KEYWORDS: Breast, Mammography, Digital breast tomosynthesis, Image compression, Breast cancer, Tissues, Image analysis, X-rays, Statistical analysis, Digital mammography
This study aims to verify the relationship of MGD between four different types of manufacturing mammograms and models and to verify patient characteristic factors and GDM. Using the Volpara software were analyzed a total of 7,000 3D and 2D images. From this analysis were obtained the breast volume density (DVB) and the MGD. Using the DICOM header of the image, we collected the patient's age and compressed breast thickness. The sample of patients presented a mean of 57 (±15) mm of compressed breast thickness(CBT) for the Hologic equipment (range from 19.82 to 100.75 mm) and the medians for the other variables were 51 years (range 25 to 87 years old), 1.75 mGy MGD (0.43 to 4.68 mGy range), and 7.61% DVB (2.16% to 36.89% range). The MGD for GE Senoclaire system and Hologic were higher compared the other evaluated tomosynthesis systems as also higher for MLO projection when compared to CC projection. The Siemens equipment was the system that gave the lowest dose in all breast thicknesses evaluated.
The aim of this work is to estimate the percentage depth dose (PDD) and the mean glandular dose (MGD) at anthropomorphic breast phantoms using calibrated TLDs. For this task the TLD-100H was initially selected and calibrated in terms of air kerma, using a Radcal ionization chamber (IC). The experimental procedure was performed at a mammograph Mammomat 3000 Nova, located at the CDTN/CNEN facilities and all the detectors were exposed with 28 kV with distinct anode/filter combination (Mo/Mo, Mo/Rh and W/Rh). Furthermore, the TLDs were placed at the surface of anthropomorphic compressed breast phantoms (36-85 mm) and at 1,2 cm for depth doses measures, for PDD analyses. The MGD were estimated from entrance surface doses and using Dance´s method. The dose–response curves for the TLDs indicated a good correlation coefficient (R2 = 0,99) for all anode-filter combination with an uncertainty lower than 17%. The uncertainties of the measurements increased to maximum 35 % when the TLDs are placed the anthropomorphic breast phantom. The PDD were maximum 70%, at 1,2 cm, for the Mo/Mo target-filter combination. Regardless the target/filter (T/F) combination, the TL responses and consequently the MGDs substantially increased with the breast thickness. A maximum MGD of approximately 4.5 mGy was estimated for the 85 mm thickness breast, exposed to the Mo/Mo combination.
KEYWORDS: Breast, Digital breast tomosynthesis, Polymethylmethacrylate, Mammography, X-rays, Digital mammography, Breast cancer, Sensors, Imaging systems, Tissues
The objective of this work is to present the results for quality control tests applied to projection images acquisition in digital mammography and breast tomosynthesis (DBT). Mean glandular doses (MGD) were measured for the examination of series of women and for breast-simulating polymethyl methacrylate phantoms, thus assessing the suitability of the phantoms used for dosimetry in 2D mammography for DBT dosimetry. Moreover, X-ray tube output and half value layer measurements for MGD estimation using phantoms are also presented. Three different mammography/DBT systems were considered in this work: Hologic Selenia Dimensions, General Electric Senoclaire and Pristina and Siemens Inspiration. The results obtained for the different projections were compared with the 2D acquisitions and the differences between the two image modalities were compared.
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.
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.
In this study we analyze the impact of new x-ray beam spectra on the mean glandular doses (MGD) delivered by a digital breast tomosynthesis system. The new polyenergetic spectra are generated with a rhodium (Rh) target and a 30 μm silver (Ag) filter. To evaluate the influence of the new spectra on patient doses, we compare the MGD values with those delivered with a regular Rh/Rh target/filter combination. Individual glandularity (%) of the patients in the study was estimated using the commercial software Volpara. Median of MGD values for CC and MLO views are around 38% and 46% lower with the Rh/Ag combination than with the Rh/Rh combination. Results suggest that the new spectra, with reduced dose properties, could be very useful in breast cancer screening programs.
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