MC model of the Varian CL21EX linear accelerator head (a) Group A—target, primary collimator, monitor chamber, mylar mirror, and phase space A. (b) Group B—monitor chamber, mylar mirror, secondary collimation (jaws) and phase space B.
Dose distribution from a single beamlet. Solid line: PTV.
Open-field phase space is segmented into beamlets. Each beamlet, , contributes dose to a voxel, , within a structure-of-interest. This data is stored in a beamlet dose distribution matrix.
Water equivalent AVID phantom with air cavity. (a) Structure set with C-shaped PTV and spinal cord-like OAR. (b) Field placement.
Anterior bias beam arrangement for nasopharynx recurrence example.
Open field percentage depth dose through air cavity. Dotted line: PBK algorithm (without inhomogeneity correction), Dashed line: PBK (with modified Batho correction), Solid line: Monte Carlo.
3D representation of the 95% prescription isodose surface encompassing the C-shaped target. The air cavity surface rendering is not shown for clarity; however, the box drawing indicates its relative position. (a) PBK algorithm optimization/PBK final forward calculation (b) Same plan from (a) recalculated using MC simulation (c) MC-DAO plan with six apertures per field.
DVHs for phantom example. (a) Eclipse TPS plan (solid line) is recalculated using MC (dashed line). (b) MC-DAO plan (solid line) compared to same dashed line in (a) (PBK optimized/MC forward calculation).
Coronal dose plane MC-DAO plan: (a) film measurement (left) and Monte Carlo (right). Arrows show tongue and groove effect. Profiles (b) parallel and (c) perpendicular to leaf motion. Solid line: MC dose. Dashed line: Film measured dose. (d) Cropped film plane (e) Corresponding dose-difference (DD)/distance-to-agreement (DTA) map.36 or DD passed. . (Pass/Fail: DD max dose/DTA .)
Nasopharynx recurrence: MC-DAO optimization/MC-forward calculation. Solid line: PTV contour. Dotted line: 95% isodose.
Monte Carlo reveals 9.0% underdosage of PTV (mean dose) for this IMRT plan. Solid line: PBK optimized/PBK forward calculation. Dashed line: PBK optimized/MC forward calculation.
The optimized DVH (before final calculation) and final DVH (after final dose calculation) are compared for the (a) fluence-based optimization and (b) DAO plans. Dashed DVH. Solid DVH.
Treatment field/optimization parameters for AVID phantom with C-shaped target.
DVH planning objectives—phantom example (C-shape).
Treatment field/optimization parameters for nasopharynx recurrence example.
DVH planning objectives—Nasopharynx recurrence example.
Phantom example: Comparison of monitor unit (MU) delivery efficiency for Varian Eclipse fluence-based plan and MC-DAO.
Doses to structures of interest for nasopharynx example. Prescription .
Ion chamber point dose measurements in cylindrical verification phantom.
Nasopharynx example: comparison of monitor unit (MU) delivery efficiency for Varian eclipse fluence-based plan and MC-DAO.
Doses to structures-of-interest for AVID phantom example.
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