Full-field Digital Mammography System Research Articles

Performance evaluation of six digital mammography systems

The strong advance in digital mammography as a tool for breast cancer screening requires that the new systems be characterized. Quality control protocols describe the methodology to evaluate systems performance. Detective quantum efficiency (DQE) is the most suitable parameter for describing the imaging performance of an X-ray imaging device. The objective of this study was to characterize in terms of DQE six digital mammography systems, at different detector air kerma (DAK) levels for a variety of beam qualities. A Carestream EHR-M3 CR detector, a small field digital mammography system Siemens Opdima, and full field digital mammography systems Planmed Clarity, GE Essential, GE Pristina and GE Crystal Nova were characterized using the European Guidelines protocol. Modulation transfer function (MTF), normalized noise power spectrum (NNPS) and DQE were determined, for an extended detector air kerma range. Attenuated beam qualities (obtained by adding 2 mm Al to the corresponding beam qualities) used were 28 kV with anode/filter combination Mo/Mo for the EHR-M3, Opdima, Essential and Pristina systems; 28 kV W/Ag for the Clarity; 28 kV W/Rh for the Crystal Nova; 28 kV Mo/Rh for the EHR-M3; and 34 kV Rh/Ag for the Pristina. Two groups were identified in MTF analysis, and the group composed of Clarity, Opdima and Essential presented the highest MTF values. In NNPS analysis, three main groups were identified, in which the systems Crystal Nova and Essential presented lower and higher NNPS, respectively. Crystal Nova system also exhibited higher DQE values for low spatial frequencies, while Opdima and Clarity presented higher DQE values for medium to high spatial frequency. Agreement with data from literature indicates that the systems evaluated are operating under typical conditions. Evidence of improvement in detectors performance was found.

A comparison of physical image quality of two hologic digital mammography systems that utilise linear and 2D anti-scatter grids

Objective. Full-field digital mammography (FFDM) systems manufactured by Hologic that utilise either a 2D or linear anti-scatter grid have recently been installed in our clinic. The manufacturer advise that for matched dose, both grids deliver comparable image quality. The aim of this study was to test the manufacturer’s claim using advanced physical image quality metrics and to inform whether the different grids are indeed dose neutral. Approach. Effective detective quantum efficiency (eDQE), effective noise equivalent quanta (eNEQ) and effective dose efficiency (eDE) were measured on a Hologic Dimensions (2D grid) and a Hologic 3Dimensions (linear grid) FFDM system, both calibrated at installation to provide matched threshold contrast, according to the EUREF protocol. eDQE, eNEQ and eDE were calculated and compared using 2, 4, 6 and 7 cm thicknesses of poly (methyl methacrylate) (PMMA) to simulate a clinically appropriate range of breast thicknesses. The beam qualities (target/filter and kilovoltage) chosen were identical between the two systems. Main results. All image quality metrics investigated show that the 2D grid outperforms the linear grid across all spatial frequencies. Furthermore, mean glandular dose (MGD) must be increased by up to 38% on those units that utilise the linear grid if eNEQ is to be matched, although MGD to the standard breast remains within NHSBSP tolerance and below the UK diagnostic reference level. The gradient and shape of each curve was the same irrespective of which grid was used, suggesting that subtle lesions (low frequency information) and micro-calcifications (high frequency information) will be imaged just as efficiently with a linear or 2D grid. Significance. If image quality is to be matched between those units utilising 2D and linear grids, dose must be increased on the latter. This information will be useful to the medical physicist tasked with the optimisation and standardisation of Hologic FFDM units.

Study of the performance change in digital mammography systems depending on the total number of examinations

