Thomas Mertelmeier PhD, Presenter: Nothing to Disclose

Philipp Bernhardt PhD, Abstract Co-Author: Nothing to Disclose

Nanna Palmberg, Abstract Co-Author: Nothing to Disclose

Martin Hoheisel PhD, Abstract Co-Author: Nothing to Disclose

To optimize the radiographic technique for a new full-field digital mammography system based on an amorphous selenium detector and a dual-target tube with various filters.

We optimize the exposure parameters by simulation and phantom experiments. Figure of merit (FOM) is the squared signal-difference-to-noise-ratio divided by mean glandular dose. The simulations take into account real spectra, the absorption properties of the new a-Se detector, and scattered radiation with and without grid using Monte-Carlo methods. A set of breast equivalent phantoms (50% fat, 50% glandular) with breast thickness between 2 and 8 cm is used for simulations and measurements. The measurements are carried out with the FFDM system Siemens Mammomat Novation DR* employing a dual target (Tungsten(W) and Molybdenum(Mo)) anode with Mo and Rhodium(Rh) filtration.

Restricting the parameter space to anode/filter combinations available today, W/Rh gives a higher FOM than Mo/Mo or Mo/Rh for all cases investigated. The dose saving for constant image quality increases from approximately 10% for thin objects to more than 50% for thick objects. These results are confirmed by the phantom experiments. Exposure tables for W/Rh are found close to the optimum values. The highest FOM deviates about 20% from the simulation results achieved with monoenergetic radiation that can be regarded as a benchmark.

For the specific system studied, a W anode with Rh filtration achieves higher image quality than Mo/Mo. Keeping the image quality constant, W/Rh can reduce the dose by more than 50% employing an a-Se detector.* This product is under review and not currently available for sale in the U.S.

T.M.,P.B.,N.P.,M.H.: The authors work for Siemens AG Medical Solutions

Mertelmeier, T, Bernhardt, P, Palmberg, N, Hoheisel, M, Dose Reduction by Technique Optimization for FFDM Based on an Amorphous Selenium Detector.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4404256.html