Andreas Fieselmann, Presenter: Employee, Siemens AG

Daniel Fischer, Abstract Co-Author: Employee, Siemens AG

Ghani Hilal, Abstract Co-Author: Nothing to Disclose

Thomas Mertelmeier MD, Abstract Co-Author: Employee, Siemens AG Stockholder, Siemens AG

Detlev Uhlenbrock, Abstract Co-Author: Research Grant, Siemens AG

To investigate dose saving and image quality of digital mammography by acquisition without anti-scatter grid in combination with a novel software-based scatter correction (SBSC).

A novel scatter correction algorithm for grid-less acquisition was initially validated by numerical simulations and physical phantom studies. Patient dose may be reduced by grid-less acquisition (no grid attenuation of primary radiation) and optimized breast-thickness-(BT)-dependent dose reduction factors (DRF) were determined from these measurements. For clinical evaluation, an ethics-committee-approved feature analysis study with informed consent of 75 female patients having known mammographic findings (68% masses, 28% calcifications, 25% architectural distortions) was conducted. Each patient underwent two mammography exams during one compression phase: 1. with grid; 2. without grid, with SBSC. The tube current-time product of the second acquisition was reduced according to the DRF, all other imaging parameters were fixed. For each case, comparison of both mammograms with respect to general image quality and 7 additional metrics was performed by 5 blinded readers using a 7-point Likert scale.

The simulations and phantom studies showed a linear function of the DRF (slope: -0.34% /mm of BT). Thus dose saving is highest for smaller breasts. The actual DRF in the clinical study ranged from 33% (20mm≤BT<30mm) to 15% (80mm≤BT<90mm). Weighted with the BT-distribution of a typical screening population, the average dose reduction is 23%. The average of the general mammographic image quality compared between the two acquisitions was less than 0.3 points on the Likert-scale with a 95% confidence level. Similar results were obtained for the 7 additional metrics. Based on these results, the grid-less acquisition with SBSC was rated to be of equivalent image quality as the acquisition with grid.

Grid removal in combination with SBSC may reduce patient dose in digital mammography while maintaining image quality. The SBSC is investigational software and is limited by U.S. law to investigational use. It is not commercially available in the U.S. and its future availability cannot be ensured.

Anti-scatter grids increase patient dose in mammography due to attenuation of primary radiation. With SBSC the grid may be removed for digital mammography and patient dose may be reduced.

Fieselmann, A, Fischer, D, Hilal, G, Mertelmeier, T, Uhlenbrock, D, Dose Saving in Full-field Digital Mammography by Grid-less Acquisition Combined with a Novel Software-based Scatter Correction.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12025007.html