Comparison of contrast detail curves of full field digital with screen film breast phantom images.

In this investigation, we imaged a standard breast phantom and compared the contrast detail curves from a prototype full breast digital mammography system with the corresponding curves for a conventional, analog screen-film system. The full breast digital system exhibited superior contrast detail detectability. The results from this study will be used to plan future clinical evaluations comparing full breast digital and screen film mammography.

Evaluation of medical students in radiology. Written testing using uncued multiple-choice questions.

RATIONALE AND OBJECTIVES: Evaluation of uncued multiple-choice questions (UMCQ) was compared with traditional multiple-choice questions (MCQ) for assessing medical student performance during radiology electives. Methods for analyzing and improving the quality of UMCQ examinations are described. METHODS: The authors compared the performance of radiology medical students on similarly constructed MCQ and UMCQ tests. For the UMCQ examination, the reliability (coefficient alpha), standard error of measurement, item difficulty index, and corrected item-to-total test coefficient (point biserial correlation) were analyzed. RESULTS: Students' level of performance was lower on UMCQs (mean percent correct score = 68.9 +/- 10.2 standard deviation [SD]) than on MCQs (mean percent correct score = 75.6 +/- 12.4 SD). Coefficient alpha for the UMCQ format was .7690 (standard error of measurement mean = 4.89%). Analysis of the item difficulty index and point biserial correlation for each test item provided information for improving the quality of the UMCQ examination. CONCLUSIONS: Because the UMCQ measures students' abilities to recall critical information without providing cues, this format can be used to overcome some of the limitations of conventional MCQs. With simple computerization, analysis of UMCQ testing instruments provides important feedback to both the examinees and the examiner.

Correlation between breast parenchymal patterns and mammographers' certainty of diagnosis.

The density of breast tissue on a mammogram may affect radiologists' diagnostic decisions. To evaluate possible correlations among breast parenchymal pattern and diagnostic confidence, six radiologists classified 655 mammograms as N1, P1, P2, and DY, according to Wolfe's criteria. Evaluation of radiologists' confidence interpreting the mammograms (1 = absolutely certain, 2 = fairly certain, 3 = uncertain), shows a significant correlation between decreasing diagnostic certainty and increasing complexity of the mammographic breast parenchymal pattern. That readers are less confident in their interpretation of P2 and DY breast parenchymal patterns has implications for the operation of breast cancer screening programs.

Biodistribution and clearance of liposomal gadolinium-DTPA.

Gadolinium-DTPA (Gd-DTPA) liposomes have been studied previously as liver contrast agents and have been shown to improve the detection of hepatic metastases in rats. We synthesized 100-nm and 50-nm liposomes that encapsulated Gd-DTPA and did biodistribution and clearance studies in rats. Parallel magnetic resonance imaging (MRI) studies were also done. Biodistribution showed a prolonged blood pool phase for Gd-DTPA liposomes with a blood pool half-life of approximately 4 hours for the 100-nm liposomes. The highest uptake per gram of tissue was achieved by the spleen. Clearance of gadolinium from the liver and spleen showed a half-life of 3 to 4 days. The smaller 50-nm Gd-DTPA liposomes resulted in a longer blood pool phase and a higher delivery of gadolinium to the liver, bone marrow, and spleen. Imaging studies after intravenous (IV) administration of liposomal Gd-DTPA showed organ enhancement that paralleled the data on biodistribution studies, with appreciable hepatic enhancement at doses as low as 0.025 mm/kg of liposomal Gd-DTPA.

Diagnostic performance of teleradiology in cervical spine fracture detection.

