Showing papers on "Digital mammography published in 2009"

Screening for Breast Cancer: US Preventive Services Task Force Recommendation Statement

Abstract: Description: Update of the 2002 U. S. Preventive Services Task Force (USPSTF) recommendation statement on screening for breast cancer in the general population. Methods: The USPSTF examined the evidence on the efficacy of 5 screening modalities in reducing mortality from breast cancer: film mammography, clinical breast examination, breast self-examination, digital mammography, and magnetic resonance imaging in order to update the 2002 recommendation. To accomplish this update, the USPSTF commissioned 2 studies: 1) a targeted systematic evidence review of 6 selected questions relating to benefits and harms of screening, and 2) a decision analysis that used population modeling techniques to compare the expected health outcomes and resource requirements of starting and ending mammography screening at different ages and using annual versus biennial screening intervals. Recommendations: The USPSTF recommends against routine screening mammography in women aged 40 to 49 years. The decision to start regular, biennial screening mammography before the age of 50 years should be an individual one and take into account patient context, including the patient's values regarding specific benefits and harms. (Grade C recommendation) The USPSTF recommends biennial screening mammography for women between the ages of 50 and 74 years. (Grade B recommendation) The USPSTF concludes that the current evidence is insufficient to assess the additional benefits and harms of screening mammography in women 75 years or older. (I statement) The USPSTF concludes that the current evidence is insufficient to assess the additional benefits and harms of clinical breast examination beyond screening mammography in women 40 years or older. (I statement) The USPSTF recommends against clinicians teaching women how to perform breast self-examination. (Grade D recommendation) The USPSTF concludes that the current evidence is insufficient to assess additional benefits and harms of either digital mammography or magnetic resonance imaging instead of film mammography as screening modalities for breast cancer. (I statement)

Digital breast tomosynthesis: observer performance study.

Abstract: OBJECTIVE. The purpose of this study was to compare in a retrospective observer study the diagnostic performance of full-field digital mammography (FFDM) with that of digital breast tomosynthesis.MATERIALS AND METHODS. Eight experienced radiologists interpreted images from 125 selected examinations, 35 with verified findings of cancer and 90 with no finding of cancer. The four display conditions included FFDM alone, 11 low-dose projections, reconstructed digital breast tomosynthesis images, and a combined display mode of FFDM and digital breast tomosynthesis images. Observers rated examinations using the screening BI-RADS rating scale and the free-response receiver operating characteristic paradigm. Observer performance levels were measured as the proportion of examinations prompting recall of patients for further diagnostic evaluation. The results were presented in terms of true-positive fraction and false-positive fraction. Performance levels were compared among the acquisitions and reading modes. Time ...

The myth of the 50-50 breast.

Abstract: Purpose: For dosimetry and for work in optimization of x-ray imaging of the breast, it is commonly assumed that the breast is composed of 50% fibroglandular tissue and 50% fat. The purpose of this study was to assess whether this assumption was realistic. Methods: First, data obtained from an experimental breast CT scanner were used to validate an algorithm that measures breast density from digitized film mammograms. Density results obtained from a total of 2831 women, including 191 women receiving CT and from mammograms of 2640 women from three other groups, were then used to estimate breast compositions. Results: Mean compositions, expressed as percent fibroglandular tissue (including the skin), varied from 13.7% to 25.6% among the groups with an overall mean of 19.3%. The mean compressed breast thickness for the mammograms was 5.9 cm ({sigma}=1.6 cm). 80% of the women in our study had volumetric breast density less than 27% and 95% were below 45%. Conclusions: Based on the results obtained from the four groups of women in our study, the ''50-50'' breast is not a representative model of the breast composition.

Studies comparing screen-film mammography and full-field digital mammography in breast cancer screening: updated review.

Abstract: Full-field digital mammography (FFDM) has several potential benefits as compared with screen-film mammography (SFM) in mammography screening. Digital technology also opens for implementation of advanced applications, including computer-aided detection (CAD) and tomosynthesis. Phantom studies and experimental clinical studies have shown that FFDM is equal or slightly superior to SFM for detection and characterization of mammographic abnormalities. Despite obvious advantages, the conversion to digital mammography has been slower than anticipated, and not only due to higher costs. Until very recently, some countries did not even permit the use of digital mammography in breast cancer screening. The reason for this reluctant attitude was concern about lower spatial resolution and about using soft-copy reading. Furthermore, there was a lack of data supporting improved diagnostic accuracy using FFDM in a screening setting, since two pioneer trials both showed nonsignificantly lower cancer detection rate at FFDM....

