David J. Getty

Enhanced interpretation of diagnostic images.

In radiology, as in various other fields, observers study images to detect and diagnose underlying conditions. They make assessments of several image features and merge them into an overall decision. Demonstration is given here, in the context of mammography, that objective aids to this interpretative process can substantially improve accuracy, even for sophisticated and motivated radiologists. The aids are a checklist that solicits explicit, quantitative, systematic assessments of the important features of an image and a computer program that merges those assessments with optimal weights. The computer issues estimates of the likelihoods that specified conditions are present (in this study, the likelihood that a localized abnormality is malignant), and the radiologist benefits from taking those estimates as guidance.

Signal detection and identification at successive stages of observation.

The relationship of signal identification to signal detection was examined in a series of experiments. The signals were idealized lines and patterns of lines in a spectrographic display. On each trial, progressively more of the complete spectrogram was exposed in successive observation intervals, and after each interval the observer made both detection and identification responses that were based on the accumulating evidence. One model we employed conceives of detection and identification as proceeding together over time as parts of a unified process. A second model used shows how thejoint detection-and-identification ROC—a relative operating characteristic that relates the joint probability of correct detectionand correct identification to the probability of a false detection—may be predicted from the simple detection ROC. Both models were supported by the data.

On the prediction of confusion matrices from similarity judgments

Three observers viewed visual representations of eight complex sounds in both a pairwise similarity-judgment task and an identification task. A multidimensional scaling procedure applied to the similarity judgments yielded a three-dimensional perceptual space and the relative positions of the stimuli in that space. A probabilistic decision model based on weighted interstimulus distances served to predict well the confusion matrices of the identification task. Three conditions of the identification task, calling for identification of different subsets of the eight stimuli, led the observers to vary the weights they placed on the dimensions; they apparently adjusted the weights to maximize the percent correct identification. An additional group of 14 subjects, participating only in the similarity-judgment task, manifested the same three dimensions as the observers (corresponding to the locus of low-frequency energy, the locus of midfrequency energy, and visual contrast), and also a fourth dimension (corresponding to the periodicity, or waxing and waning, of the sound). Although not evident in the scaling analysis for the three observers, our utilization of the additional dimension increased significantly the variance accounted for in their identification responses. The overall accuracy of the predictions from a perceptual space to identification responses supplies a substantial validation of the use of multidimensional scaling procedures to reveal perceptual structure in demonstrating the ability of that structure to account for behavior in an independent task. The empirical success of this approach, furthermore, suggests a relatively simple and practical means of predicting, and possibly enhancing, identification performance for a given set of visual or auditory stimuli.

Clinical applications for stereoscopic 3-D displays

Abstract— Stereoscopic 3-D digital imaging holds the promise of improving the detection, diagnosis, and treatment of disease as well as enhancing the training and preparation of medical professionals through use of stereoscopic 3-D displays in concert with the many volumetric visualization techniques/modalities developed in recent years. While so-called 3-D graphics have improved the state of computer visualization in general, 3-D displays make full use of the human-visual perception, and thus can provide critical insight in complex computer-generated and video 3-D data. The stereo 3-D applications reviewed in this paper include screening of breast cancer and diabetic retinopathy, visualization for minimally invasive surgery, and the teaching of anatomy. Also included is a discussion of ground-breaking results from a stereo digital mammography clinical trial under way at Emory University.

Stereoscopic Digital Mammography: Improved Specificity and Reduced Rate of Recall in a Prospective Clinical Trial

PURPOSE To compare stereoscopic digital mammography (DM) with standard DM for the rate of patient recall and the detection of cancer in a screening population at elevated risk for breast cancer. MATERIALS AND METHODS Starting in September 2004 and ending in December 2007, this prospective HIPAA-compliant, institutional review board-approved screening trial, with written informed consent, recruited female patients at elevated risk for breast cancer (eg, personal history of breast cancer or breast cancer in a close relative). A total of 1298 examinations from 779 patients (mean age, 58.6 years; range, 32-91 years) comprised the analyzable data set. A paired study design was used, with each enrolled patient serving as her own control. Patients underwent both DM and stereoscopic DM examinations in a single visit, findings of which were interpreted independently by two experienced radiologists, each using a Breast Imaging Reporting and Data System (BI-RADS) assessment (BI-RADS category 0, 1, or 2). All patients determined to have one or more findings with either or both modalities were recalled for standard diagnostic evaluation. The results of 1-year follow-up or biopsy were used to determine case truth. RESULTS Compared with DM, stereoscopic DM showed significantly higher specificity (91.2% [1167 of 1279] vs 87.8% [1123 of 1279]; P = .0024) and accuracy (90.9% [1180 of 1298] vs 87.4% [1135 of 1298]; P = .0023) for detection of cancer. Sensitivity for detection of cancer was not significantly different for stereoscopic DM (68.4% [13 of 19]) compared with DM (63.2% [12 of 19], P .99). The recall rate for stereoscopic DM was 9.6% (125 of 1298) and that for DM was 12.9% (168 of 1298) (P = .0018). CONCLUSION Compared with DM, stereoscopic DM significantly improved specificity for detection of cancer, while maintaining comparable sensitivity. The recall rate was significantly reduced with stereoscopic DM compared with DM. SUPPLEMENTAL MATERIAL http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120382/-/DC1.

