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M J Yaffe

Publications and source records attributed to M J Yaffe.

At least 55 records · Page 3Linked to original sources
PubMed1995

Recommended specifications for new mammography equipment: report of the ACR-CDC Focus Group on mammography equipment.

The American College of Radiology has published a report that describes desirable features for new mammography x-ray units that will contribute to high-quality imaging. It encompasses all aspects of x-ray equipment performance including mechanical considerations, the x-ray tube focal spot and spectrum, generator performance, collimation, scatter rejection, and the automatic exposure control. The report is intended to provide guidance to equipment manufacturers and to purchasers of mammography systems with regard to basic performance levels that should be expected.

Female↗
PubMed1995

Digital mammography, computer-aided diagnosis, and telemammography.

Film-screen x-ray mammography is an effective tool for the detection and diagnosis of breast cancer. Several limitations of current mammographic technology have been identified, and there is now good evidence that improved image quality and possibly reduced radiation dose could be achieved if mammograms are acquired directly in digital form. In this article, the rationale for digital mammography is presented and various approaches to the design of a digital mammography system are described. Current challenges in developing a practical, clinically acceptable digital mammography system are discussed and applications of digital mammography to computer-aided diagnosis, telemammography, and quantitative imaging are suggested.

Artifacts↗
PubMed1994

The quantitative analysis of mammographic densities.

Quantitative classification of mammographic parenchyma based on radiological assessment has been shown to provide one of the strongest estimates of the risk of developing breast cancer. Existing classification schemes, however, are limited by coarse category scales. In addition, subjectivity can lead to sizeable interobserver and intraobserver variations. Here, we propose an interactive thresholding technique applied to digitized film-screen mammograms, which assesses the proportion of the mammographic image representing radiographically dense tissue. Observers viewed images on a CRT display and selected grey-level thresholds from which the breast and regions of dense tissue in the breast were identified. The proportion of radiographic density was then calculated from the image histogram. The technique was evaluated for the mammograms of 30 women and is well correlated (R > 0.91, Spearman coefficient) with a six-category subjective classification of radiographic density by radiologists. The technique was found to be very reliable with an intraclass correlation coefficient between observers typically R > 0.9. This technique may have a role in routine mammographic analysis for the purpose of assessing risk categories and as a tool in studies of the etiology of breast cancer, in particular for monitoring changes in breast parenchyma during potential preventive interventions.

Absorptiometry, Photon↗
PubMed1994

Physician characteristics and the recognition of depression and anxiety in primary care.

We examined physician characteristics associated with the recognition of depression and anxiety in primary care. Fifty-five physicians treating a total of 600 patients completed measures of psychosocial orientation, psychological mindedness, self-rating of sensitivity to hidden emotions, and a video test of sensitivity to nonverbal communication. Patients were classified as cases of psychiatric distress based on the CES-D scale and the Diagnostic Interview Schedule. Physician recognition was determined by notation of any psychosocial diagnosis in the medical charts over the ensuing 12 months. Of 192 patients scoring 16 or above on the CES-D, 44% (83) were recognized as psychiatrically distressed. Three findings were central to this study: 1) Physicians who are more sensitive to nonverbal expressions of emotion made more psychiatric or psychosocial assessment of their patients and appeared to be over-inclusive in their judgments of psychosocial problems; 2) Physicians who tended to blame depressed patients for causing, exaggerating, or prolonging their depression made fewer psychosocial assessments and were less accurate in detecting psychiatric distress; 3) False positive labeling of patients who had no evidence of psychiatric distress was rare. Surprisingly, more severe medical illness increased the likelihood of labeling and accurate recognition. Physician factors that increased recognition may indicate a greater willingness to formulate a psychiatric diagnosis and an ability notice nonverbal signs of distress.

Adult↗
PubMed1994

Optimization of spectral shape in digital mammography: dependence on anode material, breast thickness, and lesion type.

It has been proposed that breast cancer detection can be improved through the use of digital mammography. It is hypothesized that the choice of proper shape of the x-ray spectrum incident upon the breast can yield an improved image signal-to-noise ratio (SNR) for a given dose. To test this hypothesis, an energy transport model incorporating measured breast tissue attenuation coefficients and published exposure-to-dose conversion values was developed to describe the image acquisition process. The choice of applied kilovoltage and filter for Mo and W target x-ray sources has been optimized with respect to SNR and absorbed dose for detectors based on a Gd2O2S scintillating screen under the conditions of perfect coupling of light between the screen and a solid state photodetector. For the W spectra, the optimum filter-kVp combinations could provide 41%, 13%, and 42% improvements in SNR for 2-cm, 6-cm and 8-cm breasts, respectively, over the conventional Mo filtration, for a practical imaging time of 1.0 s. W and Mo spectra produce similar SNR values for a given filter thickness except for the 4-cm breast. Given the limitations of current technology, however, the W spectra produce the optimum SNRs in a shorter imaging time for breast thicknesses greater than and less than 4 cm. The maximum SNR for imaging both infiltrating ductal carcinoma and calcifications is provided by the same filter-kVp combination, allowing optimization based on breast thickness and composition only. The model can now be used to compare and improve upon novel detector designs.

