Using diffusion MRI for measuring the temperature of cerebrospinal fluid within the lateral ventricles

Abstract

Aim:Hypothermia is often induced to reduce brain injury in newborns, following perinatal hypoxic–ischaemic events, and in adults following traumatic brain injury, stroke or cardiac arrest. We aimed to devise a method, based on diffusion-weighted MRI, to measure non-invasively the temperature of the cerebrospinal fluid in the lateral ventricles.Methods:The well-known temperature dependence of the water diffusion constant was used for the estimation of temperature. We carried out diffusion MRI measurements on a 3T Philips Achieva Scanner involving phantoms (filled with water or artificial cerebrospinal fluid while slowly cooling from 41 to 32°C) and healthy adult volunteers.Results:The estimated temperature of water phantoms followed that measured using a mercury thermometer, but the estimates for artificial cerebrospinal fluid were 1.04°C lower. After correcting for this systematic difference, the estimated temperature within the lateral ventricles of volunteers was 39.9°C. Using diffusion directions less sensitive to cerebrospinal fluid flow, it was 37.7°C, which was in agreement with the literature.Conclusion:Although further improvements are needed, measuring the temperature within the lateral ventricles using diffusion MRI is a viable method that may be useful for clinical applications. We introduced the method, identified sources of error and offered remedies for each.

Automated temperature calculation method for DWI-thermometry: The usefulness of LV probability map on healthy subjects

“…The diffusion coefficient along the direction of motion probe gradient i was calculated by equation (1) and converted to a temperature [1] …”

“…Previous papers [1][2][3][4][5][6] have employed manual extraction of the LV area. The method proposed in this paper allows the user to automatically extract the effective CSF region for DWI thermometry.…”

“…This method has already been applied for measuring deep brain temperature in healthy volunteers [1], for determining the relationship between tympanic temperature and deep brain temperature [2], the age-dependence of deep brain temperature in healthy volunteers [3], and applications for Moya moya disease [4] ,head trauma [5], and idiopathic normal pressure hydrocephalus [6].…”

Acquisition Guidelines and Quality Assessment Tools for Analyzing Neonatal Diffusion Tensor MRI Data

“…A 1°difference in temperature leads to a 2-3% difference in ADC. 51,52 It will therefore be necessary to maintain the child at a constant temperature during scanning. Also, consistent core temperatures are necessary in studying group differences or performing a longitudinal study because the differences in MD or FA between ages, groups, and therapies are small.…”

Ventricular Temperatures in Idiopathic Normal Pressure Hydrocephalus (iNPH) Measured with DWI-based MR Thermometry

“…6 -12 Of the various MR imaging methods, post-processing of the diffusion-weighted image (DWI) is clinically useful. 11,12 MR images are constructed from the encoding spin of molecules, and diffusion is a parameter that reflects the thermal motion of molecules. Based on the MR characteristics of the brain, the diffusion coefficient increases with the elevation of brain temperature and increased activity of free water.…”