Comparison of 64-slice CT Perfusion Imaging with Contrast-enhanced CT for Evaluating the Target Volume for Three-dimensional Conformal Radiotherapy in the Rabbit VX2 Brain Tumor Model

CT perfusion imaging is a promising technique for delineating the target volume for three-dimensional conformal radiotherapy, but it is difficult in humans to obtain gross pathological samples at the same level of the brain tumor to evaluate this technique. The aim of this study was to use the BV map of CT perfusion imaging to assess the target volume in the rabbit VX2 brain tumor model, which has similar characteristics to human brain tumor, and compare the results to those of CECT. New Zealand white rabbits were used for the animal model. After tumor cell implantation 21 rabbits underwent 64-slice CT scanning. The target slice was selected and the maximum major axis length and minimum minor axis length of the tumor in the target slice on BV maps and contrast-enhanced CT images were measured. Pathological specimens were obtained from the rabbit brains which were removed intact. The GTV and CTV of the imaging methods were compared. Scanning was successful in 20 rabbits. The CECT images showed the target area for the VX2 tumor in 16 rabbits. The BV maps showed the target area for the tumor in 20 rabbits. The probability was 95% that the GTV determined by pathology can be covered completely when BV maps are used. CT perfusion imaging appears to be a promising technique for delineating the GTV of brain tumors in clinical practice.