Digital mammography equipment should operate at a high-performance level for detecting breast cancer over the lifetime of the systems. This study investigates the performance of the Fujifilm Amulet Innovality full-field digital mammography system in relation to the number of exposures. The performance of twelve systems, from new and up to 17 000 examinations, was compared. The x-ray output, half-value layer (HVL), contrast-detail (C-D) detectability, contrast-to-noise ratio (CNR), mean glandular dose (MGD), signal transfer property (STP), pre-sampled modulation transfer function (MTF), normalized noise power spectra (NNPS), detective quantum efficiency (DQE) tests were performed to determine the performance change. The noise sources were also analyzed in the spatial domain. The x-ray output and HVL values at 28 kV with tungsten anode and rhodium filter were 15 μGy/mAs ± 1.0 (coefficient of variation (cov) = 7.0%) and 0.54 mmAl ± 0.008 (cov = 1.5%), respectively. The average MGDs for 60 mm equivalent breast to reach the achievable image quality level for 0.1 mm and 0.25 mm detail diameters of circular discs on the CDMAM 3.4 phantom image were 1.17 mGy ± 0.13 (cov = 11%) and 1.40 mGy ± 0.09 (cov = 6%), respectively. The average MGD for 53 mm equivalent breast was 1.08 mGy ± 0.14 (cov = 13%) at dose setting Normal in automatic exposure control (AEC) mode. All tested devices demonstrated good linearity with R2 ≥ 0.999 in the STP curves. The average MTF at 5.0 mm−1 spatial frequency was 0.66 ± 0.007 (cov = 1.0%). The average NNPS was 2.38 × 10−6 mm2 ± 2.13 × 10−7 (cov = 9.0%) at 5.0 mm−1. The average DQE value at 5.0 mm−1 was 0.33 ± 0.02 (cov = 5.0%), and the mean peak DQE was 0.66 ± 0.03 (cov = 5.0%). The mean power coefficient (b), determined from the power relationship between linearised standard deviation and detector dose while analyzing noise sources, was 0.49 ± 0.007 (cov = 1.4%). There was no gradual change in the x-ray tube and detector performance by the number of exposures, and taking up to 68 000 images did not decrease the quality of the systems.

Investigation of polyvinyl alcohol (PVAL) composite gels and the outcome of variation in breast phantom densities on image quality and dose in full-field digital mammography

This study evaluates the possibility of using a blend of polyvinyl alcohol (PVAL) and graphite powder as phantom materials to stimulate an extremely dense breast tissue for mammography based on the Breast Imaging-Reporting and Data System (BIRADS). The linear (μ) and mass attenuation coefficients (μ/ρ), computed tomography (CT) number, and physical and relative electron densities of the fabricated PVAL materials were determined. Mammography images of the fabricated PVAL materials and standard RMI 156 mammography phantoms were acquired using full-field digital mammography (FFDM) system at 28 kVp. The effect of breast density on contrast (Cn), contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR), and mean glandular dose (MGD) were evaluated. The fabricated phantoms made from PVAL + 4% graphite powder (G4) showed good resemblance to extremely dense breast tissues (BIRADS D). Higher Cn, CNR, and SNR values were achieved with lower density breast equivalent phantoms. Density correlated positively with mean glandular dose (MGD) and the values of the MGD for the different categories of phantoms were within the acceptable limit of 3.0 mGy consistent with the ACR protocol.

Dual-energy tissue cancellation in mammography for improved detection of microcalcifications and neoplasms: A phantom study

Dual-energy mammography and the tissue-cancellation algorithm were applied to the problem of enhancing the detectability of calcifications and lesions in cluttered mammogram background. A multicomponent (plexiglass (PMMA), polypropylene (PP), water) tissue-equivalent breast phantom and a standard full-field digital mammography system operating in two of its standard operating modes (26 kVp, 40 mAs, Mo/Mo and 49 kVp, 6.3 mAs, Rh/Rh target/filter) were used. We studied to what extent the contrast between the tissue substitutes can be eliminated depending on the difference in their attenuation properties, and whether the obtained level of contrast cancellation is sufficient to unambiguously discriminate microcalcifications and inserts from the background.Mixed results were obtained. It was shown that the tissue-cancellation method can provide nearly perfect elimination of the background clutter (17-fold decrease in standard deviation) for homogeneous materials with close attenuation properties (PMMA and water) while increasing the contrast of a third material (PP, 1.7 times increase in contrast-to-noise ratio), thus facilitating its detection and delineation.However, canceling the contrast between materials with more different attenuation properties (PP and water) does not simultaneously lead to any significant enhancement of the contrast of a third material (PMMA), if its attenuation properties are close to those of either PP or water. Moreover, intrinsic inhomogeneity of the phantom constituents becomes important as it results in incomplete contrast cancellation and preservation of visually significant background clutter. Although contrast cancellation increased the signal-to-noise ratio of microcalcifications by about 33%, the relative contrast calcifications—background​ can diminish, making it possible for the remaining clutter to obscure the microcalcifications.

