Conventional Digital Mammography Research Articles

Diagnostic Role of Digital Breast Tomosynthesis

Since its introduction in 2011, digital breast tomosynthesis has been adopted rapidly worldwide for screening mammography. Digital breast tomosynthesis is a new technology that acquires a series of low-dose images of the compressed breast from different angles while the x-ray tube moves along an overhead arc.1 This projection image dataset is then used to reconstruct 1-mm thin-section images in standard mammographic views. Displaying the breast tissue in 1-mm-thin slices results in decreased tissue overlap, improved lesion visibility, better delineation of lesion margins, and more accurate characterization of lesion architecture.1 Numerous studies have established that digital breast tomosynthesis increases the sensitivity and specificity of screening mammography. With the addition of digital breast tomosynthesis to conventional digital mammography, Skaane et al2 documented a 27% increase in the detection rate for in situ and invasive cancers combined, and a 40% increase in the detection rate for invasive cancers. Haas et al3 reported a significant reduction in screening recall rates from 12.0% to 8.4% with combined digital breast tomosynthesis and digital mammography, especially in women younger than age 50 years and those with dense breasts.

Transfer Learning From Convolutional Neural Networks for Computer-Aided Diagnosis: A Comparison of Digital Breast Tomosynthesis and Full-Field Digital Mammography

With the growing adoption of digital breast tomosynthesis (DBT) in breast cancer screening, we compare the performance of deep learning computer-aided diagnosis on DBT images to that of conventional full-field digital mammography (FFDM). In this study, we retrospectively collected FFDM and DBT images of 78 biopsy-proven lesions from 76 patients. A region of interest was selected for each lesion on FFDM, synthesized 2D, and DBT key slice images. Features were extracted from each lesion using a pretrained convolutional neural network (CNN) and served as input to a support vector machine classifier trained in the task of predicting likelihood of malignancy. From receiver operating characteristic (ROC) analysis of all 78 lesions, the synthesized 2D image performed best in both the cradiocaudal view (area under the ROC curve [AUC] = 0.81, SE = 0.05) and mediolateral oblique view (AUC = 0.88, SE = 0.04) in the task of lesion characterization. When cradiocaudal and mediolateral oblique data of each lesion were merged through soft voting, DBT key slice image performed best (AUC = 0.89, SE = 0.04). When only masses and architectural distortions (ARDs) were considered, DBT performed significantly better than FFDM (p = 0.024). DBT performed significantly better than FFDM in the merged view classification of mass and ARD lesions. The increased performance suggests that the information extracted by the CNN from DBT images may be more relevant to lesion malignancy status than the information extracted from FFDM images. Therefore, this study provides supporting evidence for the efficacy of computer-aided diagnosis on DBT in the evaluation of mass and ARD lesions.

Evaluation of a computer-aided detection (CAD)-enhanced 2D synthetic mammogram: comparison with standard synthetic 2D mammograms and conventional 2D digital mammography

To evaluate the diagnostic performance of computer-aided detection (CAD)-enhanced synthetic mammograms in comparison with standard synthetic mammograms and full-field digital mammography (FFDM). A CAD-enhanced synthetic mammogram, a standard synthetic mammogram, and FFDM were available in 68 breast-screening cases recalled for soft-tissue abnormalities (masses, parenchymal deformities, and asymmetric densities). Two radiologists, blinded to image type and final assessment outcome, retrospectively read oblique and craniocaudal projections for each type of mammogram. The resulting 204 pairs of 2D images were presented in random order and scored on a five-point scale (1, normal to 5, malignant) without access to the Digital breast tomosynthesis (DBT) slices. Receiver operating characteristic (ROC) curve analysis was performed. There were 34 biopsy-proven malignancies and 34 normal/benign cases. Diagnostic accuracy was significantly improved for the CAD-enhanced synthetic mammogram compared to the standard synthetic mammogram (area under the ROC curve [AUC]=0.846 and AUC=0.683 respectively, p=0.004) and compared to the conventional 2D FFDM (AUC=0.724, p=0.027). The CAD-enhanced synthetic mammogram had the highest diagnostic accuracy for all soft-tissue abnormalities, and for malignant lesions sensitivity was not affected by tumour size. For all 68 cases, there was an average of 3.2 areas enhanced per image. For the 34 cancer cases, 97.4% of lesions were correctly enhanced, with 2.1 false areas enhanced per image. CAD enhancement significantly improves performance of synthetic 2D mammograms and also exhibits improved diagnostic accuracy compared to conventional 2D FFDM.

