Synthetic quantitative MRI through relaxometry modelling

Abstract

Quantitative MRI (qMRI) provides standardized measures of specific physical parameters that are sensitive to the underlying tissue microstructure and are a first step towards achieving maps of biologically relevant metrics through in vivo histology using MRI. Recently proposed models have described the interdependence of qMRI parameters. Combining such models with the concept of image synthesis points towards a novel approach to synthetic qMRI, in which maps of fundamentally different physical properties are constructed through the use of biophysical models. In this study, the utility of synthetic qMRI is investigated within the context of a recently proposed linear relaxometry model. Two neuroimaging applications are considered. In the first, artefact‐free quantitative maps are synthesized from motion‐corrupted data by exploiting the over‐determined nature of the relaxometry model and the fact that the artefact is inconsistent across the data. In the second application, a map of magnetization transfer (MT) saturation is synthesized without the need to acquire an MT‐weighted volume, which directly leads to a reduction in the specific absorption rate of the acquisition. This feature would be particularly important for ultra‐high field applications. The synthetic MT map is shown to provide improved segmentation of deep grey matter structures, relative to segmentation using T 1‐weighted images or R 1 maps. The proposed approach of synthetic qMRI shows promise for maximizing the extraction of high quality information related to tissue microstructure from qMRI protocols and furthering our understanding of the interrelation of these qMRI parameters.

Gray Matter Alterations in Early and Late Relapsing-Remitting Multiple Sclerosis Evaluated with Synthetic Quantitative Magnetic Resonance Imaging

“…Quantitative MRI (qMRI) provides an absolute measurement of the physical parameters of the underlying tissue microstructure and hence enables a more objective evaluation of disease 8 . In MS, qMRI allows evaluation of the development and progression of GM pathology by, for example, indirect mapping of myelin density 6 .…”

The Combined Quantification and Interpretation of Multiple Quantitative Magnetic Resonance Imaging Metrics Enlightens Longitudinal Changes Compatible with Brain Repair in Relapsing-Remitting Multiple Sclerosis Patients

“…Combining multiple qMRI techniques in a clinically compatible protocol is challenging (e.g., due to motion, scan time, reproducibility, etc.) but there are currently ongoing efforts toward fast and reproducible protocols applying combined and accelerated acquisitions ( 21 – 23 ), synthetic computation of qMRI metrics ( 22 ) and qMRI fingerprinting ( 24 ).…”

Mapping human laryngeal motor cortex during vocalization

“…The location of the ventral 647 boundary of the somatomotor cortex, indicated by a steep gradient of myelin values, slightly 648 varies across the four maps, but this boundary is consistently more ventrally located in the 649 right compared with the left hemisphere. 650The fours maps that correlate with cortical myelin (T1w/T2w, MPMMT, MPMR1 and MPMR2*) 652 are sensitive to different biophysical properties of the myelin, but it should be noted that their 653 sensitivity profiles are not completely independent(Callaghan et al 2016). Therefore, some 654 dissimilarities regarding the distribution of myelin along the cortex can be observed across the655 maps.…”