Full-field digital versus screen-film mammography: comparison within the UK breast screening program and systematic review of published data.

Abstract: Purpose: To (a) compare the performance of full-field digital mammography (FFDM), using hard-copy image reading, with that of screen-film mammography (SFM) within a UK screening program (screening once every 3 years) for women aged 50 years or older and (b) conduct a meta-analysis of published findings along with the UK data. Materials and Methods: The study complied with the UK National Health Service Central Office for Research Ethics Committee guidelines; informed patient consent was not required, since analysis was carried out retrospectively after data anonymization. Between January 2006 and June 2007, a London population-based screening center performed 8478 FFDM and 31 720 SFM screening examinations, with modality determined by the type of machine available at the screening site. Logistic regression was used to assess whether breast cancer detection rates and recall rates differed between screening modalities. For the meta-analysis, random-effects models were used to combine study-specific estimate...

Optimization of the acquisition geometry in digital tomosynthesis of the breast

Abstract: Digital tomosynthesis of the breast continues to be intensively studied as an adjunct or replacement of conventional mammography. Although many of the acquisition parameters found in tomosynthesis imaging are also found in conventional mammography and therefore most of the traditional values from mammography have been used in the former, two acquisition geometry parameters, the angular range covered during acquisition and the number of projections per projection set, are applicable only to tomosynthesis. Therefore, in the preclinical and clinical studies reported on tomosynthesis of the breast, a wide variety of values have been used for these two parameters. In this study, 63 different combinations of angular range and number of projections were evaluated using computer simulation methods to characterize how these two parameters affect reconstruction quality and to find which of these combinations maximize it. For this, a computer simulation of a digital tomosynthesis system that included empirically determined system response characteristics was developed and used to generate 9450 different breast tissue volume reconstructions. These reconstructions were analyzed objectively using metrics for in-plane lesion visibility and vertical resolution in the form of the contrast-to-noise ratio and artifact spread function (ASF). It was found that although maximizing the angular range covered does always increase the vertical resolution in tomosynthesis, increasing the number of projections in the acquisition set beyond a relatively low threshold does not further improve the vertical resolution. This threshold value for the minimal number of projections needed to minimize the ASF was found to vary proportionally with angular range. For example, for a 60 degrees angular range, the threshold number of projections was found to be 13. Given the clear inverse relationship between the number of projections and in-plane reconstruction quality under a limited total glandular dose condition, the optimum acquisition geometry in tomosynthesis imaging of the breast is that which maximizes the angular range while maintaining the number of projections close to the threshold values found. Finally, of the 63 acquisition geometries studied, the one that resulted in the highest quality reconstruction, considering both in-plane quality and vertical resolution, consisted of the acquisition of 13 projections over a 60 degrees angular range.

Breast Cancer Screening Results 5 Years after Introduction of Digital Mammography in a Population-based Screening Program

Abstract: Results indicate that with full-field digital mammography (FFDM) using computer-aided diagnosis (CAD) and double reading, the detection is as good as that with screen-film mammography, and detection of clustered microcalcifications and ductal carcinoma in situ is improved with FFDM using CAD.

Multimodality Screening of High-Risk Women: A Prospective Cohort Study

Abstract: Purpose Mammography has been established as the primary imaging screening method for breast cancer; however, the sensitivity of mammography is limited, especially in women with dense breast tissue. Given the limitations of mammography, interest has developed in alternative screening techniques. This interest has led to numerous studies reporting mammographically occult breast cancers detected on magnetic resonance imaging (MRI) or ultrasound. In addition, digital mammography was shown to be more sensitive than film mammography in selected populations. Our goal was to prospectively compare cancer detection of digital mammography (DM), whole-breast ultrasound (WBUS), and contrast-enhanced MRI in a high-risk screening population previously screened negative by film screen mammogram (FSM). Methods During a 2-year period, 609 asymptomatic high-risk women with nonactionable FSM examinations presented for a prospective multimodality screening consisting of DM, WBUS, and MRI. The FSM examinations were reinterpret...

