Flat panel detector-based cone beam CT lung imaging: preliminary system evaluation

The purpose of this study is to perform a preliminary evaluation of a newly constructed flat panel detector (FPD)-based system for cone beam CT imaging applications. A prototype flat-panel detector-based cone beam CT imaging system has been designed and constructed by modifying a GE HiSpeed Advantage CT scanner. The prototype consists of a modified GE CT HiSpeed Advantage CT gantry, an x-ray tube, a 397mm x 298mm Varian PaxScan 4030CB real time flat-panel detector mounted on the gantry, a CT table and an on-gantry PC to control image acquisition. Another PC workstation serving as an operating console controls the CT gantry and CT table, and sends trigger pulses to dedicated electronic interface modules to control radiographic exposure and to initiate data acquisition. Captured image data sets are first stored in the on-gantry computer and then downloaded from the on-gantry PC to the operating console for high-speed 3D image reconstruction. During data acquisition, the x-ray tube and the FPD can be rotated on the gantry over Nx360 degrees due to integrated slip ring technology. With a single scan, this device is able to acquire up to three hundred two-dimensional projections (1024x768 x 16 bits) for direct 3D reconstruction within 10 seconds. This system was used for a series of preliminary phantom studies and small animal studies. Using the continuous scan mode of the scanner, a few hundred projections were acquired for all volume scans. Direct 3D reconstructions were obtained to evaluate the system for cone beam CT for lung imaging applications. The preliminary results indicate that the newly built flat panel detector-based cone beam CT scanner works as expected and the low contrast resolution of the FPD-based CBCT system is approaching that of a multi-slice CT.