Evaluation of the dosimetric properties of a synthetic single crystal diamond detector in high energy clinical proton beams.

Purpose: To investigate the dosimetric properties of a synthetic single crystal diamond Schottky diode for accurate relative dose measurements in large and small field high-energy clinical proton beams.

Methods: The dosimetric properties of a synthetic single crystal diamond detector were assessed by comparison with a reference Markus parallel plate ionization chamber, an Exradin A16 microionization chamber, and Exradin T1a ion chamber. The diamond detector was operated at zero bias voltage at all times.

Conditions for reliable time-resolved dosimetry of electronic portal imaging devices for fixed-gantry IMRT and VMAT.

Purpose: The continuous scanning mode of electronic portal imaging devices (EPID) that offers time-resolved information has been newly explored for verifying dynamic radiation deliveries. This study seeks to determine operating conditions (dose rate stability and time resolution) under which that mode can be used accurately for the time-resolved dosimetry of intensity-modulated radiation therapy (IMRT) beams.

Methods: The authors have designed the following test beams with variable beam holdoffs and dose rate regulations: a 10 × 10 cm open beam to serve as a reference beam; a sliding window (SW) beam utilizing the motion of a pair of multileaf collimator (MLC) leaves outside the 10 × 10 cm jaw; a step and shoot (SS) beam to move the pair in step; a volumetric modulated arc therapy (VMAT) beam.

Development and test of a GEM-based TEPC for neutron protection dosimetry.

A novel tissue-equivalent proportional counter (TEPC) based on a gas electron multiplier (GEM) for measuring H*(10) for neutrons was designed and constructed. The pulse height spectra (PHS) of two different neutron sources (a 252Cf source and a AmBe source) were measured using the new TEPC. The measurements were made with the TEPC filled with two different gases (10P gas and a propane-based tissue-equivalent gas) at various pressures.

Design and simulation of a GEM-based TEPC as a neutron REM meter.

A new plate-like tissue equivalent proportional counter (TEPC) based on the gas electron multiplier (GEM) is being developed for use as a neutron rem meter. The advantage of a plate-like TEPC over a conventional spherical TEPC is that several of the plate-like TEPCs can be stacked together as one unit to increase sensitivity to neutrons. A GEM-based TEPC consists of four layers of materials in a series: the front cover made of polyethylene, the cathode made of A-150 plastic, the gas region containing 1/3 atm of P-10 and 1/3 atm of nitrogen and the anode made of a copper-coated printed circuit board.