E2206. Application of High Spectral and Spatial Resolution (HiSS) MRI in Prostate: A Pilot Study
  1. Milica Medved; The University of Chicago
  2. Aritrick Chatterjee; The University of Chicago
  3. Ajit Devaraj; Philips Research North America
  4. Carla Harmath; The University of Chicago
  5. Grace Lee; The University of Chicago
  6. Aytekin Oto; The University of Chicago
  7. Gregory Karczmar; The University of Chicago
High Spectral and Spatial resolution (HiSS) MRI is an echo-planar spectroscopic imaging (EPSI)-based method that focuses on water and fat resonances. It acquires multi-echo and spectral information and has demonstrated high diagnostic potential in breast cancer. [1-3] Here, we evaluate its diagnostic potential in prostate cancer.

Materials and Methods:
Six patients scheduled for prostatectomy underwent prostate MRI without an endorectal (ER) coil, including T2-weigthed MRI, DWI, DCEMRI, and HiSS MRI (in-plane resolution 0.8-1.25 mm, three 3.0 mm slices, 0.5 mm gap, spectral resolution 2.6-3.5 Hz, TR/TE 463/230 - 652/162 ms, flip angle 90 deg, SENSE factor 1.5) acquired after contrast injection. The HiSS MRI slab was centered on the largest lesion seen on MRI and yielded a train of 127 phase-coherent gradient echo images. The echo train was Fourier transformed to obtain the proton spectrum in each voxel, reproducibly revealing water resonance detail. In the temporal domain, changes in voxel intensity were analyzed and linear (R) and quadratic (R1, R2) quantifiers of signal logarithm decay were calculated. [4] In the spectral domain, three signal scaling-independent parameters were calculated: water resonance peak width (PW), relative peak asymmetry (PRA), and relative peak distortion from ideal Lorentzian shape (PRD). [5-8] MRI and prostatectomy reports were consulted for outlining of 7 cancerous and 5 benign regions of interest (ROIs). The 6 parameters (R, R1, R2, PW, PRA, PRD) were calculated on a voxel-by-voxel basis and averaged over the ROIs. Differences between cancerous and benign ROIs were evaluated using the one-sided t-test. Diagnostic performance was evaluated via ROC analysis.

Spectral domain quantifiers performed better than temporal domain quantifiers, with receiver operator characteristic areas under the curve (ROC AUCs) of 0.89 (PW), 0.83 (PRA), and 0.94 (PRD). For R, R1 and R2, the corresponding values were 0.77, 0.86, and 0.66, respectively. Low absolute values of the coefficients of correlation between PW, PRD, and R1 (0.36 – 0.68) indicate that complementary information could be leveraged to improve accuracy.

These results demonstrated the feasibility of HiSS MRI in the prostate at 3T without an endorectal coil and its potential utility for lesion characterization. Water resonance structure quantifiers are complementary to the standard multi-parametric MRI of the prostate and could improve diagnostic accuracy. Morphological lesion information could provide further improvement.