Comparison of Digital Mammography and Screen-Film Mammography in Breast Cancer Screening: A Review in the Irish Breast Screening Program

Abstract: OBJECTIVE. Clinical trials to date into the use of full-field digital mammography (FFDM) for breast cancer screening have shown variable results. The aim of this study was to review the use of FFDM in a population-based breast cancer screening program and to compare the results with screen-film mammography.MATERIALS AND METHODS. The study included 188,823 screening examinations of women between 50 and 64 years old; 35,204 (18.6%) mammograms were obtained using FFDM. All films were double read using a 5-point rating scale to indicate the probability of cancer. Patients with positive scores were recalled for further workup. The recall rate, cancer detection rate, and positive predictive value (PPV) of FFDM were compared with screen-film mammography.RESULTS. The cancer detection rate was significantly higher for FFDM than screen-film mammography (6.3 vs 5.2 per 1,000, respectively; p = 0.01). The cancer detection rate for FFDM was higher than screen-film mammography for initial screening and subsequent scree...

Imaging Nanoprobe for Prediction of Outcome of Nanoparticle Chemotherapy by Using Mammography

Abstract: Purpose: To prospectively predict the effectiveness of a clinically used nanochemotherapeutic agent by detecting and measuring the intratumoral uptake of an x-ray contrast agent nanoprobe by using digital mammography. Materials and Methods: All animal procedures were approved by the institutional animal care and use committee. A long-circulating 100-nm-scale injectable liposomal probe encapsulating 155 mg/mL iodine was developed. Preliminary studies were performed to identify the agent dose that would result in adequate tumor enhancement without enhancement of the normal vasculature in rats. This dose was used to image a rat breast tumor (n = 14) intermittently for 3 days by using a digital mammography system; subsequently, the animals were treated with liposomal doxorubicin. The predictive capability of the probe was characterized by creating good- and bad-prognosis subgroups, on the basis of tumor enhancement found during imaging, and analyzing the tumor growth after treatment of the animals in these tw...

Design and characterization of a spatially distributed multibeam field emission x-ray source for stationary digital breast tomosynthesis

Abstract: Digital breast tomosynthesis (DBT) is a limited angle computed tomography technique that can distinguish tumors from its overlying breast tissues and has potentials for detection of cancers at a smaller size and earlier stage. Current prototype DBT scanners are based on the regular full-field digital mammography systems and require partial isocentric motion of an x-ray tube over certain angular range to record the projection views. This prolongs the scanning time and, in turn, degrades the imaging quality due to motion blur. To mitigate the above limitations, the concept of a stationary DBT (s-DBT) scanner has been recently proposed based on the newly developed spatially distributed multibeam field emission x-ray (MBFEX) source technique using the carbon nanotube. The purpose of this article is to evaluate the performance of the 25-beam MBFEX source array that has been designed and fabricated for the s-DBT system. The s-DBT system records all the projection images by electronically activating the multiple x-ray beams from different viewing angles without any mechanical motion. The configuration of the MBFEX source is close to the published values from the Siemens Mammomat system. The key issues including the x-ray flux, focal spot size, spatial resolution, scanning time, beam-to-beam consistency, and reliability are evaluated using the standard procedures. In this article, the authors describe the design and performance of a distributed x-ray source array specifically designed for the s-DBT system. They evaluate the emission current, current variation, lifetime, and focal spot sizes of the source array. An emission current of up to 18 mA was obtained at 0.5×0.3 mm effective focal spot size. The experimentally measured focal spot sizes are comparable to that of a typical commercial mammography tube without motion blurring. Trade-off between the system spatial resolution, x-ray flux, and scanning time are also discussed. Projection images of a breast phantom were collected using the x-ray source array from 25 different viewing angles without motion. These preliminary results demonstrate the feasibility of the proposed s-DBT scanner. The technology has the potential to increase the resolution and reduce the imaging time for DBT. With the present design of 25 views, they demonstrated experimentally the feasibility of achieving 11 s scanning time at full detector resolution with 0.5×0.3 mm source resolution without motion blur. The flexibility in configuration of the x-ray source array will also allow system designers to consider imaging geometries that are difficult to achieve with the conventional single-source rotating approach.

