1,720,982 research outputs found
Niobium/molybdenum K-edge filtration in mammography: Contrast and dose evaluation
No full textThe use of a dual K-edge filter (niobium-molybdenum) with a Mo anode x-ray tube for application to mammography is investigated. The incident and transmitted energy spectral distributions are compared with those provided by a molybdenum anode molybdenum filter tube (standard source). The imaging characteristics in terms of contrast and mean glandular dose have been evaluated for various phantom thicknesses. The niobium filtration removes the molybdenum Kβ line almost completely from the beam spectrum whereas a Mo filtration is needed to avoid the increases both in the low-energy component of the incident beam and in the higher energy component of the transmitted one. The contrast is improved with respect to the standard source and the mean glandular dose is only slightly increased for moderate transmission phantoms (thickness 2-4 cm)
Radiation Exposure in Biliary Procedures Performed to Manage Anastomotic Strictures in Pediatric Liver Transplant Recipients: Comparison Between Radiation Exposure Levels Using an Image Intensifier and a Flat-Panel Detector-Based System
No full textThe aim of this study was to estimate radiation exposure in pediatric liver transplants recipients who underwent biliary interventional procedures and to compare radiation exposure levels between biliary interventional procedures performed using an image intensifier-based angiographic system (IIDS) and a flat panel detector-based interventional system (FPDS
A survey of radiation dose and image quality in mammography: An ongoing program in Italy
No full textA program for mammography optimization in individual x-ray units, named Dose and Quality in Mammography (DQM), is now underway in Italy. The project has three stages: (a) measurement of the parameters that affect dose and image quality by means of devices that are practical to use (specifically designed for the purpose), (b) analysis of data to evaluate dose and image quality and (c) suggestion of possible improvements to each unit operator. Instruments and methods employed in our survey are described. Our results, like those of the American survey (Je78) Breast Exposure: Nationwide Trends (BENT), show widespread variations of exposure, half value layer (HVL), optical density, dose and resolution. Facilities using the same type of x-ray apparatus (Mo target-Mo filter) and film-screen combinations present very different exposure values, ranging from 1.6 × 10-4 to 27.6 × 10-4 C kg-1. The causes of these variations-ascribable to the individual units, radiologist preferences, processing condition, kVp indicator and timer accuracy-are being explored. 1987 Health Physics Society. © 1987 Health Physics Society Pergamon Press Ltd
Synchrotron radiation: a new source in x-ray mammography
No full textThis work was aimed at evaluating the image quality obtainable in X-ray mammography using synchrotron radiation monochromatic lines. After a short review of the current mammographic techniques, the main features of synchroton radiation in the X-ray field are analyzed, especially of that emitted by the Adone storage ring. Its features are then compared with the radiation emitted by a Coolidge tube. The experimental unit used in this study, including beamline, monochromator and mammograph, is then described together with the experimental method for carrying out a series of experiments in the mammographic field employing both monochromatic lines (E = 17 keV) and white radiation from conventional sources. The first series of experiments is described, which employed standard phantoms: the dependence of resolution and contrast on both wavelength and thickness of breast specimens is reported. Several mammograms of neoplastic breast specimens were obtained after mastectomy: they were acquired using both synchrotron monochromatic lines and radiation emitted by a conventional tube and employing the same acquisition system. The comparison of the two series of images shows that synchrotron radiation can demonstrate a high number of anatomopathologic details with high definition, contrast and resolution which cannot be obtained by means of a conventional source. Our results appear very promising and suggest synchrotron radiation as the major tool in the early diagnosis of neoplastic breast lesions
Radiation probe for indirect evaluation of the high-voltage waveform of a Mo anode mammography unit
No full textA radiation probe was designed for indirectly determining the high voltage of a Mo anode mammography unit. The real time processing of the probe outputs yields exposure time, voltage waveform, kVp, and ripple in the range 24-40 kVp useful for screen-film mammography. The probe, connected to a portable computer, will be employed in a survey of radiation dose and image quality in mammography as part of an ongoing program in Ital
Differences in membrane electrical properties between C3H 10T1/2 mouse embryo fibroblasts and their ionizing radiation and chemically transformed counterparts.
No full textA 50-Hz sinusoidal magnetic field induces changes in the membrane electrical properties of K562 leukemic cells
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Quality control in mammography: A pilot programme for first level activity
No full textQuality control programmes are the best tools for maintaining optimal performances of mammographic units. Programmes to spread quality control activities have been organised in various countries. This study presents the results of an educational programme having three main objectives: quality assurance promotion, operator training with simple instruments and procedures, and operator training in quality control data analysis. Special kits have been distributed to several mammographic centres. In each centre the kit has been used to execute the following tests: AEC performance, processing conditions, entrance exposure and image quality. The data gathered in 53 centres for a period of 4 weeks are compared and discussed. Several centres were found not to satisfy completely the technical recommendations of the italian protocol, implying training for radiographers and radiologists in QC procedures is desirable
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