The detecting module based on gallium arsenide detectors in digital mammography
Success in early breast cancer diagnostic depends on technical characteristics of detecting module. The most important is detector resolution. In this paper we represent quantum-sensitive detectors of X-rays based on GaAs for digital mammography systems. Electron/hole pairs created by radiation, which interact with the GaAs detectors, result current pulse at the detector output and specialist can see image immediately. Progress in development and investigation of a semiconductor material capable to provide reliable registration of single quanta of roentgen radiation. It is supposed to reduce patient radiation doze. At the same time, the system delivers high-quality images with resolution, contrast and clarity equal to film X-rays, or even better. Main advantages which can be achieved by using these detectors are analyzed.
THE DOSE AND IMAGE QUALITY IN MAMMOGRAPHY PRACTICE IN FINLAND
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UV-B radiometry and dosimetry for solar measurements.
Biologically effective irradiance or dose of solar UV radiation was determined using a spectroradiometer, two broadband radiometers and two types of passive UV-dosimeters. The absolute erythema irradiance and the actinic irradiance were calculated from the solar spectrum measured with the spectroradiometer. It was demonstrated that the erythema irradiance is proportional to the actinic irradiance of solar radiation. The erythema irradiance was also determined using the two broadband radiometers which utilize a filter transmitting erythema spectra. Personal UV-dosimeters such as polysulphone and CR-39 were used to determine the erythema dose for a selected period of time. These results were used to estimate the accuracy of the broadband radiometers and UV-dosimeters. It was found that the results obtained from the broadband radiometers deviate from the absolute erythema irradiance by less than 20% during clear days between the hours of 11:00 and 13:00 Eastern Standard Time (EST) in Australia. The assessment of the erythema dose using passive dosimeters such as polysulphone and CR-39 could introduce an error as high as 40% if the calibration was not performed before undertaking experimental measurements.