Potential of Diffusion Tensor Imaging and Relaxometry for the Detection of Specific Pathological Alterations in Parkinson's Disease (PD)

Abstract

The purpose of the present study was to evaluate the potential of multimodal MR imaging including mean diffusivity (MD), fractional anisotropy (FA), relaxation rates R2 and R2* to detect disease specific alterations in Parkinson's Disease (PD). We enrolled 82 PD patients (PD-all) with varying disease durations (≤5 years: PD≤5, n = 43; >5 years: PD>5, n = 39) and 38 matched healthy controls (HC), receiving diffusion tensor imaging as well as R2 and R2* relaxometry calculated from multi-echo T2*-weighted and dual-echo TSE imaging, respectively. ROIs were drawn to delineate caudate nucleus (CN), putamen (PU), globus pallidus (GP) and substantia nigra (SN) on the co-registered maps. The SN was divided in 3 descending levels (SL 1–3). The most significant parameters were used for a flexible discrimination analysis (FDA) in a training collective consisting of 25 randomized subjects from each group in order to predict the classification of remaining subjects. PD-all showed significant increases in MD, R2 and R2* within SN and its subregions as well as in MD and R2* within different basal ganglia regions. Compared to the HC group, the PD≤5 and the PD>5 group showed significant MD increases within the SN and its lower two subregions, while the PD≤5 group exhibited significant increases in R2 and R2* within SN and its subregions, and tended to elevation within the basal ganglia. The PD>5 group had significantly increased MD in PU and GP, whereas the PD≤5 group presented normal MD within the basal ganglia. FDA achieved right classification in 84% of study participants. Micro-structural damage affects primarily the SN of PD patients and in later disease stages the basal ganglia. Iron contents of PU, GP and SN are increased at early disease stages of PD.

Quantitative Susceptibility Mapping in Parkinson's Disease

“…Related studies have found regional susceptibility or R2* differences in single individual anatomical structures such as the putamen, caudate nucleus or the globus pallidus [17,34,35]. Extending these findings, we were able to demonstrate a more widespread involvement of the deep gray matter structures by applying QSM, including the substantia nigra, nucleus ruber, thalamus, and globus pallidus.…”

Comparative Study of MRI Biomarkers in the Substantia Nigra to Discriminate Idiopathic Parkinson Disease

“…2,3 A possible explanation for the lack of R2* changes is that R2* may decrease with disease progression. 34 Although iron accumulation leads to an increase in R2*, neuronal degeneration and gliosis induce a decrease in R2 relaxation rates within the tissue. 35 We found reduced T2*WI SN volume in PD at 7T, in line with previous studies.…”

The role of high‐field magnetic resonance imaging in parkinsonian disorders: Pushing the boundaries forward

“…It seems that late‐stage PD might have lower nigral R2* values than early‐stage PD. A possible explanation of this finding may be that consecutive gliosis with neuronal degeneration in late‐stage PD might lengthen T2 relaxation times within the tissue and thus counteract the increase of relaxation rates . This could also explain that some authors found no difference in iron content between PD patients and HCs, whereas most studies did .…”

“…A possible explanation of this finding may be that consecutive gliosis with neuronal degeneration in late‐stage PD might lengthen T2 relaxation times within the tissue and thus counteract the increase of relaxation rates . This could also explain that some authors found no difference in iron content between PD patients and HCs, whereas most studies did . Although relaxometry might track disease progression early in the disease process, available evidence suggests that relaxometry may not be a sufficient staging biomarker by itself .…”

“…Iron content can be quantified using iron‐sensitive techniques such as the R2* relaxation rate or susceptibility‐weighted imaging and QSM, 2 techniques that use information in phase images about variations in the local magnetic field. Nigral changes reflecting increases have been consistently reported in PD at 1.5T and 3T . However, PD values overlapped with those of HCs, and a few studies found no changes in PD, limiting its clinical use as disease marker today .…”