Studies on clinical significance of metabolic or functional tumor imaging by clinical MR machine

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In addition to orient a tumor itself, specific characterization such as tumor grading and its viability on therapeutic intervention should be necessary to complete imaging diagnosis. PET is appeared to suit for this and with its ability of metabolic imaging, but it is not widely available. At present, we have attempted to use clinical MR machine as an alternative for PET as metabolic or functional imaging of brain tumor on radiation therapy and its clinical significance has been evaluated. Present studies consist of two parts : (1) metabolic imaging by in vivo ^1H MR spectroscopy (MRS), and (2) functional imaging by dynamic suceptiblity contrast MR imaging (DISC MRI).(1) Metabolic imaging by in vivo ^1H MR spectroscopy. To determine whether assessment of ^1H MRS is useful for predicting the outcome of radiotherapy on brain tumor, ^1H MRS studies were performed in eight patients with primary or metastatic brain tumor before and during radiotherapy. Among various spectroscopic metabolite peaks, lactate peak, that is represented by anaerobic glycolysis, substantially decreased in the radio sensitive cases as early as 20Gy, whereas the lactate peak did not decrease even at the end of therapy in radioresistant cases. It is concluded that assessment of the lactate peak on MRS adjunctivecly contribute to the early prediction of radiotherapeutic effect on brain tumors.(2) Functional imaging by dynamic susceptibility contrast MR imaging (DISC MRI). DISC MRI was performed on eleven patients with brain tumors before and after radiotherapy to determine whether this method is clinically useful for monitoring radiotherapeutic effect on brain tumors. The calculated integrating images, that represent regional cerebral blood volume (rCBV), were also produced for evaluation of the tumor vascular beds. Changes of the tumor vascular bed, angiogenesis, on radiotherapy were also appeared to be a good indicator of therapeutic effect as well as ^1H-MRS.