Effect of Compression Force and Target or Target/Filter Combination on Mean Glandular Dose for Japanese Women in Full-Field Digital Mammography System

We constructed a mammography database of 807 Japanese women and 2,772 images obtained using five commercial full-field digital mammography (FFDM) devices at four different facilities. Five types of mammography devices fabricated by four manufacturers were used: one with a Mo target (AMULET F), one with Mo and Rh targets (Senographe DS), one with Mo and W targets (AMULET), and two with a W target (MAMMOMAT Fusion and Selenia Dimensions). The purpose of this study was to focus on the mean glandular dose (MGD) in the database and analyze the difference in the MGD of Japanese women radiographed by mammographic devices with different targets or target/filter combinations. Furthermore, we clarify the difference between the displayed and measured MGDs for the three types of mammography devices. The average compression pressure and compression breast thickness of the Japanese women in the mammography in this study were 90.9±21.7 N and 43.3±12.9 mm, respectively. The breast compression pressure slightly varied depending on the facility or FFDM device, while the compression breast thickness decreased with the increase in the compression pressure for all FFDM devices. Differences in breast compression thickness existed depending on the mammography devices. The MGDs of the two types of mammography devices using the W target were smallest (1.335±0.358, 1.218±0.464 mGy). The displayed and measured MGDs of the three types of FFDM devices had a good correlation. However, the difference between the displayed and measured MGDs of the two devices increased with the MGD.

Kuwait National Mammography Screening Program: outcomes of 5 years of screening in Kuwaiti women.

BACKGROUND: Breast cancer is the most common malignancy among women in Kuwait, representing 39.8% of all female cancer cases.OBJECTIVES: Report the data of the Kuwait National Mammography Screening Program (KNMSP) for a 5-year period.DESIGN: Prospective data collection.SETTING: Population-based screening.SUBJECTS AND METHODS: We included mammography screens done for Kuwaiti women (age 40 years and older) who attended the KNMSP from 2014 to 2019 to screen for breast cancer. A full-field digital mammography system was used to acquire the mammographic images in craniocaudal and mediolateral oblique projections. Independent double-blind reading of the mammograms was performed by two radiologists.MAIN OUTCOME MEASURE: Early detection of breast cancer.SAMPLE SIZE: 14 773 asymptomatic women met inclusion criteria (mean [SD] age, 51.8 (8.2).RESULTS: Lesions were detected in 551 women (3.7%). These included 233 malignant lesions (233/551, 42.3%), 57 high-risk lesions (10.3%) and 261 benign lesions (47.4%). The participation rate was 7.8% of the target population of women 40–69 years of age. The majority of breast cancer cases were reported in the age group 45–49 years (23.2%). The KNMSP study recall rate for 5 consecutive years was in a range of 11.9–16.5% (mean, 14.3%). The detection rate of ductal/lobular carcinoma in situ and invasive breast cancer were 2.5 and 13.6 per 1000 screened women, respectively. Invasive ductal carcinoma was the most common type. Only 4314 women followed up within 12–15 months of the first mammography for a retention rate of 29.2%.CONCLUSIONS: Screening mammography improves early detection of breast cancer in women older than 40 years but poor participation is a limitation. We are aiming to increase the participation rate to 70% of the population.LIMITATIONS: Lack of participation by women.CONFLICT OF INTEREST: None.

A history of DMIST and its implications - Limited resources should be better spent

