Mammography and tomosynthesis diagnostic techniques contribute to the patient dose and the estimation of the Mean Glandular Dose (MGD) for x-ray based imaging modalities forms an essential part of quality control (QC) and for system optimization. This study compares three solid‐state dosimeters (SStDs) and one thermoluminescence dosimeter (TLD) with a half value layer (HVL) measurements by ion chamber. These electronics SStDs instruments are very efficient in clinical practice. However, a specialized technician is required for its operation and the clinics do not have this instrumentation. Thus, the application of a TLD system becomes an important means for determining the MGD through the evaluation of Ka,i and HVL. For measurements used a Siemens Mammomat 3000 Nova mammography to evaluate the dosimetry systems. The three electronics SStDs detectors (Accu-Gold Radcal, Unfors RaySafe Xi and Piranha), TLD system and TRS457 table were compared with ion chamber results for HVL. The results showed that SStDs and TLD dosimeters have a flat HVL response under clinical conditions (less than 5%). However, the SStDs detectors tended to overestimate the measurements. However, all results were equivalent (p<0,05) for all HVL evalueted.
Evaluation of the performance of all mammographic equipment requires the imaging and interpretation of test objects or phantoms and risk evaluation. The Mean glandular dose (MGD) is the relevant quantity for dosimetric regulatory actions in screening mammography and its evaluated usually obtained with a polymethylmethacrylate (PMMA) phantom. This study evaluated by spectrometry technique the linear attenuation coefficients by transmitted intensity of commercially tissue-equivalent phantom for mammography, Computerized Imaging Reference System (CIRS) with different glandularity-adipose content (0-100, 30-70, 50-50, 70-70 and 100-0) % and PMMA. The measurements were realized with x-ray beams produced by Mo/Mo, Mo/Rh and W/Rh. The results are available for the x-ray characteristic photo-peaks (kα1 Mo 17.48 keV and kα2 Mo 19.61 keV). For spectrometry measurements use an AMPTEK XR-100T Cadmium Telluride (CdTe) detector. Simulations using the MCNPx Monte Carlo code were performed to evaluate the detector response. The results of corrections performed using the methodology presented here were compared with spectra corrected by other authors, for validation purposes. The comparisons showed that this methodology was adequate for the correction of spectra from 2 keV to 200 keV. The results of linear attenuation coefficients here were compared with experimental and theoretical values that were previously reported. In this work we show the adequacy of the results found for PMMA and CIRS 50-50 compared. In addition, it brings the evaluation of the attenuation coefficient for kα2 Mo with 19.61 keV for all CIRS combinations.
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