Eric A. Berns

Comparison of Acquisition Parameters and Breast Dose in Digital Mammography and Screen-Film Mammography in the American College of Radiology Imaging Network Digital Mammographic Imaging Screening Trial

OBJECTIVE The purpose of our study was to compare the technical performance of full-field digital mammography (FFDM) and screen-film mammography. MATERIALS AND METHODS The American College of Radiology Imaging Network Digital Mammographic Imaging Screening Trial enrolled 49,528 women to compare FFDM and screen-film mammography for screening. For quality assurance purposes, technical parameters including breast compression force, compressed breast thickness, mean glandular dose, and the number of additional views needed for complete breast coverage were recorded and analyzed for both FFDM and screen-film mammography on approximately 10% of study subjects at each site. RESULTS Technical data were compiled on 5,102 study subjects at 33 sites. Clean data were obtained for 4,366 (88%) of those cases. Mean compression force was 10.7 dN for screen-film mammography and 10.1 dN for FFDM (5.5% difference, p < 0.001). Mean compressed breast thickness was 5.3 cm for screen-film mammography and 5.4 cm for FFDM (1.7% difference, p < 0.001). Mean glandular dose per view averaged 2.37 mGy for screen-film mammography and 1.86 mGy for FFDM, 22% lower for digital than screen-film mammography, with sizeable variations among digital manufacturers. Twelve percent of screen-film mammography cases required more than the normal four views, whereas 21% of FFDM cases required more than the four normal views to cover all breast tissue. When extra views were included, mean glandular dose per subject was 4.15 mGy for FFDM and 4.98 mGy for screen-film mammography, 17% lower for FFDM than screen-film mammography. CONCLUSION Our results show that differences between screen-film mammography and FFDM in compression force and indicated compressed breast thickness were small. On average, FFDM had 22% lower mean glandular dose than screen-film mammography per acquired view, with sizeable variations in average FFDM doses by manufacturer.

Performance comparison of full-field digital mammography to screen-film mammography in clinical practice.

Results of acceptance testing 18 full-field digital mammography systems for clinical use and of conducting annual physics surveys of 38 screen-film mammography systems were compared in terms of exposure times, mean glandular breast doses, and image quality. These evaluations were made using the same test tools on all systems, with emphasis on assessing automatic exposure control performance and image quality on both digital and screen-film systems using clinical techniques. Survey results indicated that digital mammography systems performed similarly to screen-film systems in terms of exposure times and mean glandular doses for thin to intermediate breasts, but that digital mammography systems selected shorter exposure times and lower mean glandular doses for thicker breasts. For all breast thicknesses, digital mammography systems yielded mean contrast-detail scores higher than those for screen-film systems. For all breast thicknesses, the 18 digital mammography systems demonstrated less variance in terms of exposure times, mean glandular doses, and contrast-detail scores than did the 38 screen-film systems tested. These results indicate that the clinical use of digital mammography may generally improve image quality for equal or lower breast doses, while providing tighter control on exposures and image quality than screen-film mammography.

Mammography Facility Characteristics Associated With Interpretive Accuracy of Screening Mammography

Background Although interpretive performance varies substantially among radiologists, such variation has not been examined among mammography facilities. Understanding sources of facility variation could become a foundation for improving interpretive performance. Methods In this cross-sectional study conducted between 1996 and 2002, we surveyed 53 facilities to evaluate associations between facility structure, interpretive process characteristics, and interpretive performance of screening mammography (ie, sensitivity, specificity, positive predictive value [PPV1], and the likelihood of cancer among women who were referred for biopsy [PPV2]). Measures of interpretive performance were ascertained prospectively from mammography interpretations and cancer data collected by the Breast Cancer Surveillance Consortium. Logistic regression and receiver operating characteristic (ROC) curve analyses estimated the association between facility characteristics and mammography interpretive performance or accuracy (area under the ROC curve [AUC]). All P values were two-sided. Results Of the 53 eligible facilities, data on 44 could be analyzed. These 44 facilities accounted for 484 463 screening mammograms performed on 237 669 women, of whom 2686 were diagnosed with breast cancer during follow-up. Among the 44 facilities, mean sensitivity was 79.6% (95% confidence interval [CI] = 74.3% to 84.9%), mean specificity was 90.2% (95% CI = 88.3% to 92.0%), mean PPV1 was 4.1% (95% CI = 3.5% to 4.7%), and mean PPV2 was 38.8% (95% CI = 32.6% to 45.0%). The facilities varied statistically significantly in specificity (P < .001), PPV1 (P < .001), and PPV2 (P = .002) but not in sensitivity (P = .99). AUC was higher among facilities that offered screening mammograms alone vs those that offered screening and diagnostic mammograms (0.943 vs 0.911, P = .006), had a breast imaging specialist interpreting mammograms vs not (0.932 vs 0.905, P = .004), did not perform double reading vs independent double reading vs consensus double reading (0.925 vs 0.915 vs 0.887, P = .034), or conducted audit reviews two or more times per year vs annually vs at an unknown frequency (0.929 vs 0.904 vs 0.900, P = .018). Conclusion Mammography interpretive performance varies statistically significantly by facility.

