Purpose: To describe the practical technical aspects of magnetic resonance imaging (MRI) and magnetic resonance spectroscopic imaging (MRSI) and to summarize the current and potential future status of MRI and MRSI in the localization, staging, treatment planning, and post-treatment follow-up of prostate cancer. Technique: Published contemporary series of patients with prostate cancer evaluated by MRI and MRSI before or after radiation therapy were reviewed, with particular respect to the role of MRI and MRSI in treatment planning, outcome prediction, and detecting local recurrence. Results: Volumetric localization is of limited accuracy for tumors less than 0.5 cm 3. Staging by MRI, which is improved by the addition of MRSI, is of incremental prognostic significance in patients with moderate and high-risk tumors. The finding of more than 5 mm of extracapsular extension prior to radiation seems to be of particular negative prognostic significance, and the latter group may be candidates for more aggressive supplemental therapy. The use of MRI to assist radiation treatment planning has been shown to improve outcome. MRSI may be helpful in the detection of local recurrence after radiation. Conclusions: Only MRI and MRSI allow combined structural and metabolic evaluation of prostate cancer location, aggressiveness, and stage. Combined MRI and MRSI provide clinically and therapeutically relevant information that may assist in planning and post-treatment monitoring in patients undergoing radiation therapy.
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