A Survey of Image Processing Algorithms in Digital Mammography

Abstract: Mammography is at present the best available technique for early detection of breast cancer. The most common breast abnormalities that may indicate breast cancer are masses and calcifications. In some cases, subtle signs that can also lead to a breast cancer diagnosis, such as architectural distortion and bilateral asymmetry, are present. Breast abnormalities are defined with wide range of features and may be easily missed or misinterpreted by radiologists while reading large amount of mammographic images provided in screening programs. To help radiologists provide an accurate diagnosis, a computer-aided detection (CADe) and computer-aided diagnosis (CADx) algorithms are being developed. CADe and CADx algorithms help reducing the number of false positives and they assist radiologists in deciding between follow up and biopsy. This chapter gives a survey of image processing algorithms that have been developed for detection of masses and calcifications. An overview of algorithms in each step (segmentation step, feature extraction step, feature selection step, classification step) of the mass detection algorithms is given. Wavelet detection methods and other recently proposed methods for calcification detection are presented. An overview of contrast enhancement and noise equalization methods is given as well as an overview of calcification classification algorithms.

Single x-ray absorptiometry method for the quantitative mammographic measure of fibroglandular tissue volume.

Abstract: Purpose: This study describes the design and characteristics of a highly accurate, precise, and automated single-energy method to quantify percent fibroglandular tissue volume (%FGV) and fibroglandular tissue volume (FGV) using digital screening mammography. Methods: The method uses a breast tissue-equivalent phantom in the unused portion of the mammogram as a reference to estimate breast composition. The phantom is used to calculate breast thickness and composition for each image regardless of x-ray technique or the presence of paddle tilt. The phantom adheres to the top of the mammographic compression paddle and stays in place for both craniocaudal and mediolateral oblique screening views. We describe the automated method to identify the phantom and paddle orientation with a three-dimensional reconstruction least-squares technique. A series of test phantoms, with a breast thickness range of 0.5–8 cm and a %FGV of 0%–100%, were made to test the accuracy and precision of the technique. Results: Using test phantoms, the estimated repeatability standard deviation equaled 2%, with a ±2% accuracy for the entire thickness and density ranges. Without correction, paddle tilt was found to create large errors in the measured density values of up to 7%/mm difference from actual breast thickness. This new density measurement is stable over time, with no significant drifts in calibration noted during a four-month period. Comparisons of %FGV to mammographic percent density and left to right breast %FGV were highly correlated ( r = 0.83 and 0.94, respectively). Conclusions: An automated method for quantifying fibroglandular tissue volume has been developed. It exhibited good accuracy and precision for a broad range of breast thicknesses, paddle tilt angles, and %FGV values. Clinical testing showed high correlation to mammographic density and between left and right breasts.

Image Feature Extraction in the Last Screening Mammograms Prior to Detection of Breast Cancer

Abstract: Image feature extraction was utilized to retrospectively analyze screening mammograms taken prior to the detection of a malignant mass for early detection of breast cancer. The mammograms of 58 biopsy proven breast cancer patients were collected. In each case, the mammograms taken 10 to 18 months prior to cancer detection were evaluated. For each of the two mammographic projections of the abnormal breast, two regions were marked: 1) region one, which corresponded to the site where the malignant mass subsequently developed and 2) a region which appeared similar to region one on the same mammogram. On each projection of the normal breast a third region which corresponds to region one but on the opposite breast was also marked (mirror-image site). Sixty-two texture and photometric image features were then calculated for all of the marked areas. A stepwise discriminant analysis showed that six of these features could be used to best distinguish between the normal and abnormal regions. The best linear classification function resulted in a 72% average classification. At its current stage, the system can be used by a radiologist to examine any pattern in a mammogram. The regions which are flagged by the system have a 72% chance of developing a malignant mass by the time of the next screening. Therefore, further evaluation of these patients (e.g., a screening examination sooner than the normal one year interval) could result in earlier detection of breast cancer. The ultimate goal is to run the system automatically over the whole mammogram and flag any suspicious area.