Mass detection in digital breast tomosynthesis data using convolutional neural networks and multiple instance learning

Digital breast tomosynthesis (DBT) was developed in the field of breast cancer screening as a new tomographic technique to minimize the limitations of conventional digital mammography breast screening methods. A computer-aided detection (CAD) framework for mass detection in DBT has been developed and is described in this paper. The proposed framework operates on a set of two-dimensional (2D) slices. With plane-to-plane analysis on corresponding 2D slices from each DBT, it automatically learns complex patterns of 2D slices through a deep convolutional neural network (DCNN). It then applies multiple instance learning (MIL) with a randomized trees approach to classify DBT images based on extracted information from 2D slices. This CAD framework was developed and evaluated using 5040 2D image slices derived from 87 DBT volumes. The empirical results demonstrate that this proposed CAD framework achieves much better performance than CAD systems that use hand-crafted features and deep cardinality-restricted Bolzmann machines to detect masses in DBTs.

Dose and diagnostic performance comparison between phase-contrast mammography with synchrotron radiation and digital mammography: a clinical study report

Two dosimetric quantities [mean glandular dose (MGD) and entrance surface air kerma (ESAK)] and the diagnostic performance of phase-contrast mammography with synchrotron radiation (MSR) are compared to conventional digital mammography (DM). Seventy-one patients (age range, 41 to 82 years) underwent MSR after a DM examination if questionable or suspicious breast abnormalities were not clarified by ultrasonography. The MGD and the ESAK delivered in both examinations were evaluated and compared. Two on-site radiologists rated the images in consensus according to the Breast Imaging Reporting and Data System assessment categories, which were then correlated with the final diagnoses by means of statistical generalized linear models (GLMs). Receiver operating characteristic curves were also used to assess the diagnostic performance by comparing the area under the curve (AUC). An important MGD and ESAK reduction was observed in MSR due to the monoenergetic beam. In particular, an average 43% reduction was observed for the MGD and a reduction of more than 50% for the ESAK. GLM showed higher diagnostic accuracy, especially in terms of specificity, for MSR, confirmed by AUC analysis ([Formula: see text]). The study design implied that the population was characterized by a high prevalence of disease and that the radiologists, who read the DM images before referring the patient to MSR, could have been influenced in their assessments. Within these limitations, the use of synchrotron radiation with the phase-contrast technique applied to mammography showed an important dose reduction and a higher diagnostic accuracy compared with DM. These results could further encourage research on the translation of x-ray phase-contrast imaging into the clinics.

Experimental characterization of a direct conversion amorphous selenium detector with thicker conversion layer for dual-energy contrast-enhanced breast imaging.

