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.

Breast imaging fellowship programs. A survey of the fellows of the Society of Breast Imaging.

RATIONALE AND OBJECTIVES: Breast imaging, a subspecialty of diagnostic radiology, is becoming more important with the increased performance of screening mammography. Fellowships in breast imaging are being offered at many institutions. Information regarding the contents and structure of such fellowships is important for potential trainees and departments considering offering such programs. METHODS: All 79 fellows of the Society of Breast Imaging (SBI) were surveyed by mail. Those with breast imaging fellowships were asked questions about their program. All were asked their opinions about the appropriate features of a breast imaging fellowship. RESULTS: Forty-six (58%) surveys were returned. Nineteen respondents described breast imaging fellowships offered at 18 different institutions. CONCLUSIONS: This information may be useful as radiologists consider establishing fellowship standards within this subspecialty.

Real-time radiologist review of remote ultrasound using low-cost video and voice.

RATIONALE AND OBJECTIVES: A radiologist practicing remote ultrasound occasionally needs to review a case in real time before releasing the patient. The authors conducted a pilot study to evaluate one solution in which the radiologist views real-time images on a video monitor while conversing with the technologist via a headset telephone. METHODS: Two experienced ultrasonographers and five technologies participated in a 5-week pilot study in adjacent rooms. RESULTS: Subjective assessment indicated that the system could function well enough for use at a remote site. CONCLUSIONS: Although this technology appears effective, an ongoing training environment is recommended.

A formal curriculum in breast imaging for radiology residents.

RATIONAL AND OBJECTIVES: Training in breast imaging is highly variable among radiology programs. The authors have developed a standardized breast imaging curriculum for radiology residents. METHODS: This curriculum has been implemented within the residency program at the University of North Carolina at Chapel Hill. It includes nine standardized components: 1) the clinical activities of the service; 2) the study of breast imaging teaching file films and contribution of new cases; 3) selected readings; 4) formal discussion with faculty on the readings; 5) review of this material using an interactive computer program; 6) formal conferences; 7) technical and quality control activities; 8) research activities; and 9) an evaluation. The participating residents have been surveyed regarding their opinions of their educational experience. RESULTS AND CONCLUSION: The standardized curriculum has been well received by the participating residents. Conclusions about the educational efficacy of such a curriculum cannot be made until more residents have used it.

Effects of delayed processing on mammographic phantom object detection.

OBJECTIVES: Delayed processing of films is a common occurrence in mobile mammography screening programs. The effects of such delayed processing on radiologists' detection of phantom test objects are investigated. METHODS: Twelve screen-film combinations were exposed using a phantom and developed after delays of 0, 1, 2, 3, 5, and 7 days. Films were scored by three board-certified radiologists specializing in mammography, based on visibility of calcifications, masses, fibrils, and line pairs. RESULTS: Variance analyses of mean scores indicate that, across screen-film combinations, there are no statistically significant decreases in object detection associated with delayed processing. The analyses do indicate, however, a statistically significant difference in scores unrelated to delay, attributable to the screen-film combination used. CONCLUSIONS: Delayed processing of mammography film does not lead to a decrease in the visibility of phantom test objects, despite large decreases in overall image optical density.

Effect of display luminance on the feature detection rates of masses in mammograms.

Our purpose in this study was to determine the importance of the luminance range of the display system for the detection of simulated masses in mammograms. Simulated masses were embedded in selected portions (512 x 512 pixels) of mammograms digitized at 50 micro pixels, 12 bits deep. The masses were embedded in one of four quadrants in the image. An observer experiment was conducted in which the observer's task was to determine in which quadrant the mass is located. The key variables involved in each trial included the position of the mass, the contrast level of the mass, and the luminance of the display. The contrast of the mass with respect to the background was fixed to one of four selected contrast levels. The digital images were printed to film, and displayed on a mammography lightbox. The display luminance was controlled by placing neutral density films between the laser printed films of mammographic backgrounds and the lightbox. The resulting maximum luminances examined in this study ranged from 34 cd/m2 to 2056 cd/m2. Twenty observers viewed 80 different images (20 observations at each of 4 different mass contrast levels) under each of the 5 luminance conditions for a total of 800 independent observations per observer. An analysis of variance yielded no statistically significant correlation between the luminance range of the display and the feature detection rate of the simulated masses in mammograms. However, the performance of the lower luminance display systems (less than 300 cd/m2), may be reduced due to the high levels of ambient light found in many reading environments.

The politics of mammography.

Mammography has had a major impact on the earlier detection, treatment options, and management decisions and survival and mortality rates of breast cancer. Consequences include overwhelming demand for mammography; problems with optimum response by radiology; limited availability of the examination, especially to the socioeconomically disadvantaged; self-referral for mammography by unqualified physicians for less than altruistic reasons; and unrealistic expectations of mammography by women, physicians, and lawyers. Responses to the overwhelming demand for high-quality mammography include ACR postgraduate and continuing education courses and its mammography accreditation program; a more comprehensive examination on mammography for certification by the ABR; and increasing state and federal government interest and legislation for reimbursement, quality assurance, and delivery of mammography. The precedents this sets for radiology if not all of medicine suggests that collaboration of the private and public sectors offers the greatest promise of an appropriate response, namely reproducible optimum mammography accurately interpreted with the lowest possible radiation dose for all eligible women in the United States.

