Implementation and Evaluation of Phantomless Intensity Modulated Radiotherapy Delivery Verification Using FractionCHECK.

Introduction: The objective was to implement the DynaLog file-based automated FractionCHECKTM software which verifies the delivery accuracy of all patient treatments without any measuring devices and evaluate this tool for dynamic IMRT delivery verification of 40 cases. The present work was aimed to find the generalized results with user-defined tolerances of all treatment deliveries and asses the delivery results in terms of Pass/Warn/fail analysis. In addition to this, an in-depth analysis of mean RMS error of each BANK of the MLC's and mean 95th Percentile error of all the leaves and percentage of pixels passing Gamma between the planned and delivered fluences for all 40 dynamic IMRT cases.

Can Civility Norms Boost Positive Effects of Management Commitment to Safety?

We proposed that civility norms would strengthen relationships between management commitment to safety and workers' safety motivation, safety behaviors, and injuries. Survey data were obtained from working adults in hazardous jobs-those for which physical labor is required and/or a realistic possibility of physical injury is present (N = 290). Results showed that management commitment positively related to workers' safety motivation, safety participation, and safety compliance, and negatively related to minor injuries.

A multi-institution evaluation of MLC log files and performance in IMRT delivery.

Background: The multileaf collimator (MLC) is a critical component to accurate intensity-modulated radiotherapy (IMRT) delivery. This study examined MLC positional accuracy via MLC logs from Varian machines from six institutions and three delivery techniques to evaluate typical positional accuracy and treatment and mechanical parameters that affect accuracy. Typical accuracy achieved was compared against TG-142 recommendations for MLC performance; more appropriate recommendations are suggested.

Investigation of various energy deposition kernel refinements for the convolution∕superposition method.

Purpose: Several simplifications used in clinical implementations of the convolution∕superposition (C∕S) method, specifically, density scaling of water kernels for heterogeneous media and use of a single polyenergetic kernel, lead to dose calculation inaccuracies. Although these weaknesses of the C∕S method are known, it is not well known which of these simplifications has the largest effect on dose calculation accuracy in clinical situations. The purpose of this study was to generate and characterize high-resolution, polyenergetic, and material-specific energy deposition kernels (EDKs), as well as to investigate the dosimetric impact of implementing spatially variant polyenergetic and material-specific kernels in a collapsed cone C∕S algorithm.

Implementation and evaluation of an end-to-end IGRT test.

The goal of this work was to develop and evaluate an end-to-end test for determining and verifying image-guided radiation therapy setup accuracy relative to the radiation isocenter. This was done by placing a cube phantom with a central tungsten sphere directly on the treatment table and offset from isocenter either by 5.0 mm in the longitudinal, lateral, and vertical dimensions or by a random amount.

SU-E-T-510: Calculation of High Resolution and Material-Specific Photon Energy Deposition Kernels.

Purpose: To calculate photon energy deposition kernels (EDKs) used for convolution/superposition dose calculation at a higher resolution than the original Mackie et al. 1988 kernels and to calculate material-specific kernels that describe how energy is transported and deposited by secondary particles when the incident photon interacts in a material other than water.

Methods: The high resolution EDKs for various incident photon energies were generated using the EGSnrc user-code EDKnrc, which forces incident photons to interact at the center of a 60 cm radius sphere of water.

Retrospective analysis of 2D patient-specific IMRT verifications.

We performed 858 two-dimensional (2D) patient-specific intensity modulated radiotherapy verifications over a period of 18 months. Multifield, composite treatment plans were measured in phantom using calibrated Kodak EDR2 film and compared with the calculated dose extracted from two treatment planning systems. This research summarizes our findings using the normalized agreement test (NAT) index and the percent of pixels failing the gamma index as metrics to represent the agreement between measured and computed dose distributions.

Dosimetric accuracy of Kodak EDR2 film for IMRT verifications.

Patient-specific intensity-modulated radiotherapy (IMRT) verifications require an accurate two-dimensional dosimeter that is not labor-intensive. We assessed the precision and reproducibility of film calibrations over time, measured the elemental composition of the film, measured the intermittency effect, and measured the dosimetric accuracy and reproducibility of calibrated Kodak EDR2 film for single-beam verifications in a solid water phantom and for full-plan verifications in a Rexolite phantom. Repeated measurements of the film sensitometric curve in a single experiment yielded overall uncertainties in dose of 2.

Detection of IMRT delivery errors using a quantitative 2D dosimetric verification system.

We investigated the feasibility of detecting intensity modulated radiotherapy delivery errors automatically using a scalar evaluation of two-dimensional (2D) transverse dose measurement of the complete treatment delivery. Techniques using the gamma index and the normalized agreement test (NAT) index were used to parametrize the agreement between measured and computed dose distributions to seven different scalar metrics. Simulated verifications with delivery errors calculated using a commercially available treatment planning system for 9 prostate and 7 paranasal sinus cases were compared to 433 clinical verifications.

Interactively exploring optimized treatment plans.

Purpose: A new paradigm for treatment planning is proposed that embodies the concept of interactively exploring the space of optimized plans. In this approach, treatment planning ignores the details of individual plans and instead presents the physician with clinical summaries of sets of solutions to well-defined clinical goals in which every solution has been optimized in advance by computer algorithms.

Methods And Materials: Before interactive planning, sets of optimized plans are created for a variety of treatment delivery options and critical structure dose-volume constraints.

Effect of processing time delay on the dose response of Kodak EDR2 film.

Kodak EDR2 film is a widely used two-dimensional dosimeter for intensity modulated radiotherapy (IMRT) measurements. Our clinical use of EDR2 film for IMRT verifications revealed variations and uncertainties in dose response that were larger than expected, given that we perform film calibrations for every experimental measurement. We found that the length of time between film exposure and processing can affect the absolute dose response of EDR2 film by as much as 4%-6%.

The design and testing of novel clinical parameters for dose comparison.

Purpose: New multidimensional dose comparison parameters, normalized agreement test (NAT) values and the NAT index, are introduced and compared with an ideal dose comparison parameter. In this article, we analyze a clinically based two-dimensional (2D) quantitative dose comparison case using a wide range of new and old comparison tools. In doing so, we address the benefits and limitations of many common dose comparison tools.

Rapid radiographic film calibration for IMRT verification using automated MLC fields.

A method for measuring a film sensitometric curve using a single sheet of film exposed with a two field step-and-shoot MLC treatment was developed and tested with Kodak XV2 and EDR2 films. With this technique a film sensitometric curve can be completed in only 10 minutes, making it practical to generate new film calibrations daily. This method is applicable to film calibrations for all purposes, but is particularly useful in IMRT treatment verification due to the method's use of small fields.