Quantitative Susceptibility Mapping in Parkinson's Disease.

BACKGROUND:Quantitative susceptibility mapping (QSM) and R2* relaxation rate mapping have demonstrated increased iron deposition in the substantia nigra of patients with idiopathic Parkinson's disease (PD). However, the findings in other subcortical deep gray matter nuclei are converse and the sensitivity of QSM and R2* for morphological changes and their relation to clinical measures of disease severity has so far been investigated only sparsely. METHODS:The local ethics committee approved this study and all subjects gave written informed consent. 66 patients with idiopathic Parkinson's disease and 58 control subjects underwent quantitative MRI at 3T. Susceptibility and R2* maps were reconstructed from a spoiled multi-echo 3D gradient echo sequence. Mean susceptibilities and R2* rates were measured in subcortical deep gray matter nuclei and compared between patients with PD and controls as well as related to clinical variables. RESULTS:Compared to control subjects, patients with PD had increased R2* values in the substantia nigra. QSM also showed higher susceptibilities in patients with PD in substantia nigra, in the nucleus ruber, thalamus, and globus pallidus. Magnetic susceptibility of several of these structures was correlated with the levodopa-equivalent daily dose (LEDD) and clinical markers of motor and non-motor disease severity (total MDS-UPDRS, MDS-UPDRS-I and II). Disease severity as assessed by the Hoehn & Yahr scale was correlated with magnetic susceptibility in the substantia nigra. CONCLUSION:The established finding of higher R2* rates in the substantia nigra was extended by QSM showing superior sensitivity for PD-related tissue changes in nigrostriatal dopaminergic pathways. QSM additionally reflected the levodopa-dosage and disease severity. These results suggest a more widespread pathologic involvement and QSM as a novel means for its investigation, more sensitive than current MRI techniques

Univariate correlations of R2* and magnetic susceptibility with clinical parameters for patients with PD.

<p>Univariate correlations of R2* and magnetic susceptibility with clinical parameters for patients with PD.</p

Regional magnetic susceptibility and R2* values.

<p>Regional magnetic susceptibility and R2* values.</p

Clinical and demographic data of the study cohort.

<p>Clinical and demographic data of the study cohort.</p

Univariate correlations of R2* and magnetic susceptibility for patients with shorter and longer disease duration dichotomized by median disease duration (3.4 years).

<p>Univariate correlations of R2* and magnetic susceptibility for patients with shorter and longer disease duration dichotomized by median disease duration (3.4 years).</p

Regional mean susceptibilities and R2* (±standard deviation).

<p>Asterisks denote significant differences between controls and patients with Parkinson’s disease (*p<0.05; **p<0.01; ***p< = 0.001).</p

Morphological data.

<p>Morphological data.</p

Representative T1-weighted MP-RAGE image (left) with color overlay of segmented deep gray matter structures, R2* relaxation rate constant map (center) and quantitative susceptibility map (right) of a 62-years patient with PD (MDS-UPDRS 46; Hoehn & Yahr 2).

<p>High R2* rates and paramagnetic susceptibilities are found in the basal ganglia. Note the improved gray-white matter contrast on the QSM map compared to the R2* map.</p