Dual-energy contrast-enhanced imaging is being investigated as a tool to identify and localize angiogenesis in the breast, a possible indicator of malignant tumors. This imaging technique requires that x-ray images are acquired at energies above the k-shell binding energy of an appropriate radiocontrast agent. Iodinated contrast agents are commonly used for vascular imaging, and require x-ray energies greater than 33 keV. Conventional direct conversion amorphous selenium (a-Se) flat-panel imagers for digital mammography show suboptimal absorption efficiencies at these higher energies. We use spatial-frequency domain image quality metrics to evaluate the performance of a prototype direct conversion flat-panel imager with a thicker a-Se layer, specifically fabricated for dual-energy contrast-enhanced breast imaging. Imaging performance was evaluated in a prototype digital breast tomosynthesis (DBT) system. The spatial resolution, noise characteristics, detective quantum efficiency, and temporal performance of the detector were evaluated for dual-energy imaging for both conventional full-field digital mammography (FFDM) and DBT. The zero-frequency detective quantum efficiency of the prototype detector is improved by approximately 20% over the conventional detector for higher energy beams required for imaging with iodinated contrast agents. The effect of oblique entry of x-rays on spatial resolution does increase with increasing photoconductor thickness, specifically for the most oblique views of a DBT scan. Degradation of spatial resolution due to focal spot motion was also observed. Temporal performance was found to be comparable to conventional mammographic detectors. Increasing the a-Se thickness in direct conversion flat-panel imagers results in better performance for dual-energy contrast-enhanced breast imaging. The reduction in spatial resolution due to oblique entry of x-rays is appreciable in the most extreme clinically relevant cases, but may not profoundly affect reconstructed images due to the algorithms and filters employed. Degradation to projection domain spatial resolution is thus outweighed by the improvement in detective quantum efficiency for high-energy x-rays.

A randomised trial of screening with digital breast tomosynthesis plus conventional digital 2D mammography versus 2D mammography alone in younger higher risk women

IntroductionDigital breast tomosynthesis (DBT) has been shown to increase invasive cancer detection rates at screening compared to full field digital (2D) mammography alone, and some studies have reported a reduction in the screening recall rate. No prospective randomised studies of DBT have previously been published. This study compares recall rates with 2D mammography with and without concurrent DBT in women in their forties with a family history of breast cancer undergoing incident screening. Materials and methodsAsymptomatic women aged 40–49 who had previously undergone mammography for an increased risk of breast cancer were recruited in two screening centres. Participants were randomised to screening with 2D mammography only at the first study screen followed a year later by screening with 2D plus DBT, or vice versa. Recall rates were compared using an intention to treat analysis. Reading performance was analysed for the larger centre. Results1227 women were recruited. 1221 first screens (604 2D, 617 2D+DBT) and 1124second screens (558 2D+DBT, 566 2D) were analysed. Eleven women had screen-detected cancers: 5 after 2D, 6 after 2D+DBT. The false positive recall rates were 2.4% for 2D and 2.2% for 2D+DBT (p=0.89). There was a significantly greater reduction between rounds in the number of women with abnormal reads who were not recalled after consensus/arbitration with 2D+DBT than 2D (p=0.023). ConclusionThe addition of DBT to 2D mammography in incident screening did not lead to a significant reduction in recall rate. DBT may increase reader uncertainty until DBT screening experience is acquired.

Diffusion of digital breast tomosynthesis among women in primary care: associations with insurance type.

Digital breast tomosynthesis (DBT) has shown potential to improve breast cancer screening and diagnosis compared to digital mammography (DM). The FDA approved DBT use in conjunction with conventional DM in 2011, but coverage was approved by CMS recently in 2015. Given changes in coverage policies, it is important to monitor diffusion of DBT by insurance type. This study examined DBT trends and estimated associations with insurance type. From June 2011 to September 2014, DBT use in 22 primary care centers in the Dartmouth ‐Brigham and Women's Hospital Population‐based Research Optimizing Screening through Personalized Regimens research center (PROSPR) was examined among women aged 40–89. A longitudinal repeated measures analysis estimated the proportion of DBT performed for screening or diagnostic indications over time and by insurance type. During the study period, 93,182 mammograms were performed on 48,234 women. Of these exams, 16,506 DBT tests were performed for screening (18.1%) and 2537 were performed for diagnosis (15.7%). Between 2011 and 2014, DBT utilization increased in all insurance groups. However, by the latest observed period, screening DBT was used more frequently under private insurance (43.4%) than Medicaid (36.2%), Medicare (37.8%), other (38.6%), or no insurance (32.9%; P < 0.0001). No sustained differences in use of DBT for diagnostic testing were seen by insurance type. DBT is increasingly used for breast cancer screening and diagnosis. Use of screening DBT may be associated with insurance type. Surveillance is required to ensure that disparities in breast cancer screening are minimized as DBT becomes more widely available.

