Evaluating QUANTEC Small Bowel Dose-Volume Guidelines for Rectal Cancer Patients Treated Using a Couch Top Inclined Belly Board.

Purpose: The goal of this work was to analyse small bowel (SB) dose-volume following the Quantitative Analyses of Normal Tissue Effects in the Clinic (QUANTEC) guidelines for rectal cancer patients treated using a couch top inclined belly board (iBB). As part of this, the consistency in SB displacement was evaluated using on-treatment cone-beam computed tomographic (CBCT) imaging.

Methods: Twenty-four patients with rectal cancer were treated on a commercially available iBB.

A methodological approach to reporting corrected small field relative outputs.

Purpose: The goal of this work was to set out a methodology for measuring and reporting small field relative output and to assess the application of published correction factors across a population of linear accelerators.

Methods And Materials: Measurements were made at 6 MV on five Varian iX accelerators using two PTW T60017 unshielded diodes. Relative output readings and profile measurements were made for nominal square field sizes of side 0.

Planning target volume margin evaluation and critical structure sparing for rectal cancer patients treated prone on a bellyboard.

Aims: To calculate a planning target volume (PTV) margin that would account for inter-fractional systematic and random clinical target volume positional errors for patients treated prone on a recently available couch top bellyboard and to evaluate potential critical structure dose reduction using intensity-modulated radiotherapy (IMRT) techniques.

Materials And Methods: Twenty-four patients (12 men and 12 women) were included in this study, all treated on a commercial bellyboard. Cone beam computed tomography (CBCT) data were acquired once every five fractions for a total of five images per patient.

Experimental small field 6 MV output ratio analysis for various diode detector and accelerator combinations.

Background And Purpose: The goal of this work was to measure 6MV small field, detector specific, output ratios (OR(det)) using the IBA stereotactic field diode (SFD) and the PTW T60008, T60012, T60016 and T60017 field diodes on both Varian iX and Elekta Synergy accelerators, to establish estimates for the experimental uncertainty and characterize the measurement precision under various conditions.

Materials And Methods: Data were acquired at depths of 1.5, 5.

Using kV-kV and CBCT imaging to evaluate rectal cancer patient position when treated prone on a newly available belly board.

The goal of this work was to use daily kV-kV imaging and weekly cone-beam CT (CBCT) to evaluate rectal cancer patient position when treated on a new couch top belly board (BB). Quality assurance (QA) of the imaging system was conducted weekly to ensure proper performance. The positional uncertainty of the combined kV-kV image match and subsequent couch move was found to be no more than ± 1.

An enhanced HOWFARLESS option for DOSXYZnrc simulations of slab geometries.

The Monte Carlo code DOSXYZnrc is a valuable instrument for calculating absorbed dose within a three-dimensional Cartesian geometry. DOSXYZnrc includes several variance reduction techniques used to increase the efficiency of the Monte Carlo calculation. One such technique is HOWFARLESS which is used to increase the efficiency of beam commissioning calculations in homogeneous phantoms.

A treatment planning investigation into the dosimetric effects of systematic prostate patient rotational set-up errors.

The purpose of this study was to investigate the potential dosimetric effects of systematic rotational setup errors on prostate patients planned according to the RTOG P-0126 protocol, and to identify rotational tolerances about either the anterior-posterior (AP) or left-right (LR) axis, under which no correction in setup is required. Eight 3-dimensional conformal radiation therapy (3D-CRT) treatment plans were included in the study, half planned to give 7020 cGy in 39 fractions (P-0126 Arm 1) and the other half planned to give 7920 cGy in 44 fractions (P-0126 Arm 2). Systematic rotations of the pelvic anatomy were simulated in a commercial treatment planning system by rotating opposing apertures in the opposite direction to the simulated anatomy rotation.

Increasing the speed of DOSXYZnrc Monte Carlo simulations through the introduction of nonvoxelated geometries.

This article presents a method for increasing the speed of DOSXYZnrc Monte Carlo simulations through the introduction of nonvoxelated geometries defined in any coordinate system. Nonvoxelated geometries are used to isolate regions of uniform density and composition from the scoring grid. Particle transport within these geometric regions is not restricted by the boundary constraints of the scoring grid.