WE-G-BRB-06: Real-Time Radiation Field Tracking Using Long Scintillating Fibers.

Purpose: To ensure the quality assurance of small field, dynamic radiotherapy, we present and validate a radiation tracking system based on long scintillating fibers that allows for the real-time measurement of the position and energetic fluence of a small incident radiation field.

Method: We aligned 60 parallel scintillating fibers on a thin grooved acrylic slab with a 100-cm source-to-fibers distance. Both ends of each scintillating fiber were coupled to clear optical fibers to enable light collection by a single CCD camera using an f/0.

SU-E-T-265: Reducing Pacemaker Doses with a Lead Sheet: A Multi-Detector Study.

Purpose: Evaluate the usability of lead shielding to reduce the dose to pacemakers. The efficiency and risk of this type of skin block will be presented.

Methods: A solid water phantom was used and all measurements were made at a depth of 0.

Platelets and platelet-like particles mediate intercellular RNA transfer.

The role of platelets in hemostasis and thrombosis is clearly established; however, the mechanisms by which platelets mediate inflammatory and immune pathways are less well understood. Platelets interact and modulate the function of blood and vascular cells by releasing bioactive molecules. Although the platelet is anucleate, it contains transcripts that may mirror disease.

ALGEBRA: ALgorithm for the heterogeneous dosimetry based on GEANT4 for BRAchytherapy.

Task group 43 (TG43)-based dosimetry algorithms are efficient for brachytherapy dose calculation in water. However, human tissues have chemical compositions and densities different than water. Moreover, the mutual shielding effect of seeds on each other (interseed attenuation) is neglected in the TG43-based dosimetry platforms.

Exploring (57)Co as a new isotope for brachytherapy applications.

Purpose: The characteristics of the radionuclide (57)Co make it interesting for use as a brachytherapy source. (57)Co combines a possible high specific activity with the emission of relatively low-energy photons and a half-life (272 days) suitable for regular source exchanges in an afterloader. (57)Co decays by electron capture to the stable (57)Fe with emission of 136 and 122 keV photons.

Consequences of dose heterogeneity on the biological efficiency of ¹⁰³Pd permanent breast seed implants.

Brachytherapy is associated with highly heterogeneous spatial dose distributions. This heterogeneity is usually ignored when estimating the biological effective dose (BED). In addition, the heterogeneities of the medium including the tissue heterogeneity (TH) and the interseed attenuation (ISA) are also contributing to the heterogeneity of the dose distribution, but they are both ignored in Task Group 43 (TG43)-based protocols.

Medical physics staffing for radiation oncology: a decade of experience in Ontario, Canada.

The January 2010 articles in The New York Times generated intense focus on patient safety in radiation treatment, with physics staffing identified frequently as a critical factor for consistent quality assurance. The purpose of this work is to review our experience with medical physics staffing, and to propose a transparent and flexible staffing algorithm for general use. Guided by documented times required per routine procedure, we have developed a robust algorithm to estimate physics staffing needs according to center-specific workload for medical physicists and associated support staff, in a manner we believe is adaptable to an evolving radiotherapy practice.

Dosimetric performance and array assessment of plastic scintillation detectors for stereotactic radiosurgery quality assurance.

Purpose: To compare the performance of plastic scintillation detectors (PSD) for quality assurance (QA) in stereotactic radiosurgery conditions to a microion-chamber (IC), Gafchromic EBT2 films, 60 008 shielded photon diode (SD) and unshielded diodes (UD), and assess a new 2D crosshair array prototype adapted to small field dosimetry.

Methods: The PSD consists of a 1 mm diameter by 1 mm long scintillating fiber (BCF-60, Saint-Gobain, Inc.) coupled to a polymethyl-methacrylate optical fiber (Eska premier, Mitsubishi Rayon Co.

A new water-equivalent 2D plastic scintillation detectors array for the dosimetry of megavoltage energy photon beams in radiation therapy.

Purpose: The objective of this work is to present a new 2D plastic scintillation detectors array (2D-PSDA) designed for the dosimetry of megavoltage (MV) energy photon beams in radiation therapy and to characterize its basic performance.

Methods: We developed a 2D detector array consisting of 781 plastic scintillation detectors (PSDs) inserted into a plane of a water-equivalent phantom. The PSDs were distributed on a 26 × 26 cm(2) grid, with an interdetector spacing of 10 mm, except for two perpendicular lines centered on the detection plane, where the spacing was 5 mm.

Tissue modeling schemes in low energy breast brachytherapy.

Breast tissue is heterogeneous and is mainly composed of glandular (G) and adipose (A) tissues. The proportion of G versus A varies considerably among the population. The absorbed dose distributions in accelerated partial breast irradiation therapy with low energy photon brachytherapy sources are very sensitive to tissue heterogeneities.

Extraction of depth-dependent perturbation factors for silicon diodes using a plastic scintillation detector.

Purpose: This work presents the experimental extraction of the perturbation factor in megavoltage electron beams for three models of silicon diodes (IBA Dosimetry, EFD and SFD, and the PTW 60012 unshielded) using a plastic scintillation detector (PSD).

Methods: The authors used a single scanning PSD mounted on a high-precision scanning tank to measure depth-dose curves in 6-, 12-, and 18-MeV clinical electron beams. They also measured depth-dose curves using the IBA Dosimetry, EFD and SFD, and the PTW 60012 unshielded diodes.

Modeling a hypothetical 170Tm source for brachytherapy applications.