Evaluation of patient dose saving in grid-less x-ray mammography acquisition compared with full field digital mammography (FFDMG) acquisition

Purpose. To investigate the patient radiation dose saving of grid-less x-ray mammography acquisitions compared with conventional full-field digital mammography (FFDMG). Methods and materials. The Siemens Inspiration MAMMOMAT PRIME system with software based scatter correction was used to investigate the dose saving in grid-less acquisition compared with conventional full-field digital mammography (FFDMG) acquisitions. A Piranha 657 solid-state detector was used to measure the entrance exposure. The entrance exposure was directly measured on different PMMA thicknesses of 20–70 mm in steps of 10 mm. The PMMA block thicknesses were then converted to an equivalent compressed breast tissue thicknesses. The average glandular dose (AGD) is calculated. Results. Dose reduction in both the directly measured entrance exposure and the calculated AGD is between 13% and 32% in the grid-less mammography acquisition. The contrast to noise ratio calculated in the grid-less and the FFDMG acquisition also was the same. Conclusion. It was possible to save patient dose (13%–32%) in grid-less mammography acquisition without affecting the image quality.

An Overview of Digital Breast Tomosynthesis

Digital breast tomosynthesis is a new imaging technology, which provides a more accurate view of the breast as compared to digital mammography. Conventional digital mammography produces a two-dimensional image of overlapping tissue, potentially obscuring malignancies. In addition, complex areas of normal tissue may be perceived as suspicious. Digital breast tomosynthesis is being implemented at breast centers throughout the country as clinical data demonstrate it addresses the limitations of conventional mammography. Studies of breast tomosynthesis have shown decreased false-positive recall rates and increased rates of cancer detection associated with the technology’s ability to minimize the effect of superimposed tissue and improve lesion visibility and characterization. We have experienced favorable results with breast tomosynthesis at our facility.

Strategies to Increase Cancer Detection: Review of True-Positive and False-Negative Results at Digital Breast Tomosynthesis Screening.

Digital breast tomosynthesis (DBT) represents a valuable addition to breast cancer screening by decreasing recall rates while increasing cancer detection rates. The increased accuracy achieved with DBT is due to the quasi-three-dimensional format of the reconstructed images and the ability to "scroll through" breast tissue in the reconstructed images, thereby reducing the effect of tissue superimposition found with conventional planar digital mammography. The margins of both benign and malignant lesions are more conspicuous at DBT, which allows improved lesion characterization, increased reader confidence, and improved screening outcomes. However, even with the improvements in accuracy achieved with DBT, there remain differences in breast cancer conspicuity by mammographic view. Early data suggest that breast cancers may be more conspicuous on craniocaudal (CC) views than on mediolateral oblique (MLO) views. While some very laterally located breast cancers may be visualized on only the MLO view, the increased conspicuity of cancers on the CC view compared with the MLO view suggests that DBT screening should be performed with two-view imaging. Even with the improved conspicuity of lesions at DBT, there may still be false-negative studies. Subtle lesions seen on only one view may be discounted, and dense and/or complex tissue patterns may make some cancers occult or extremely difficult to detect. Therefore, radiologists should be cognizant of both perceptual and cognitive errors to avoid potential pitfalls in lesion detection and characterization. ©RSNA, 2016 Online supplemental material is available for this article.

