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BS EN 61262-6:1995 Characteristics of electro-optical X-ray image intensifiers for medical electrical equipment. - Part 6. Determination of the contrast ratio and veiling glare index

Description Printed version of this is available at library. To request, please e-mail to referencepk@usm.my and include a copy of this record in your e-mail. Abstract This International Standard applies to electro-optical X-ray image intensifiers for medical use, as components of diagnostic X-ray equipment. This International Standard describes a method of determining the contrast ratio (CR) and the vetting glare index (VGI) of electro-optical X-ray image intensifiers. The contrast ratio (CR) and the veiling glare index (VGI), which is defined as the reciprocal of the CR, are measures of the spatial frequency response of an imaging system at low frequencies and, as such, complement the limiting spatial resolution, which is a measure of a system's high-frequency response. Although the CR and the VGI can, in principle, be estimated from the modulation transfer function, it is simpler to measure them directly. The contrast represented by the difference in X-ray fluence between an object and its surroundings can be diminished by the imaging device. Generally, this loss of contrast is due to scattering of the image-carrying quanta away from the ideal paths. The radiance in the image due to imaging the scattered quanta is called "veiling glare." Processes that contribute to veiling glare include the scattering of X-radiation at the electro-optical X-ray image intensifier input and the scattering of light at its output. For an electro-optical X-ray image intensifier, the CR is the ratio of the luminance at the centre of the output image with no test device in the X-ray beam to the luminance at the centre of the output image with a CR test device in the X-ray beam. While the CR is unbounded, ranging from 1 to infinity, the VGI is bounded between 0 and 1.

Contributor(s): MAR - Data Entry Person Primary Item Type: British Standard Identifiers: ISBN 0580240363 ICS 11.040.50 Radiographic equipment Language: English Subject Keywords: Medical equipment; Optical instruments; Contrast (optical); Ratios; X-ray apparatus; Optical properties of materials; Glare; Electrical medical equipment; Optical measurement; Radiography; Image intensifiers; X-rays First presented to the public: 6/23/2023 Original Publication Date: 4/15/1995 Previously Published By: British Standards Institution Place Of Publication: London, United Kingdom Citation: Extents: Number of Pages - 14 License Grantor / Date Granted:   / ( View License ) Date Deposited 2023-06-23 11:39:20.76 Submitter: Muhamad Azmil Ramli

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