Digital and screen-film mammography: comparison of image acquisition and interpretation times.

OBJECTIVE The objective of our study was to compare acquisition times and interpretation times of screening examinations using screen-film mammography and soft-copy digital mammography. MATERIALS AND METHODS Technologist study acquisition time from examination initiation to release of the screenee was measured for both screen-film and digital mammography (100 cases each) in routine clinical practice. The total interpretation time for screening mammography was also measured for 183 hard-copy screen-film cases and 181 soft-copy digital cases interpreted by a total of seven breast imaging radiologists, four experienced breast imagers, and three breast imaging fellows. RESULTS Screening mammography acquisition time averaged 21.6 minutes for screen-film and 14.1 minutes for digital, a highly significant 35% shorter time for digital than screen-film (p < 10(-17)). The average number of images per case acquired with digital mammography was higher than that for screen-film mammography (4.23 for screen-film, 4.50 for digital; p = 0.047). The total interpretation time averaged 1.4 minutes for screen-film mammography and 2.3 minutes for digital mammography, a highly significant 57% longer interpretation time for digital (p < 10(-11)). In addition, technical problems delaying interpretation were encountered in none of the 183 screen-film cases but occurred in nine (5%) of the 181 digital cases. CONCLUSION Compared with screen-film mammography, the use of digital mammography for screening examinations significantly shortened acquisition time but significantly increased interpretation time. In addition, more technical problems were encountered that delayed the interpretation of digital cases.

Optimization of technique factors for a silicon diode array full‐field digital mammography system and comparison to screen‐film mammography with matched average glandular dose

Contrast-detail experiments were performed to optimize technique factors for the detection of low-contrast lesions using a silicon diode array full-field digital mammography (FFDM) system under the conditions of a matched average glandular dose (AGD) for different techniques. Optimization was performed for compressed breast thickness from 2 to 8 cm. FFDM results were compared to screen-film mammography (SFM) at each breast thickness. Four contrast-detail (CD) images were acquired on a SFM unit with optimal techniques at 2, 4, 6, and 8 cm breast thicknesses. The AGD for each breast thickness was calculated based on half-value layer (HVL) and entrance exposure measurements on the SFM unit. A computer algorithm was developed and used to determine FFDM beam current (mAs) that matched AGD between FFDM and SFM at each thickness, while varying target, filter, and peak kilovoltage (kVp) across the full range available for the FFDM unit. CD images were then acquired on FFDM for kVp values from 23-35 for a molybdenum-molybdenum (Mo-Mo), 23-40 for a molybdenum-rhodium (Mo-Rh), and 25-49 for a rhodium-rhodium (Rh-Rh) target-filter under the constraint of matching the AGD from screen-film for each breast thickness (2, 4, 6, and 8 cm). CD images were scored independently for SFM and each FFDM technique by six readers. CD scores were analyzed to assess trends as a function of target-filter and kVp and were compared to SFM at each breast thickness. For 2 cm thick breasts, optimal FFDM CD scores occurred at the lowest possible kVp setting for each target-filter, with significant decreases in FFDM CD scores as kVp was increased under the constraint of matched AGD. For 2 cm breasts, optimal FFDM CD scores were not significantly different from SFM CD scores. For 4-8 cm breasts, optimum FFDM CD scores were superior to SFM CD scores. For 4 cm breasts, FFDM CD scores decreased as kVp increased for each target-filter combination. For 6 cm breasts, CD scores decreased slightly as kVp increased for Mo-Mo, but did not change significantly as a function of kVp for either Mo-Rh or Rh-Rh. For 8 cm breasts, Rh/Rh FFDM CD scores were superior to other target-filter combinations and increased significantly as kVp increased. These results indicate that low-contrast lesion detection was optimized for FFDM by using a softer x-ray beam for thin breasts and a harder x-ray beam for thick breasts, when AGD was kept constant for a given breast thickness. Under this constraint, optimum low-contrast lesion detection with FFDM was superior to that for SFM for all but the thinnest breasts.

