Characterization of diffraction-enhanced imaging contrast in breast cancer.

Diffraction-enhanced imaging (DEI) is a new x-ray imaging modality that has been shown to enhance contrast between normal and cancerous breast tissues. In this study, diffraction-enhanced imaging in computed tomography (DEI-CT) mode was used to quantitatively characterize the refraction contrasts of the organized structures associated with invasive human breast cancer. Using a high-sensitivity Si (3 3 3) reflection, the individual features of breast cancer, including masses, calcifications and spiculations, were observed. DEI-CT yields 14, 5 and 7 times higher CT numbers and 10, 9 and 6 times higher signal-to-noise ratios (SNR) for masses, calcifications and spiculations, respectively, as compared to conventional CT of the same specimen performed using the same detector, x-ray energy and dose. Furthermore, DEI-CT at ten times lower dose yields better SNR than conventional CT. In light of the recent development of a compact DEI prototype using an x-ray tube as its source, these results, acquired at a clinically relevant x-ray energy for which a pre-clinical DEI prototype currently exists, suggest the potential of clinical implementation of mammography with DEI-CT to provide high-contrast, high-resolution images of breast cancer (Parham 2006 PhD Dissertation University of North Carolina at Chapel Hill).

Mass density images from the diffraction enhanced imaging technique.

Conventional x-ray radiography measures the projected x-ray attenuation of an object. It requires attenuation differences to obtain contrast of embedded features. In general, the best absorption contrast is obtained at x-ray energies where the absorption is high, meaning a high absorbed dose. Diffraction-enhanced imaging (DEI) derives contrast from absorption, refraction, and extinction. The refraction angle image of DEI visualizes the spatial gradient of the projected electron density of the object. The projected electron density often correlates well with the projected mass density and projected absorption in soft-tissue imaging, yet the mass density is not an "energy"-dependent property of the object, as is the case of absorption. This simple difference can lead to imaging with less x-ray exposure or dose. In addition, the mass density image can be directly compared (i.e., a signal-to-noise comparison) with conventional radiography. We present the method of obtaining the mass density image, the results of experiments in which comparisons are made with radiography, and an application of the method to breast cancer imaging.

Improving the detection of simulated masses in mammograms through two different image-processing techniques.

RATIONALE AND OBJECTIVES: The purpose of this study was to determine whether contrast-limited adaptive histogram equalization (CLAHE) or histogram-based intensity windowing (HIW) improves the detection of simulated masses in dense mammograms. MATERIALS AND METHODS: Simulated masses were embedded in portions of mammograms of patients with dense breasts; the mammograms were digitized at 50 microm per pixel, 12 bits deep. In two different experiments, images were printed both with no processing applied and with related parameter settings of two image-processing methods. A simulated mass was embedded in a realistic background of dense breast tissue, with its position varied. The key variables in each trial included the position of the mass, the contrast levels of the mass relative to the background, and the selected parameter settings for the image-processing method. RESULTS: The success in detecting simulated masses on mammograms with dense backgrounds depended on the parameter settings of the algorithms used. The best HIW setting performed better than the best fixed-intensity window setting and better than no processing. Performance with the best CLAHE settings was no different from that with no processing. In the HIW experiment, there were no significant differences in observer performance between processing conditions for radiologists and nonradiologists. CONCLUSION: HIW should be tested in clinical images to determine whether the detection of masses by radiologists can be improved. CLAHE processing will probably not improve the detection of masses on clinical mammograms.

Factors affecting phantom scores at annual mammography facility inspections by the U.S. Food and Drug Administration.

RATIONALE AND OBJECTIVES: The authors performed this study to evaluate the factors affecting phantom image score at the annual inspection of mammography facilities. MATERIALS AND METHODS: In 1997, three U.S. Food and Drug Administration (FDA)-trained inspectors performed inspections of all mammography facilities in North Carolina. All federal and state inspection data were collected and evaluated by using linear regression analysis. Factors affecting the American College of Radiology phantom scores were assessed. RESULTS: Phantom score was affected by inspector identity, view box luminance, and optical density. All of these factors had a statistically significant effect on mass score (P < .05). Inspector identity yielded a statistically significant effect on speck group score, fibril score, and total score. Luminance yielded a statistically significant effect on both speck group score and total score. CONCLUSION: Phantom scoring should be automated to allow for more consistent interobserver scoring. In addition, radiology facilities can improve the likelihood of receiving a passing phantom score by reducing the ambient light and increasing the view box luminance in the location where the images are evaluated and the phantom is scored routinely. Radiologists should also consider increasing phantom and clinical image optical density to allow for improved phantom testing outcomes.

What every surgical oncologist should know about digital mammography.

