High-resolution characterisation of the aging brain using simultaneous quantitative susceptibility mapping (QSM) and R2* measurements at 7 T

Abstract

Quantitative susceptibility mapping (QSM) has recently emerged as a novel magnetic resonance imaging (MRI) method to detect non-haem iron deposition, calcifications, demyelination and vascular lesions in the brain. It has been suggested that QSM is more sensitive than the more conventional quantifiable MRI measure, namely the transverse relaxation rate, R2*. Here, we conducted the first high-resolution, whole-brain, simultaneously acquired, comparative study of the two techniques using 7 Tesla MRI. We asked which of the two techniques would be more sensitive to explore global differences in tissue composition in elderly adults relative to young subjects. Both QSM and R2* revealed strong agerelated differences in subcortical regions, hippocampus and cortical grey matter, particularly in superior frontal regions, motor/premotor cortices, insula and cerebellar regions. Within the basal ganglia system-but also hippocampus and cerebellar dentate nucleus-, QSM was largely in agreement with R2* with the exception of the globus pallidus. QSM, however, provided superior anatomical contrast and revealed age-related differences in the thalamus and in white matter, which were otherwise largely undetected by R2* measurements. In contrast, in occipital cortex, age-related differences were much greater with R2* compared to QSM. The present study, therefore, demonstrated that in vivo QSM using ultra-high field MRI provides a novel means to characterize age-related differences in the human brain, but also combining QSM and R2* using multigradient recalled echo imaging can potentially provide a more complete picture of mineralization, demyelination and/or vascular alterations in aging and disease.

Quantitative Evaluation of Iron Content in Idiopathic Rapid Eye Movement Sleep Behavior Disorder

“…In addition, long scanning periods may be accompanied by significant head movement in PD patients, thus resulting in worse image quality. Therefore, taking resolution and scan time into account, the application of nonisotropic resolution is accepted and has been applied in several studies on PD …”

The choice of embedding media affects image quality, tissue R2*, and susceptibility behaviors in post‐mortem brain MR microscopy at 7.0T

“…Turning to R 2 * and QSM, the present study investigated parametric maps that were overall in agreement with known patterns of tissue iron concentration in the human brain (i.e., ROIs were assorted from the highest to lowest R 2 * and QSM as follows: GP, putamen, CN, WM, and cortex). In addition, higher intersubject variability of R 2 * and/or QSM measurements were observed for basal ganglia compared to WM and cortex, presumably because of heterogenous age‐related iron deposition . Despite the effects of embedding media on the SNR and CNR of GRE images, the overall quality and CNR of deep grey matter nuclei in R 2 * parametric maps were similar irrespective of embedding medium used.…”

Combined Diffusion Tensor Imaging and Apparent Transverse Relaxation Rate Differentiate Parkinson Disease and Atypical Parkinsonism

“…It is known that age significantly affects iron and R2* values in basal ganglia structures. 37 Thus, these age effects may mask the disease-related changes in the PUT. Second, different R2* technique used among the studies may influence results.…”