SU‐F‐I‐53: Coded Aperture Coherent Scatter Spectral Imaging of the Breast: A Monte Carlo Evaluation of Absorbed Dose

Purpose:Coherent scatter based imaging has shown improved contrast and molecular specificity over conventional digital mammography however the biological risks have not been quantified due to a lack of accurate information on absorbed dose. This study intends to characterize the dose distribution and average glandular dose from coded aperture coherent scatter spectral imaging of the breast. The dose deposited in the breast from this new diagnostic imaging modality has not yet been quantitatively evaluated. Here, various digitized anthropomorphic phantoms are tested in a Monte Carlo simulation to evaluate the absorbed dose distribution and average glandular dose using clinically feasible scan protocols.Methods:Geant4 Monte Carlo radiation transport simulation software is used to replicate the coded aperture coherent scatter spectral imaging system. Energy sensitive, photon counting detectors are used to characterize the x‐ray beam spectra for various imaging protocols. This input spectra is cross‐validated with the results from XSPECT, a commercially available application that yields x‐ray tube specific spectra for the operating parameters employed. XSPECT is also used to determine the appropriate number of photons emitted per mAs of tube current at a given kVp tube potential. With the implementation of the XCAT digital anthropomorphic breast phantom library, a variety of breast sizes with differing anatomical structure are evaluated. Simulations were performed with and without compression of the breast for dose comparison.Results:Through the Monte Carlo evaluation of a diverse population of breast types imaged under real‐world scan conditions, a clinically relevant average glandular dose for this new imaging modality is extrapolated.Conclusion:With access to the physical coherent scatter imaging system used in the simulation, the results of this Monte Carlo study may be used to directly influence the future development of the modality to keep breast dose to a minimum while still maintaining clinically viable image quality.

Fetal Implications of Diagnostic Radiation Exposure During Pregnancy: Evidence-based Recommendations.

The purpose of this article is to review the fetal and long-term implications of diagnostic radiation exposure during pregnancy. Evidence-based recommendations for radiologic imaging modalities utilizing exposure of diagnostic radiation during pregnancy, including conventional screen-film mammography, digital mammography, tomosynthesis, and contrast-enhanced mammography are described.

Clinical evaluation of contrast-enhanced digital mammography and contrast enhanced tomosynthesis—Comparison to contrast-enhanced breast MRI

PurposeTo compare the diagnostic accuracy of contrast-enhanced digital mammography (CEDM) and contrast-enhanced tomosynthesis (CET) to dynamic contrast enhanced breast MRI (DCE-MRI) using a multireader-multicase study. MethodsInstitutional review board approval and informed consents were obtained. Total 185 patients (mean age 51.3) with BI-RADS 4 or 5 lesions were evaluated before biopsy with mammography, tomosynthesis, CEDM, CET and DCE-MRI. Mediolateral-oblique and cranio-caudal views of the target breast CEDM and CET were acquired at 2 and 4min after contrast agent injection. A mediolateral-oblique view of the non-target breast was taken at 6min. Each lesion was scored with forced BI-RADS categories by three readers. Each reader interpreted lesions in the following order: mammography, tomosynthesis, CEDM, CET, and DCE-MRI during a single reading session. ResultsHistology showed 81 cancers and 144 benign lesions in the study. Of the 81 malignant lesions, 44% (36/81) were invasive and 56% (45/81) were non-invasive. Areas under the ROC curve, averaged for the 3 readers, were as follows: 0.897 for DCE-MRI, 0.892 for CET, 0.878 for CEDM, 0.784 for tomosynthesis and 0.740 for mammography. Significant differences in AUC were found between the group of contrast enhanced modalities (CEDM, CET, DCE-MRI) and the unenhanced modalities (all p<0.05). No significant differences were found in AUC between DCE-MRI, CET and CEDM (all p>0.05). ConclusionCET and CEDM may be considered as an alternative modality to MRI for following up women with abnormal mammography. All three contrast modalities were superior in accuracy to conventional digital mammography with or without tomosynthesis.

