MR Imaging and MR Spectroscopy in Prostate Cancer

Abstract

Multiparametric MR Imaging with high resolution T2-weighted imaging (HR-T2WI), diffusion weighted imaging (DWI), dynamic contrast enhanced MRI (DCE-MRI), and MR spectroscopy (MRS) plays a crucial role in the assessment, localization, staging, biopsy planning, and therapy monitoring of prostate cancer (PCa) through delivering unmatched soft tissue contrast as well as functional information especially regarding cell density, vascularization, and metabolism. It also helps identifying tumors missed on PSA testing, DRE, and TRUS-guided biopsy. HR-T2WI provides a clear depiction of the prostate zonal anatomy and is indispensable for PCa detection, localization, and accurate tumor staging. DWI adds information about cellular density by quantifying Brownian motion of interstitial water molecules and thereby enabling the differentiation of benign from malignant tissue. DCE-MRI is another functional imaging technique which allows for characterizing pharmacokinetic features reflecting the prostatic vascularization through a series of high temporal resolution T1-weighted images following the administration of contrast medium. In-vivo proton MRS investigates the biochemical constituents of prostate tissue noninvasively. Metabolic alterations caused by cancerous infiltration can be identified as well as metabolic response in the course of radiotherapy. While in the healthy gland citrate provides the predominant signal in MR spectra, strong accumulation of choline compounds indicates PCa, and the choline/citrate ratio may serve as suitable biomarker for malignancy. MRS allows simultaneous acquisition of spatially localized spectra from a multitude of tissue volumes as small as 1 cm3 or below, with complete prostate coverage.