Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “MAMMOGRAPHY”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,783 records · Page 99Linked to original sources
PubMed2002

Dual-energy tissue cancellation in mammography with quasi-monochromatic x-rays.

Dual-energy radiography has not evolved into a routine clinical examination yet due to intrinsic limitations of both dual-kVp imaging and single-exposure imaging with conventional x-ray sources. The recent introduction of novel quasi-monochromatic x-ray sources and detectors could lead to interesting improvements, especially in mammography where the complex structure of healthy tissues often masks the detectability of lesions. A dual-energy radiography technique based on a tissue cancellation algorithm has been developed for mammography, with the aim of maximizing the low intrinsic contrast of pathologic tissues while being able to minimize or cancel the contrast between glandular and fat tissues. Several images of a plastic test object containing various tissue equivalent inserts were acquired in the energy range 17-36 keV using a quasi-monochromatic x-ray source and a scintillator-coated CCD detector. Images acquired at high and low energies were nonlinearly combined to generate two energy-independent basis images. Suitable linear combinations of these two basis images result in the elimination of the contrast of a given material with respect to another. This makes it possible to selectively cancel certain details in the processed image.

Algorithms↗
PubMed2004

Quantitative evaluation of dual-energy digital mammography for calcification imaging.

Dual-energy digital mammography (DEDM), where separate low- and high-energy images are acquired and synthesized to cancel the tissue structures, may improve the ability to detect and visualize microcalcifications. Under ideal imaging conditions, when the mammography image data are free of scatter and other biases, DEDM could be used to determine the thicknesses of the imaged calcifications. We present quantitative evaluation of a DEDM technique for calcification imaging. The phantoms used in the evaluation were constructed by placing aluminium strips of known thicknesses (to simulate calcifications) across breast-tissue-equivalent materials of different glandular-tissue compositions. The images were acquired under narrow-beam geometry and high exposures to suppress the detrimental effects of scatter and random noise. The measured aluminium thicknesses were found to be approximately linear with the true aluminium thicknesses and independent of the underlying glandular-tissue composition. However, the dual-energy images underestimated the true aluminium thickness due to the presence of scatter from adjacent regions. Regions in the DEDM image that contained no aluminium yielded very low aluminium thicknesses (<0.07 mm). The aluminium contrast-to-noise ratio in the dual-energy images increased with the aluminium thickness and decreased with the glandular-tissue composition. The changes to the aluminium contrast-to-noise ratio and the contrast of the tissue structures between the low-energy and DEDM images are also presented.

Algorithms↗
PubMed2004

Monte carlo simulation of x-ray spectra in diagnostic radiology and mammography using MCNP4C.

The general purpose Monte Carlo N-particle radiation transport computer code (MCNP4C) was used for the simulation of x-ray spectra in diagnostic radiology and mammography. The electrons were transported until they slow down and stop in the target. Both bremsstrahlung and characteristic x-ray production were considered in this work. We focus on the simulation of various target/filter combinations to investigate the effect of tube voltage, target material and filter thickness on x-ray spectra in the diagnostic radiology and mammography energy ranges. The simulated x-ray spectra were compared with experimental measurements and spectra calculated by IPEM report number 78. In addition, the anode heel effect and off-axis x-ray spectra were assessed for different anode angles and target materials and the results were compared with EGS4-based Monte Carlo simulations and measured data. Quantitative evaluation of the differences between our Monte Carlo simulated and comparison spectra was performed using student's t-test statistical analysis. Generally, there is a good agreement between the simulated x-ray and comparison spectra, although there are systematic differences between the simulated and reference spectra especially in the K-characteristic x-rays intensity. Nevertheless, no statistically significant differences have been observed between IPEM spectra and the simulated spectra. It has been shown that the difference between MCNP simulated spectra and IPEM spectra in the low energy range is the result of the overestimation of characteristic photons following the normalization procedure. The transmission curves produced by MCNP4C have good agreement with the IPEM report especially for tube voltages of 50 kV and 80 kV. The systematic discrepancy for higher tube voltages is the result of systematic differences between the corresponding spectra.

Algorithms↗
PubMed2005

A prototype of a quasi-monochromatic system for mammography applications.

