Community site development for family medicine residency programs.
Explore the source record for details and available documents.
Family Practice↗
Biomedical subjects
M J Yaffe
Publications and source records attributed to M J Yaffe.
Evaluation of mammographic image quality: pilot study comparing five methods.
A radiograph is considered of high quality when it allows a radiologist to identify abnormalities with high sensitivity and specificity. Although many methods for assessing image quality have been devised, it is not clear which is most meaningful or how well these methods correlate with one another. A pilot study was undertaken to compare five methods of evaluating mammographic image quality. Each of the methods was used to form separate rankings of 11 mammographic system configurations. In two of the methods, observers (three radiologists and three physicists) subjectively ranked the "image quality" of radiographs of phantoms obtained with each configuration. The third method ranked the systems according to contrast as measured densitometrically with an aluminum step wedge, and the fourth, in terms of lowest to highest mean glandular radiation doses to the breast. In the final method, observers based their rankings on mammograms of patients. The intra- and interobserver variabilities of each ranking method were assessed, as well as the correlations between methods, by using standard nonparametric statistical tests. Intraobserver consistency was high with any of the image quality ranking methods; however, image quality rankings based on either of the two phantoms provided better agreement among observers than did rankings based on images of patients. Surprisingly, no significant degree of correlation was found between any two image quality evaluation methods. Our work may have two implications for the American College of Radiology Mammography Accreditation Program: (1) small variations in phantom scores do not necessarily correlate with subjective variation in image quality in radiographs of patients, and (2) when small numbers of radiographs are used, the assessment of the quality of mammograms of patients may vary considerably among radiologists.
Accreditation↗
Composite materials for x-ray protection.
We have developed and tested a radiation protection material that provides similar attenuation for diagnostic x-ray spectra to that of conventional Pb apron materials with approximately 30% reduced weight. By combining a number of elements with different K absorption energies, such as Ba, W, and Pb, energy attenuation for given spectra can be optimized with respect to total cross-sectional mass loading. Alternatively, garments with much higher protective factors at equivalent weight to conventional garments could be produced. The reduction in the amount of Pb used also reduces problems associated with the toxicity of the material during manufacture and disposal. Back strain can be reduced for personnel performing special radiological procedures that require wearing protective garments for long periods of time.
Barium↗
Comment on 'Composite materials for x-ray protection'.
Explore the source record for details and available documents.
Humans↗
Characterisation of mammographic parenchymal pattern by fractal dimension.
A consistent, quantitative, observer-independent method of characterising mammographic parenchymal pattern is described. The method is based on the calculation of the 'fractal dimension' of digitised mammograms. The degree of correlation between the parenchymal pattern classifications by a fractal-based system and those of radiologists is assessed. For a set of 70 mammograms, average weighted proportion agreement among three radiologists in calling Wolfe grades was 85%, while agreement between the radiologists and our fractal classifier was 84%. The method developed may prove to be useful in establishing an index of risk for breast cancer and, ultimately, in determining intervals between examinations for individuals in a mammographic screening programme.
Breast Neoplasms↗
AAPM tutorial. Physics of mammography: image recording process.
The many physical factors that influence image processing and image quality in mammography are reviewed in this tutorial. The physics principles that are at work in the function of screen-film mammographic image receptors are discussed in detail. The author reviews methods of quality control for screen-film mammography and the principles for xeromammography and magnification mammography.
Female↗
Mortality from breast cancer after irradiation during fluoroscopic examinations in patients being treated for tuberculosis.
The increasing use of mammography to screen asymptomatic women makes it important to know the risk of breast cancer associated with exposure to low levels of ionizing radiation. We examined the mortality from breast cancer in a cohort of 31,710 women who had been treated for tuberculosis at Canadian sanatoriums between 1930 and 1952. A substantial proportion (26.4 percent) had received radiation doses to the breast of 10 cGy or more from repeated fluoroscopic examinations during therapeutic pneumothoraxes. Women exposed to greater than or equal to 10 cGy of radiation had a relative risk of death from breast cancer of 1.36, as compared with those exposed to less than 10 cGy (95 percent confidence interval, 1.11 to 1.67; P = 0.001). The data were most consistent with a linear dose-response relation. The risk was greatest among women who had been exposed to radiation when they were between 10 and 14 years of age; they had a relative risk of 4.5 per gray, and an additive risk of 6.1 per 10(4) person-years per gray. With increasing age at first exposure, there was substantially less excess risk, and the radiation effect appeared to peak approximately 25 to 34 years after the first exposure. Our additive model for lifetime risk predicts that exposure to 1 cGy at the age of 40 increases the number of deaths from breast cancer by 42 per million women. We conclude that the risk of breast cancer associated with radiation decreases sharply with increasing age at exposure and that even a small benefit to women of screening mammography would outweigh any possible risk of radiation-induced breast cancer.