Purpose: To perform absorbed dose calculations based on Monte Carlo simulations for a hypothetical (170)Tm source and to investigate the influence of encapsulating material on the energy spectrum of the emitted electrons and photons.

Methods: GEANT4 Monte Carlo code version 9.2 patch 2 was used to simulate the decay process of (170)Tm and to calculate the absorbed dose distribution using the GEANT4 Penelope physics models.

Functional avoidance of lung in plan optimization with an aperture-based inverse planning system.

Purpose: To implement SPECT-based optimization in an anatomy-based aperture inverse planning system for the functional avoidance of lung in thoracic irradiation.

Material And Methods: SPECT information has been introduced as a voxel-by-voxel modulation of lung importance factors proportionally to the local perfusion count. Fifteen cases of lung cancer have been retrospectively analyzed by generating angle-optimized non-coplanar plans, comparing a purely anatomical approach and our functional approach.

Further evaluation of response-independent delivery of preferred stimuli and child compliance.

The effect of a fixed-time (FT) schedule involving the delivery of preferred stimuli prior to the issuance of a low-probability instruction was evaluated with 2 young children with autism. The FT schedule was introduced according to a reversal design with 3 target instructions, 1 for the first child and 2 for the second child. Compliance increased for 2 of the 3 cases.

Extracting atomic numbers and electron densities from a dual source dual energy CT scanner: experiments and a simulation model.

Background And Purpose: Dual energy CT (DECT) imaging can provide both the electron density ρ(e) and effective atomic number Z(eff), thus facilitating tissue type identification. This paper investigates the accuracy of a dual source DECT scanner by means of measurements and simulations. Previous simulation work suggested improved Monte Carlo dose calculation accuracy when compared to single energy CT for low energy photon brachytherapy, but lacked validation.

Simulation study on potential accuracy gains from dual energy CT tissue segmentation for low-energy brachytherapy Monte Carlo dose calculations.

This work compares Monte Carlo (MC) dose calculations for (125)I and (103)Pd low-dose rate (LDR) brachytherapy sources performed in virtual phantoms containing a series of human soft tissues of interest for brachytherapy. The geometries are segmented (tissue type and density assignment) based on simulated single energy computed tomography (SECT) and dual energy (DECT) images, as well as the all-water TG-43 approach. Accuracy is evaluated by comparison to a reference MC dose calculation performed in the same phantoms, where each voxel's material properties are assigned with exactly known values.

3D heterogeneous dose distributions for total body irradiation patients.

One major objective of total body irradiation (TBI) treatments is to deliver a uniform dose in the entire body of the patient. Looking at 3D dose distributions for constant speed (CstSpeed) and variable speed (VarSpeed) translating couch TBI treatments, dose uniformity and the effect of body heterogeneities were evaluated. This study was based on retrospective dose calculations of 10 patients treated with a translating couch TBI technique.

Accurate calibration of a polymer gel dosimeter with a plastic scintillation detector.

Purpose: Three dimensional dose polymer gel dosimetry measurements provide unique information on sophisticated dose distributions. In this study, the authors propose a novel method to improve the accuracy of polymer gel dosimeters by inserting a plastic scintillation detector (PSD) to provide a dose reference.

Methods: PSD dosimeters were calibrated using chromatic deconvolution and then inserted into polyacrylanide gel (PAG) dosimeters.

A phantom study of an in vivo dosimetry system using plastic scintillation detectors for real-time verification of 192Ir HDR brachytherapy.

Purpose: The goal of the present work was to evaluate the accuracy of a plastic scintillation detector (PSD) system to perform in-phantom dosimetry during 192Ir high dose rate (HDR) brachytherapy treatments.

Methods: A PSD system capable of stem effect removal was built. A red-green-blue photodiode connected to a dual-channel electrometer was used to detect the scintillation light emitted from a green scintillation component and transmitted along a plastic optical fiber.

The elderly in the psychiatric emergency service (PES); a descriptive study.

Background: The impact of an aging population on the psychiatric emergency service (PES) has not been fully ascertained. Cognitive dysfunctions aside, many DSM-IV disorders may have a lower prevalence in the elderly, who appear to be underrepresented in the PES. We therefore attempted to more precisely assess their patterns of PES use and their clinical and demographic characteristics.

An opposite view data replacement approach for reducing artifacts due to metallic dental objects.

Purpose: To present a conceptually new method for metal artifact reduction (MAR) that can be used on patients with multiple objects within the scan plane that are also of small sized along the longitudinal (scanning) direction, such as dental fillings.

Methods: The proposed algorithm, named opposite view replacement, achieves MAR by first detecting the projection data affected by metal objects and then replacing the affected projections by the corresponding opposite view projections, which are not affected by metal objects. The authors also applied a fading process to avoid producing any discontinuities in the boundary of the affected projection areas in the sinogram.

Technical note: removing the stem effect when performing Ir-192 HDR brachytherapy in vivo dosimetry using plastic scintillation detectors: a relevant and necessary step.

Purpose: The purpose of this study was to investigate whether or not a stem effect removal technique is necessary when performing Ir-192 HDR brachytherapy in vivo dosimetry using a scintillation detector.

Methods: A red-green-blue photodiode connected to a multichannel electrometer was used to detect the light emitted from a plastic scintillation detector (PSD) during irradiation with an Ir-192 HDR brachytherapy source. Accuracy in dose measurement was compared with and without the use of stem effect removal techniques.