Introduction: Multiparametric magnetic resonance imaging (MRI) of the prostate involves morphologic and functional imaging techniques, which could potentially enable to distinguish between common benign prostate diseases, especially prostatitis and prostate cancer. The aim of this study was to determine the apparent diffusion coefficient (ADC) and the tissue sodium concentration (TSC) in 2 different regions of the human prostate, that is, the central gland (CG) and the peripheral gland (PG), by means of standard hydrogen-1 (H) MRI and quantitative sodium-23 (Na) MRI at 3 T to increase the spectrum of diagnostic parameters for prostate examinations.
Methods: All measurements were performed on a 3-T clinical whole-body magnetic resonance (MR) scanner. Na MR images were acquired with density-adapted 3-dimensional radial sequence and isotropic voxel resolution of 5 × 5 × 5 mm. After approval by the institutional review board and informed consent were obtained, 8 healthy volunteers were included in this study. Diffusion-weighted imaging and T2-weighted images were also recorded and hence enabled the correlation of measured TSC values with current state-of-the-art H MRI techniques.
Results: The ADC in both subregions was measured to be at normal levels (CG, 1.19 [0.09] ×10 mm/s; PG, 1.54 [0.14] × 10 mm/s) in all 8 volunteers. Good spatial resolution of the Na images allowed for an easy identification of the same subregions from the Na MR images. In healthy adult volunteers (age, 29 [2] years), the TSC was measured lower in central (55 [15] mmol/L) and higher in peripheral (69 [16] mmol/L) prostate tissue. A correlation between the TSC and the ADC in the 2 subregions was found in the same volunteer group (Pearson correlation coefficient = 0.87).
Discussion: For the first time, TSC was spatially resolved in human prostate tissue by means of Na MRI. Interestingly, the herein found TSC values of ∼60 mmol/L were half as high as in a previously reported Na MRI study where prostate TSC was measured in 5-month-old mice. Future studies are required to determine the prostate TSC in cancer patients as well as in older volunteers. In conclusion, TSC can be measured in humans with sufficiently high spatial and temporal resolution at 3 T and could hence provide an additional noninvasive marker for the diagnosis of various prostate pathologies.