Improvement in image contrast and dose reduction, in mammographic x-ray imaging, can be achieved using narrow energy band x-ray beams in the 16-24 keV range. As part of an Italian Government funded project, a quasi-monochromatic system for mammography applications has been developed. The system is based on a tunable narrow energy band x-ray source operating in the 16-24 keV energy range. The bremsstrahlung beam is monochromatized via Bragg diffraction by a highly oriented pyrolytic graphite mosaic crystal (HOPG). The scanning system provides a large field (18 x 24 cm2) of quasi-monochromatic x-rays with energy resolution ranging from 10% at 18 keV to 17.2% at 24 keV. The system has been characterized in terms of fluence rate and energy resolution. An x-ray tube developed ad hoc allows us to acquire images in a reasonable time to minimize the motion blur. A qualitative analysis has been performed in order to know if the prototype system performances are far from a clinical application, by evaluating the spatial resolution, the field uniformity and the image quality as a function of the quasi-monochromatic beam energy. Dose evaluation has been performed as a function of the energy and compared to a conventional system for mammography. The quasi-monochromatic prototype system can produce comparable image quality at half the dose.

Equipment Design↗
PubMed2005

A search for optimal x-ray spectra in iodine contrast media mammography.

The aim of this work was to search for the optimal x-ray tube voltage and anode-filter combination in digital iodine contrast media mammography. In the optimization, two entities were of interest: the average glandular dose, AGD, and the signal-to-noise ratio, SNR, for detection of diluted iodine contrast medium. The optimum is defined as the technique maximizing the figure of merit, SNR2/AGD. A Monte Carlo computer program was used which simulates the transport of photons from the x-ray tube through the compression plate, breast, breast support plate, anti-scatter grid and image detector. It computes the AGD and the SNR of an iodine detail inside the compressed breast. The breast thickness was varied between 2 and 8 cm with 10-90% glandularity. The tube voltage was varied between 20 and 55 kV for each anode material (Rh, Mo and W) in combination with either 25 microm Rh or 0.05-0.5 mm Cu added filtration. The x-ray spectra were calculated with MCNP4C (Monte Carlo N-Particle Transport Code System, version 4C). A CsI scintillator was used as the image detector. The results for Rh/0.3 mmCu, Mo/0.3 mmCu and W/0.3 mmCu were similar. For all breast thicknesses, a maximum in the figure of merit was found at approximately 45 kV for the Rh/Cu, Mo/Cu and W/Cu combinations. The corresponding results for the Rh/Rh combination gave a figure of merit that was typically lower and more slowly varying with tube voltage. For a 4 cm breast at 45 kV, the SNR2/AGD was 3.5 times higher for the Rh/0.3 mmCu combination compared with the Rh/Rh combination. The difference is even larger for thicker breasts. The SNR2/AGD increases slowly with increasing Cu-filter thickness. We conclude that tube voltages between 41 and 55 kV and added Cu-filtration will result in significant dose advantage in digital iodine contrast media mammography compared to using the Rh/Rh anode/filter combination at 25-32 kV.

Algorithms↗
PubMed2005

Analyser-based mammography using single-image reconstruction.

We implement an algorithm that is able to decode a single analyser-based x-ray phase-contrast image of a sample, converting it into an equivalent conventional absorption-contrast radiograph. The algorithm assumes the projection approximation for x-ray propagation in a single-material object embedded in a substrate of approximately uniform thickness. Unlike the phase-contrast images, which have both directional bias and a bias towards edges present in the sample, the reconstructed images are directly interpretable in terms of the projected absorption coefficient of the sample. The technique was applied to a Leeds TOR[MAM] phantom, which is designed to test mammogram quality by the inclusion of simulated microcalcifications, filaments and circular discs. This phantom was imaged at varying doses using three modalities: analyser-based synchrotron phase-contrast images converted to equivalent absorption radiographs using our algorithm, slot-scanned synchrotron imaging and imaging using a conventional mammography unit. Features in the resulting images were then assigned a quality score by volunteers. The single-image reconstruction method achieved higher scores at equivalent and lower doses than the conventional mammography images, but no improvement of visualization of the simulated microcalcifications, and some degradation in image quality at reduced doses for filament features.

Algorithms↗
PubMed2005

Monte Carlo simulation of primary electron production inside an a-selenium detector for x-ray mammography: physics.

Selenium is among the materials under investigation that may form effective detectors and provide a major contribution to digital mammography. Till the final image formation, there is an intervention of the x-ray photons transformation to primary electrons and their subsequent ionizing drift towards the electrodes that collect them. The characteristics of the generated primary electrons inside a-Se material such as their angular, spatial and energy distribution affect the characteristics of the final image. A Monte Carlo based model has been developed that simulates the x-ray irradiation of an a-Se detector plate, including primary photon interactions (photoelectric absorption, coherent and incoherent scattering), as well as secondary ones, such as fluorescence (Kalpha, Kbeta) and emission of Auger electrons. The angular, spatial and energy distributions for the generated primary electrons inside a-Se have been produced for various mammographic x-ray spectra and their usefulness in designing and optimizing a detector made of a-Se for digital mammography is discussed.

