Jochen Cammin PhD, Presenter: Nothing to Disclose

Somesh Srivastava PhD, Abstract Co-Author: Nothing to Disclose

Katsuyuki Taguchi PhD, Abstract Co-Author: Research grant, Siemens AG Research grant, Koninklijke Philips Electronics NV

To compare the performance of a tabletop photon counting x-ray detector CT system (PCXD-CT) with a clinical dual energy CT system (DECT).

The tabletop CT scanner, designed to perform single source spectral CT in a configuration similar to clinical CT, consisted of CdTe photon counting x-ray detectors, an x-ray tube manufactured for clinical multislice CT systems, and a bowtie filter. Ellipsoidal water phantoms were scanned with various inserts, including Gadolinium contrast agent, bone, and oil. PCXD-specific deadtime losses at high count rates were corrected, and images of multiple energy windows were reconstructed using filtered backprojection. The phantoms were also scanned on a clinical DECT system using a 100kVp/140kVp+Sn dual energy protocol at comparable dose. Images from both systems were evaluated in a low contrast region in terms of normalized noise and contrast-noise-ratio (CNR).

The image quality of the PCXD scanner under clinical configuration was comparable to DECT. The normalized noise (|sigma/mean|) was 0.46 at 46 keV, 0.25 at 76 keV and, 0.14 at 99 keV for PCXD-CT and 0.24 at 70 keV for the DECT mixed image. CNR was 2.0 at 46 keV, 3.3 at 76 keV and 6.1 at 99 keV for PCXD-CT and 4.2 at 70 keV for DECT. The relative increase in CNR from the first to second energy bin in PCXD-CT is 65% and 85% from the second to third bin and can be explained by the noise decreasing faster than the contrast. Reconstructed CT numbers of inserts were in agreement between both systems and showed the expected decrease with energy.

We have developed a tabletop CT scanner with photon counting detectors and clinical configuration and scanned water phantoms with various inserts. Noise and CNR with this new detector technology were similar to clinical DECT.

The study shows that CT with PCXDs under clinical configuration yields image quality comparable to that of conventional CT. PCXDs may increase contrast further and improve tissue identification.

Cammin, J, Srivastava, S, Taguchi, K, Performance Comparison: A Tabletop Photon Counting X-ray Detector CT System vs Clinical Dual-Energy X-ray CT.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11009477.html