WALL THICKNESS OPTIMISATION OF AN IONISATION CHAMBER FOR DIRECTIONAL DOSE EQUIVALENT RATE MEASUREMENT AT LOW AND MEDIUM PHOTON ENERGIES

Abstract

Abstract A thin and plane wall ionisation chamber having 900 cc volume was designed and fabricated to study the calibration coefficient dependency on ionisation chamber wall thickness for directional dose equivalent rate (Ḣ′(d)) at various low and medium energy X-ray beam qualities. Optimised wall thickness was established through measurements to achieve a near flat energy response using the developed ionisation chamber. The measurement shows that in the energy range 12–213 keV, the average calibration coefficient for directional dose equivalent rate lies within ±10% for wall thickness 1.2 mg/cm2 and 480 mg/cm2 (4 mm poly methyl methacrylate) for skin and eye lens dose monitoring, respectively. The study could be useful for the estimation of skin and eye lens doses for the paramedical staff and patient during the interventional radiology and interventional cardiology procedures by monitoring the directional dose equivalent rate.