Algorithms↗
PubMed2005

Method for determination of the mean fraction of glandular tissue in individual female breasts using mammography.

The nationwide breast cancer screening programme using mammography has been in full operation in the Netherlands since 1997. Quality control of the screening programme has been assigned to the National Expert and Training Centre for Breast Cancer Screening. Limits are set to the mean glandular dose and the centre monitors these for all facilities engaged in the screening programme. This procedure is restricted to the determination of the entrance dose on a 5 cm thick polymethylmethacrylate (PMMA) phantom. The mean glandular dose for a compressed breast is estimated from these data. Individual breasts may deviate largely from this 5 cm PMMA breast model. Not only may the compressed breast size vary from 2 to 10 cm, but breast composition varies also. The mean glandular dose is dependent on the fraction of glandular tissue (glandularity) of the breast. To estimate the risk related to individual mammograms requires the development of a method for determination of the glandularity of individual breasts. A method has been developed to derive the glandularity using the attenuation of mammography x-rays in the breast. The method was applied to a series of mammograms at a screening unit. The results, i.e., a glandularity of 93% within the range of 0 to 1, were comparable with data in the literature. The glandularity as a function of compressed breast thickness is similar to results from other investigators using differing methods.

Breast↗
PubMed2006

A comparison between objective and subjective image quality measurements for a full field digital mammography system.

This paper presents pre-sampling modulation transfer function (MTF), normalized noise power spectrum (NNPS) and detective quantum efficiency (DQE) results for an amorphous selenium (a-Se) full field digital mammography system. MTF was calculated from the image of an angled 0.5 mm thick Cu edge, acquired without additional beam filtration. NNPS data were acquired at detector air-kerma levels ranging from 9.1 microGy to 331 microGy, using a standard mammography x-ray spectrum of 28 kV, Mo/Mo target/filter combination and 4 cm of PMMA additional filtration. Prior to NNPS estimation, the image statistics were assessed using a variance image. This method was able to easily identify a detector artefact and should prove useful in routine quality assurance (QA) measurements. Detector DQE, calculated from the NNPS and MTF data, dropped to 0.3 for low detector air-kerma settings but reached an approximately constant value of 0.6 above 50 microGy at the detector. Subjective image quality data were also obtained at these detector air-kerma settings using the CDMAM contrast-detail (c-d) test object. The c-d data reflected the trend seen in DQE, with threshold contrast increasing at low detector air-kerma values. The c-d data were then compared against predictions made using two established models, the Rose model and a standard signal detection theory model. Using DQE(0), the Rose model gave results within approximately 15% on average for all the detector air-kerma values studied and for detail diameters down to 0.2 mm. Similar agreement was also found between the measured c-d data and the signal detection theory results, which were calculated using an ideal human visual response function and a system magnification of unity. The use of full spatial frequency DQE improved the agreement between the calculated and observer results for detail sizes below 0.13 mm.

Algorithms↗
PubMed2006

Monte Carlo generated conversion factors for the estimation of average glandular dose in contact and magnification mammography.

Magnification mammography is a special technique used in the cases where breast complaints are noted by a woman or when an abnormality is found in a screening mammogram. The carcinogenic risk in mammography is related to the dose deposited in the glandular tissue of the breast rather than the adipose, and average glandular dose (AGD) is the quantity taken into consideration during a mammographic examination. Direct measurement of the AGD is not feasible during clinical practice and thus, the incident air KERMA on the breast surface is used to estimate the glandular dose, with the help of proper conversion factors. Additional conversion factors adapted for magnification and tube voltage are calculated, using Monte Carlo simulation. The effect of magnification degree, tube voltage, various anode/filter material combinations and glandularity on AGD is also studied, considering partial breast irradiation. Results demonstrate that the estimation of AGD utilizing conversion factors depends on these parameters, while the omission of correction factors for magnification and tube voltage can lead to significant underestimation or overestimation of AGD. AGD was found to increase with filter material's k-absorption edge, anode material's k-emission edge, tube voltage and magnification. Decrease of the glandularity of the breast leads to higher AGD due to the increased penetrating ability of the photon beam in thick breasts with low glandularity.

