Three-dimensional magnetic resonance spectroscopic imaging of brain and prostate cancer

Clinical applications of magnetic resonance spectroscopic imaging (MRSI) fo r the study of brain and prostate cancer have expanded significantly over t he past 10 years. Proton MRSI studies of the brain and prostate have demons trated the feasibility of noninvasively assessing human cancers based on me tabolite levels before and after therapy in a clinically reasonable amount of time, MRSI provides a unique biochemical "window" to study cellular meta bolism noninvasively, MRSI studies have demonstrated dramatic spectral diff erences between normal brain tissue (low choline and high N-acetyl aspartat e, NAA) and prostate (low choline and high citrate) compared to brain (low NAA, high choline) and prostate (low citrate, high choline) tumors. The pre sence of edema and necrosis in both the prostate and brain was reflected by a reduction of the intensity of all resonances due to reduced cell density . MRSI was able to discriminate necrosis (absence of all metabolites, excep t lipids and lactate) from viable normal tissue and cancer following therap y. The results of current MRSI studies also provide evidence that the magni tude of metabolic changes in regions of cancer before therapy as well as th e magnitude and time course of metabolic changes after therapy can improve our understanding of cancer aggressiveness and mechanisms of therapeutic re sponse. Clinically, combined MRI/MRSI has already demonstrated the potentia l for improved diagnosis, staging and treatment planning of brain and prost ate cancer. Additionally, studies are under way to determine the accuracy o f anatomic and metabolic parameters in providing an objective quantitative basis for assessing disease progression and response to therapy.