Randomized, Controlled Trials (RCT), the most rigorous tests of efficacy, had proven that mammography screening reduces deaths by early detection. This had been validated in studies that showed that screening in the community also resulted in fewer deaths. Film mammography (FM) had been replaced by Xeroradiography (XM) which had been replaced by Screen/Film Mammography (SFM) which was being replaced by Full Field Digital Mammography (FFDM). The FDA required FFDM to undergo a Premarket Approval (PMA) instead of the usual 510 K required for conversion for other x-ray studies to digital imaging. In addition, the FDA was going to require that even after a PMA, the FFDM systems were going to have to undergo a post approval RCT comparison to SFM. Experience and science were able to convince the FDA that a post-approval trial was not needed, and the requirement was dropped. Congress, however, had earmarked $25 million to support the trial that was no longer required. It appears that the Digital Mammographic Imaging Screening Trial (DMIST) was undertaken to take advantage of the earmarked money and was used to compare SFM to FFDM for cancer detection. The historical issues involved with DMIST provide an important background for the Tomosynthesis Mammographic Imaging Screening Trial (TMIST). Just as the monies for DMIST could have been better spent on an RCT of MRI for screening, the monies for TMIST could be better spent to improve our ability to detect more breast cancers at a time in their growth when cure may be possible.

Survey of Mean Glandular Dose to Patients During Mammography Examinations: A Retrospective Study

The radiation dose delivered to patients undergoing mammography examination is of utmost importance because of the risk of cancer induction due to the process. In this work, we analyze the dose to 109 patients (214 images) who underwent mammographic examinations with a full-field digital mammography (FFDM) system. Quality control assessment was first performed using the International Atomic Energy Agency (IAEA) Human Health Series 2 and 17 protocol and the European guidelines for quality assurance in breast cancer screening and diagnosis. The results from the quality control test performed indicates that the system is functioning well. The mean glandular dose of patients analyzed shows that 23 out of 109 patients received averaged doses higher than the acceptable level at the same equivalent breast thickness of a phantom. The mammography system at the department is recommended for continuous use for imaging and screening of patients.

Using aluminum for scatter control in mammography: preliminary work using measurements of CNR and FOM.

Full-field digital mammography (FFDM) systems provide the current gold standard in mammographic examinations. Although FFDM provides the lowest mammographic doses, the radiation dose to the breast during mammographic examinations is still a concern. Thus, image quality optimization at the lowest dose is a major goal. In planar X-ray imaging, thin sheets of aluminum (Al) are used as filtration to reduce the number of low-energy X-ray photons reaching the patient. The goal of this work was to evaluate whether Al can be used in FFDM to remove scatter radiation from reaching the image detector, hence improving image quality. Doses were compared with the use of a grid. A Hologic Selenia mammographic unit was used to acquire images of two phantoms, namely, the ACR phantom and a Perspex phantom of 5cm. Images were acquired using two tube voltages (kVp) and filter combinations under two exposure/dose conditions. Al sheets of various thicknesses were placed between the phantom and the image detector. Contrast-to-noise ratio (CNR) and figure of merit (FOM) values were measured and compared with images acquired using a grid. When a constant dose was delivered to the image detector, the highest CNR was achieved using a grid; however, the highest FOM values were achieved when using 0.05mm thick Al sheets. This study successfully demonstrates that thin sheets of Al can be used in mammography examinations to reduce scattered radiation and improve image quality, as indicated by the measured CNR values. Given the limitations of this work, further kVp and target/filter combinations and various methods of image quality measurement need to be studied.

Breast phantoms for 2D digital mammography with realistic anatomical structures and attenuation characteristics based on clinical images using 3D printing

The aim of this work was to develop a production process for breast phantoms for 2D digital mammography (DM) with realistic anatomical structures and attenuation characteristics based on clinical images using 3D printing.The presented production process is based on PolyJet 3D printing technology using a polypropylene like printing material. First, an attenuation calibration function for this material and the achievable lateral resolution of the printing process of about 200 µm was determined. Subsequently, to generate the digital 3D model of the breast phantom, the pixel intensities of the unprocessed clinical image that are related to the attenuation along the z-axis of the breast, were converted to corresponding phantom heights using the calibration function.To validate the process, an image of the 3D printed breast phantom was acquired on the full field digital mammography (FFDM) system used for calibration and compared with the clinical image in terms of anatomical structures and associated attenuation characteristics. The exposure parameters and image impression of the phantom were evaluated using five other FFDM systems of different manufacturers and types.Results demonstrated that the anatomical structures in the images and the attenuation characteristics of a female breast and the derived phantom agreed on the FFDM system used for calibration. The automatic exposure control segmentation, the automatically selected exposure parameters and the image postprocessing of the clinical and phantom image indicated a high level of conformity. As shown, the phantom is also suitable for other FFDM systems.In conclusion, an approach to produce anthropomorphic breast phantoms for DM offering realistic anatomical structures and attenuation characteristics based on clinical images was successfully developed. As shown, the phantom realistically simulated the original female breast. Therefore, it is expected that such phantoms are promising to support bridging the gap between physical-technical and diagnostic image quality assessment. In addition, they enable a variety of practical and scientific applications for which present technical phantoms are not suitable.

