Luisa P. Wallace

Comparison of Two-dimensional Synthesized Mammograms versus Original Digital Mammograms Alone and in Combination with Tomosynthesis Images

PURPOSE To assess interpretation performance and radiation dose when two-dimensional synthesized mammography (SM) images versus standard full-field digital mammography (FFDM) images are used alone or in combination with digital breast tomosynthesis images. MATERIALS AND METHODS A fully crossed, mode-balanced multicase (n = 123), multireader (n = 8), retrospective observer performance study was performed by using deidentified images acquired between 2008 and 2011 with institutional review board approved, HIPAA-compliant protocols, during which each patient signed informed consent. The cohort included 36 cases of biopsy-proven cancer, 35 cases of biopsy-proven benign lesions, and 52 normal or benign cases (Breast Imaging Reporting and Data System [BI-RADS] score of 1 or 2) with negative 1-year follow-up results. Accuracy of sequentially reported probability of malignancy ratings and seven-category forced BI-RADS ratings was evaluated by using areas under the receiver operating characteristic curve (AUCs) in the random-reader analysis. RESULTS Probability of malignancy-based mean AUCs for SM and FFDM images alone was 0.894 and 0.889, respectively (difference, -0.005; 95% confidence interval [CI]: -0.062, 0.054; P = .85). Mean AUC for SM with tomosynthesis and FFDM with tomosynthesis was 0.916 and 0.939, respectively (difference, 0.023; 95% CI: -0.011, 0.057; P = .19). In terms of the reader-specific AUCs, five readers performed better with SM alone versus FFDM alone, and all eight readers performed better with combined FFDM and tomosynthesis (absolute differences from 0.003 to 0.052). Similar results were obtained by using a nonparametric analysis of forced BI-RADS ratings. CONCLUSION SM alone or in combination with tomosynthesis is comparable in performance to FFDM alone or in combination with tomosynthesis and may eliminate the need for FFDM as part of a routine clinical study.

Recall and detection rates in screening mammography: A review of clinical experience: Implications for practice guidelines

The authors investigated the correlation between recall and detection rates in a group of 10 radiologists who had read a high volume of screening mammograms in an academic institution.

Detection and classification performance levels of mammographic masses under different computer-aided detection cueing environments1

Abstract Rationale and objectives The authors evaluated the impact of different computer-aided detection (CAD) cueing conditions on radiologists’ performance levels in detecting and classifying masses depicted on mammograms. Materials and methods In an observer performance study, eight radiologists interpreted 110 subtle cases six times under different display conditions to detect depicted masses and classify them as benign or malignant. Forty-five cases depicted biopsy-proven masses and 65 were negative. One mass-based cueing sensitivity of 80% and two false-positive cueing rates of 1.2 and 0.5 per image were used in this study. In one mode, radiologists first interpreted images without CAD results, followed by the display of cues and reinterpretation. In another mode, radiologists viewed CAD cues as images were presented and then interpreted images. Free-response receiver operating characteristic method was used to analyze and compare detection performance. The receiver operating characteristic method was used to evaluate classification performance. Results At these performance levels, providing cues after initial interpretation had little effect on the overall performance in detecting masses. However, in the mode with the highest false-positive cueing rate, viewing CAD cues immediately upon display of images significantly reduced average performance for both detection and classification tasks ( P Conclusion CAD systems with low sensitivity (≤80% on mass-based detection) and high false-positive rate (≥0.5 per image) in a dataset with subtle abnormalities had little effect on radiologists’ performance in the detection and classification of mammographic masses.

