COMPUTING PATIENT DOSES OF X-RAY EXAMINATIONS USING A PATIENT SIZE-ADJUSTABLE AND SEX-ADJUSTABLE PHANTOM

Both the use of traditional fluoroscopy and the increasing use of mode rn digital techniques in radiology and interventional radiology demand the development of versatile computer programs for patient dose deter minations. Long computing times restrict the use of Monte Carlo (MC) m ethods in dose monitoring applications where the radiological views ch ange frequently. In the Organ Doses Calculation Software application ( ODS-60), the phantom model is similar in principle to the Alderson-Ran do (A-R) phantom, but its sex! size and shape is modified according to a particular patient. Organ and effective doses are computed online ( in a few seconds) using a method similar to the traditional dose plann ing systems used in radiotherapy. In this paper, the new ODS-60 softwa re is presented in detail and its capabilities are demonstrated. Softw are performance was determined by comparing the results with those fro m independent methods. In the case of a reference man-sized male, the effective dose was about 7% larger than the effective dose given in an other publication. In the case of a reference woman-sized female, the disagreement with the other method was greater (33%). Anatomical diffe rences between the phantom models (ODS-60 and MC) were found to be the main reasons for these findings. This paper shows the advantage of us ing a patient size- and sex-adaptable phantom for patient dose determi nations; the conversion coefficient from entrance surface dose-to-effe ctive dose ratio between male (170 cm, 85 kg) and a female (160 cm, 43 kg) varies in the range 1.5-2.