ASTM Contrast sensitivity gauges

ASTM E 1647-03, "Standard Practice for Determining Contrast Sensitivity in Radiology" specifies a convenient method for the initial qualification and subsequent monitoring of the imaging performance level of radiographic (film based) and, especially, radioscopic (filmless)imaging systems.

The performance level is expressed as a combination of contrast sensitivity (C) and spatial resolution (U). U in millimetres is the total unsharpness measurement obtained from examining the image of a duplex IQI to EN 462-5. C in % is obtained from one of the gauges described below. To quote from paragraph 5.3 of the Standard, 'As an example, an imaging system that exhibits 2% contrast sensitivity and images the 0.1 mm EN 462-5 paired wires (equivalent to imaging 5 line-pairs/millimeter resolution on a line-pair gage) performs at a 2%-0.2mm sensitivity level.'

Gauge size

Each gauge comprises a rectangular block with four flat-bottom recesses that represent 1%, 2%, 3% and 4% of the gauge total thickness (T). There are four specified gauge sizes, ranging in length from 3in to 12in. The appropriate gauge size depends on thickness of the test specimen with which it is to be used.

Gauge thickness

The gauge thickness (T) is the same as that of the test specimen (+/- 5%).

Gauge material

The gauges can be manufactured in the following materials:

Group 03 Magnesium

Group 02 Aluminium

Group 01 Titanium

Group 1   Steel or stainless steel

Group 2   Aluminium bronze alloy

Group 3   Inconel

Group 4   Monel

Group 5   Tin bronze alloy

All gauges are made specially to order. Please specify the required gauge thickness (T) and gauge material.