This study was done to assess the diagnostic accuracy of high-resolution (5 lp/mm) teleradiology for detecting cervical spine fractures. Single radiographs from 25 patients with and 25 patients without cervical spine fractures were transmitted between two units of our teleradiology system (Dupont DTR 2000) located 5 miles apart. Each image was examined by four readers. Fracture detection accuracy was assessed by generating receiver operating characteristic (ROC) curves and comparing the areas under each reader's curves for original and transmitted images. Two readers had statistically significant better fracture detection using nontransmitted images, whereas two had no significant differences in accuracy. The authors conclude that high resolution in and of itself is not adequate for fracture detection, and that issues concerning image contrast manipulation also will have to be addressed before teleradiology systems can be used for clinical cervical spine fracture screening.

Microvascular changes in rabbit kidneys after extracorporeal shock wave treatment.

Concerns about the safety of extracorporeal shock wave lithotripsy include the risk of vascular damage and the genesis of hypertension. We evaluated gross specimens and barium microangiograms of the right kidneys of 14 rabbits exposed to shock waves; the untreated left kidneys served as controls. Six rabbits were assessed immediately after shock wave treatment, whereas the other eight rabbits had the same procedure 3 months later. All six acute phase animals showed microangiographic changes indicative of shock wave trauma, including cortical, subcapsular, and medullary extravasation of barium and patchy loss of efferent vessels. No significant vascular abnormalities were seen in the control kidneys. All kidneys treated from the animals that had delayed microangiography showed macroscopic evidence of fibrotic capsular thickening and parenchymal scarring. Microscopically, there was crowding of glomeruli and areas of avascularity. In this model, shock waves damaged the cortical circulation and resulted in persistent alterations of the microvasculature that potentially could be responsible for the abnormal secretion of renin.

Factors influencing radiologists to choose research careers.

The future of radiology is threatened by the paucity of competent researchers who are radiologists. To determine what influences are most important in selecting and training potential radiology researchers, we conducted a survey of 5000 practicing radiologists, including all members of the Association of University Radiologists. We also surveyed 3000 randomly selected radiology trainees. A research career was empirically defined as 20% or more of a radiologist's time being involved with research. Response to the practicing radiologists and radiology trainees surveys was 28% and 19%, respectively. Radiologists who attended medical school or trained in radiology at an institution among the top 20 for research funding more frequently chose careers in research than those who matriculated and trained elsewhere. Publishing at least one research article, having a dedicated radiology research fellowship, having access to grant funds, and using computers during medical school or radiology training were factors typifying radiologists who chose research careers. Research radiologists were more concerned about the value of performing research and less concerned about personal income than those choosing careers not focusing on research. These results suggest that it might be possible to select radiology trainees who are more likely to become researchers based on their backgrounds and attitudes. An appropriate milieu during training enhances the likelihood of radiologists choosing research careers.

Factors influencing the success of academic radiologists in publishing research.

To guide changes that might improve radiologists' research productivity, we surveyed 1400 members of the Association of University Radiologists. We evaluated the impact of influences related to background, education, training, attitudes, and practice environment on 558 respondents' frequency of research publication. Attending medical school, obtaining radiology training, and practicing at an institution among the 20 with the highest amount of research funding was associated with the highest research productivity in academic practice. Taking a radiology research fellowship, regularly attending research seminars, and association with a research mentor during training were also associated with higher career productivity. Virtually all aspects of the academic practice milieu, and particularly having time set aside for research, were significant influences on radiologists' frequency of publication. Men published research more frequently than women. This phenomenon appears related to women being afforded fewer research experiences during radiology training and a greater concern on the part of women about obstacles that hinder their doing research. These data might be employed to guide changes that would improve the selection and nurturing of individuals likely to be productive in research.

Research and research training in academic radiology departments. A survey of department chairmen.

We surveyed 121 chairmen of academic radiology departments to assess how these departments select and educate their residents and fellows in research. Eighty-six chairmen responded (71%). The majority of their programs select at least some of their trainees for their potential as researchers and nearly all encourage trainees to perform research. The more the selection process focuses on research, the greater the percentage of residents and fellows that participate in research during training. Nonetheless, only about one-third of residents and half of the fellows perform and publish research. Only half the programs offer formal research seminars and few trainees opt for additional research training. These results may relate to the relatively small percentage of faculty performing prospective clinical and laboratory research. These findings are disappointing in the light of previous results suggesting that performing research, publication, and formal research education during training correlate highly with the development of successful research careers. Chairmen could increase the likelihood of trainees choosing research careers and being successful in publishing research by providing early exposure to research experiences and providing formalized research training.

