On imaging with or without grid in digital mammography
2014 (English)In: Proceedings of SPIE, the International Society for Optical Engineering, ISSN 0277-786X, Vol. 9033, 903346- p.Article in journal (Refereed) Published
The grids used in digital mammography to reduce scattered radiation from the breast are not perfect and lead to partial absorption of primary radiation at the same time as not all of the scattered radiation is absorbed. It has therefore lately been suggested to remove the grids and correct for effects of scattered radiation by post-processing the images. In this paper, we investigated the dose reduction that might be achieved if the gird were to be removed. Dose reduction is determined as a function of PMMA thickness by comparing the contrast-to-noise ratios (CNRs) of images acquired with and without grid at a constant exposure. We used a theoretical model validated with Monte Carlo simulations and phantom studies. To evaluate the CNR, we applied aluminum filters of two different sizes, 4x8 cm2 and 1x1 cm 2. When the large Al filter was used, the resulting CNR value for the grid-less images was overestimated as a result of a difference in amount of scattered radiation in the background region and of the region covered by the filter, a difference that could be eliminated by selecting a region of interest close to the edge of the filter. The optimal CNR when the PMMA thickness was above about 4 cm was obtained with a grid, whereas removing the grid leaded to a dose saving in thinner PMMAs. The results suggest not removing grids in breast cancer screening.
Place, publisher, year, edition, pages
SPIE - International Society for Optical Engineering, 2014. Vol. 9033, 903346- p.
CNR, grid, Mammography, phantom, scattered radiation
Radiology, Nuclear Medicine and Medical Imaging
IdentifiersURN: urn:nbn:se:kth:diva-146792DOI: 10.1117/12.2043017ISI: 000338775800144ScopusID: 2-s2.0-84901624717OAI: oai:DiVA.org:kth-146792DiVA: diva2:725443
Medical Imaging 2014: Physics of Medical Imaging; San Diego, CA; United States; 17 February 2014 through 20 February 2014
QC 201406162014-06-162014-06-162014-08-19Bibliographically approved