Evaluation of clinical image processing algorithms used in digital mammography

Abstract: Screening is the only proven approach to reduce the mortality of breast cancer, but significant numbers of breast cancers remain undetected even when all quality assurance guidelines are implemented. With the increasing adoption of digital mammography systems, image processing may be a key factor in the imaging chain. Although to our knowledge statistically significant effects of manufacturer-recommended image processings have not been previously demonstrated, the subjective experience of our radiologists, that the apparent image quality can vary considerably between different algorithms, motivated this study. This article addresses the impact of five such algorithms on the detection of clusters of microcalcifications. A database of unprocessed (raw) images of 200 normal digital mammograms, acquired with the Siemens Novation DR, was collected retrospectively. Realistic simulated microcalcification clusters were inserted in half of the unprocessed images. All unprocessed images were subsequently processed with five manufacturer-recommended image processing algorithms (Agfa Musica 1, IMS Raffaello Mammo 1.2, Sectra Mamea AB Sigmoid, Siemens OPVIEW v2, and Siemens OPVIEW v1). Four breast imaging radiologists were asked to locate and score the clusters in each image on a five point rating scale. The free-response data were analyzed by the jackknife free-response receiver operating characteristic (JAFROC) method and, for comparison, also with the receiver operating characteristic (ROC) method. JAFROC analysis revealed highly significant differences between the image processings (F = 8.51, p < 0.0001), suggesting that image processing strongly impacts the detectability of clusters. Siemens OPVIEW2 and Siemens OPVIEW1 yielded the highest and lowest performances, respectively. ROC analysis of the data also revealed significant differences between the processing but at lower significance (F = 3.47, p = 0.0305) than JAFROC. Both statistical analysis methods revealed that the same six pairs of modalities were significantly different, but the JAFROC confidence intervals were about 32% smaller than ROC confidence intervals. This study shows that image processing has a significant impact on the detection of microcalcifications in digital mammograms. Objective measurements, such as described here, should be used by the manufacturers to select the optimal image processing algorithm.

Compositional breast imaging using a dual-energy mammography protocol

Abstract: Purpose: Mammography has a low sensitivity in dense breasts due to low contrast between malignant and normal tissue confounded by the predominant water density of the breast. Water is found in both adipose and fibroglandular tissue and constitutes most of the mass of a breast. However, significant protein mass is mainly found in the fibroglandular tissue where most cancers originate. If the protein compartment in a mammogram could be imaged without the influence of water, the sensitivity and specificity of the mammogram may be improved. This article describes a novel approach to dual-energy mammography, full-field digital compositional mammography (FFDCM), which can independently image the three compositional components of breast tissue: water, lipid, and protein. Methods: Dual-energy attenuation and breast shape measures are used together to solve for the three compositional thicknesses. Dual-energy measurements were performed on breast-mimicking phantoms using a full-field digital mammography unit. The phantoms were made of materials shown to have similar x-ray attenuation properties of the compositional compartments. They were made of two main stacks of thicknesses around 2 and 4 cm. Twenty-six thickness and composition combinations were used to derive the compositional calibration using a least-squares fitting approach. Results: Very high accuracy was achieved with a simple cubic fitting function with root mean square errors of 0.023, 0.011, and 0.012 cm for the water, lipid, and protein thicknesses, respectively. The repeatability (percent coefficient of variation) of these measures was tested using sequential images and was found to be 0.5%, 0.5%, and 3.3% for water, lipid, and protein, respectively. However, swapping the location of the two stacks of the phantom on the imaging plate introduced further errors showing the need for more complete system uniformity corrections. Finally, a preliminary breast image is presented of each of the compositional compartments separately. Conclusions: FFDCM has been derived and exhibited good compositional thickness accuracy on phantoms. Preliminary breast images demonstrated the feasibility of creating individual compositional diagnostic images in a clinical environment.

Diagnosis of breast cancer in women age 40 and younger: delays in diagnosis result from underuse of genetic testing and breast imaging

Abstract: Background The impact of newer breast imaging technologies and genetic testing on the detection of breast cancer in women age 40 and younger remains unknown. Methods A records review identified 628 women age 40 and younger diagnosed with breast cancer from 1996 to 2008. Patient and tumor characteristics, means of diagnosis, imaging results, and genetic testing were examined. Results Tumors were first detected by self-examination in 71%, with a median invasive tumor size of 2.0 cm. Imaging performed at or after diagnosis visualized most tumors; mammography visualized 86%, magnetic resonance imaging (MRI) visualized 96%, and mammography plus MRI visualized more than 98% of tumors. For 81% of patients, the mammogram at diagnosis was their first mammogram. Although 50% had a family history of breast or ovarian cancer, few underwent genetic testing before their cancer diagnosis; 61 of 247 (25%) ultimately tested had a BRCA mutation. Conclusions Better use of genetic testing, mammography, and MRI could improve breast cancer detection in young women.

