Monte Carlo Computation of Dose-Volume Histograms in Structures at Risk of an Eye Irradiated with Heterogeneous Ruthenium-106 Plaques.

Background/aims: The aim of this work is to compare Monte Carlo simulated absorbed dose distributions obtained from Ru eye plaques, whose heterogeneous emitter distribution is known, with the common homogeneous approximation. The effect of these heterogeneities on segmented structures at risk is analyzed using an anthropomorphic phantom.

Methods: The generic CCA and CCB, with a homogeneous emitter map, and the specific CCA1364 and CCB1256 Ru eye plaques are modeled with the Monte Carlo code PENELOPE.

Monte Carlo Simulation of the Treatment of Uveal Melanoma Using Measured Heterogeneous Ru Plaques.

Background/aims: Ruthenium plaques are used for the treatment of ocular tumors. The aim of this work is the comparison between simulated absorbed dose distributions tallied in an anthropomorphic phantom, obtained from ideal homogeneous plaques, and real eye plaques in which the actual heterogeneous distribution of Ru was measured. The placement of the plaques with respect to the tumor location was taken into consideration to optimize the effectiveness of the treatment.

Dose Distributions and Treatment Margins in Ocular Brachytherapy with 106Ru Eye Plaques.

Brachytherapy with Ru eye plaques is the most common treatment modality for small to medium-sized uveal melanomas in Europe. So far, no standardized or widely accepted dose prescription protocol for the irradiation of intraocular tumors with Ru eye plaques has been defined. For I plaques, the minimum dose required for tumor control should be at least 85 Gy.

Monte Carlo Estimation of Absorbed Dose Distributions Obtained from Heterogeneous Ru Eye Plaques.

Background: The distribution of the emitter substance in Ru eye plaques is usually assumed to be homogeneous for treatment planning purposes. However, this distribution is never homogeneous, and it widely differs from plaque to plaque due to manufacturing factors.

Methods: By Monte Carlo simulation of radiation transport, we study the absorbed dose distribution obtained from the specific CCA1364 and CCB1256 Ru plaques, whose actual emitter distributions were measured.

Air core detectors for Cerenkov-free scintillation dosimetry of brachytherapy β-sources.

Purpose: Plastic scintillation detectors are used for dosimetry in small radiation fields with high dose gradients, e.g., provided by β-emitting sources like Ru/ Rh eye plaques.

Energy dependent response of plastic scintillation detectors to photon radiation of low to medium energy.

Purpose: Plastic scintillation detectors are promising candidates for the dosimetry of low- to medium-energy photons but quantitative knowledge of their energy response is a prerequisite for their correct use. The purpose of this study was to characterize the energy dependent response of small scintillation detectors (active volume <1 mm(3)) made from the commonly used plastic scintillator BC400.

Methods: Different detectors made from BC400 were calibrated at a number of radiation qualities ranging from 10 to 280 kV and at a (60)Co beam.

Polyethylene Naphthalate Scintillator: A Novel Detector for the Dosimetry of Radioactive Ophthalmic Applicators.

Background: Dosimetric measurements in small radiation fields with large gradients, such as eye plaque dosimetry with β or low-energy photon emitters, require dosimetrically almost water-equivalent detectors with volumes of <1 mm(3) and linear responses over several orders of magnitude. Polyvinyltoluene-based scintillators fulfil these conditions. Hence, they are a standard for such applications.

Integral image rendering procedure for aberration correction and size measurement.

The challenge in rendering integral images is to use as much information preserved by the light field as possible to reconstruct a captured scene in a three-dimensional way. We propose a rendering algorithm based on the projection of rays through a detailed simulation of the optical path, considering all the physical properties and locations of the optical elements. The rendered images contain information about the correct size of imaged objects without the need to calibrate the imaging device.

Development of a high precision dosimetry system for the measurement of surface dose rate distribution for eye applicators.

Purpose: The therapeutic outcome of the therapy with ophthalmic applicators is highly dependent on the application of a sufficient dose to the tumor, whereas the dose applied to the surrounding tissue needs to be minimized. The goal for the newly developed apparatus described in this work is the determination of the individual applicator surface dose rate distribution with a high spatial resolution and a high precision in dose rate with respect to time and budget constraints especially important for clinical procedures. Inhomogeneities of the dose rate distribution can be detected and taken into consideration for the treatment planning.