Feasibility of Multiparametric Magnetic Resonance Imaging of the Prostate at 7 T

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Abstract

Objectives

The aim of this study was to evaluate the technical feasibility of prostate multiparametric magnetic resonance imaging (mpMRI) at a magnetic field strength of 7 T.

Materials and Methods

In this prospective institutional review board–approved study, 14 patients with biopsy-proven prostate cancer (mean age, 65.2 years; median prostate-specific antigen [PSA], 6.2 ng/mL), all providing signed informed consent, underwent 7 T mpMRI with an external 8-channel body-array transmit coil and an endorectal receive coil between September 2013 and October 2014. Image and spectral quality of high-resolution T2-weighted (T2W) imaging (0.3 × 0.3 × 2 mm), diffusion-weighted imaging (DWI; 1.4 × 1.4 × 2 mm or 1.75 × 1.75 × 2 mm), and (1H) MR spectroscopic imaging (MRSI; real voxel size, 0.6 mm3 in 7:16 minutes) were rated on a 5-point scale by 2 radiologists and a spectroscopist.

Results

Prostate mpMRI including at least 2 of 3 MR techniques was obtained at 7 T in 13 patients in 65 ± 12 minutes. Overall T2W and DWI image quality at 7 T was scored as fair (38% and 17%, respectively) to good or very good (55% and 83%, respectively). The main artifacts for T2W imaging were motion and areas of low signal-to-noise ratio, the latter possibly caused by radiofrequency field inhomogeneities. For DWI, the primary artifact was ghosting of the rectal wall in the readout direction. Magnetic resonance spectroscopic imaging quality was rated fair or good in 56% of the acquisitions and was mainly limited by lipid contamination.

Conclusions

Multiparametric MRI of the prostate at 7 T is feasible at unprecedented spatial resolutions for T2W imaging and DWI and within clinically acceptable acquisition times for high-resolution MRSI, using the combination of an external 8-channel body-array transmit coil and an endorectal receive coil. The higher spatial resolutions can yield improved delineation of prostate anatomy, but the robustness of the techniques needs to be improved before clinical adoption of 7 T mpMRI.

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