Breast border extraction and pectoral muscle detection using wavelet decomposition

Abstract: Digital mammography is used more and more each day in comparison with screen film mammography (SFM). Main advantage of digital mammography for image processing is the use of images with few or no artifacts that can occur on SFM images. Finding breast border contour is therefore easier and gives more precise results. On the other hand, detection of pectoral muscle and breast abnormalities has almost the same results in both cases. The presence of pectoral muscle can affect results of lesion detection algorithms so it is recommended to have it removed from the image. Detection and segmentation of pectoral muscle can also help in image registration for further analysis of breast abnormalities such as bilateral asymmetry. Algorithm presented in this paper uses hybrid method for the pectoral muscle detection. Proposed method uses bit depth reduction and wavelet decomposition for finding pectoral muscle border. Algorithm has been tested on the set of 40 digital mammography images.

Implementation of digital mammography in a population-based breast cancer screening program: effect of screening round on recall rate and cancer detection

Abstract: Purpose: To compare the effect of the introduction of digital mammography on the recall rate, detection rate, false-positive rate, and rates of invasive procedures performed in the first and successive rounds of a population-based breast cancer screening program with double reading in Barcelona, Spain. Materials and Methods: The study was approved by the ethics committee; informed consent was not required. Data were compared from 12 958 women aged 50–69 years old who participated in a screening round before the introduction of digital mammography (screen-film mammography group) with data from 6074 women who participated in another screening round after the introduction of digital mammography (digital mammography group). Groups were compared for recall rate and detection rate stratified according to first or successive screening rounds, and logistic regression analysis was performed. Results: Overall recall rates for screen-film and digital mammography groups were 5.5% and 4.2%, respectively (P < .001). Th...

Early detection of breast cancer: overview of the evidence on computer-aided detection in mammography screening.

Abstract: We review the evidence on computer-aided detection (CAD) as an adjunct to mammography interpretation, and discuss the complexity of its impact on decision-making and potential medico-legal aspects. CAD prompts the reader to review lesions on the mammogram and re-evaluate the decision on whether to recall CAD-prompted findings. Studies show that CAD can improve the sensitivity of a single reader, with an incremental cancer detection rate (from adding CAD to a single read) ranging between 1 and 19%. However, CAD will also substantially increase the recall rate (decrease the reader's specificity) causing additional recall in approximately 6-35% of women. Evidence indicates that CAD does not perform as well as double (human) reading in the context of organized breast screening where double reading is the standard of care. Although CAD can identify and prompt readers to missed cancers, the high number of false-positive prompts (1.5-4 false prompts per case) can have an adverse effect on clinical decision-making, and detracts from CAD's application in screening practice. Refinement in CAD algorithms, in combination with increasing implementation of digital mammography, may improve the potential use of CAD in mammography reading, but will require prospective evaluation.

Detection of breast cancer with full-field digital mammography and computer-aided detection.

Abstract: OBJECTIVE. The purpose of this study was to evaluate computer-aided detection (CAD) performance with full-field digital mammography (FFDM).MATERIALS AND METHODS. CAD (Second Look, version 7.2) was used to evaluate 123 cases of breast cancer detected with FFDM (Senographe DS). Retrospectively, CAD sensitivity was assessed using breast density, mammographic presentation, histopathology results, and lesion size. To determine the case-based false-positive rate, patients with four standard views per case were included in the study group. Eighteen unilateral mammography examinations with nonstandard views were excluded, resulting in a sample of 105 bilateral cases.RESULTS. CAD detected 115 (94%) of 123 cancer cases: six of six (100%) in fatty breasts, 63 of 66 (95%) in breasts containing scattered fibroglandular densities, 43 of 46 (93%) in heterogeneously dense breasts, and three of five (60%) in extremely dense breasts. CAD detected 93% (41/44) of cancers manifesting as calcifications, 92% (57/62) as masses, ...

