Taly Gilat Schmidt MS, Presenter: Nothing to Disclose

Robert Bennett, Abstract Co-Author: Nothing to Disclose

Samuel Robert Mazin MS, Abstract Co-Author: Nothing to Disclose

Josh Star-Lack PhD, Abstract Co-Author: Nothing to Disclose

Edward Solomon, Abstract Co-Author: Nothing to Disclose

Norbert Joseph Pelc ScD, Abstract Co-Author: Nothing to Disclose

A table-top inverse geometry volumetric CT (IGCT) system has been built and an initial dataset reconstructed in order to demonstrate feasibility of the new scanner geometry. The IGCT system acquires volumetric data in one circular scan with negligible cone-beam artifacts.

The prototype system consists of a C-arm gantry with a 25x25 cm scanned source opposite 2304 photon counting detectors in a 5x5 cm array (Nexray, Inc). During an acquisition an electron beam is rapidly steered across the transmission target, dwelling at an array of collimator holes which focus the beam towards the detector. For each source position the entire detector array is read out. Ideally the source and detector would have the same axial (z) extent, thus providing sufficient volumetric data. For the prototype system, this requirement is met by restricting the axial (z) FOV to 5 cm. The C-arm gantry was positioned horizontally and a rotating stage placed between the source and detector. A phantom consisting of three, 2.3 mm diameter stainless steel beads mounted on a cardboard cylinder was scanned with the system in step and shoot mode. We acquired 125 “views” of the phantom equally spaced over 360 degrees, along with 110 flat-field views. Each view includes projections from all source spots. Additionally, eight lower noise views of the phantom were acquired and used to determine the geometric misalignment. The raw phantom dataset was normalized by the averaged flat-field views. The data were reconstructed with a previously described algorithm. The algorithm corrects for misalignment and rebins the data into 2D parallel ray projections at multiple tilt angles, followed by a 3D filtered backprojection.

The resulting axial images show the beads and cylinder reconstructed accurately without significant artifacts. The noise in the resulting 0.4 mm slices, with 0.4 mm in-plane resolution, was 48 HU compared to a theoretically predicted 47 HU.

The successful acquisition and reconstruction of the initial IGCT dataset indicates system feasibility. Future work is planned to further characterize the system, including MTF, noise performance and acquisition of anatomical data.

J.S.,E.S.: Josh Star-Lack and Edward Solomon are employees of NexRay, Inc.N.J.P.,S.R.M.,T.G.,R.B.: Research funding was provided by GE Medical Systems

Gilat Schmidt, T, Bennett, R, Mazin, S, Star-Lack, J, Solomon, E, Pelc, N, First Images from a Table-top Inverse Geometry Volumetric CT System with a Large-area Scanned Source.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4415879.html