Geometric distortion is the inaccurate representation of the size or shape of a structure in the radiographic image. Exaggerated distortion makes radiography unacceptable for diagnosis. A new algorithm that was developed by us provides data on geometric distortion (GD) and ghost artifact-distortion (GAD) of digital breast tomosynthesis (DBT) images. This algorithm is similar to the one developed by the National Coordinating Centre for the Physics of Mammography (NCCPM), with the advantage of allowing the user to select the best-fit region of interest (ROI). The selection ensures that no information about the artifact dispersion contained in a ROI is lost. The aim of this study was to evaluate the dependence of ROI dimension (width and height) on the GD and GDA evaluation in digital breast tomosynthesis images using the new algorithm and to compare the results obtained with the limit values of reference, based on routine quality control tests for breast tomosynthesis. For the analyzes, the images were initially acquired with a 5 mm thick rectangular phantom composed of polymethyl methacrylate (PMMA) containing 1 mm diameter aluminum spheres. The phantom was inserted in the 60 mm thick PMMA phantom, positioned 25 mm away from the compression tray. The height of in-focus plane, the accuracy of positioning in the focus plane, and the appearance of aluminum spheres in the adjacent in-focus planes were analyzed for different ROI dimensions.
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.
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