Target CNR Calculator
Target CNR CalculatorIn order to apply the standards in the European protocol, it is necessary to relate the image quality measured using the CDMAM for an equivalent breast thickness of 60mm, to that for other breast thicknesses using CNR measurements. The method of measuring CNR in the NHSBSP protocol is the same as that described in the European protocol. The European protocol gives the relationship between threshold contrast and CNR measurements. This enables the calculation of a target CNR value for a particular level of image quality on a particular mammography system, which can be compared to CNR measurements made at other breast thicknesses. A spreadsheet is provided here to enable this task. A description of the method used in the spreadsheet can be downloaded here. Examples of the use of target CNR values can be found in the technical evaluations conducted by NCCPM on new digital mammography systems described elsewhere on this website.