Fetal MR Thermometry Using Diffusion MRI.

Motivation: Fetal absolute temperature monitoring ensures safety and stability during fetal MR scans, assessing thermoregulation, and pathological conditions. Noninvasive methods are needed. Goal(s): To develop a noninvasive method for computing fetal absolute temperature by leveraging mean diffusivity from fetal brain DTI and true diffusivity from IVIM-based calculations in the amniotic fluid. Approach: Mean diffusivity estimates from cerebrospinal-fluid (CSF), and pure water diffusion in amniotic fluid were obtained. Absolute temperature maps were estimated using a biophysical model. Results: The study confirms that diffusivity-based temperature estimates in fetal CSF and amniotic fluid align with physiological expectations in four fetuses across different gestational ages and acquisition settings. Impact: We implemented a method to directly compute the average fetal temperature from the CSF and the amniotic fluid diffusivity to measure the absolute fetal temperature.