]  Iwan Kawrakow,et al.  DOSXYZnrc Users Manual , 2016 .

[5]  Emiliano Spezi,et al.  Gamma histograms for radiotherapy plan evaluation. , 2006, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

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

[7]  J. Cygler,et al.  Commissioning and quality assurance of treatment planning computers. , 1993, International journal of radiation oncology, biology, physics.

[8]  D. Mercier,et al.  The delta envelope: a technique for dose distribution comparison. , 2009, Medical physics.

[9]  Benjamin E Nelms,et al.  Moving from gamma passing rates to patient DVH-based QA metrics in pretreatment dose QA. , 2011, Medical physics.

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

[11]  D. Huyskens,et al.  A quantitative evaluation of IMRT dose distributions: refinement and clinical assessment of the gamma evaluation. , 2002, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[12]  D. Low,et al.  A technique for the quantitative evaluation of dose distributions. , 1998, Medical physics.

[13]  J. Deasy,et al.  Geometric interpretation of the gamma dose distribution comparison technique: interpolation-free calculation. , 2008, Medical physics.

[14]  L. Bogner,et al.  Monte Carlo simulations to replace film dosimetry in IMRT verification. , 2011, Zeitschrift fur medizinische Physik.

[15]  Sara Bresciani,et al.  Pretreatment patient-specific IMRT quality assurance: a correlation study between gamma index and patient clinical dose volume histogram. , 2012, Medical physics.

[16]  M. Alber,et al.  A revision of the gamma-evaluation concept for the comparison of dose distributions. , 2003, Physics in medicine and biology.

[17]  Núria Jornet,et al.  3D DVH-based metric analysis versus per-beam planar analysis in IMRT pretreatment verification. , 2012, Medical physics.

[18]  Jan-Jakob Sonke,et al.  A fast algorithm for gamma evaluation in 3D. , 2007, Medical physics.

[19]  I. Rosen,et al.  The design and testing of novel clinical parameters for dose comparison. , 2003, International journal of radiation oncology, biology, physics.

[20]  J. Moran,et al.  A dose‐gradient analysis tool for IMRT QA , 2005, Journal of applied clinical medical physics.

[21]  M. Stock,et al.  Interpretation and evaluation of the γ index and the γ index angle for the verification of IMRT hybrid plans , 2005 .

[22]  D. G. Lewis,et al.  A DICOM-RT-based toolbox for the evaluation and verification of radiotherapy plans. , 2002, Physics in medicine and biology.

[23]  E Sterpin,et al.  Monte carlo evaluation of the AAA treatment planning algorithm in a heterogeneous multilayer phantom and IMRT clinical treatments for an Elekta SL25 linear accelerator. , 2007, Medical physics.

[24]  C. Ma,et al.  BEAM: a Monte Carlo code to simulate radiotherapy treatment units. , 1995, Medical physics.