Multiparametric magnetic resonance imaging in prostate cancer: present and future

Abstract

Purpose of review: The purpose of this article is to review the current status of advanced MRI techniques based on anatomic, metabolic and physiologic properties of prostate cancer with a focus on their impact in managing prostate cancer patients.

Recent findings: Prostate cancer can be identified based on reduced T2 signal intensity on MRI, increased choline and decreased citrate and polyamines on magnetic resonance spectroscopic imaging (MRSI), decreased diffusivity on diffusion tensor imaging (DTI), and increased uptake on dynamic contrast enhanced (DCE) imaging. All can be obtained within a 60-min 3T magnetic resonance exam. Each complementary method has inherent advantages and disadvantages: T2 MRI has high sensitivity but poor specificity; magnetic resonance spectroscopic imaging has high specificity but poor sensitivity; diffusion tensor imaging has high spatial resolution, is the fastest, but sensitivity/specificity needs to be established; dynamic contrast enhanced imaging has high spatial resolution, but requires a gadolinium based contrast agent injection, and sensitivity/specificity needs to be established.

Summary: The best characterization of prostate cancer in individual patients will most likely result from a multiparametric (MRI/MRSI/DTI/DCE) exam using 3T magnetic resonance scanners but questions remain as to how to analyze and display this large amount of imaging data, and how to optimally combine the data for the most accurate assessment of prostate cancer. Histological correlations or clinical outcomes are required to determine sensitivity/specificity for each method and optimal combinations of these approaches.

Figure 1

An example of a multiparametric 3T magnetic resonance exam of a 55-year-old patient with a prostate specific antigen of 8.46 ng/ml and biopsy-proven cancer (left apex, 1/12 cores having 5 mm of G3+3) (a) T₂ weighted MRI showing a region of low signal intensity lesion (red arrows) in the right apex. (b) Corresponding spectral 0.16cm³ array showing abnormal spectra (red box) in the same region as the suspicious region of low T₂ signal intensity. (c) A calculated water diffusion image demonstrating a reduction in intensity in the region of prostate cancer. (d) The contrast uptake curves from the region of prostate cancer (yellow) was more dramatic and washed-out faster than healthy prostate peripheral zone (green) tissue on dynamic contrast enhanced MRI. Prostate cancer in the left apex was confirmed at surgery.