Clinical implementation of a Monte Carlo treatment planning system.

The purpose of this study was to implement the Monte Carlo method for clinical radiotherapy dose calculations. We used the EGS4/BEAM code to obtain the phase-space data for 6-20 MeV electron beams and 4, 6, and 15 MV photon beams for Varian Clinac 1800, 2100C, and 2300CD accelerators. A multiple-source model was used to reconstruct the phase-space data for both electron and photon beams, which retained the accuracy of the Monte Carlo beam data. The multiple-source model reduced the phase-space data storage requirement by a factor of 1000 and the accelerator simulation time by a factor of 10 or more. Agreement within 2% was achieved between the Monte Carlo calculations and measurements of the dose distributions in homogeneous and heterogeneous phantoms for various field sizes, source-surface distances, and beam modulations. The Monte Carlo calculated electron output factors were within 2% of the measured values for various treatment fields while the heterogeneity correction factors for various lung and bone phantoms were within 1% for photon beams and within 2% for electron beams. The EGS4/DOSXYZ Monte Carlo code was used for phantom and patient dose calculations. The results were compared to the dose distributions produced by a conventional treatment planning system and an intensity-modulated radiotherapy inverse-planning system. Significant differences (>5% in dose and >5 mm shift in isodose lines) were found between Monte Carlo calculations and the analytical calculations implemented in the commercial systems. Treatment sites showing the largest dose differences were for head and neck, lung, and breast cases.

[1]  A. Boyer,et al.  Underdosing of lesions resulting from lack of electronic equilibrium in upper respiratory air cavities irradiated by 10MV x-ray beams. , 1977, International journal of radiation oncology, biology, physics.

[2]  R Mohan,et al.  Energy and angular distributions of photons from medical linear accelerators. , 1985, Medical physics.

[3]  E. Mok,et al.  A photon dose distribution model employing convolution calculations. , 1985, Medical physics.

[4]  J. Battista,et al.  A convolution method of calculating dose for 15-MV x rays. , 1985, Medical physics.

[5]  David W. O. Rogers,et al.  Presta: The parameter reduced electron-step transport algorithm for electron monte carlo transport , 1986 .

[6]  R. Mohan,et al.  Differential pencil beam dose computation model for photons. , 1986, Medical physics.

[7]  K R Shortt,et al.  Electron beam dose distributions near standard inhomogeneities , 1986 .

[8]  J. Cygler,et al.  Electron dose distributions in experimental phantoms: a comparison with 2D pencil beam calculations. , 1987, Physics in medicine and biology.

[9]  J. Wong,et al.  Photon dose perturbations due to small inhomogeneities. , 1987, Medical physics.

[10]  A. Boyer,et al.  X-ray dose computations in heterogeneous media using 3-dimensional FFT convolution , 1990 .

[11]  J. Wong,et al.  On methods of inhomogeneity corrections for photon transport. , 1990, Medical physics.

[12]  P. Andreo.  Monte Carlo techniques in medical radiation physics. , 1991, Physics in medicine and biology.

[13]  R Mohan,et al.  A Monte Carlo model of photon beams used in radiation therapy. , 1995, Medical physics.

[14]  T D Solberg,et al.  Implications of tissue heterogeneity for radiosurgery in head and neck tumors. , 1995, International journal of radiation oncology, biology, physics.

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

[16]  R Muller-Runkel,et al.  Evaluation of a commercial three-dimensional electron pencil beam algorithm. , 1997, Medical physics.

[17]  C. Ma,et al.  Accurate characterization of Monte Carlo calculated electron beams for radiotherapy , 1997 .

[18]  Chang-ming Ma,et al.  Characterization of computer simulated radiotherapy beams for Monte-Carlo treatment planning , 1998 .

[19]  C. Ma,et al.  Monte Carlo calculations of electron beam output factors for a medical linear accelerator. , 1998, Physics in medicine and biology.

[20]  J J DeMarco,et al.  A CT-based Monte Carlo simulation tool for dosimetry planning and analysis. , 1998, Medical physics.

[21]  C. Chui,et al.  A patient-specific Monte Carlo dose-calculation method for photon beams. , 1998, Medical physics.

[22]  C M Ma,et al.  Theoretical considerations of monitor unit calculations for intensity modulated beam treatment planning. , 1999, Medical physics.