The location and field size of the incident X-ray beam in panoramic dental radiography cannot be ascertained visually most of the time. However, these parameters are needed for quality control and dosimetry determination. To alleviate this problem, we tested GafChromic XR-QA film on two panoramic systems. For each system, we used the length of a cross-sectional image of the incident beam and th...

Purpose: Cylindrical ionization chambers as the PinPoint and the CC01 have high-spatial resolution and cylindrical symmetry in relevance to small fields. Dosimetry of newly advanced technologies that include non-coplanar beams, such as in Gamma-Knife, VMAT and IMRT treatment plans, the angular dependence of the ion chamber is essential. Therefore in this study we simulated two common used ion c...

introduction for dose measurement in megavoltage (mv) photon beams with ion chambers, the effect of volume occupied by the air cavity is not negligible. therefore, the result of measurement should be corrected with a displacement perturbation correction factor (pdis) or using an effective point of measurement (epom). the aim of this study is to calculate the epom for cylindrical ion chamber and...

Over the course of the last decade, routine monitoring of the alanine dosimetry system revealed a small but significant observation that, after examination, led to the characterization of a previously unknown absorbed-dose-dependent, dose-rate effect for the alanine system. The newly discovered rate effect is of potential concern for electron-beam dosimetry, since electron-beam dosimetry typica...

Computed tomography (CT) dosimetry normally uses an ionization chamber 100 mm long to estimate the computed tomography dose index (CTDI), however some reports have already indicated that small devices could replace the long ion chamber to improve quality assurance procedures in CT dosimetry. This paper presents a novel dosimetry system based in a commercial phototransistor evaluated for CT dosi...

Introduction For dose measurement in Megavoltage (MV) photon beams with ion chambers, the effect of volume occupied by the air cavity is not negligible. Therefore, the result of measurement should be corrected with a displacement perturbation correction factor (Pdis) or using an effective point of measurement (EPOM). The aim of this study is to calculate the EPOM for cylindrical ion chamber and...

A considerable amount of work has been reported in the literature on the effect of x-rays on antibody formation and immunity. With the exception of the reports from our laboratory,5"' the depressing effect of cobalt-60 gamma radiation upon immunity and antibody formation has not been reported. It would seem logical that x-rays and gamma rays should have a similar physiological effect. However, ...