Calibrated Breast Density Measurements

Mammographic density is an important risk factor for breast cancer, but translation to the clinic requires assurance that prior work based on mammography is applicable to current technologies. The purpose of this work is to evaluate whether a calibration methodology developed previously produces breast density metrics predictive of breast cancer risk when applied to a case-control study. A matched case control study (n = 319 pairs) was used to evaluate two calibrated measures of breast density. Two-dimensional mammograms were acquired from six Hologic mammography units: three conventional Selenia two-dimensional full-field digital mammography systems and three Dimensions digital breast tomosynthesis systems. We evaluated the capability of two calibrated breast density measures to quantify breast cancer risk: the mean (PGm) and standard deviation (PGsd) of the calibrated pixels. Matching variables included age, hormone replacement therapy usage/duration, screening history, and mammography unit. Calibrated measures were compared to the percentage of breast density (PD) determined with the operator-assisted Cumulus method. Conditional logistic regression was used to generate odds ratios (ORs) from continuous and quartile (Q) models with 95% confidence intervals. The area under the receiver operating characteristic curve (Az) was also used as a comparison metric. Both univariate models and models adjusted for body mass index and ethnicity were evaluated. In adjusted models, both PGsd and PD were statistically significantly associated with breast cancer with similar Az of 0.61-0.62. The corresponding ORs and confidence intervals were also similar. For PGsd, the OR was 1.34 (1.09, 1.66) for the continuous measure and 1.83 (1.11, 3.02), 2.19 (1.28, 3.73), and 2.20 (1.26, 3.85) for Q2-Q4. For PD, the OR was 1.43 (1.16, 1.76) for the continuous measure and 0.84 (0.52, 1.38), 1.96 (1.19, 3.23), and 2.27 (1.29, 4.00) for Q2-Q4. The results for PGm were slightly attenuated and not statistically significant. The OR was 1.22 (0.99, 1.51) with Az = 0.60 for the continuous measure and 1.24 (0.78, 1.97), 0.98 (0.60, 1.61), and 1.26, (0.77, 2.07) for Q2-Q4 with Az = 0.60. The calibrated PGsd measure provided significant associations with breast cancer comparable to those given by PD. The calibrated PGm performed slightly worse. These findings indicate that the calibration approach developed previously replicates under more general conditions.

74. Mean glandular dose survey in the Emilia-Romagna region breast screening program

Purpose We have evaluated the Mean Glandular Doses (MGDs) of Full Field Digital Mammography (FFDM) systems, actually implemented in the Emilia Romagna Screening Program, using the same Plexiglas phantoms. This work aims to evidence the relevance of a large survey to estimate the variability of the doses provided by different mammographic systems available in this screening program. Methods 75 FFDM systems, consisting of 1 Photon-Counting, 33 a-Se Direct, 30 CsI Indirect and 11 Computed Radiography (CR), were characterized by the average values of MGD (mGy) measurements of semi-circular phantom thicknesses of 20 mm, 45 mm and 60 mm. Images were acquired in automatic mode. MGDs were measured in accordance with the Mammo Protocol of the European Federation of Organisations for Medical Physics (EFOMP) [1] . Where available, Organ Doses (ODGs), calculated by manufacturers, were collected from the Header DICOM of the corresponding images and the differences with respect MGDs were evaluated. Results All the MGDs values are within the EFOMP Mammo Protocol limits. Differences from MGDs and ODGs values are in between ±20% for the majority of systems, except for few ones. For 20 mm, 45 mm and 60 mm phantom thickness, the ranges of MGDs extend from 0.37 mGy to 1.00 mGy, 0.65 mGy to 2.40 mGy and from 1.33 mGy to 4.19 mGy respectively. As expected, MGDs show a strong dependence on FFDM system technology: the Photon Counting system has the lowest MGDs values, while the CR systems exhibit the highest ones. Conclusions Our results confirm the importance of monitoring periodically the level of technology employed in a regional screening program by means of a dose survey, in order to promote a renewal of the FFDM imaging systems in accordance with the image quality preferences of the radiologists involved. This survey procedure would be functional also to guarantee the homogeneity of the Risk-Benefit Ratio.

