PURPOSE: A new Collaborative Ocular Melanoma Study (COMS)-like 24 mm eye plaque was experimentally characterized using physical and dosimetric measurements in preparation for clinical usage. The new eye plaque will enable surgeons and radiation oncologists to accommodate patients who have larger ocular melanoma tumors. METHODS AND MATERIALS: Physical measurement of the Modulay radius of curvature was performed using a FARO Edge, and the base thickness of the Silastic insert was measured with a depth gauge and Vernier caliper. Dosimetric measurements, using Gafchromic film, were used to determine the absolute dose as a function of the depth along the plaque's central axis, profiles as a function of polar angle, and basal coverage at the inner sclera. The measured results were compared with a theoretical model, which incorporated the plaque's heterogeneities using a modified TG-43 formalism. RESULTS: The Modulay radius of curvature measured 14.7 mm (specification 5 14.55 mm). The Silastic base thickness measured 0.9 mm (specification 5 1.0 mm). For a 24 mm plaque fully loaded with 1.27 U 125 I model 2301 seeds, the dose rate at a prescription depth of 5 mm from the inner sclera was measured to be 36 cGy U À1 hr À1. The basal coverage for the same prescription depth was 17.9 mm. The experimental measurements were in close agreement with the theoretical predictions. CONCLUSIONS: The new 24 mm COMS-like plaque was experimentally validated for clinical use. Physical and dosimetric measurements for the 24 mm plaque agreed with nominal specifications and theoretical predictions. The 24 mm plaque provides greater basal coverage and lower surface doses than existing COMS plaques.

A 24 mm COMS‐like eye plaque was developed to meet the treatment needs of our eye plaque brachytherapy practice. As part of commissioning, it was necessary to determine the new plaque's seed coordinates. The FARO Edge, a commercially available measurement arm, was chosen for this purpose. In order to validate the FARO Edge method, it was first used to measure the seed marker coordinates in the silastic molds for the standard 10, 18, and 20 mm COMS plaques, and the results were compared with the standard published Task Group 129 coordinates by a nonlinear least squares match in MATLAB version R2013a. All measured coordinates were within 0.60 mm, and root mean square deviation was 0.12, 0.23, and 0.35 mm for the 10, 18, and 20 mm molds, respectively. The FARO Edge was then used to measure the seed marker locations in the new 24 mm silastic mold. Those values were compared to the manufacturing specification coordinates and were found to demonstrate good agreement, with a maximum deviation of 0.56 mm and a root mean square deviation of 0.37 mm. The FARO Edge is deemed to be a reliable method for determining seed coordinates for COMS silastics, and the seed coordinates for the new 24 mm plaque are presented.PACS number: 87.53.Jw

In an effort to determine the chronic stability, sensitivity, and thus the potential viability of various neurochemical recording electrode designs and compositions, we have developed a custom device called the Voltammetry Instrument for Neurochemical Applications (VINA). Here, we describe the design of the VINA and initial testing of its functionality for prototype neurochemical sensing electrodes. The VINA consists of multiple electrode fixtures, a flowing electrolyte bath, associated reservoirs, peristaltic pump, voltage waveform generator, data acquisition hardware, and system software written in National Instrument's LabVIEW. The operation of VINA was demonstrated on a set of boron-doped diamond neurochemical recording electrodes, which were subjected to an applied waveform for a period of eighteen days. Each electrode's cyclic voltammograms (CVs) were recorded, and sensitivity calibration to dopamine (DA) was performed. Results showed an initial decline with subsequent stabilization in the CV current measured during the voltammetric sweep, corresponding closely with changes in electrode sensitivity to DA. The VINA has demonstrated itself as a useful tool for the characterization of electrode stability and chronic electrochemical performance.