Breast↗
PubMed1994

Binary vascular reconstruction from a limited number of cone beam projections.

This paper describes a method to perform reconstruction of vascular cross-sectional images from a limited number of x-ray angiographic cone-beam projections. It is assumed that the projection data can be simplified by identifying blood vessels in each angiogram and removing signals due to other structures. Under these conditions, the x-ray attenuation coefficient, mu, can be modeled as a binary variable having a value mu 0 within the vessel and "0" outside. The reconstruction is performed by minimizing a cost function using the method of simulated annealing. In this paper, we demonstrate that the introduction of a priori information allows one to reconstruct a sphere and a simulated branched vessel from three views with, respectively, 97% and 93% of voxels having correct values. The addition of a continuity constraint for the reconstruction of the branched vessel resulted in further reduction in the percentage of misplaced voxels. Calculations require from one to six hours of CPU time on a Sun SparcStation 2 computer for the cases investigated here. The effect of noise, "cooling" schedule, and number of views on the reconstruction are examined using simulated vessel projections. Modifications to our approach to accelerate the reconstruction are also discussed.

Angiography↗
PubMed1994

Performance of glass fiber antiscatter devices at mammographic energies.

Using fiber optic manufacturing techniques, it is possible to produce a radiographic grid that discriminates against scattered radiation in two dimensions. Such grids consist of septa composed of glass with a high lead content; the interspace material is air, so that approximately 80% of the grid area is open. In this way, effective high ratio grids can be produced with relatively low Bucky factors. The performance of samples of such grid material is characterized in terms of both scatter rejection and dose efficiency for application in digital mammography in both slot-beam and area-beam geometry. For area beams, five- to tenfold improved scatter rejection relative to conventional grids was observed. In slot configurations, such grids could provide improved SNR/dose performance and more effective utilization of the heat loading capability of the x-ray source.

Fiber Optic Technology↗
PubMed1994

Analysis of the spatial-frequency-dependent DQE of optically coupled digital mammography detectors.

The effect of optical coupling efficiency on the spatial-frequency-dependent propagation of signal and noise is considered for x-ray image detectors for digital mammography in which a phosphor screen is optically coupled to a charge-coupled device (CCD) image array. For experimental purposes, optical coupling between a Gd2O2S:Tb phosphor screen and a CCD image array was provided by relay lenses. Neutral density filters were inserted between the lenses to vary the optical coupling efficiency without altering the inherent spatial resolution. The total coupling efficiency, defined as the number of electrons (e-) recorded in the CCD per x-ray interaction in the phosphor, was calculated in each case. The modulation transfer function, and the contributions to the total noise power spectrum (NPS) of x-ray quantum noise, secondary quantum noise, and inherent detector noise were measured as a function of coupling efficiency. These data were used to calculate the spatial-frequency-dependent detective quantum efficiency [DQE(f)]. The NPS due to x-ray quantum noise had a significant spatial-frequency dependence for coupling efficiencies of more than 9 e- per x-ray interaction, but little spatial-frequency dependence for coupling efficiencies of less than 2 e- per x-ray interaction. These results indicate that to preserve high spatial-frequency values of DQE(f), and to ensure that images are x-ray quantum-noise limited at high spatial frequencies, a coupling efficiency on the order of 10 e- per x-ray interaction is required.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrons↗
PubMed1994

A model for optimization of spectral shape in digital mammography.

X-ray mammography is the most sensitive imaging modality available for the detection of breast cancer. The highest performance can only be achieved, however, if the complete imaging system is optimized. The development of digital mammography offers an opportunity to obtain improved sensitivity in mammography. In such systems, the decoupling of the recording and display processes allows each component of the imaging system to be optimized separately. In this paper we describe a method for optimizing the recording process for digital mammographic techniques. Our method uses an energy transport model of the propagation of signal and noise through the imaging system. The computations make use of experimentally determined data wherever possible so that the number of assumptions in the model can be minimized. The model predicts the signal-to-noise ratio for a constant dose to the breast, and therefore allows comparison and optimization both for different x-ray spectra and for different imaging tasks. The major energy-dependent components of the model have been verified, and good agreement is demonstrated between predictions by the model of both contrast and SNR and experimentally measured values. Calculations for a particular imaging task, detection of a 200-microns cubic calcification in a 6-cm, 50% adipose-50% glandular breast, illustrate application of the model for optimization of spectral shape.

Breast Neoplasms↗
PubMed1994

Determination of thresholds for detection of cerebellar blood flow deficits in brain SPECT images.

