Early-stage prostate cancer is widely treated by iodine-125 (I-125) seed implantation. While quality assurance methods are in place to assure consistency in I-125 seed source strength, current methods involve the breaking of the sterilization package, raising issues concerning sterility and time limitations. The purpose of this study was to develop a method of characterizing the total source st...

The ionization of the gas molecules by X-rays results in electron-ion pair production. The positive ions need several milliseconds to move from the generation position to the cathode. Conversely, the electrons require few microseconds to reach the anode plates. The accumulation of the positive ions inside the active volume, according to their slower drift, leads to space charge effect which has...

T h e method of CERMAK and HERMAN has been appl ied to mass spectrometr ic studies of symmetrical electron and proton transfer processes. The characteristics of the ion source used have been investigated both experimental ly and theoretical ly. A new type of ionization ef f ic iency curve is obtained if the current of a secondary ion is plotted as a funct ion of the voltage between ionization c...

Chemical Vapor Deposited (CVD) diamond has great advantages for use as thermoluminescent dosimeters in radiotherapy environment because of the reproducible high quality and controlled doping. This study compares CVD diamond Thermally Stimulated Luminescence response to that of a classical ionization chamber. Clinicallyrelevant features like the depth-dose distributions as well as the absorbed d...

Dose rate measurements have been performed around the cupper, tungsten and aluminum targets bombarded by 18, 25 and 34 MeV electrons. The detectors were set at 500 mm from the target and the angles were 0, 30, 60, 90 and 120 degrees in the direction to the beam line. Three kinds of detectors were applied for the measurements, miniature ionization chamber and glass dosimeter for photons, and CR-...

PURPOSE To validate absolute dose measurements for a MR-IGRT system without presence of the magnetic field. METHODS The standard method (AAPM's TG-51) of absolute dose measurement with ionization chambers was tested with and without the presence of the magnetic field for a clinical 0.32-T Co-60 MR-IGRT system. Two ionization chambers were used - the Standard Imaging (Madison, WI) A18 (0.123 c...

Absorbed dose to water in a cobalt-60 gamma-ray beam has been determined using a thick-walled graphite ionization chamber. The chamber was calibrated in a graphite phantom against a graphite calorimeter, and the graphite calibration factor was converted to a water calibration factor using published energy absorption coefficient ratios and a measured replacement factor. Comparisons between the g...

In this paper we present the results of a dosimetric evaluation of a 2D ionization chamber array with the objective of its implementation for quality assurance in clinical routine. The pixel ionization chamber MatriXX (Scanditronix Wellhofer, Germany) consists of 32x32 chambers with a distance of 7.6 mm between chamber centres. The effective depth of measurement under the surface of the detecto...

A two dimensional allaJog of a free-air ionization chamber for the measurement of fi eld distortion was obtained by painting conducting lines on resistance paper to represent cross sections of the electrodes. Guard wires were simulated by driving record p layer needles into the paper . The volume of the chamber from which charge was collected was related to the resistance between two of the lin...

A cold plasma ionization device has been designed to monitor freeze-drying processes in situ by monitoring lyophilization chamber moisture content. This plasma device, which consists of a probe that can be mounted directly on the lyophilization chamber, depends upon the ionization of nitrogen and water molecules using a radiofrequency generator and spectrometric signal collection. The study per...