Air↗
PubMed2006

Ambient dose equivalent and effective dose from scattered x-ray spectra in mammography for Mo/Mo, Mo/Rh and W/Rh anode/filter combinations.

In this study, scattered x-ray distributions were produced by irradiating a tissue equivalent phantom under clinical mammographic conditions by using Mo/Mo, Mo/Rh and W/Rh anode/filter combinations, for 25 and 30 kV tube voltages. Energy spectra of the scattered x-rays have been measured with a Cd(0.9)Zn(0.1)Te (CZT) detector for scattering angles between 30 degrees and 165 degrees . Measurement and correction processes have been evaluated through the comparison between the values of the half-value layer (HVL) and air kerma calculated from the corrected spectra and measured with an ionization chamber in a nonclinical x-ray system with a W/Mo anode/filter combination. The shape of the corrected x-ray spectra measured in the nonclinical system was also compared with those calculated using semi-empirical models published in the literature. Scattered x-ray spectra measured in the clinical x-ray system have been characterized through the calculation of HVL and mean photon energy. Values of the air kerma, ambient dose equivalent and effective dose have been evaluated through the corrected x-ray spectra. Mean conversion coefficients relating the air kerma to the ambient dose equivalent and to the effective dose from the scattered beams for Mo/Mo, Mo/Rh and W/Rh anode/filter combinations were also evaluated. Results show that for the scattered radiation beams the ambient dose equivalent provides an overestimate of the effective dose by a factor of about 5 in the mammography energy range. These results can be used in the control of the dose limits around a clinical unit and in the calculation of more realistic protective shielding barriers in mammography.

Body Burden↗
PubMed1989

An instrument for monitoring the force applied by breast compression devices on mammography x-ray sets.

Automatic breast compression devices are commonly fitted to mammographic x-ray sets. The force exerted by these compression devices should be limited and periodically checked. This article describes the design and construction of an instrument for the routine assessment of the force applied by breast compression devices on mammography x-ray sets. Results obtained on four different mammography x-ray units are presented. In addition, data on the effect of compression plate design on compression force is given for one unit. The instrument has proved to be a simple and quick method of monitoring the force applied by the compression plates on mammographic x-ray units.

Female↗
PubMed2002

The personal costs and convenience of screening mammography.

BACKGROUND: Few studies have examined the impact of women's personal costs on obtaining a screening mammogram in the United States. METHODS: All women obtaining screening mammograms at nine Connecticut mammography facilities during a 2-week study period were asked to complete a questionnaire. Facilities included urban and rural fixed sites and mobile sites. The survey included questions about insurance coverage, mammogram payment, and personal costs in terms of transportation, family care, parking, and lost work time from the women's perspective. RESULTS: The response rate was 62% (731 of 1189). Thirty-two percent of respondents incurred some type of personal cost, including lost work time, family care, and parking. Women incurring personal costs were more likely than those without personal costs to attend an urban facility (46% vs. 23%, p < 0.01) and be under the age of 50 (40% vs. 26%, p < 0.01). Overall, 61% of women listed convenience and 17% listed cost as a reason for choosing a mammography facility; 23% reported that cost might prevent them from obtaining a future mammogram. CONCLUSIONS: One third of women obtaining mammograms may be incurring personal costs. These personal costs should be considered in future cost-effectiveness analyses.

Adult↗
PubMed1999

Psychological factors related to stage of mammography adoption.

This study examined the differences among women at different stages of mammography adoption on Health Belief Model variables, response efficacy, knowledge, and avoidance. A random sample of 361 women aged > or =40 years were grouped into six stages of mammography adoption (precontemplation, contemplation, action, maintenance, relapse precontemplation, relapse contemplation). A multivariate analysis of variance (ANOVA) revealed significant differences among women on all components of the Health Belief Model except perceived seriousness, as well as differences on response efficacy, knowledge, and avoidance. Results indicate that there are significant differences between women who have never had a mammogram (precontemplation and contemplation stages) and women who have had a mammogram in the past but are currently noncompliant (relapse stages). Further, significant differences were found between compliant women who have had one mammogram (action) and compliant women who have had multiple mammograms (maintenance) on barriers, motivation, confidence, and avoidance.

Adult↗
PubMed1999

Confusion about mammography: prevalence and consequences.