Automated daily quality control analysis for mammography in a multi-unit imaging center.

The high requirements for mammography image quality necessitate a systematic quality assurance process. Digital imaging allows automation of the image quality analysis, which can potentially improve repeatability and objectivity compared to a visual evaluation made by the users. To develop an automatic image quality analysis software for daily mammography quality control in a multi-unit imaging center. An automated image quality analysis software using the discrete wavelet transform and multiresolution analysis was developed for the American College of Radiology accreditation phantom. The software was validated by analyzing 60 randomly selected phantom images from six mammography systems and 20 phantom images with different dose levels from one mammography system. The results were compared to a visual analysis made by four reviewers. Additionally, long-term image quality trends of a full-field digital mammography system and a computed radiography mammography system were investigated. The automated software produced feature detection levels comparable to visual analysis. The agreement was good in the case of fibers, while the software detected somewhat more microcalcifications and characteristic masses. Long-term follow-up via a quality assurance web portal demonstrated the feasibility of using the software for monitoring the performance of mammography systems in a multi-unit imaging center. Automated image quality analysis enables monitoring the performance of digital mammography systems in an efficient, centralized manner.

Design, Construction, and Initial Results of a Prototype Multi-Contrast X-Ray Breast Imaging System.

By integrating a grating-based interferometer with a clinical full field digital mammography (FFDM) system, a prototype multi-contrast (absorption, phase, and dark field) x-ray breast imaging system was developed in this work. Unlike previous benchtop-based multi-contrast x-ray imaging systems that usually have relatively long source-to-detector distance and vibration isolators or dampers for the interferometer, the FFDM hardware platform is subject to mechanical vibration and the constraint of compact system geometry. Current grating fabrication technology also imposes additional constraints on the design of the grating interferometer. Based on these technical constraints and the x-ray beam properties of the FFDM system, three gratings were designed and integrated with the FFDM system. When installing the gratings, no additional vibration damping device was used in order to test the robustness of multi-contrast imaging system against mechanical vibration. The measured visibility of the diffraction fringes was 23±3%, and two images acquired 60 minutes apart demonstrated good system reproducibility with no visible signal drift. Preliminary results generated from the prototype system demonstrate the multi-contrast imaging capability of the system. The three contrast mechanisms provide mutually complementary information of the phantom object. This prototype system provides a much needed platform for evaluating the true clinical utility of the multi-contrast x-ray imaging method for the diagnosis of breast cancer.

Measurement of effective detective quantum efficiency for a photon counting scanning mammography system and comparison with two flat panel full-field digital mammography systems

Effective detective quantum efficiency (eDQE) describes the resolution and noise properties of an imaging system along with scatter and primary transmission, all measured under clinically appropriate conditions. Effective dose efficiency (eDE) is the eDQE normalised to mean glandular dose and has been proposed as a useful metric for the optimisation of clinical imaging systems. The aim of this study was to develop a methodology for measuring eDQE and eDE on a Philips microdose mammography (MDM) L30 photon counting scanning system, and to compare performance with two conventional flat panel systems.A custom made lead-blocker was manufactured to enable the accurate determination of dose measurements, and modulation transfer functions were determined free-in-air at heights of 2, 4 and 6 cm above the breast support platform. eDQE were calculated for a Philips MDM L30, Hologic Dimensions and Siemens Inspiration digital mammography system for 2, 4 and 6 cm thick poly(methyl methacrylate) (PMMA). The beam qualities (target/filter and kilovoltage) assessed were those selected by the automatic exposure control, and anti-scatter grids were used where available.Measurements of eDQE demonstrate significant differences in performance between the slit- and scan-directions for the photon counting imaging system. MTF has been shown to be the limiting factor in the scan-direction, which results in a rapid fall in eDQE at mid-to-high spatial frequencies. A comparison with two flat panel mammography systems demonstrates that this may limit image quality for small details, such as micro-calcifications, which correlates with a more conventional image quality assessment with the CDMAM phantom. eDE has shown the scanning photon counting system offers superior performance for low spatial frequencies, which will be important for the detection of large low contrast masses. Both eDQE and eDE are proposed as useful metrics that should enable optimisation of the Philips MDM L30.

