Author: Mitya M. Barreto, Nichole A. Harris 👨🔬
Affiliation: Department of Radiology, University Hospitals Cleveland Medical Center 🌍
Purpose: To evaluate dosimeter dependence of measured AGD, and to develop a dosimeter independent method for evaluating the AGD, for CEDM exposures.
Methods: Three solid-state dosimeters (Raysafe-X2, RTI-Piranha, Radcal-Accugold) were used to acquire HVL and radiation output (R/mAs) data on three CEDM units (Hologic Dimensions). The manufacturer’s mammography manual offered two methods for calculating the AGD for high energy (HE) and low energy (LE) exposures using direct or indirect measurements. This study compared the indirect method (-mfg) to an experimental method (-exp). The manufacturers quality control manual’s CEDM AGD procedure was used to record mAs for LE, HE, and measure total exposure. LE-AGD was calculated using the radiation output (R/mAs), acquired during W/Rh AGD test, and mAs from LE-CEDM image and mGy/R conversion factor. The indirect method calculated HE exposure by subtracting the LE from total exposure. The experimental method acquired separate 28 kVp W/Rh and 45 kVp W/Cu R/mAs data with each dosimeter. HE-AGD were calculated by multiplying corresponding mAs, R/mAs and mGy/R conversion factors.
Averages and percentage difference (PD) from the manufacturer’s target value for LE, HE-mfg and HE-exp across each meter were compared.
Results: Manufacturer’s target AGD values are 1.2mGy for LE and 0.3mGy for HE. The average LE-AGD were within 8% PD for each of the three meters. Average HE-AGD-mfg were 0.24/0.48/0.26mGy with PD greater than 10% [12-60%] from target value. Average HE-AGD-exp were 0.29/0.31/0.30mGy with less than 5% difference between dosimeter and target values.
Conclusion: The results of this study show that CEDM AGD measurements described in the manual depend on the dosimeter used. LE measurements are within dosimeter calibration error (10%). Dosimeter dependencies for HE AGD are reduced when using the output measurements for each of the individual filters and the mAs values displayed for the CEDM images to calculate the AGD.