Introducing DeBRa: a detailed breast model for radiological studies

Abstract: Currently, x-ray mammography is the method of choice in breast cancer screening programmes. As the mammography technology moves from 2D imaging modalities to 3D, conventional computational phantoms do not have sufficient detail to support the studies of these advanced imaging systems. Studies of these 3D imaging systems call for a realistic and sophisticated computational model of the breast. DeBRa (Detailed Breast model for Radiological studies) is the most advanced, detailed, 3D computational model of the breast developed recently for breast imaging studies. A DeBRa phantom can be constructed to model a compressed breast, as in film/screen, digital mammography and digital breast tomosynthesis studies, or a non-compressed breast as in positron emission mammography and breast CT studies. Both the cranial-caudal and mediolateral oblique views can be modelled. The anatomical details inside the phantom include the lactiferous duct system, the Cooper ligaments and the pectoral muscle. The fibroglandular tissues are also modelled realistically. In addition, abnormalities such as microcalcifications, irregular tumours and spiculated tumours are inserted into the phantom. Existing sophisticated breast models require specialized simulation codes. Unlike its predecessors, DeBRa has elemental compositions and densities incorporated into its voxels including those of the explicitly modelled anatomical structures and the noise-like fibroglandular tissues. The voxel dimensions are specified as needed by any study and the microcalcifications are embedded into the voxels so that the microcalcification sizes are not limited by the voxel dimensions. Therefore, DeBRa works with general-purpose Monte Carlo codes. Furthermore, general-purpose Monte Carlo codes allow different types of imaging modalities and detector characteristics to be simulated with ease. DeBRa is a versatile and multipurpose model specifically designed for both x-ray and γ-ray imaging studies.

Timed efficiency of interpretation of digital and film-screen screening mammograms.

Abstract: OBJECTIVE. Our objective was to compare interpretation speeds for digital and film-screen screening mammograms to test whether other variables might affect interpretation times and thus contribute to the apparent difference in interpretation speed between digital mammograms and film-screen mammograms, and to test whether the use of digital rather than film comparison studies might result in significant time savings.MATERIALS AND METHODS. Four readers were timed in the course of actual clinical interpretation of digital mammograms and film-screen mammograms. Interpretation times were compared for subgroups of studies based on the interpretation of the study by BI-RADS code, the number of images, the presence or absence of comparison studies and the type of comparison study, and whether the radiologist personally selected and hung additional films; the same comparisons were made among individual readers.RESULTS. For all four readers, mean interpretation times were longer for digital mammograms than for film...

Physical and psychophysical characterization of a novel clinical system for digital mammography.

Abstract: Purpose: In recent years, many approaches have been investigated on the development of full-field digital mammography detectors and implemented in practical clinical systems. Some of the most promising techniques are based on flat panel detectors, which, depending on the mechanism involved in the x-ray detection, can be grouped into direct and indirect flat panels. Direct detectors display a better spatial resolution due to the direct conversion of x rays into electron-hole pairs, which do not need an intermediate production of visible light. In these detectors the readout is usually achieved through arrays of thin film transistors (TFTs). However, TFT readout tends to display noise characteristics worse than those from indirect detectors. To address this problem, a novel clinical system for digital mammography has been recently marketed based on direct-conversion detector and optical readout. This unit, named AMULET and manufactured by FUJIFILM, is based on a dual layer of amorphous selenium that acts both as a converter of x rays (first layer) and as an optical switch for the readout of signals (second layer) powered by a line light source. The optical readout is expected to improve the noise characteristics of the detector. The aim is to obtain images with high resolution and low noise, thanks to the combination of optical switching technology and direct conversion with amorphous selenium. In this article, the authors present a characterization of an AMULET system. Methods: The characterization was achieved in terms of physical figures as modulation transfer function(MTF),noise power spectra (NPS), detective quantum efficiency (DQE), and contrast-detail analysis. The clinical unit was tested by exposing it to two different beams: 28 kV Mo/Mo (namely, RQA-M2) and 28 kV W/Rh (namely, W/Rh). Results: MTF values of the system are slightly worse than those recorded from other direct-conversion flat panels but still within the range of those from indirect flat panels: The MTF values of the AMULET system are about 45% and 15% at 5 and 8 lp/mm, respectively. On the other hand, however, AMULET NNPS results are consistently better than those from direct-conversion flat panels (up to two to three times lower) and flat panels based on scintillation phosphors. DQE results lie around 70% when RQA-M2 beams are used and approaches 80% in the case of W/Rh beams. Contrast-detail analysis, when performed by human observers on the AMULET system, results in values better than those published for other full-field digital mammography systems. Conclusions: The novel clinical unit based on direct-conversion detector and optical reading presents great results in terms of both physical and psychophysical characterizations. The good spatial resolution, combined with excellent noise properties, allows the achievement of very good DQE, better than those published for clinical FFDM systems. The psychophysical analysis confirms the excellent behavior of the AMULET unit.