Quantitative comparison of clustered microcalcifications in for-presentation and for-processing mammograms in full-field digital mammography.

Mammograms acquired with full-field digital mammography (FFDM) systems are provided in both "for-processing'' and "for-presentation'' image formats. For-presentation images are traditionally intended for visual assessment by the radiologists. In this study, we investigate the feasibility of using for-presentation images in computerized analysis and diagnosis of microcalcification (MC) lesions. We make use of a set of 188 matched mammogram image pairs of MC lesions from 95 cases (biopsy proven), in which both for-presentation and for-processing images are provided for each lesion. We then analyze and characterize the MC lesions from for-presentation images and compare them with their counterparts in for-processing images. Specifically, we consider three important aspects in computer-aided diagnosis (CAD) of MC lesions. First, we quantify each MC lesion with a set of 10 image features of clustered MCs and 12 textural features of the lesion area. Second, we assess the detectability of individual MCs in each lesion from the for-presentation images by a commonly used difference-of-Gaussians (DoG) detector. Finally, we study the diagnostic accuracy in discriminating between benign and malignant MC lesions from the for-presentation images by a pretrained support vector machine (SVM) classifier. To accommodate the underlying background suppression and image enhancement in for-presentation images, a normalization procedure is applied. The quantitative image features of MC lesions from for-presentation images are highly consistent with that from for-processing images. The values of Pearson's correlation coefficient between features from the two formats range from 0.824 to 0.961 for the 10 MC image features, and from 0.871 to 0.963 for the 12 textural features. In detection of individual MCs, the FROC curve from for-presentation is similar to that from for-processing. In particular, at sensitivity level of 80%, the average number of false-positives (FPs) per image region is 9.55 for both for-presentation and for-processing images. Finally, for classifying MC lesions as malignant or benign, the area under the ROC curve is 0.769 in for-presentation, compared to 0.761 in for-processing (P = 0.436). The quantitative results demonstrate that MC lesions in for-presentation images are highly consistent with that in for-processing images in terms of image features, detectability of individual MCs, and classification accuracy between malignant and benign lesions. These results indicate that for-presentation images can be compatible with for-processing images for use in CAD algorithms for MC lesions.

A novel physical anthropomorphic breast phantom for 2D and 3D x-ray imaging.

Physical phantoms are central to the evaluation of 2D and 3D breast-imaging systems. Currently, available physical phantoms have limitations including unrealistic uniform background structure, large expense, or excessive fabrication time. The purpose of this work is to outline a method for rapidly creating realistic, inexpensive physical anthropomorphic phantoms for use in full-field digital mammography (FFDM) and digital breast tomosynthesis (DBT). The phantom was first modeled using analytical expressions and then discretized into voxels of a specified size. The interior of the breast was divided into glandular and adipose tissue classes using Voronoi segmentation, and additional structures like blood vessels, chest muscle, and ligaments were added. The physical phantom was then fabricated from the virtual model in a slice by slice fashion through inkjet printing, using parchment paper and a radiopaque ink containing 33% (I33% ) or 25% (I25% ) iohexol by volume. Three types of parchment paper (P1, P2, and P3) were examined. The phantom materials were characterized in terms of their effective linear attenuation coefficients (μeff ) using full-field digital mammography (FFDM) and their energy-dependent linear attenuation coefficients (μ(E)) using a spectroscopic energy discriminating detector system. The printing method was further validated on the basis of accuracy, print consistency, and the reproducibility of ink batches. The μeff of two types of parchment paper were close to that of adipose tissue, with μeff = 0.61 ± 0.05 cm-1 for P1, 0.61 ± 0.04 cm-1 for P2, and 0.57 ± 0.03 cm-1 for adipose tissue. The addition of the iodinated ink increased the effective attenuation to that of glandular tissue, with μeff = 0.89 ± 0.06 cm-1 for P1 + I25% and 0.94 ± 0.06 cm-1 for P1 + I33% compared to 0.90 ± 0.03 cm-1 for glandular tissue. Spectroscopic measurements showed a good match between the parchment paper and reference values for adipose and glandular tissues across photon energies. Good accuracy was found between the model and the printed phantom by comparing a FFDM of the virtual model simulated through Monte Carlo with a real FFDM of the fully printed phantom. High consistency was found over multiple prints, with 3% variability in mean ink signal across various samples. Reproducibility of ink consistency was very high with <1% variation signal from multiple batches of ink. Imaging of the phantom using FFDM and DBT systems showed promising utility for 2D and 3D imaging. A novel, realistic breast phantom can be created using an analytically defined breast model and readily available materials. The work provides a method to fabricate any virtual phantom in a manner that is accurate, inexpensive, easily accessible, and can be made with different materials or breast models.

