PURPOSE: Understanding the internal dynamics of prostate injections, particularly injection pattern distribution is a key step to developing new therapies for prostate disease that may be best served with a direct injection approach Due to excellent properties involving liquid contrast agents, MRI can be used for targeting, monitoring of injections into organs, tissues MATERIALS AND METHODS: Eleven intraprostatic injections were performed in vivo with canines using a custom transrectal guiding, imaging system for use in a standard 1 5 T MR scanner In addition, 25 injections were performed on excised cadaveric human prostates, using a MedRad Spectris injector system MRI was used to guide the injections, monitor intraparenchymal injection distribution RESULTS: T1, T2-weighted MR images were correlated with histology to produce three-dimensional data sets that can be used to analyze trends in injection patterns This analysis was used to develop strategies for injection prediction such as gadolinium pre-injections, diffusion-weighted imaging guidance In addition, a rough model of prostate injections is described, and a preliminary injection guide is developed that takes into account the individual clinician’s goals for therapy CONCLUSIONS: MR visualization of injected therapeutic agents allows for prediction, monitoring of drug distributions, possibly improving efficacy, reducing side effects Injection analysis, modeling may be used to assist in optimizing clinical treatments that require or would benefit from focal parenchymal injections into the prostate