Noninvasive assessment of perfusion in virus-associated VX2 tumors using MR spin labeling technique

The purpose of this study was to evaluate an MR arterial spin-labeling technique to characterize regions of hyper- and hypovascularity in virus-associated rabbit VX2 tumors. Shope papillomavirus-associated VX2 carcinoma cells were implanted bilaterally in the thigh musculature of 17 New Zealand White rabbits. MR imaging sequences included a T2-weighted sequence and the arterial spin-labeling technique, flow-sensitive alternating inversion recovery with an extra radiofrequency pulse (FAIRER). Areas of viable and non-viable tumor were estimated based on the spin echo imaging sequences. Perfusion images were obtained from a magnitude subtraction of the labeled from the unlabeled images from the FAIRER sequence. Region of interest (ROI) analysis was performed in muscle, viable tumor regions, and necrotic tumor regions. Mean ROI signal intensities for viable tumor vs. muscle and necrotic tumor vs. muscle were compared using the student t-test. Spin echo imaging demonstrated tumors in 30 of 34 thighs. Perfusion images were successfully obtained in all cases. Mean ROIs were significantly greater in regions of viable tumor compared to those in muscle (p < 0.001). Mean ROIs were significantly less in regions of necrotic tumor compared to those in muscle (p < 0.001). Virus-associated VX2 tumors serve a good model for evaluating arterial spin labeling technique. This technique may be valuable in diagnosing hypervascular areas of tumors that would be amenable to preoperative embolization, such as intracranial meningiomas.