Characterization of Prostate Cancer With 3T MR

In our laboratory we have combined the use of new 3T clinical magnetic resonance (MR) technology, dynamic-contrast enhancement (DCE), and a unique endorectal-coil (ERC) probe in order to non-invasively obtain images of the prostate gland with higher signal-to-noise resolution and better spectral dispersion than has been previously achieved. This imaging strategy acquires higher-resolution images with smaller voxel sizes than has been possible with prior MR technology and more comprehensive tissue sampling compared to other pre-surgical assessments. This methodology should make it feasible to assess prostate-tissue morphology and additional features of prostate cancer such as tissue metabolism, tissue kinetics, and the vascular microenvironment, and thus provide a non-invasive tool to: 1) detect extra-capsular spread, 2) detect specific areas within the prostate that harbor cancer, 3) determine the aggressiveness of the cancer and 4) direct biopsy and treatment specifically to diseased areas.

In order to prospectively validate these goals we will recruit successive patients who have been scheduled for prostate removal to participate to our protocol. Each patient will be studied with an ERC MRI at 3T using T2-weighted (T2W) imaging, DCE 3D T1-weighted imaging and MR spectroscopy (MRS). A pathologist using whole mount preparations will independently analyze each patient's prostate specimen. The whole mount data will be used as the standard against which we will compare the observations and data obtained from the 3T MRI findings.

Aim 1: To evaluate the accuracy of T2W MRI, DCE-MRI and their combined data for staging prostate cancer.

Supplementing T2W imaging with the high-resolution capability of 3TMR, we will apply standard morphologic criteria used at 1.5T to determine the presence or absence of extracapsular extension (ECE) of disease. The possible incremental value of high spatial resolution, dynamic contrast-enhanced data will be investigated. MRI results will be compared to ECE determination at whole-mount pathology.

Aim 2: To evaluate the accuracy of MRI in determining tumor volume in the prostate gland.

Using dynamic-contrast enhanced MRI with parametric analyses and T2-weighted images, both at smaller voxel sizes than have been used previously, will be our approach. Tumor volumes determined with MRI will be compared to those determined at pathology.

Aim 3: To evaluate the accuracy of MRI in grading prostate cancer.

The enhanced resolution available at 3T offers new opportunities to compare Gleason grades with independent and combined assessments of tissue kinetics and metabolism. Pixel by pixel parametric analyses will be obtained. Furthermore, choline to citrate and choline plus creatine to citrate ratios determined using MRS techniques will be obtained. Single voxel techniques will first be employed, followed by 3D chemical shift imaging, when the latter becomes available at 3T. DCE and MRS data will be compared both separately and in combination to the histologic Gleason scores of the comparable tumor identified at whole mount pathology.