Effect of the Availability of Prior Full-Field Digital Mammography and Digital Breast Tomosynthesis Images on the Interpretation of Mammograms

PURPOSE To assess the effect of and interaction between the availability of prior images and digital breast tomosynthesis (DBT) images in decisions to recall women during mammogram interpretation. MATERIALS AND METHODS Verbal informed consent was obtained for this HIPAA-compliant institutional review board-approved protocol. Eight radiologists independently interpreted twice deidentified mammograms obtained in 153 women (age range, 37-83 years; mean age, 53.7 years ± 9.3 [standard deviation]) in a mode by reader by case-balanced fully crossed study. Each study consisted of current and prior full-field digital mammography (FFDM) images and DBT images that were acquired in our facility between June 2009 and January 2013. For one reading, sequential ratings were provided by using (a) current FFDM images only, (b) current FFDM and DBT images, and (c) current FFDM, DBT, and prior FFDM images. The other reading consisted of (a) current FFDM images only, (b) current and prior FFDM images, and (c) current FFDM, prior FFDM, and DBT images. Fifty verified cancer cases, 60 negative and benign cases (clinically not recalled), and 43 benign cases (clinically recalled) were included. Recall recommendations and interaction between the effect of prior FFDM and DBT images were assessed by using a generalized linear model accounting for case and reader variability. RESULTS Average recall rates in noncancer cases were significantly reduced with the addition of prior FFDM images by 34% (145 of 421) and 32% (106 of 333) without and with DBT images, respectively (P < .001). However, this recall reduction was achieved at the cost of a corresponding 7% (23 of 345) and 4% (14 of 353) reduction in sensitivity (P = .006). In contrast, availability of DBT images resulted in a smaller reduction in recall rates (false-positive interpretations) of 19% (76 of 409) and 26% (71 of 276) without and with prior FFDM images, respectively (P = .001). Availability of DBT images resulted in 4% (15 of 338) and 8% (25 of 322) increases in sensitivity, respectively (P = .007). The effects of the availability of prior FFDM images or DBT images did not significantly change regardless of the sequence in presentation (P = .81 and P = .47 for specificity and sensitivity, respectively). CONCLUSION The availability of prior FFDM or DBT images is a largely independent contributing factor in reducing recall recommendations during mammographic interpretation.

A Multisite Telemammography System for Remote Management of Screening Mammography: An Assessment of Technical, Operational, and Clinical Issues

ObjectiveThis paper describes a high-quality, multisite telemammography system to enable “almost real-time” remote patient management while the patient remains in the clinic. One goal is to reduce the number of women who would physically need to return to the clinic for additional imaging procedures (termed “recall”) to supplement “routine” imaging of screening mammography.Materials and MethodsMammography films from current and prior (when available) examinations are digitized at three remote sites and transmitted along with other pertinent information across low-level communication systems to the central site. Images are automatically cropped, wavelet compressed, and encrypted prior to transmission to the central site. At the central site, radiologists review and rate examinations on a high-resolution workstation that displays the images, computer-assisted detection results, and the technologists communication. Intersite communication is provided instantly via a messaging “chat” window.ResultsThe technologists recommended additional procedures at 2.7 times the actual clinical recall rate for the same cases. Using the telemammography system during a series of “off-line” clinically simulated studies, radiologists recommended additional procedures at 1.3 times the actual clinical recall rate. Percent agreement and kappa between the study and actual clinical interpretations were 66.1% and 0.315, respectively. For every physical recall potentially avoided using the telemammography system, approximately one presumed “unnecessary” imaging procedure was recommended.ConclusionRemote patient management can reduce the number of women recalled by as much as 50% without performing an unreasonable number of presumed “unnecessary” procedures.

Different Search Patterns and Similar Decision Outcomes: How Can Experts Agree in the Decisions They Make When Reading Digital Mammograms?

Experts may agree in most decisions that they make when they read a case set of digital mammograms, but eye-position tracking studies suggest that they use very different visual search strategies to make such decisions. If indeed each expert uses a unique strategy, it may be very difficult to teach radiology trainees effective ways to search the background parenchyma. In this study, we examined how much agreement exists in the actual locations used by the experts in their decision making process when reading digital mammograms.

