Michael James Flynn PhD, Presenter: Researcher, F. Hoffmann-La Roche Ltd (Roche Diagnostics) Researcher, Shimadzu Corporation

Jamal Samih Ksar MD, Abstract Co-Author: Nothing to Disclose

Joseph C. Blechinger PhD, Abstract Co-Author: Nothing to Disclose

Robert M. McGee BS, Abstract Co-Author: Nothing to Disclose

Experimentally measure the 3D (X,Y,Z) spatial response of a high resolution x-ray tomosynthesis (TS) system and compare the results to that of 64 slice computed tomography (CT) systems.

TS images were acquired using a selenium digital detector in a linear tomography table (Shimadzu). 75 square images of 23 to 43 cm size were acquired at 30 frames per second over an angle of 40 degrees. Detector elements of 0.15 mm dimension were binned at 2x2 for an effective size of 0.30 mm. TS images were reconstructed using a filtered backprojection method. Resolution was measured using a 0.08 mm diameter tungsten wire angulated 6 degrees from the X, Y, and Z TS coordinates. The line spread function (LSF) and slice sensitivity function (SSF) was deduced by subpixel reprojection of the data. Comparative CT response was measured using a teflon sphere embedded in a silicone cylinder. Volumetric CT scan data (GE, Siemens) was analyzed to determine the transaxial and axial plane spread function (PlSF).

Measured CT FWHM PlSF is 1.14 +- 0.05 mm transverse and 0.87 +- 0.11 mm axial. The corresponding frequency for an MTF of 0.10 is 0.74 0.02 cycles/mm transverse and 0.92 0.11 axial. For comparison this is expressed as 1.00 mm and 0.83 cycles/mm. In the TS direction associated with linear acquisition motion, Y, the TS response is 2.41 mm FWHM LSF. Since the LSF has a zero DC average value, the frequency response at 0.20 of maximum, 2.62 cycles/mm, was used for comparison. The TS X,Y response is 2.42 and 3.16 times larger than typical CT for the response width and spatial frequency limit. TS slice sensitivity is 3.02 mm (Z direction). The difference was demonstrated using cadaver examinations.

In the X,Y plane, TS images have about 3 times better resolution than 64 slice CT images. However, in the Z direction TS slice sensitivity is about 3 times worse than the axial response of CT. Additionally, TS has no response for frequencies in a wedge about the X,Z plane due to the limited acquisition angle.

In plane natomic detail is significantly improved with TS relative to CT at the expense of slice thickness. However, artifacts associated with limited angle acquisition must be understood.

Flynn, M, Ksar, J, Blechinger, J, McGee, R, Spatial Response of X-ray Tomosynthesis in Relation to Computed Tomography.  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/5015908.html