Adolescent↗
The medi-drama as an instrument to teach doctor-patient relationships.
This paper reviews an experience of the Curriculum Development Group of the College of Family Physicians of Canada in describing the doctor-patient relationship and its value in the clinical process. It proposes the use of a medi-drama or multi-scene script encompassing a broad range of bio-psycho-social-ethical issues as a practical tool to teach the doctor-patient relationship. Principles for conducting a medi-drama are presented, as are the advantages of this experiential teaching modality. An example of a specific script developed along the theme of Adult Children of Ageing Parents is described, and an evaluation of its usefulness in teaching the doctor-patient relationship is presented from feedback from seven different family medicine residency or faculty development groups. Finally, examples of the breadth of topics that can be generated from a single medi-drama are presented.
Curriculum↗
Implications of caring for an aging parent.
The burden of care for the aged often falls on their adult children, who are themselves stressed by the developmental tasks of middle age. These people are frequently unprepared for the role of caregiver, in which they become parents to their own parents. The author describes the potentially turbulent effect of this role and discusses the origin of the stresses that the caregiver may experience. Doctors need to recognize and deal with the negative feelings, such as resentment, anger, frustration, ambivalence, guilt and demoralization, that may arise in adult children who care for their parents. These emotions must be put into proper context if the mental and physical health of the caregivers as well as the vital support they provide for their elderly parents are to be maintained.
Aged↗
X-ray characterisation of normal and neoplastic breast tissues.
Normal and neoplastic breast tissues have been characterised in terms of x-ray attenuation. Samples of normal fat and fibrous tissue were obtained from reduction mammoplasty and autopsy, and infiltrating duct carcinoma specimens from mastectomy and lumpectomy. A high-purity germanium spectroscopy system and a beam of 120 kV constant potential x-rays were used to determine the linear attenuation coefficient from 18 to 110 keV. Densities were determined from buoyancy measurements and were used to obtain mass attenuation coefficients. Infiltrating duct carcinomas and fat are well distinguished by x-ray attenuation. For photon energies used for film-screen mammography, infiltrating duct carcinomas are more attenuating than fibrous tissue. Above 31 keV, the ranges of attenuation of the two tissue types overlap. The attenuation coefficients of tissues have been concisely represented by equivalent thicknesses of lucite and aluminium. Analysis based on the average attenuation properties of tissues indicates that dual-energy mammography, using an ideal imaging system, would require 0.06 cGy to provide images in which 1 cm infiltrating duct carcinomas are displayed with a signal to noise ratio of 5 against a background over which the fat/fibrous contrast has been suppressed. This dose is similar to that currently used in conventional film-screen mammography.
Adenofibroma↗
Anthropomorphic radiologic phantoms.
A technique is being developed for the design and fabrication of anthropomorphic phantoms for diagnostic x-ray imaging. Anatomic information extracted from actual patient radiographs is incorporated into the phantoms using computer image processing and computer-assisted machining methods. In this paper, the technique is described as applied to a breast phantom, and preliminary images that closely mimic human anatomy on radiographs are shown.
Automation↗
Patients' attitudes to the relevance of nonmedical problems in family medicine care.
A questionnaire was designed to document middle-aged patients' attitudes toward their family physicians' approach to their problems of daily living. Middle-aged patients were studied because they face numerous adaptational challenges and receive substantial medical care. Almost 90 percent of 116 patients interviewed indicated that they wanted to be asked about nonmedical problems as measured by life events, with this preference being more common among those under 55 years of age. Physicians expressed comfort in inquiring about life events; however, the patients reported that they were asked about such issues rarely or only occasionally. Although over two thirds of patients felt their physicians were sufficiently aware of their life events, those who recalled frequent questions by their physician were most likely to feel their physician was sufficiently aware. Implications of these findings on the physician-patient relationship are discussed.
Adult↗
Factors influencing doctors' awareness of the life problems of middle-aged patients.
Because individuals who deal effectively with life events may be healthier, doctors may need to be aware of the important events in their patients' lives. This study was designed to document the actual level of awareness that 20 community family practitioners had of their middle-aged patients' life events. A total of 116 patients completed a life events questionnaire when they visited their family doctors. The physicians completed a similar questionnaire for each patient. A comparison between the patients' and physicians' responses provided the measure of doctors' awareness. Doctors were found to be aware of approximately 25% of all patients' life events. Awareness was inversely associated with patients' self-reliance and directly associated with age of patients and with those events having a negative effect. The observed level of knowledge may be unacceptably low, in which case physicians must find ways to improve their knowledge. Alternatively, this level of knowledge may be realistic, given that some patients may not need to discuss their life events, particularly self-reliant patients or patients experiencing events that did not affect them negatively. If this is the case, family physicians need to find ways of determining the patients and events for which their knowledge would be helpful.