Subjective assessment of high-level image compression of digitized mammograms

This study was designed to evaluate radiologists’ ability to identify highly-compressed, digitized mammographic images displayed on high-resolution, monitors. Mammography films were digitized at 50 micron pixel dimensions using a high-resolution laser film digitizer. Image data were compressed using the irreversible (lossy), wavelet-based JPEG 2000 method. Twenty images were randomly presented in pairs (one image per monitor) in three modes: mode 1, non-compressed versus 50:1 compression; mode 2, non-compressed versus 75:1 compression; and mode 3, 50:1 versus 75:1 compression with 20 random pairs presented twice (80 pairs total). Six radiologists were forced to choose which image had the lower level of data compression in a two-alternative forced choice paradigm. The average percent correct across the six radiologists for modes 1, 2 and 3 were 52.5% (+/-11.3), 58.3% (+/-14.7), and 58.3% (+/-7.5), respectively. Intra-reader agreement ranged from 10 to 50% and Kappa from -0.78 to -0.19. Kappa for inter-reader agreement ranged from -0.47 to 0.37. The “monitor effect” (left/right) was of the same order of magnitude as the radiologists’ ability to identify the lower level of image compression. In this controlled evaluation, radiologists did not accurately discriminate non-compressed and highly-compressed images. Therefore, 75:1 image compression should be acceptable for review of digitized mammograms in a telemammography system.

Changes in frequency of recall recommendations of examinations depicting cancer with the availability of either priors or digital breast tomosynthesis

Performance changes in a binary environment when using additional information is affected only when changes in recommendations are made due to the additional information in question. In a recent study, we have shown that, contrary to general expectation, introducing prior examinations improved recall rates, but not sensitivity. In this study, we assessed cancer detection differences when prior examinations and/or digital breast tomosynthesis (DBT) were made available to the radiologist. We identified a subset of 21 cancer cases with differences in the number of radiologists who recalled these cases after reviewing either a prior examination or DBT. For the cases with differences in recommendations after viewing either priors or DBT, separately, we evaluated the total number of readers that changed their recommendations, regardless of the specific radiologist in question. Confidence intervals for the number of readers and a test for the hypothesis of no difference was performed using the non-parameteric bootstrap approach addressing both case and reader-related sources of variability by resampling cases and readers. With the addition of priors, there were 14 cancer cases (out of 15) where the number of “recalling radiologists” decreased. With the addition of DBT, the number of “recalling radiologists” decreased in only five cases (out of 15) while increasing in the remaining 9 cases. Unlike most new approaches to breast imaging DBT seems to improve both recall rates and cancer detection rates. Changes in recommendations were noted by all radiologists for all cancers by type, size, and breast density.

Preliminary clinical evaluation of a multi-site telemammography system in a screening mammography environment

We evaluated a telemammography system for reviewing and rating screening mammography in a clinical setting. Three remote sites transmitted 306 exams to a central site. Films were digitized at 50 micron pixel dimensions and compressed at a 50:1 ratio. At the central site images were displayed on a workstation with two high-resolution monitors. Five radiologists reviewed and rated the screens without the availability of prior images or additional information indicating: 1) if additional procedures were needed, 2) which breast was involved, and 3) when appropriate, the recommended additional procedures. During the actual clinical interpretation 13.7% (42 cases) of the patients were recalled for additional procedures. During the retrospective review radiologists 1, 2, 3, 4, and 5 recommended additional procedures for 26.1%, 29.1%, 36.3%, 45.1%, and 54.2% of the cases, respectively. The agreements between the clinical interpretation and radiologists 1, 2, 3, 4, and 5 were 77.8%, 76.1%, 69.0%, 62.7%, and 53.6%, respectively. The exceedingly high percentage of recommended additional procedures using the workstation was attributed to lack of prior images or additional information, the knowledge that case management was not affected, and the observers’ expectation for an enriched case mix.