UNLABELLED: Two observer studies were performed to determine the threshold (i.e., ratio of the counts in a lesion area to the counts in the corresponding contralateral region) at which two experienced observers diagnosed blood flow deficits in the cerebellum in 99mTc-HMPAO SPECT scans to be clinically significant, and investigate the effect of the intensity mapping scale on the detectability of lesions. METHODS: Lesions representing blood flow deficits varying from no decrease to a 12.5% decrease were simulated in 300 patient images. The first study, a receiver-operator characteristics (ROC) experiment, used two observers to compare the detectability of lesions with three intensity mapping scales: two pseudocolor scales, and a linear gray scale. A second "threshold-criterion" study was done to estimate the threshold at which observers determine deficits to be clinically significant. RESULTS: In the ROC study, the observers were more accurate in detecting lesions displayed in pseudocolor than in gray scale. In the threshold-criterion study, the threshold at which observers assessed clinically significant deficits was found to range between 0.900 and 0.950 (corresponding to a 5%-10% decrease in counts), depending on the observer, and the intensity mapping scale. For both observers, the detection threshold was higher (i.e., closer to 1.0) with the pseudocolor scale than with the gray scale. CONCLUSION: The definition of a threshold value for use in quantitative techniques is dependent on both the observer and the intensity mapping scale. Observers were more accurate with the pseudocolor scales.

Cerebellum↗
PubMed1994

Are physicians meeting the needs of family caregivers of the frail elderly?

OBJECTIVE: To explore expressed needs, both formal and informal, of family caregivers of frail elderly. To evaluate roles of physicians. DESIGN: Questionnaire survey of members of the Montreal Jewish community providing care for frail elderly family members. SETTING: Jewish community of Montreal. PARTICIPANTS: Volunteer caregivers who were caring for a family member or friend 60 years or older, who had greatest responsibility for providing physical or emotional support to an elderly person, who saw themselves as caregivers, and who could speak English or French were studied. Of 118 volunteers, 32 were excluded because they withdrew for personal reasons or because they did not meet study criteria. MAIN OUTCOME MEASURES: Demographic variables, functional status of the care receiver, use of home care services, and needs assessment to identify additional services. RESULTS: An average of 75.4% respondents did not use formal support services. Just under half of caregivers were dissatisfied with the attention they received from the health care system, and more than one third expressed feelings of stress, depression, guilt, and isolation. CONCLUSIONS: Hypotheses for this discontent are presented. Physicians may be uninterested in helping caregivers; even if they were receptive to counseling caregivers, they could be poorly remunerated for the types of counseling sessions that are usual for caregivers; and being a professional caregiver to family caregivers is demanding in itself.

Activities of Daily Living↗
PubMed1994

Diagnosing and treating lateral epicondylitis.

Lateral epicondylitis is often encountered in primary care. Although its diagnosis can be fairly straightforward, its treatment is often difficult. This review examines the epidemiology, pathophysiology, and clinical presentation of tennis elbow. Management options are discussed.

Humans↗
PubMed1993

Somatization and the recognition of depression and anxiety in primary care.

OBJECTIVE: The authors examined the effect of patients' style of clinical presentation on primary care physicians' recognition of depression and anxiety. METHOD: The subjects were 685 patients attending family medicine clinics on self-initiated visits. They completed structured interviews assessing presenting complaints, self-report measures of symptoms and hypochondriacal worry, the Diagnostic Interview Schedule (DIS), and the Center for Epidemiologic Studies Depression Scale (CES-D). Physician recognition was determined by notation of any psychiatric condition in the medical chart over the ensuing 12 months. RESULTS: The authors identified three progressively more persistent forms of somatic presentations, labeled "initial," "facultative," and "true" somatization. Of 215 patients with CES-D scores of 16 or higher, 80% made somatized presentations; of 75 patients with DIS-diagnosed major depression or anxiety disorder, 76% made somatic presentations. Among patients with DIS major depression or anxiety disorder, somatization reduced physician recognition from 77%, for psychosocial presenters, to 22%, for true somatizers. The same pattern was found for patients with high CES-D scores. In logistic regression models education, seriousness of concurrent medical illness, hypochondriacal worry, and number of lifetime medically unexplained symptoms each increased the likelihood of recognition, while somatized presentations decreased the rate of recognition. CONCLUSIONS: While physician recognition of psychiatric distress in primary care varied widely with different criteria for recognition, the same pattern of reduction of recognition with increasing level of somatization was found for all criteria. In contrast, hypochondriacal worry and medically unexplained somatic symptoms increased the rate of recognition.

Adolescent↗
PubMed1993

Direct digital mammography using a scanned-slot CCD imaging system.

In this paper, the rationale for digital mammography is presented in terms of the limitations of conventional mammography. Various approaches to digital image acquisition are discussed and the design of a scanned-slot digital mammography system currently under development is described. Preliminary results including an image of an anthropomorphic breast phantom are presented.

Equipment Design↗
PubMed1993

Anthropomorphic radiological phantoms for mammography.

Anthropomorphic radiological phantoms are useful in evaluating image quality in mammography by providing realistic detection tasks to the observer. Methods for creating such phantoms, based on original patient mammograms, are described. Photochemical enhancement techniques and application of fractal interpolation methods for improving the fine detail information contained in such phantoms are discussed. Approaches to incorporating additional calibrated test targets within the phantom are also described.

Anthropometry↗