A comparative study of speech in the call center: natural language call routing vs. touch-tone menus

This paper presents a field study that compares natural language call routing with standard touch-tone menus. Call routing is the task of getting callers to the right place in the call center, which could be the appropriate live agent or automated service. Natural language call routing lets callers describe the reason for their call in their own words, instead of presenting them with a list of menu options to select from using the telephone touch-tone keypad. The field study was conducted in a call center of a large telecommunication service provider. Results show that with natural language call routing, more callers respond to the main routing prompt, more callers are routed to a specific destination (instead of defaulting to a general operator who may have to transfer them), and more callers are routed to the correct agent. Our survey data show that callers overwhelmingly prefer natural language call routing over standard touch-tone menus. Furthermore, natural language call routing can also deliver significant cost savings to call centers

Stereoscopic Digital Mammography: Improved Accuracy of Lesion Detection in Breast Cancer Screening

We report on a clinical trial comparing stereoscopic full-field digital mammography to standard (non-stereo) full-field digital mammography for detection of true breast lesions in a screening population. Each of 1458 enrolled patients received both a standard screening examination and a stereoscopic screening examination, which were read independently by different radiologists. Compared to standard digital mammography, stereo mammography significantly reduced false positive lesion detections by 46% (p< 0.0001), and significantly increased true positive lesion detections by 23% (p< 0.05).

Stereoscopic digital mammography: improving detection and diagnosis of breast cancer

Abstract Detecting and interpreting subtle breast lesions with standard film mammography is often difficult because of underlying and overlying normal tissue superimposed on the lesion in standard 2D views. Stereoscopic digital mammography may solve this and other problems of ambiguity by permitting the radiologist to view the lesion in the volume, separated from the superimposed tissue in depth. We have acquired both film and stereo mammograms on women prior to biopsy of a suspicious lesion. In a reading study with experienced mammographers, stereo mammography, as an adjunct to film, was shown to significantly improve diagnostic accuracy. But even more importantly, readers detected many new lesions in the stereo mammograms that were not visible in the films.

Detection of rib fractures in an abused infant using digital radiography: A laboratory study

Abstract Purpose. To assess the diagnostic performance of digital radiography using charge-coupled device (CCD) technology in the detection of rib fracture in infant abuse. Materials and methods. Four fractured posterior rib arcs and eight normal ribs removed at autopsy from a 10-month-old abused infant were radiographed using a CCD prototype, four clinical film-screen systems, and direct-exposure film. Each rib was viewed with these six systems in nine different projections. The resultant 648 images were assessed for probability of fracture (0–100%) by four pediatric radiologists. The calculated area under the resultant ROC curves (Az) for the CCD was compared with those obtained with direct-exposure, high-detail, medium and fast film-screen radiographic systems. Results. The mean Az for the CCD (0.937) fell within the range of the high-detail systems (0.934–0.940) and was significantly higher (p<0.05) than the medium and fast system (0.861 and 0.858, respectively). Despite a lower spatial resolution than direct-exposure film (7 line pairs per millimeter vs. >20 line pairs per millimeter) the CCD performance was comparable (Az=0.944 vs. 0.937). The similar performance can be explained by the higher contrast resolution of the digital technology. Conclusion. This study indicates that in the ex vivo setting, digital radiology can perform comparably to high-detail film-screen imaging. The findings suggest that digital radiography has the potential to replace film-screen imaging in the evaluation of inflicted skeletal injury in infants.

Curing the menu blues in touch-tone voice interfaces

This paper presents a study on touch-tone menu design. In particular, we investigated whether short or long menus route callers more efficiently to the destination that can handle the call. A short menu offers a small number of broad selections, while a long menu offers a larger number of more specific choices. Results obtained from thousands of live calls to a commercial customer service center, show that callers route themselves more effectively using the long menu. In addition, in complex voice interfaces, using long menus reduces the number of menu layers required, thus reducing the need to navigate through multiple menu layers, one of the most severe usability problems of existing touch-tone interfaces.