Implementation and evaluation of 4D cone beam CT (CBCT) reconstruction

Tumor angiogenesis is the process by which new blood vessels are formed from the existing vessels in a tumor to promote tumor growth. Tumor angiogenesis has important implications in the diagnosis and treatment of various solid tumors. Flat panel detector based cone beam CT opens up a new way for detection of tumors, and tumor angiogenesis associated with functional CBCT has the potential to provide more information than traditional functional CT due to more overall coverage during the same scanning period and the reconstruction being isotropic resulting in a more accurate 3D volume intensity measurement. A functional study was conducted by using CBCT to determine the degree of the enhancement within the tumor after injecting the contrast agent intravenously. For typical doses of contrast material, the amount of enhancement is proportional to the concentration of this material within the region of interest. A series of images obtained at one location over time allows generation of time-attenuation data from which a number of semi-quantitative parameters, such as enhancement rate, can be determined. Computer simulations prove the superiority of half scan over full scan in terms of more accurately delineating the time-intensity curve, and all the simulation parameter settings are based on the actual CBCT prototype. An experiment study was conducted on our prototype CBCT system, and a full and half scan scheme is used to determine the time-intensity curve within the ROI of the mouse. The CBCT has an x-ray tube, a gantry with slip ring technology, and a 40x30 cm Varian Paxscan 4030CB real time FPD.