Digital breast tomosynthesis and breast ultrasound: Additional roles in dense breasts with category 0 at conventional digital mammography

PurposeTo compare the diagnostic performances of digital breast tomosynthesis (DBT) and ultrasound for the dense breasts with category 0 at conventional digital mammography. Materials and methodsThis retrospective study was approved by the institutional review board, and informed consent was waived. Among the 1103 patients who underwent screening digital mammography at our institution, 769 (69.7%) patients had dense breasts. Of the 769 patients, 229 (29.8%) lesions were categorized as 0. DBT, breast ultrasound and digital mammography were performed in 108 (47.2%) patients. BI-RADS final assessments for DBT and ultrasound were recorded. Categories 1–3 were clinically considered as benign, and categories 4 and 5 were clinically considered as malignant. The diagnostic performances of breast ultrasound and DBT were correlated with final pathologic reports or follow-up images. ResultsAmong 108 lesions, 17 (15.7%) were malignant and 91 (84.3%) were benign. Sensitivity was 100% for both ultrasound (17/17) and DBT (17/17) and negative predictive value was also 100% for both ultrasound (49/49) and DBT (74/74). Specificity and positive predictive value for ultrasound were 53.9% (49/91) and 28.8% (17/59), respectively. Specificity and positive predictive value for DBT were 81.3% (74/91) and 50% (17/34), respectively. DBT showed higher diagnostic accuracy than that of breast ultrasound (DBT: 84.3%, 91/108; ultrasound: 61.1%, 66/108; p<0.001). The benign biopsy rate of DBT (50%, 17/34) was lower than that of ultrasound (71.2%, 42/59). ConclusionDBT showed better diagnostic performance than breast ultrasound for dense breasts with category 0. DBT may reduce the benign biopsy rate and short term follow-up.

Comparative study of breast tissue coverage in cone-beam breast CT versus digital mammography

Objective To evaluate the d breast tissue coverage of cone-beam breast computed tomography (CBBCT) compared with conventional digital mammography. Methods CBBCT scans and digital mammography in 96 patients (141 breasts) over the age of 35 were prospectively assessed in the study. CBBCT scans were performed within 1 week after digital mammography. Superior, inferior, medial, lateral, posterior coverage of breast tissue in CBBCT and digital mammography were evaluated, respectively. It wasconsidered as positive if there was a breast coverage. McNemar test was used to assess differences in breast coverage between CBBCT and digital mammography. Results Within all the 141 cases, digital mammography covers the superior aspects in 141 cases (100.0%), inferior aspects in 88 cases (62.4%), medial aspects in 52 cases (36.9%), lateral aspects in 60 cases (42.6%), and posterior aspects in 17 cases (12.0%). CBBCT covers the superior aspects in 136 cases (96.4%), the inferior aspects in 136 cases (96.4%), the medial aspects in 129 cases (91.5%), the lateral aspects in 129 cases (91.5%), and the posterior aspects in 129 cases (91.5%). CBBCT had statistically significant better coverage than digital mammography in the inferior, medial, lateral, and posterior aspects (χ2 values were 42.48, 67.95, 60.05 and 108.08, respectively; all P values<0.01) regions. No statistically significant difference (χ2 value=3.20,P=0.074) was found in the superior aspects. Conclusion CBBCT has better breast tissue coverage than conventional digital mammography, especially in posterior aspects of breast tissues. Key words: Mammography; Cone beam computed tomography

Suspicious Findings at Digital Breast Tomosynthesis Occult to Conventional Digital Mammography: Imaging Features and Pathology Findings.

To review the imaging and pathologic features of a series of lesions detected at digital breast tomosynthesis (DBT), which are occult to conventional digital mammography (DM). We retrospectively reviewed 268 consecutive breast imaging reporting and data system 4 and 5 lesions imaged with both DM and DBT at our facility from July 2012 through April 2013. For each lesion, we recorded the mammographic finding, breast density, mode of biopsy, and pathology results. A total of 19 lesions were identified at DBT that were occult to DM. Sixty three percent (12/19) of these lesions were identified in dense breasts. Architectural distortion was seen in 74% (14/19) of cases and spiculated masses accounted for the remaining 26% (5/19). The positive predictive value of biopsy was 53% (10/19). Seven cases were infiltrating ductal carcinomas and three were infiltrating lobular carcinomas. High-risk lesions accounted for 47% (9/19) of the lesions, the majority of which were radial scars 67% (6/9). Eighty four percent (16/19) of the lesions underwent ultrasound guided core biopsy while the remainder underwent magnetic resonance imaging guided core biopsy. DBT may demonstrate suspicious lesions that are occult to DM, particularly in women with dense breasts. Such lesions have a high likelihood of malignancy and warrant biopsy.