Sonographic image degradation after barium enema.

RATIONALE AND OBJECTIVES: The authors previously showed that barium does not interfere with abdominal sonography performed after a biphasic upper gastrointestinal tract examination. This study was designed to assess the impact of a barium enema (BE) examination on the quality of abdominal sonography performed immediately after the barium enema. METHODS: Forty patients scheduled for routine barium enemas (22 air contrast and 18 solid column) were prospectively examined with abdominal sonography before and after their BEs. The resulting 80 sonograms were randomized; three radiologists blindly assessed the quality of images of each of six anatomic areas (aorta, pancreas, porta hepatis, gallbladder, and the right and left lobes of the liver). RESULTS: There was no statistically significant degradation of the images for the right and left lobes of the liver and the pancreas. However, the images for the gallbladder, porta hepatis, and aorta had a statistically significant (P < .05) degradation of their ultrasound quality following barium enema. CONCLUSIONS: Unlike upper gastrointestinal tract examination, BE examination does interfere with the quality of a subsequent abdominal ultrasonography. Thus, when both studies are required, sonography should be performed first.

AUR memorial award--1987. The impact of focused instruction on learning mammography.

Recent promotion of breast cancer screening has increased the demand for mammography services and well-trained mammographers. To determine whether focused instruction, which may occur in continuing medical education courses, is effective in imparting mammography skills and knowledge, an instructional program was developed and evaluated. Seventeen physicians were tested before and after six 1-hour instructional sessions about breast disease and cancer screening, mammogram interpretation, and determining appropriate patient disposition. Twelve weeks after instruction, subjects demonstrated significant improvement in factual knowledge, in decision-making ability regarding patient disposition, and in recognition of benign disease on mammograms. There also was significant improvement in specificity, but no improvement in cancer detection. Further, no correlation between participants' subjective self-assessment of improvement and their actual performance on the postinstruction evaluation was found. Evaluation of instructional programs is necessary to determine their effectiveness, and promotes improvement in instructional offerings.

Detection of breast abnormalities on teleradiology transmitted mammograms.

The authors conducted an observer performance study to compare breast lesion detection of conventional mammography (CM) with teleradiology (TE) transmitted mammograms. One hundred four abnormal, single-projection mammographic images were transmitted by teleradiology. Abnormalities included 11 cases with skin thickening or retraction, 48 cases with microcalcifications, and 52 with parenchymal masses. The CM and TE images were reviewed by four mammographers who indicated the type and location of abnormalities and a level of confidence for their diagnostic decisions. For each of three detection tasks--skin and nipple abnormalities, microcalcifications, and masses--receiver operating characteristic curve analysis was performed for individual readers and all readers as a group. For detecting skin and nipple abnormalities, readers performed significantly better with CM than with TE (z = 2.05, P = less than 0.04). However, no significant differences were found among readers for detection of either microcalcifications or masses. Further improvements in hardware and imaging parameters may improve detection of soft tissue abnormalities. Further evaluation is necessary to determine whether teleradiology might be applicable to breast cancer screening.

Occurrence of fibroadenomas in postmenopausal women referred for breast biopsy.

