Effects of Crossover and Low-intensity Reciprocity Law Failure on LSF

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"MTF's and Wiener Spectra of Radiographic Screen-Film Systems", a book published in 1982 by BRH, covers methods to measure LSF. These methods have been known as the standard for MTF measurement. However, in measuring MTFs with the same sample it has been revealed to produce different values measured at different facilities. Several researches have shown that this occurs because of differences in the methods of irradiation, film processing, and density measurement methods. The authors have additionally believed that the essential cause lay in the crossover effect and low-intensity reciprocity law failure. Thus, the present study aimed to clarify how these two factors affect on the LSF measurements.The results of research have clearly shown that they are deeply involved in LSF measurement. Based on newly obtained knownledge, it is necessary to ensure experimental conditions in addition to the methods described in the book for compensation of the differences among acilities. The results obtained were as follows: 1. With respect to the crossover effect, approx.30% of the amount of luminescence from screens affect the opposite emulsion on SR-Gfilm. 2. Low-intensity reciprocity law failure occurs with SR-G film when illuminance is 0.2 lx or below. 3. It is not possible to measure accurately LSF unless one performs the following in addition to the items described by the BRH's authors. 1) The two slit images of low or high density should be photographed under an identical exposure time with different X-ray intensities. 2) The sensitometric strip should completely be produced by the intensity scale method, and the exposure time should be the identical time with that of the slit image photograph.
Medical Imaging and Information Sciencesの論文

Effects of Crossover and Low-intensity Reciprocity Law Failure on LSF

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Medical Imaging and Information Sciences | 論文

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