Design and application of a structured phantom for detection performance comparison between breast tomosynthesis and digital mammography

This paper introduces and applies a structured phantom with inserted target objects for the comparison of detection performance of digital breast tomosynthesis (DBT) against 2D full field digital mammography (FFDM). The phantom consists of a 48 mm thick breast-shaped polymethyl methacrylate (PMMA) container filled with water and PMMA spheres of different diameters. Three-dimensionally (3D) printed spiculated masses (diameter range: 3.8–9.7 mm) and non-spiculated masses (1.6–6.2 mm) along with microcalcifications (90–250 µm) were inserted as targets.Reproducibility of the phantom application was studied on a single system using 30 acquisitions. Next, the phantom was evaluated on five different combined FFDM & DBT systems and target detection was compared for FFDM and DBT modes. Ten phantom images in both FFDM and DBT modes were acquired on these 5 systems using automatic exposure control. Five readers evaluated target detectability. Images were read with the four-alternative forced-choice (4-AFC) paradigm, with always one segment including a target and 3 normal background segments. The percentage of correct responses (PC) was assessed based on 10 trials of each reader for each object type, size and imaging modality. Additionally, detection threshold diameters at 62.5 PC were assessed via non-linear regression fitting of the psychometric curve. The reproducibility study showed no significant differences in PC values. Evaluation of target detection in FFDM showed that microcalcification detection thresholds ranged between 110 and 118 µm and were similar compared to the detection in DBT (range of 106–158 µm). In DBT, detection of both mass types increased significantly (p = 0.0001 and p = 0.0002 for non-spiculated and spiculated masses respectively) compared to FFDM, achieving almost 100% detection for all spiculated mass diameters.In conclusion, a structured phantom with inserted targets was able to show evidence for detectability differences between FFDM and DBT modes for five commercial systems. This phantom has potential for application in task-based assessment at acceptance and commissioning testing of DBT systems.

Spectrum optimization for computed radiography mammography systems

PurposeTechnical quality assurance is a key issue in breast screening protocols. While full-field digital mammography systems produce excellent image quality at low dose, it appears difficult with computed radiography (CR) systems to fulfill the requirements for image quality, and to keep the dose below the limits. However, powder plate CR systems are still widely used, e.g., they represent ∼30% of the devices in the Austrian breast cancer screening program. For these systems the selection of an optimal spectrum is a key issue. MethodsWe investigated different anode/filter (A/F) combinations over the clinical range of tube voltages. The figure-of-merit (FOM) to be optimized was squared signal-difference-to-noise ratio divided by glandular dose. Measurements were performed on a Siemens Mammomat 3000 with a Fuji Profect reader (SiFu) and on a GE Senograph DMR with a Carestream reader (GECa). ResultsFor 50mm PMMA the maximum FOM was found with a Mo/Rh spectrum between 27kVp and 29kVp, while with 60mm Mo/Rh at 28kVp (GECa) and W/Rh 25kVp (SiFu) were superior. For 70mm PMMA the Rh/Rh spectrum had a peak at about 31kVp (GECa). FOM increases from 10% to >100% are demonstrated. ConclusionOptimization as proposed in this paper can either lead to dose reduction with comparable image quality or image quality improvement if necessary. For systems with limited A/F combinations the choice of tube voltage is of considerable importance. In this work, optimization of AEC parameters such as anode-filter combination and tube potential was demonstrated for mammographic CR systems.