OBJECTIVE: To examine the occurrence of breast fibroadenomas in postmenopausal patients referred for breast biopsy. DESIGN: A retrospective review of breast biopsy outcome and of patient demographics, including menstrual and hormonal status. SETTING: The Tucson Breast Center, a large outpatient breast cancer detection clinic affiliated with the University of Arizona Health Sciences Center in Tucson, Arizona. PARTICIPANTS: All women seen at the Tucson Breast Center between 1985 and 1990 who were referred for breast biopsy. RESULTS: A total of 100 fibroadenomas were found in 709 breast biopsies whose results were known. Fifty-two of these were in premenopausal women and 44 in postmenopausal women; the menopausal status of four women was unknown. In postmenopausal women, 11 of the 44 patients reported hormone use. Fibroadenomas constituted 20% (39 of 195) of the benign masses and 12% (39 of 339) of all breast masses in postmenopausal women. Fibroadenomas constituted 10% (44 of 447) of all biopsies in postmenopausal women, including those with breast masses, abnormal calcifications, or other lesions. CONCLUSION: Noncalcified fibroadenomas of the breast are not confined to young women and may constitute a small but noteworthy proportion of lesions coming to breast biopsy in postmenopausal women.

Optical processing architecture and its potential application for digital and analog radiography.

In this report we introduce the fundamental architectures and the potential applications of optical processing techniques in medical imaging. Three basic optical processing architectures were investigated for digital and analog radiography. The processors consist of a module that converts either the analog or the digital radiograph into a coherent light distribution; a coherent optical processing architecture that performs various mathematical operations; a programmable digital-optical interface and other accessories. Optical frequency filters were implemented for mammographic and other clinical feature enhancement. In medical image processing, digital computers offer the advantages of programmability and flexibility. In contrast, optical processors perform parallel image processing with high speed. Optical processors also offer analog nature, compact size, and cost effectiveness. With technical advances of digital-optical interface devices, the medical image processor, in the foreseeable future, may be a hybrid device, namely, a programmable optical architecture.

A localization algorithm and error analysis for stereo x-ray image guidance.

Stereo x-ray radiography attracts increasing attention in major clinical applications. The purpose of this paper is to analyze the 3D localization error for breast biopsy procedures and provide guidelines for improving its accuracy. Our prototype is a CCD based digital stereo x-ray imaging system. The mathematical model consists of two x-ray sources and one stationary detector plane. A closed form least-squares solution is derived for 3D localization of feature points, particularly a biopsy needle tip, from a pair of 2D digital radiographs. Based on the least-squares formula and its first order approximation, the 3D localization error is analyzed in terms of object location, measurement error, separation between the two x-ray sources, and distance from the source to the detector. The stereo imaging and error estimation formulas are numerically simulated and experimentally validated. The data are in agreement with theoretical prediction. These results can be used for the purpose of system design and protocol optimization.

Lens distortion in optically coupled digital x-ray imaging.

UNLABELLED: The objectives of this research are to analyze geometrical distortions introduced by relay lenses in optically coupled digital x-ray imaging systems and to introduce an algorithm to correct such distortions. METHODS: The radial and tangential errors introduced by a relay lens in digital x-ray imaging were experimentally measured, using a lens-coupled CCD (charge coupled device) prototype. An algorithm was introduced to correct these distortions. Based on an x-ray image of a standard calibration grid, the algorithm first identified the location of the optical axis, then corrected the radial and tangential distortions using polynomial transformation technique. RESULTS: Lens distortions were classified and both radial and tangential distortions introduced by lenses were corrected using polynomial transformation. For the specific lens-CCD prototype investigated, the mean positional error caused by the relay lens was reduced by the correction algorithm from about eight pixels (0.69 mm) to less than 1.8 pixels (0.15 mm). Our investigation also shows that the fourth order of polynomial for the correction algorithm provided the best correction result. CONCLUSIONS: Lens distortions should be considered in position-dependent, quantitative x-ray imaging and such distortions can be minimized in CCD x-ray imaging by appropriate algorithm, as demonstrated in this paper.

Stereotactic fine-needle aspiration cytology of nonpalpable breast lesions: an analysis of 258 consecutive aspirates.