This article reviews the available information on digital mammography for surgeons who care for patients with breast cancer. The limitations of the current film-based technology and why digital mammography promises to improve breast cancer detection and breast lesion diagnosis are described. The basics of digital imaging technology are reviewed, including a description of image contrast and spatial resolution and its variance from currently available clinical digital mammography systems. The results of clinical trials completed to date are reported. An upcoming large screening trial for digital mammography, sponsored by the National Cancer Institute, is described. Future technological developments, including improvements in softcopy display, image processing, computer-aided detection and diagnosis (CADD), tomosynthesis, and digital subtraction mammography (DSM), are briefly discussed.

Perspective on digital mammography.

Digital mammography, particularly through its advanced applications, holds great promise for improved diagnostic accuracy, but the display of the images is not ideal at present. Clinical softcopy workstations are somewhat unwieldy to use, and image processing has not yet been optimized for each machine or for each clinical task. In addition, the cost-effectiveness and accuracy of the technology warrant careful study before digital mammography becomes widely disseminated and potentially replaces screen-film mammography, a technology that has been well documented to reduce breast cancer mortality.

Fine-needle aspiration biopsy of nonpalpable breast lesions in a multicenter clinical trial: results from the radiologic diagnostic oncology group V.

PURPOSE: To determine the diagnostic accuracy of ultrasonographically (US) and stereotactically guided fine-needle aspiration biopsy (FNAB) in the diagnosis of nonpalpable breast lesions. MATERIALS AND METHODS: At 18 institutions, 442 women who underwent 22-25-gauge imaging-guided FNAB were enrolled. Definitive surgical, core-needle biopsy, and/or follow-up information was available for 423 (95.7%) of these women. The reference standard was established from additional clinical and imaging information for an additional six (1.4%) women who did not undergo further histopathologic evaluation. The FNAB protocol was standardized at all institutions, and all specimens were reread by one of two expert cytopathologists. RESULTS: When insufficient samples were included in the analysis and classified as positive, the sensitivity and specificity of FNAB were 85%-88% and 55.6%-90.5%, respectively; accuracy ranged from 62.2% to 89.2%. The diagnostic accuracy of FNAB was significantly better for detection of masses than for detection of calcifications (67.3% vs. 53.8%, P =.006) and with US guidance than with stereotactic guidance (77.2% vs. 58.9%; P =.002). CONCLUSION: FNAB of nonpalpable breast lesions has limited value given the high insufficient sample rate and greater diagnostic accuracy of other interventions, including core-needle biopsy and needle-localized open surgical biopsy.

The American College of Radiology Imaging Network (ACRIN) and its clinical trials in breast imaging.

This paper describes the American College of Radiology Imaging Network (ACRIN), a new National Cancer Institute cooperative group, formed to perform multicenter clinical trials in diagnostic imaging and imaging-guided therapeutic technologies. The administrative structure of the organization and the mechanism by which trials are considered and approved for support are detailed. The advantages of this funding mechanism over previous NCI efforts are discussed. Detailed descriptions of the breast imaging protocols that ACRIN will open in the near future are provided. The quality of radiology as an academic discipline is likely to improve due to the infrastructure and training provided by this new organization.

Communicating results of diagnostic mammography: what do patients think?

RATIONALE AND OBJECTIVES: The purpose of this study was to investigate women's preferences for who (radiologist or referring physician) should communicate the results of diagnostic mammography. MATERIALS AND METHODS: Data from 153 women presenting to two sites for diagnostic mammography between February and June 1995 were collected with a 24-item, self-administered, closed-ended survey. For both normal and abnormal hypothetical results, contingency tables with chi2 tests and multiple logistic regression were used to determine the association, if any, between women's characteristics and their preferences. RESULTS: Women undergoing diagnostic mammography preferred that their radiologists disclose their normal (90%) and abnormal (88%) mammogram results to them immediately after their examination, rather than have their referring physicians disclose results at a later time. In the case of normal findings, women whose regular physicians were specialists were less likely to want to hear first from their radiologists (odds ratio [OR] = 0.06; 95% confidence interval [CI] = 0.01, 0.77; P = .03), but women who were nervous about learning their results were more likely to want to hear first from their radiologists (OR = 4.5; 95% CI = 1.2, 17.3; P = .03). CONCLUSION: Radiologists may want to consider assessing women's preferences for who communicates their mammogram results, as most women in this study preferred to hear these results from their radiologists rather than waiting to hear from their referring physicians.

Image processing algorithms for digital mammography: a pictorial essay.

Digital mammography systems allow manipulation of fine differences in image contrast by means of image processing algorithms. Different display algorithms have advantages and disadvantages for the specific tasks required in breast imaging-diagnosis and screening. Manual intensity windowing can produce digital mammograms very similar to standard screen-film mammograms but is limited by its operator dependence. Histogram-based intensity windowing improves the conspicuity of the lesion edge, but there is loss of detail outside the dense parts of the image. Mixture-model intensity windowing enhances the visibility of lesion borders against the fatty background, but the mixed parenchymal densities abutting the lesion may be lost. Contrast-limited adaptive histogram equalization can also provide subtle edge information but might degrade performance in the screening setting by enhancing the visibility of nuisance information. Unsharp masking enhances the sharpness of the borders of mass lesions, but this algorithm may make even an indistinct mass appear more circumscribed. Peripheral equalization displays lesion details well and preserves the peripheral information in the surrounding breast, but there may be flattening of image contrast in the nonperipheral portions of the image. Trex processing allows visualization of both lesion detail and breast edge information but reduces image contrast.

