Tuesday, 11 August 2009

Image display contrast variation negates consistent mammo readings

So it seems that much of the effects found by the DMIST Study were due to image contrast, inherent with digital imaging.................

A report in Radiology from the DMIST investigators in the August edition -
Radiology August 2009 252:348-357

Link to Journal

Readers most frequently attributed differences in DMIST cancer visibility to variations in image contrast—not differences in positioning or compression—between digital and screen-film mammography.

For women with both fatty and dense breasts, the most frequent reason given for the difference in visibility between film-screen and digital mammography was contrast differences between the two modalities. For women with dense breasts, contrast differences accounted for 70 of the 378 reasons given by the readers for better visibility. Positioning, compression, and technique differences accounted for only 37 of the reasons given for improved visibility

The odds of a cancer being more visible on a digital mammogram—rather than being equally visible on digital and screen-film mammograms—were significantly greater for women with dense breasts than for women with non-dense breasts, even with the data adjusted for patient age, lesion type, and mammography system (odds ratio, 2.28;
P < .0001).

The odds of a cancer being more visible at digital mammography—rather than being equally visible at digital and screen-film mammography—were significantly greater for lesions imaged with the General Electric digital mammography system than for lesions imaged with the Fischer (
P = .0070) and Fuji (P = .0070) devices. No comment was made about Hologic

The significantly better diagnostic accuracy of digital mammography, as compared with screen-film mammography, in women with dense breasts demonstrated in the DMIST was most likely attributable to differences in image contrast, which were most likely due to the inherent system performance improvements that are available with digital mammography. The authors conclude that the DMIST results were attributable primarily to differences in the display and acquisition characteristics of the mammography devices rather than to reader variability.