AdaBoost-based multiple SVM-RFE for classification of mammograms in DDSM

Abstract: Digital mammography is one of the most promising options to diagnose breast cancer which is the most common cancer in women. However, its effectiveness is enfeebled due to the difficulty in distinguishing actual cancer lesions from benign abnormalities, which results in unnecessary biopsy referrals. To overcome this issue, computer aided diagnosis (CADx) using machine learning techniques have been studied worldwide. Since this is a classification problem and the number of features obtainable from a mammogram image is infinite, a feature selection method that is tailored for use in the CADx systems is needed. We propose a feature selection method based on multiple support vector machine recursive feature elimination (MSVM-RFE). We compared our method with four previously proposed feature selection methods which use support vector machine as the base classifier. Experiments were performed on lesions extracted from the Digital Database of Screening Mammography, the largest public digital mammography database available. We measured average accuracy over 5-fold cross validation on the 8 datasets we extracted. Selecting from 8 features, conventional algorithms like SVM-RFE and multiple SVM-RFE showed slightly better performance than others. However, when selecting from 22 features, our proposed modified multiple SVM-RFE using boosting outperformed or was at least competitive to all others. Our modified method may be a possible alternative to SVM-RFE or the original MSVM-RFE in many cases of interest. In the future, we need a specific method to effectively combine models trained during the feature selection process and a way to combine feature subsets generated from individual SVM-RFE instances.

First epidemiological analysis of breast cancer incidence and tumor characteristics after implementation of population-based digital mammography screening.

Abstract: PURPOSE: To epidemiologically evaluate the impact of digital mammography screening on incidence rates and tumor characteristics for breast cancer. MATERIALS AND METHODS: The first German digital screening units in the clinical routine were evaluated during the implementation period by using data from the cancer registry to compare the incidence rate of breast cancers and prognostic characteristics. 74 % of women aged 50 - 69 within the region of Muenster/Coesfeld/Warendorf were invited between 10 / 2005 and 12 / 2007 for initial screening; 55 % participated (n = 35 961). RESULTS: In 2002 - 2004 the average breast cancer incidence rate (per 100 000) was 297.9. During the implementation of screening, the rate rose to 532.9 in 2007. Of the 349 cancers detected with screening, 76 % (265 / 349) were invasive compared to 90 % (546 / 608) of cases not detected with screening during the same period. 37 % (97 / 265) of cancers detected in the screening program had a diameter of ≤ 10 mm and 75 % (198 / 265) were node-negative compared to 15 % (79 / 546) and 64 % (322 / 503), respectively, in cancers detected outside the screening program. The distribution of invasive tumor size (pT categories) and the nodal status differed with statistical significance between cancers detected in and outside the program (p = 0.005 and p = 0.004, respectively). CONCLUSION: Epidemiological data shows that the implementation of a population-based screening program led to a relevant increase in the age-specific breast cancer incidence rate. The characteristics of breast cancers detected in the screening program comply with the requirements of the European guidelines and are significantly favorable compared to tumors diagnosed outside the program. These findings indicate that digital mammography screening fulfills the requirements for an early tumor detection tool.

Screening and Prevention of Breast Cancer in Primary Care

Abstract: Mammography remains the mainstay of breast cancer screening. There is little controversy that mammography reduces the risk of dying from breast cancer by about 23% among women between the ages of 50 and 69 years, although the harms associated with false-positive results and overdiagnosis limit the net benefit of mammography. Women in their 70s may have a small benefit from screening mammography, but overdiagnosis increases in this age group as do competing causes of death. While new data support a 16% reduction in breast cancer mortality for 40- to 49-year-old women after 10 years of screening, the net benefit is less compelling in part because of the lower incidence of breast cancer in this age group and because mammography is less sensitive and specific in women younger than 50 years. Digital mammography is more sensitive than film mammography in young women with similar specificity, but no improvements in breast cancer outcomes have been demonstrated. Magnetic resonance imaging may benefit the highest risk women. Randomized trials suggest that self-breast examination does more harm than good. Primary prevention with currently approved medications will have a negligible effect on breast cancer incidence. Public health efforts aimed at increasing mammography screening rates, promoting regular exercise in all women, maintaining a healthy weight, limiting alcohol intake, and limiting postmenopausal hormone therapy may help to continue the recent trend of lower breast cancer incidence and mortality among American women.