Adult↗
Sources of primary health care for women in an urban centre.
Family or general practitioners and obstetrician-gynecologists have the opportunity to provide primary health care to women. Who actually gives this care in a large urban setting was the focus of this study. In the Montreal area 297 women were asked by telephone whether they had an obstetrician-gynecologist and whether they would see another type of doctor for a cold that was not getting better. Overall, 88% of all the women indicated that they would go to a family or general practitioner for such a problem, and of the women who reported receiving some care from an obstetrician-gynecologist 78% also received care from another physician. Of the respondents seeking health care from only one type of doctor, women with English as the mother tongue were significantly more likely to attend an obstetrician-gynecologist, whereas French-speaking women much more often were cared for by family or general practitioners.
Adult↗
Coherent scatter in diagnostic radiology.
Coherent scatter is often ignored in diagnostic radiology because its cross section is relatively small, and because it is assumed to be indistinguishable from primary radiation. Single-scatter calculations, however, show that coherently scattered photons diverge sufficiently from the primary ray to degrade image contrast, and that they account for a significant fraction of the total scattered energy fluence at the image receptor. Grids and large air gaps are less effective in reducing coherent single scatter than incoherent and multiple scatter. For radiography of the abdomen, coherent first scatter comprises 10% of total scatter and 26% of the primary fluence before a grid, and on the order of 22% and 7.5%, respectively, behind a grid. Coherent first scatter comprises a higher fraction of the total amount of scatter for lower energy examinations such as mammography.
Mathematics↗
Theoretical optimization of dual-energy x-ray imaging with application to mammography.
Detection of a target object in a radiological image is often impeded by an obscuring background "clutter" resulting from the contrast between various materials in the neighborhood of the target. Dual-energy techniques can reduce or remove this clutter. In order for the target to be detectable in the image after dual-energy processing, the signal-to-noise ratio (SNR), defined as the difference between the target and the background divided by the photon noise in the difference, must exceed some threshold. A given SNR may be obtained for a wide range of the energies of the two x-ray beams and the ratio of their fluences. A theoretical model is developed which permits the choice of beams to be optimized with respect to some critical parameter--in this case, patient dose. The analysis is applied to the detection of calcifications in mammography. For an ideal imaging system, we predict that the optimum beam energies are 19 and 68 keV. A dose of 0.42 cGy is required to obtain an SNR of 5 for detection of a 0.02-cm cubic calcification in the resulting clutter-free image. This can be reduced to 0.16 cGy if the higher energy image is smoothed, prior to dual-energy processing, such that its variance is reduced to one-fourth of its unsmoothed value.
Female↗
Dual-energy mammography: initial experimental results.
Dual-energy x-ray techniques may be able to enhance the detectability of calcifications in mammographic examinations by removing the background "clutter" caused by contrast between adipose and glandular tissue. This hypothesis is examined experimentally by implementation of dual-energy imaging on a prototype digital scanned projection radiography system developed in our laboratory. A model of the propagation of signal and noise in dual-energy processing for a given radiation dose is validated by measurements from phantom images. The experimental imaging system has low spatial resolution and cannot be operated at dose-optimum energies; however, since both the single- and dual-energy images are subject to the same technical limitations, a comparison of such images allows an assessment of the benefits of dual energy. Experimental images of breast tissue specimens, showing improved detectability of calcifications when obscuring background clutter is removed, are presented. The dose required for a given signal-to-noise ratio can be reduced by smoothing the higher energy image prior to dual-energy processing. For practical implementation, it is reasonable to smooth the higher energy image such that its variance is reduced fourfold.
Computers↗
Signal-to-noise properties of mammographic film-screen systems.
The signal-to-noise ratio (SNR) and the detective quantum efficiency (DQE) have been experimentally determined as a function of spatial frequency for several mammographic film-screen systems. These two parameters were determined from our measurements of noise power spectra and sensitometric properties of each system along with modulation transfer function (MTF) data for the screens which were obtained from others. From the noise power spectra, it was found that film noise contributes significantly to the total noise of mammographic film-screen systems, comprising 30%-50% of the total noise at 1 cycle/mm and as much as 75% at 5 cycles/mm. All systems had approximately the same SNR below 1.5 cycles/mm, but differed at higher frequencies due to differences in screen MTF and in the gradient of the film's sensitometric curve. The DQE curves varied between systems at all frequencies, however, due to differences in system speed, MTF, and gradient. Generally, the DQE of mammographic film-screen systems is between 10%-30% at frequencies below 1 cycle/mm and decreases to about 1% between 8 and 12 cycles/mm. Compared to film-screen systems used in general radiography, mammographic systems have similar DQE values at low frequencies, but are superior at higher frequencies.
Breast Neoplasms↗