Evaluation of coefficients to derive organ and effective doses from cone-beam CT (CBCT) scans: a Monte Carlo study

Regular imaging is used throughout image guided radiation therapy to improve treatment delivery. In order for treatment procedures to be optimized, the doses delivered by imaging exposures should be taken into account. CT dosimetry methods based on the CT dose index (CTDI), measured with a 100 mm long pencil ionization chamber (CTDI 100 ) in standard phantoms, are not designed for cone-beam CT (CBCT) imaging systems used in radiotherapy, therefore a modified version has been proposed for CBCT by the International Electrotechnical Commission (CTDI IEC ). Monte Carlo simulations based on a Varian On-Board Imaging system were used to derive conversion coefficients that enable organ doses for ICRP reference phantoms to be determined from the CTDI IEC for different scan protocols and different beam widths (80 –320) mm. A dose–width product calculated by multiplying the CTDI IEC by the width of the CBCT beam is proposed as a quantity that can be us...
Source: Journal of Radiological Protection - Category: Physics Authors: Source Type: research