Digital mammography, sestamibi breast scintigraphy, and positron emission tomography breast imaging.

Digital mammography allows for the separate optimization of image acquisition and display. Through this technology, and the application of image processing and computer aided diagnosis, breast cancer detection and breast lesion diagnosis might be improved. Besides the obvious data storage, retrieval, and transmission advantages that digital mammography will allow, additional advances such as tomosynthesis, dual energy mammography and digital subtraction mammography are in development. The possible future utility of Sestamibi breast scintigraphy and breast imaging with positron emission tomography is also discussed.

Radiologists' preferences for digital mammographic display. The International Digital Mammography Development Group.

PURPOSE: To determine the preferences of radiologists among eight different image processing algorithms applied to digital mammograms obtained for screening and diagnostic imaging tasks. MATERIALS AND METHODS: Twenty-eight images representing histologically proved masses or calcifications were obtained by using three clinically available digital mammographic units. Images were processed and printed on film by using manual intensity windowing, histogram-based intensity windowing, mixture model intensity windowing, peripheral equalization, multiscale image contrast amplification (MUSICA), contrast-limited adaptive histogram equalization, Trex processing, and unsharp masking. Twelve radiologists compared the processed digital images with screen-film mammograms obtained in the same patient for breast cancer screening and breast lesion diagnosis. RESULTS: For the screening task, screen-film mammograms were preferred to all digital presentations, but the acceptability of images processed with Trex and MUSICA algorithms were not significantly different. All printed digital images were preferred to screen-film radiographs in the diagnosis of masses; mammograms processed with unsharp masking were significantly preferred. For the diagnosis of calcifications, no processed digital mammogram was preferred to screen-film mammograms. CONCLUSION: When digital mammograms were preferred to screen-film mammograms, radiologists selected different digital processing algorithms for each of three mammographic reading tasks and for different lesion types. Soft-copy display will eventually allow radiologists to select among these options more easily.

Informing patients of diagnostic mammography results: mammographer's opinions.

PURPOSE: The authors' purpose was to determine mammographers' practices and attitudes regarding disclosing results of diagnostic mammograms to patients. MATERIALS AND METHODS: In 1995, the authors mailed a questionnaire to 500 members of the Society of Breast Imaging; 399 (80%) responded to the survey. RESULTS: Three-quarters of respondents stated that mammographers should disclose results to their patients, and approximately half were already doing so (52% for normal results, 51% for abnormal results). A sizable minority (25%) said that not telling patients was the best practice and identified several barriers to direct disclosure, including lack of time. Although bivariate analysis showed direct disclosure to be more common among female mammographers, the sex difference did not persist in multivariate analysis. In both bivariate and multivariate analyses, reading more than 100 mammograms per week and having a radiology practice in a university or academic setting were each strongly associated with direct disclosure. CONCLUSION: Implementation of the Mammography Quality Standards Reauthorization Act of 1998 may not require a major change in mammographers' current practice. It remains critical to establish systems that help radiologists disclose results and communicate with referring physicians efficiently and effectively.

Has the mammography quality standards act affected the mammography quality in North Carolina?

OBJECTIVE: The United States Food and Drug Administration implemented federal regulations governing mammography under the Mammography Quality Standards Act (MQSA) of 1992. During 1995, its first year in implementation, we examined the impact of the MQSA on the quality of mammography in North Carolina. MATERIALS AND METHODS: All mammography facilities were inspected during 1993-1994, and again in 1995. Both inspections evaluated mean glandular radiation dose, phantom image evaluation, darkroom fog, and developer temperature. Two mammography health specialists employed by the North Carolina Division of Radiation Protection performed all inspections and collected and codified data. RESULTS: The percentage of facilities that met quality standards increased from the first inspection to the second inspection. Phantom scores passing rate was 31.6% versus 78.2%; darkroom fog passing rate was 74.3% versus 88.5%; and temperature difference passing rate was 62.4% versus 86.9%. CONCLUSION: In 1995, the first year that the MQSA was in effect, there was a significant improvement in the quality of mammography in North Carolina. This improvement probably resulted from facilities' compliance with federal regulations.

Human breast cancer specimens: diffraction-enhanced imaging with histologic correlation--improved conspicuity of lesion detail compared with digital radiography.

Seven breast cancer specimens were examined with diffraction-enhanced imaging at 18 keV with a silicon crystal with use of the silicon 333 reflection in Bragg mode. Images were compared with digital radiographs of the specimen, and regions of increased detail were identified. Six of the seven cases (86%) showed enhanced visibility of surface spiculation that correlated with histopathologic information, including extension of tumor into surrounding tissue.