ROLE OF CT PERFUSION IN ADULT BRAIN TUMORS (DIAGNOSIS, GRADING AND FOLLOW UP)

Abstract

SUMMARY C T Perfusion is a technique that can be readily incorporated into the existing CT protocols to provide an in vivo marker of tumor angiogenesis. By capturing physiological information reflecting the tumor vasculature, perfusion CT can be useful for diagnosis and therapeutic monitoring. Dynamic perfusion imaging is based on the assessment of tissue-related distribution of the contrast medium, which acts as a tracer. Micro-vascularization and diffusion across the endothelial membrane into the interstitial space determine the distribution of contrast agent after infusion. The absolute perfusion parameter correspond to the micro-vascular density, which has been considered to be the ‘gold standard’ for such an evaluation, because of its direct association with angiogenic growth factor expression, tumor growth, and metastatic occurrence (Ellika, 2008). In accordance with previously published studies, significantly increased CBV was noted in high-grade gliomas. The increased vascular proliferation of the neoplastic tissue and the hypothesis that feeding arterioles are more vasodilated than normal in neoplasm support these findings (Schramm, 2010). Increased vascular permeability has also been correlated with malignancy and has been evolving as a surrogate marker of tumor angiogenesis and, thus, tumor grade. Higher permeability has been associated with higher tumor grade like high-grade gliomas and lymphomas in comparison with healthy tissue. Both entities are characterized by a histo-pathologically proven blood-brain barrier disturbance (Schramm, 2010). In spite of the feasible advantages of PCT over PWI, the relative limitations of PCT are the radiation dose involved with the procedure and also the limited coverage area of the cerebral parenchyma compared with PWI. The latter limitation could be overcome in the future with the new volume PCT technique, which enables the measurement of the whole brain and three-dimensional qualitative and quantitative imaging. Thus, whole-brain PCT could lead to even more precise grading of intra-axial brain tumors (Schramm, 2010).