Reactions to Uncertainty and the Accuracy of Diagnostic Mammography

BackgroundReactions to uncertainty in clinical medicine can affect decision making.ObjectiveTo assess the extent to which radiologists’ reactions to uncertainty influence diagnostic mammography interpretation.DesignCross-sectional responses to a mailed survey assessed reactions to uncertainty using a well-validated instrument. Responses were linked to radiologists’ diagnostic mammography interpretive performance obtained from three regional mammography registries.ParticipantsOne hundred thirty-two radiologists from New Hampshire, Colorado, and Washington.MeasurementMean scores and either standard errors or confidence intervals were used to assess physicians’ reactions to uncertainty. Multivariable logistic regression models were fit via generalized estimating equations to assess the impact of uncertainty on diagnostic mammography interpretive performance while adjusting for potential confounders.ResultsWhen examining radiologists’ interpretation of additional diagnostic mammograms (those after screening mammograms that detected abnormalities), a 5-point increase in the reactions to uncertainty score was associated with a 17% higher odds of having a positive mammogram given cancer was diagnosed during follow-up (sensitivity), a 6% lower odds of a negative mammogram given no cancer (specificity), a 4% lower odds (not significant) of a cancer diagnosis given a positive mammogram (positive predictive value [PPV]), and a 5% higher odds of having a positive mammogram (abnormal interpretation).ConclusionMammograms interpreted by radiologists who have more discomfort with uncertainty have higher likelihood of being recalled.

Variability of interpretive accuracy among diagnostic mammography facilities

BACKGROUND Interpretive performance of screening mammography varies substantially by facility, but performance of diagnostic interpretation has not been studied. METHODS Facilities performing diagnostic mammography within three registries of the Breast Cancer Surveillance Consortium were surveyed about their structure, organization, and interpretive processes. Performance measurements (false-positive rate, sensitivity, and likelihood of cancer among women referred for biopsy [positive predictive value of biopsy recommendation {PPV2}]) from January 1, 1998, through December 31, 2005, were prospectively measured. Logistic regression and receiver operating characteristic (ROC) curve analyses, adjusted for patient and radiologist characteristics, were used to assess the association between facility characteristics and interpretive performance. All statistical tests were two-sided. RESULTS Forty-five of the 53 facilities completed a facility survey (85% response rate), and 32 of the 45 facilities performed diagnostic mammography. The analyses included 28 100 diagnostic mammograms performed as an evaluation of a breast problem, and data were available for 118 radiologists who interpreted diagnostic mammograms at the facilities. Performance measurements demonstrated statistically significant interpretive variability among facilities (sensitivity, P = .006; false-positive rate, P < .001; and PPV2, P < .001) in unadjusted analyses. However, after adjustment for patient and radiologist characteristics, only false-positive rate variation remained statistically significant and facility traits associated with performance measures changed (false-positive rate = 6.5%, 95% confidence interval [CI] = 5.5% to 7.4%; sensitivity = 73.5%, 95% CI = 67.1% to 79.9%; and PPV2 = 33.8%, 95% CI = 29.1% to 38.5%). Facilities reporting that concern about malpractice had moderately or greatly increased diagnostic examination recommendations at the facility had a higher false-positive rate (odds ratio [OR] = 1.48, 95% CI = 1.09 to 2.01) and a non-statistically significantly higher sensitivity (OR = 1.74, 95% CI = 0.94 to 3.23). Facilities offering specialized interventional services had a non-statistically significantly higher false-positive rate (OR = 1.97, 95% CI = 0.94 to 4.1). No characteristics were associated with overall accuracy by ROC curve analyses. CONCLUSIONS Variation in diagnostic mammography interpretation exists across facilities. Failure to adjust for patient characteristics when comparing facility performance could lead to erroneous conclusions. Malpractice concerns are associated with interpretive performance.

ACR–AAPM–SIIM Practice Guideline for Determinants of Image Quality in Digital Mammography

