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Significance and Use
5.1 The contrast sensitivity gauge measures contrast sensitivity independent of the imaging system spatial resolution limitations. The thickness recess dimensions of the contrast sensitivity gauge are large with respect to the unsharpness limitations of most imaging systems. Four levels of contrast sensitivity are measured: 4 %, 3 %, 2 %, and 1 %.
5.2 The contrast sensitivity gauge is intended for use in conjunction with a high-contrast resolution measuring gauge, such as Practice , ISO 19232 – 5 Duplex Wire Image Quality Indicator, or a line-pair gauge. Such gauges measure system unsharpness essentially independent of the imaging system's contrast sensitivity. Such measurements are appropriate for the qualification and performance monitoring of radiographic and radioscopic imaging systems with film, realtime devices, Computed Radiography (CR) and Digital Detector Arrays (DDA).
5.3 Radioscopic/radiographic system performance may be specified by combining the measured contrast sensitivity expressed as a percentage with the unsharpness expressed in millimetres of unsharpness. For the duplex wire image quality indicator, the unsharpness is equal to twice the wire diameter. For the line pair gauge, the unsharpness is equal to the reciprocal of the line-pair/mm value. As an example, an imaging system that exhibits 2 % contrast sensitivity and images the 0.1 mm paired wires of the duplex wire IQI (equivalent to imaging 5 line-pairs/millimeter resolution on a line-pair gauge) performs at a 2 %–0.2 mm sensitivity level. A standard method of evaluating overall radioscopic system performance is given in Practice and in EN 13068–1. A conversion table from duplex wire read out to lp/mm can be found in Practice . For CR system performance evaluation, this contrast sensitivity gauge is used in Practice .
1.1 This practice covers the design and material selection of a contrast sensitivity measuring gauge used to determine the minimum change in material thickness or density that may be imaged without regard to unsharpness limitations.
1.2 This practice is applicable to transmitted-beam radiographic imaging systems (film, radioscopy, computed radiography, and digital detector array image detectors) utilizing X-ray and gamma ray radiation sources.
1.3 The values stated in inch-pound units are to be regarded as standard. The SI units given in parentheses are for information only.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific safety statements, see NIST/ANSI Handbook 114 Section 8, Code of Federal Regulations 21 CFR 1020.40 and 29 CFR 1910.96.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
B139/B139M Specification for Phosphor Bronze Rod, Bar, and Shapes
B150/B150M Specification for Aluminum Bronze Rod, Bar, and Shapes
B161 Specification for Nickel Seamless Pipe and Tube
B164 Specification for Nickel-Copper Alloy Rod, Bar, and Wire
B166 Specification for Nickel-Chromium-Iron Alloys (UNS N06600, N06601, N06603, N06690, N06693, N06025, N06045, and N06696), Nickel-Chromium-Cobalt-Molybdenum Alloy (UNS N06617), and Nickel-Iron-Chromium-Tungsten Alloy (UNS N06674) Rod, Bar, and Wire
E747 Practice for Design, Manufacture and Material Grouping Classification of Wire Image Quality Indicators (IQI) Used for Radiology
E1025 Practice for Design, Manufacture, and Material Grouping Classification of Hole-Type Image Quality Indicators (IQI) Used for Radiology
E1255 Practice for Radioscopy
E1316 Terminology for Nondestructive Examinations
E1411 Practice for Qualification of Radioscopic Systems
E1734 Practice for Radioscopic Examination of Castings
E1742 Practice for Radiographic Examination
E2002 Practice for Determining Total Image Unsharpness and Basic Spatial Resolution in Radiography and Radioscopy
E2445 Practice for Performance Evaluation and Long-Term Stability of Computed Radiography Systems
ICS Number Code 11.040.50 (Radiographic equipment)
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ASTM E1647-16, Standard Practice for Determining Contrast Sensitivity in Radiology, ASTM International, West Conshohocken, PA, 2016, www.astm.orgBack to Top