Prostate cancer, perhaps more than any other malignant disease process, poses questions that only imaging can answer. MRI has the potential to yield more information about the prostate gland than any other imaging modality. Because of its parametric capabilities, MRI in a single exam can produce high-resolution anatomic imaging with excellent soft-tissue contrast. It also can add spectroscopic information about the function of the tissue to characterize both the aggressiveness and volume of disease. MRI can generate diffusion-weighted images that provide a microstructural picture of intracellular/extracellular water and dynamic contrast-enhanced images that depict development of the microvessels that are necessary for tumors to grow and metastasize.

Characterizing prostate cancer with MRI nevertheless is becoming more difficult now that the disease is being found at a much earlier stage in much smaller volumes.

"Years ago, with just high-resolution anatomic imaging and spectroscopy at 1.5T, we did a pretty good job with the cancers we were detecting at the time, which tended to be larger volume. But we find ourselves at 1.5T not having adequate spatial resolution for spectroscopy, or for functional data with diffusion and perfusion-weighted imaging, to deal with early-stage disease," said Dr. John Kurhanewicz, a professor of radiology at the University of California, San Francisco.

The prostate gland is a very small, highly heterogeneous organ with multiple zones, numerous structures, and varying degrees of metabolism, and it often harbors benign conditions as well as cancer, all of which make it difficult to image.

Although current platforms for 3T imaging of the prostate are not very robust and 1.5T packages do not easily translate to 3T, researchers are turning to high-field scanning because of what its higher signal-to-noise ratio can offer.

Increased SNR allows radiologists to enhance different parts of the scan. It can be used to improve pixel resolution in the same amount of scanning time or get the same pixel resolution in a faster scan.

"Higher spatial resolution will make it easier to see the margins of the tumor and determine if it is deforming the capsule of the gland and is inside or outside of the gland, which is the classic branch point for clinical decision making," said Dr. Dan Cornfeld, an assistant professor in the department of diagnostic radiology at Yale University.