The patient dose from digital mammography systems using molybdenum and tungsten targets

Abstract

Background : Two digital mammographic systems of different targets and filters offer different radiation doses to patients.

Objective : To determine the average glandular dose (AGD), the entrance surface air kerma (ESAK) from cranio-caudal (CC) and medio-lateral oblique (MLO) projections and the dose reference level (DRL) from CC projection at both breasts when two digital mammogram systems of molybdenum (Mo) target and molybdenum or rhodium (Rh) filters of one system and tungsten (W) target and rhodium filter of the other system were clinically used.

Methods : Patients’ data from two digital mammography systems were analyzed in terms of the compressed breast thickness (CBT), peak kilovoltage (kVp), milliampere-sec (mAs), average glandular dose (AGD, mGy), the entrance surface air kerma (ESAK, mGy) and dose reference level (DRL, mGy) to optimize the radiation dose to patient.

Results : Six hundred female patients were studied from two digital mammography systems from 2006 to 2009. Two hundred patient data for each target-filer of Mo-Mo, Mo-Rh and W-Rh were recorded for the CBT, kVp and mAs. The AGD was reduced by 41%, and the ESAK was reduced by 65% when W-Rh target–filter was used. The dose reference level is determined for the AGD and ESAK values.

Conclusion : The radiation dose from digital mammogram system with the W-Rh targetfilter systems was lower than the system with Mo-Mo and Mo-Rh targetfilter. The DRL from this study is less than IAEA recommendations in Basic Safety Standards.