Over the last decade, there has been significant controversy about the schedule on which women, particularly women in their 40s, should have mammograms. The purpose of the analysis reported here was to assess whether women in their 40s and 50s were confused as a result of the controversy following the January 1997 National Institutes of Health Consensus Development Conference on Breast Cancer Screening For Women Ages 40-49. We also examined if confusion was related to being off schedule for mammography. The study sample included 1287 women recruited from a random sample of 2165 Blue Cross/Blue Shield of North Carolina members. The data described in this analysis were derived from a baseline telephone interview conducted as part of a larger intervention trial. Study measures included a variety of sociodemographic, medical, belief, and behavioral variables. Overall, 28% of women were confused, and 35% were off schedule. Although a higher proportion of women in their 40s than 50s were confused, more women in their 50s were off schedule. Confusion was a significant predictor for the outcome being off schedule. Predictors of confusion included several belief variables, risk perceptions, age (40s), whether the woman had a regular physician, and whether she had enough information about mammography. Healthcare providers should ask some simple questions to determine if women are confused and then seek to meet their information needs.

Adult↗
PubMed1998

Does diagnostic accuracy in mammography depend on radiologists' experience?

This study was designed to determine if radiologists' experience in mammography is associated with their performance in correctly interpreting mammograms. Study mammograms (n = 150) were chosen by stratified random sampling from those interpreted as normal, abnormal-benign or abnormal-suspicious for cancer, with oversampling of cancer cases. Ten radiologists who had varying amounts of experience were asked to read the mammograms. Associations between the levels of the radiologists' experience and their accuracy in reading mammograms were assessed. Significant associations (p < 0.05) were found between the frequency of immediate workup recommendations in cancer patients and obtaining feedback, total lifetime mammograms read, number of mammography continuing medical education (CME) credits, and practice type. Radiologists with more experience also noted smaller cancer lesions. However, these experience variables were also associated with increased workup recommendations in the noncancer patients (p < 0.10). In multivariable analysis, obtaining regular feedback and the total lifetime number of mammograms read were independently associate with the number of times immediate workup was recommended in the cancer cases. The most experienced radiologist had the highest sensitivity in diagnosing breast cancer. Further studies are needed to assess whether the current requirements of the U.S. Food and Drug Administration for radiologists who read mammograms ensure acceptable levels of accuracy.

Breast Neoplasms↗
PubMed2003

Validity of self-reported mammography: examining recall and covariates among older women in a Health Maintenance Organization.

Self-reports of screening are frequently used in place of chart abstraction, particularly in outpatient settings, because they are generally less expensive and frequently provide the only information available. The authors expanded the literature on validation of self-reported mammography by including the validity of recall and by assessing covariates in a setting where women were examined more than once. In 1995, this study validated mammography use in a sample of 949 women aged 50-80 years who were members of a health maintenance organization with centralized automated records of mammographic examinations. The majority of women had had a mammogram within the previous 2 years according to self-reports and records, but self-reported rates exceeded record rates by 8.2%. Sensitivity was high (93.8%), whereas specificity was low (53.6%). The overall agreement between self-reports and records was 82.7%. The kappa value was 0.52, indicating fair agreement beyond chance. Modeling with logistic regression revealed that being a college graduate and having a first-degree relative with breast cancer were significantly associated with accurate recall. Comparison of actual time interval data revealed that disagreements consisted largely of women's underestimates of time since their last screening. These results add to knowledge about the validity of self-reported mammographic screening data in settings where women are screened more than once.

Aged↗
PubMed2005

MRI accurately depicts underlying DCIS in a patient with Paget's disease of the breast without palpable mass and mammography findings.

Breast-conserving therapy must be carefully indicated among patients with Paget's disease of the breast, because the disease is often associated with an underlying in situ or invasive carcinoma, even when there are no palpable mass or mammography findings. We report a 52-year-old woman who complained of skin color change of her right nipple for 11 months. No mass was palpable in her breasts, and mammography did not show any density or calcification. Nipple biopsy revealed Paget's disease of the breast with ductal carcinoma in situ (DCIS) in the breast epithelium just beneath the nipple. Magnetic resonance imaging (MRI) of the breast demonstrated diffuse segmental enhancement in two different quadrants. According to the pattern of enhancement, the lesions depicted by MRI were diagnosed as an extensively spreading type of DCIS. Based on informed consent, the patient received a total mastectomy. The histopathological examination demonstrated non-invasive ductal carcinoma with comedo-necrosis. The histological mapping with subserial sectioning demonstrated an extent of the lesions that corresponded accurately to the lesions defined by MRI. We conclude that MRI may play an important role in selecting candidates for breast-conserving therapy out of those patients with mammary Paget's disease with no clinical evidence of an underlying breast carcinoma.

Biopsy↗