Predictors of responses and sexual function for women in the St George breast boost randomized trial (StGBBT)

s / The Breast 24 (2015) 302e307 304 Resonance Imaging (CEMRI) is currently the most sensitive imaging technique for breast cancer detection; however, it suffers from many drawbacks including high cost, timely accessibility, patient contraindications and low specificity. Previous studies have shown that contrast enhanced spectral mammography (CESM) may have similar diagnostic capability to CEMRI without these associated costs (2). Methods: The study included patients with biopsy proven breast cancer aged 21 years, fit for surgery, and excluded patients with contra-indications to intravenous contrast or CEMRI, candidates for neo-adjuvant chemotherapy, or who had pure in situ carcinoma. Participants underwent both CESM and CEMRI. Studies were independently double read and results benchmarked against the final surgical histopathology, core biopsy histology or one year follow-up imaging. CESM and CEMRI were compared for 1) detection of additional lesions 2) ability to size the index lesion 3) influence on surgical plan and 4) participant satisfaction. Results: A minimum of 19 participants was analysed for each study objective. For the detection of additional lesions (n1⁄421), the addition of CESM to conventional imaging increased sensitivity from 50% to 67% with specificity unchanged (47%). Addition of CEMRI to standard imaging increased sensitivity from 50% to 100% but with considerable reduction in specificity (47% to 7%). The geometric mean of index lesion size at pathology was similar for CESM and CEMRI (n1⁄424). For 19 patients, CESM and CEMRI had identical influence on the surgery plan. Participants preferred CESM to CEMRI (n1⁄434, p1⁄40.0005). Conclusions: Results so far suggest CESM has similar diagnostic capacity to CEMRI and is preferred by patients.

Examination of the relevance of using radiochromic films in measuring entrance skin dose distribution in conventional digital mammography.

Based on manufacturer specifications, radiochromic films are sensitive enough to be used for dosimetry in digital mammography (DM). The aim of this work was to study the feasibility of measuring entrance surface dose (ESD) distribution using Gafchromic XR-QA2 films. The films were irradiated following a standard clinical two-view screening mammography protocol using a full-field digital mammography (FFDM) imaging system. The films were then digitised using a flatbed scanner. The calibration curve relating the readings from a calibrated ionisation chamber and the films' net optical density (NOD) could not be obtained. The examination of the calibration data revealed non-sensitivity of the films to resolve dose differences below 20 mGy at 28 kVp. Therefore, radiochromic films were found not to be suitable for measuring ESD profiles in DM. A 2D map of the NOD of the irradiated films obtained using in-house developed MATLAB computer program is presented.

An experimental study of the scatter correction by using a beam-stop-array algorithm with digital breast tomosynthesis

Digital breast tomosynthesis (DBT) is a technique that was developed to overcome the limitations of conventional digital mammography by reconstructing slices through the breast from projections acquired at different angles. In developing and optimizing DBT, The x-ray scatter reduction technique remains a significant challenge due to projection geometry and radiation dose limitations. The most common approach to scatter reduction is a beam-stop-array (BSA) algorithm; however, this method raises concerns regarding the additional exposure involved in acquiring the scatter distribution. The compressed breast is roughly symmetric, and the scatter profiles from projections acquired at axially opposite angles are similar to mirror images. The purpose of this study was to apply the BSA algorithm with only two scans with a beam stop array, which estimates the scatter distribution with minimum additional exposure. The results of the scatter correction with angular interpolation were comparable to those of the scatter correction with all scatter distributions at each angle. The exposure increase was less than 13%. This study demonstrated the influence of the scatter correction obtained by using the BSA algorithm with minimum exposure, which indicates its potential for practical applications.