BACKGROUND: The role of stereotactic fine-needle aspiration cytology (SFNAC) in the diagnosis of nonpalpable breast lesions is poorly defined. PATIENTS AND METHODS: Data were prospectively collected from 225 consecutive patients with nonpalpable breast lesions who had aspiration cytology followed by immediate surgical excision. RESULTS: Between 1988 and 1993, 258 such procedures were performed. The results of 84 (33%) were interpreted as benign, 84 (33%) as atypical, 28 (11%) as suspicious for malignancy, and 49 (19%) as malignant. In all, 88 (34%) surgical specimens were malignant. SFNAC had an 80% sensitivity, a 96% specificity, a 91% positive predictive value, and an 89% negative predictive value. There were 18 false-negative and 7 false-positive aspirates. CONCLUSIONS: SFNAC for diagnosing nonpalpable breast lesions is moderately sensitive and highly specific, and has a high positive and negative predictive value. In conjunction with mammography and clinical assessment, the procedure is useful for determining which patients with nonpalpable breast lesions may require surgical biopsy.

Percutaneous breast biopsy for nonpalpable lesions.

Increasingly, biopsies for suspected breast abnormalities are conducted by percutaneous needle extraction of core samples rather than by standard surgical excision or fine-needle aspiration (FNA) of cellular material. Core-needle biopsies are highly accurate and have many advantages over surgical excisions, including reduction of the morbidity and cost of breast disease diagnosis. Limitations include differentiating atypical ductal hyperplasia from ductal carcinoma in situ. Equipment and technique for stereotactic and ultrasound-guided core breast biopsy are discussed. Appropriate indications for core-needle biopsy, excisional biopsy after needle localization, and FNA are provided. Appropriate management after core-needle biopsy includes the establishment of concordance of histologic results with the level of suspicion of the mammographic findings to prevent false-negative core biopsies. A recommendation for return to regular mammographic screening, short-interval (6-month) mammographic follow-up, or repeat core or surgical appearance depends on this correlation.

The role of stereotactic biopsy in abnormal mammograms.

Core needle biopsy using either stereotactic or ultrasonographic guidance is a reasonable and accurate alternative to surgical biopsy for diagnosis of most nonpalpable breast lesions. An important component of a stereotactic core breast biopsy procedure is the mammographic and pathologic correlation of findings to plan optimal patient management. The level of suspicion of a mammographic lesion, the accuracy of stereotactic targeting, and the confirmation of microcalcifications in specimen radiographs for calcified lesions must be considered carefully and correlated with the histopathologic findings. Meticulous operator technique is essential to provide representative samples of the mammographic abnormality. Properly performed, imaging-guided percutaneous core breast biopsy has reduced the morbidity of surgical breast biopsy and the overall cost of breast cancer diagnosis. Recent work has demonstrated that stereotactic core breast biopsy can reduce the cost of diagnosing mammographically detected breast lesions by more than 50%. At a time when health-care policy and reimbursement decisions are influenced by cost considerations, increased use of stereotactic core breast biopsy is anticipated. Meticulous attention to technique allows maximal realization of the benefits of this procedure.

Signal-to-noise ratio and detective quantum efficiency analysis of optically coupled CCD mammography imaging systems.

RATIONALE AND OBJECTIVES: Design considerations for x-ray systems with optically coupled charge-coupled devices require an understanding of the characteristics of cascaded multistage imaging chains. Performance evaluations rely on accurate analyses of signal-to-noise ratio, noise power spectrum, and detective quantum efficiency. METHODS: Theoretic models of signal-to-noise ratio, noise power spectrum, and detective quantum efficiency were extended to analyze the optically coupled charge-coupled device and other electronic x-ray imaging systems. The descriptions of how to measure or compute these parameters are provided. RESULTS: The results of our quantitative analysis illustrate that x-ray quantum-noise limitation can be obtained without an image intensifier by using a low additive noise charge-coupled device. CONCLUSION: This theoretic model and experimental method provide a useful tool for developing optoelectronic x-ray imaging systems for digital mammography and other radiologic procedures.