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.

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.

Educational outreach to mammography facility staff to assist with compliance with the Mammography Quality Standards Act in rural North Carolina.

RATIONALE AND OBJECTIVES: The purpose of this project was to develop and evaluate an educational program targeted at mammography facilities in rural areas of North Carolina that were having difficulty complying with the 1992 Mammography Quality Standards Act (MQSA). MATERIALS AND METHODS: Fourteen facilities deemed at risk for closure under MQSA were identified by state inspection personnel. Problems at the facilities were evaluated by a radiologist, a physicist-educator, and a radiation physicist through a written survey, review of phantom and clinical images, and a site visit. Individual advice and instruction were provided on-site by the physicist-educator, with written materials provided in follow-up. A repeat site visit was made 4-6 months after the initial visit. RESULTS: Of 51 problems identified at the 12 institutions that completed the program, 35 (69%) were corrected. All facilities that had failing phantom scores at the inspection prior to the intervention had passing scores at the inspection after the intervention. There was a statistically significant increase in the sum of the phantom scores for the facilities offered this intervention compared with those not offered it (P = .03). CONCLUSION: This educational program improved mammography quality at participating facilities.

Patient compliance in mobile screening mammography.

RATIONALE AND OBJECTIVES: We assessed the follow-up behavior of women who had abnormal results of screening mammograms taken on a mobile van. METHODS: A retrospective cohort study was conducted between 1988 and 1991 of all women served by a mobile mammography van in rural North Carolina. Compliance with radiologist recommendations for follow-up was assessed through review of patient records and mail surveys of patients with incomplete records. RESULTS: Compliance was 44% for negative or benign mammograms, 57% for indeterminate mammograms, and 62% for probably malignant or malignant mammograms. Women who had a previous mammogram or had a malignant finding were more likely to comply with follow-up recommendations (p < .0001) than women with normal or benign results and no history of mammography. Compliers and noncompliers did not differ with respect to family history of breast cancer or personal history of breast discomfort. CONCLUSION: Compliance with recommendations in this setting was lower than expected. This may be because rural women using mobile van mammography have limited access to the resources needed for appropriate follow-up. Further research is needed to examine explanations for poor compliance in this setting.

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.

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.

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.

Effects of processing conditions on mammographic image quality.

RATIONALE AND OBJECTIVES: Any given mammographic film will exhibit changes in sensitometric response and image resolution as processing variables are altered. Developer type, immersion time, and temperature have been shown to affect the contrast of the mammographic image and thus lesion visibility. The authors evaluated the effect of altering processing variables, including film type, developer type, and immersion time, on the visibility of masses, fibrils, and speaks in a standard mammographic phantom. MATERIALS AND METHODS: Images of a phantom obtained with two screen types (Kodak Min-R and Fuji) and five film types (Kodak Min-R M, Min-R E, Min-R H; Fuji UM-MA HC, and DuPont Microvision-C) were processed with five different developer chemicals (Autex SE, DuPont HSD, Kodak RP, Picker 3-7-90, and White Mountain) at four different immersion times (24, 30, 36, and 46 seconds). Processor chemical activity was monitored with sensitometric strips, and developer temperatures were continuously measured. The film images were reviewed by two board-certified radiologists and two physicists with expertise in mammography quality control and were scored based on the visibility of calcifications, masses, and fibrils. RESULTS: Although the differences in the absolute scores were not large, the Kodak Min-R M and Fuji films exhibited the highest scores, and images developed in White Mountain and Autex chemicals exhibited the highest scores. CONCLUSION: For any film, several processing chemicals may be used to produce images of similar quality. Extended processing may no longer be necessary.

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.

An update on mammography.

For at least 7°% of breast cancers there are no known causal factors other than gender and aging. Other possible risk factors include hormonal, genetic, nutritional, morphologic, environmental (chemical, pesticides, food additives), irradiation, and viruses. Japanese women have much less breast cancer than women in the U.S.A., and after age 45, their incidence levels off or falls, whereas ours continues to rise. Furthermore, within a generation or two of moving to the U.S.A., Japanese women have a similar incidence to ours! What are we doing that increases our risk for this disease? It would certainly suggest that the other risk factors are involved and much research continues to explore this. Screening with mammography and breast physical examination is the cornerstone of earlier detection, improved survival and reduced mortality from breast cancer. A variety of studies and improvement in stage trends support this. Despite this, overall mortality from breast cancer remains unchanged. However, increasing incidence with stable mortality would suggest there is some reduction in overall mortality. Some other reasons for no reduction in overall mortality include: I. The variable biological forms and natural history of the disease. Assuming an average 100 days doubling time, cancer has been present in a woman's breast if not elsewhere for 6-7 years or longer before it is potentially detectable by mammography or breast physical examination. The extent of disease, cell type and grade, and host resistance are all important survival factors. Not enough breast cancers are at an early stage when diagnosed and treated. Not enough eligible women are being routinely screened with optimum mammography and breast physical examination. There is too much reliance on breast self-examination and breast physical examination alone for detection.