William Robert Ross PhD, Presenter: Nothing to Disclose

Dawn Cavanaugh, Abstract Co-Author: Nothing to Disclose

Paul FitzGerald, Abstract Co-Author: Nothing to Disclose

Samit Basu, Abstract Co-Author: Nothing to Disclose

Richard Beaver, Abstract Co-Author: Nothing to Disclose

Dianna Cody PhD, Abstract Co-Author: Nothing to Disclose

This study presents results obtained from a flat-panel CT (FP VCT) system, developed by GE Global Research, operating at the U.T.M.D. Anderson Cancer Center. Image quality performance, radiation dose measurement results, and typical images acquired in-vivo will be presented.

This prototype uses two 20-cm x 20-cm, 200-mm pitch a-Si panels, and a standard CT x-ray source. Maximum scanner field of view ranges from 13 cm to 33 cm. Image data typically consists of 500-2000 projections over 360 degrees. Acquisitions have been reconstructed using variants of the Feldkamp, Davis & Kress (FDK) algorithm. Image quality data were obtained using industry standard phantoms. Acquisitions were performed at energies ranging from 50-120 kVp, and tube currents ranging from 20-200 mA. Scan time per rotation ranged between 2-8 seconds.

Measured spatial resolution using a 25-micron Tungsten wire object is approximately 25 lp/cm (10% MTF), reconstructed using a custom kernel. Spatial resolution specification for a GE LightSpeed16 CT scanner is 14-15 lp/cm (10% MTF). Low contrast resolution results were 5mm at 1.5% contrast (6.5 cGy). Low contrast resolution specification for a GE LightSpeed16 CT scanner is 5mm at 0.3% contrast (1.3 cGy). Conventional CT Dose Index (CTDI) measurements were obtained using a 16 cm diameter acrylic phantom and a standard CT ion chamber. Scan parameters were 120 kV, 30 mA, 4 sec (4.2 cm z-axis coverage). CTDI for this system was measured at 3 cGy, compared to 2 cGy when a similar technique (120 kV, 120 mA, 1 sec) was used for a GE LightSpeed16 CT scanner (20 mm z-axis coverage).

Results presented here indicate a substantial gain in spatial resolution over currently available commercial CT scanners. The low-contrast performance of this flat-panel CT system is reduced compared to clinical CT scanners. The relative increase in radiation dose is due to less precise collimation and less filtration on the VCT scanner and is not necessarily a feature of flat-panel CT in general. Due to the wide x-ray beam in the z-axis direction radiation dose was likely underestimated. New methods for radiation dose assessment may be required for wider x-ray beam widths.

W.R.R.,S.B.,P.F.: Employed by General Electric Global Research

Ross, W, Cavanaugh, D, FitzGerald, P, Basu, S, Beaver, R, Cody, D, Performance and Pre-clinical Results from a Flat-panel-based Volumetric CT System.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4403667.html