Linac Photon Beam Calibration Using Virtual Simulator Program

In radiotherapy, medical physicists give a major contribution to the safe and effective radiation treatment for patients with cancer. Megavoltage linac photon outputs are determined using the IAEA TRS-398 code of practice or AAPM TG-51 and the results are compared. Beam calibration means determination of absorbed dose to water per 100 monitor units in a water phantom at reference conditions. The measured dose Dw, Q in water at the reference point is a primary parameter for planning the treatment monitor units (MU). Traceability of dose accuracy therefore still depends mainly on the calibration factor of the ion chamber/dosimeter provided by the accredited laboratories. Our data, therefore, imply that the dosimetry level maintained fo the clinical use of linear accelerator photon beams are within recommended levels of accuracy, and uncertainties are within reported values. However, in Albania, the frequent problem is related to resources with respect to both, qualified teachers and equipment, that are at disposal for teaching and training. The concepts of e-learning methods using different non-commercial software, contribute to overcoming this problem. In our case, we use an academic education method to practice radiation oncologists and medical physicists for LINAC beam calibration using a virtual simulator program and Matlab. Our group, after some experiences in calculation methods using Matlab, is focused on a PC based program which simulates the required equipment, the measurement set-up, and the measurement itself. All procedures are modeled according to the IAEA Code of Practice, TRS 398.Keywords: Radiotherapy, linac, calibration, beam, protocol, virtual simulator program

Correlation between thickness, conductivity and thermal degradation mechanisms of PEDOT:PSS films

D.c. conductivity σ and thermal degradation measurements on PEDOT:PSS films of different thicknesses d  =  50, 120 and 180 nm are reported. The experimental results are consistent with a hopping type carrier transport. For the films with thickness d  =  50 nm, which consist of almost one single layer of PEDOT:PSS conductive grains, the conductivity and the heat aging are consistent with a hopping transport in a granular metal type structure. However, for films with d  =  120 and 180 nm, in which many conductive grains constitute the film thickness, a completely different behaviour is exhibited. An explanation of this is propose