Influence of field strength on quantitative parameters and feature stability in the assessment of the ovaries using 1.5-T and 3-T MRI

BackgroundLittle is known of the influence of scanner field strength on quantitative diffusivity variables, especially kurtosis in healthy ovaries.PurposeTo evaluate the influence of scanner field strength on quantitative diffusion variables in pelvic MRI of the ovaries.Material and MethodsThis prospective, single-centre study consisted of repeated 1.5-T and 3-T examinations in 30 female volunteers (mean age=27.9 years, age range=20.3-45.2 years) from July 2017 to September 2019. Multi b-value DWI 0, 50, 100, 800, 1500, 2000 s/mm² was acquired over three timepoints during the menstrual cycle. Ovaries were segmented at b = 1500 s/mm². Median apparent diffusion coefficient (ADC) and advanced kurtosis parameters D_app and K_app were calculated. Statistical analysis was performed with the variations of diffusivity variables being compared between 1.5-T and 3-T MRI using a Mann-Whitney rank-sum test.ResultsMedian ADC and D_app (µm²/ms) did not statistically differ. Median ADC were 1.509 (range=1.371-1.610), 1.619 (range=1.463-1.747), and 1.511 (range=1.423-1.639) at 1.5 T; 1.542 (range=1.428-1.682), 1.658 (range=1.510-1.806), and 1.572 (range=1.455-1.709) at 3 T (<i>P</i> = 0.14, 0.19, and 0.07), whereas median D_app were 2.024 (range=1.913-2.152), 2.192 (range=2.010-2.327), and 2.045 (range=1.958-2.170) at 1.5 T; 2.013 (range=1.952-2.188), 2.179 (range=2.018-2.327), and 2.082 (range=1.959-2.194) at 3 T (<i>P</i> = 0.77, 0.99, and 0.34) for timepoints 1, 2, and 3, respectively. Statistical comparison of K_app revealed significant differences for all timepoints: 0.629 (range=0.595-0.652), 0.604 (range=0.574-0.651), and 0.622 (range=0.581-0.664) at 1.5 T; 0.601 (range=0.563-0.626), 0.567 (range=0.526-0.633), and 0.599 (range=0.541-0.650) at 3 T (<i>P</i> < 0.001, 0.005, and 0.03).ConclusionDiffusivity mapping in the ovaries provides similar absolute median diffusion values, but statistically significant differences in absolute kurtosis values between 1.5 T and 3 T.