This guideline was developed collaboratively by individuals with recognized expertise in breast imaging, medical physics, and imaging informatics, representing the American College of Radiology (ACR), the American Association of Physicists in Medicine (AAPM), and the Society for Imaging Informatics in Medicine (SIIM), primarily for technical guidance. It is based on a review of the clinical and physics literature on digital mammography and the experience of experts and publications from the Image Quality Collaborative Workgroup [1–3]. For purposes of this guideline, digital mammography is defined as the radiographic examination of the breast utilizing dedicated electronic detectors to record the image (rather than screen film) and having the capability for image display on computer monitors. This guideline is specific to two-dimensional (2D) digital mammography since the vast majority of digital mammography performed in the USA is 2D. Although some three-dimensional technologies are in use, they are not addressed in this guideline since they continue to evolve and are not yet in widespread clinical use. In many parts of this guideline, the level of technical detail regarding the determinants of image quality for digital mammography is advanced, and is intended to provide radiologists, qualified medical physicists, regulators, and other support personnel directly involved in clinical implementation and oversight an expanded knowledge of the issues pertinent to assessing and maintaining digital mammography image quality from the acquisition, display, and data storage aspects of the process. Where basic technical requirements for digital mammography overlap with those for digital radiography in general, users are directed to consult the referenced ACR practice guidelines [4, 5]. All interested individuals are encouraged to review the ACR digital radiography guidelines. Additionally, this guideline includes input from industry, radiologists, and other interested parties in an attempt to represent the consensus of the broader community. It was further informed by input from another working group of the Integrating the Healthcare Enterprise (IHE) Initiative [6]. Furthermore, the ACR Subcommittee on Digital Mammography is developing a quality control (QC) manual for digital mammography. Analysis of image quality has meaning primarily in the context of a particular imaging task [7]. This guideline has been developed with reference to specific imaging tasks required by mammography, using the information available in the peer-reviewed medical literature regarding digital mammography acquisition, image processing and display, storage, transmission, and retrieval. Specifically, the imaging tasks unique to mammography that determine the essential characteristics of a high-quality mammogram are its ability to visualize the following features of breast cancer: The characteristic morphology of a mass. The shape and spatial configuration of calcifications. Distortion of the normal architecture of the breast tissue. Asymmetry between images of the left and right breast. The development of anatomically definable changes when compared with prior studies. The primary goal of mammography is to detect breast cancer, if it exists, by accurately visualizing these features. At the same time, it is important that these signs of breast cancer not be falsely identified if breast cancer is not present. Two aspects of digital image quality can be distinguished: technical and clinical. It is possible to make technical measurements describing the above attributes, and it may be possible to infer a connection between these technical measures and clinical image quality. The extent to which these features are rendered optimally with a digital mammography system using current technology depends on several factors and is the major focus of this guideline.

Radiation Dose Reduction for Augmentation Mammography

OBJECTIVE Patients who undergo cosmetic augmentation have larger and denser breasts and receive higher radiation doses during mammography than women without implants. In this study we evaluated the dose increase and techniques for dose reduction. SUBJECTS AND METHODS Mean glandular dose to the breast during screening mammography was measured for 206 women who had undergone breast augmentation. For 13 of these women, mean glandular dose from preoperative mammography also was measured. Effective tube current, peak kilovoltage, and breast thickness were measured, and mean glandular dose was calculated for 1,632 images. Two screen-film combinations and three target-filter combinations were studied. RESULTS For four-view augmentation mammography with a molybdenum-molybdenum (Mo-Mo) target-filter combination, mean glandular dose was reduced 35%, from 10.7 to 7.0 mGy, by changing the screen-film combination from 100 to 190 speed. For four-view augmentation mammography, mean glandular dose was reduced 24% by changing the target-filter combination from Mo-Mo to rhodium-rhodium (Rh-Rh) for full views of breasts containing implants. For four-view augmentation mammography, mean glandular dose was reduced 50% by changing the screen-film combination from 100 to 190 speed and changing the target-filter combination from Mo-Mo to Rh-Rh for implant-full views. CONCLUSION Mean glandular dose per breast from four-view augmentation mammography with the 100-speed screen-film and Mo-Mo target-filter combinations averaged 10.7 mGy, which is 3.1 times higher than the 3.4 mGy for conventional two-view mammography of breasts without implants. In 40 years of screening, this number represents a more than tripled lifetime attributable risk of radiation-induced breast cancer--an unacceptable level. Use of faster screen-film combinations, use of Rh-Rh target-filter combinations, and acquisition of three rather than four views are dose-reduction methods that together result in a 66% dose reduction, from 10.7 to 3.6 mGy. Mean glandular dose should be kept less than 7.0 mGy per breast for screening mammography of patients with breast implants.

OPTIMIZING TECHNIQUES IN SCREEN-FILM MAMMOGRAPHY

This article provides a practical approach to the steps needed to optimize mammography techniques. Those steps consist of a series of activities that begin with the choice of mammography film, then choosing the optimum film processing for that film type, selecting the appropriate technique factors for exposure, and the proper viewing of processed mammography films. In each area, the basic physics underlying film and film processing, mammography equipment performance, image contrast, and image display, are used to determine optimized mammography techniques.