Category: Parkinson's Disease: Neuroimaging
Objective: To assess the changes in R2* occurring in PD patients compared to controls, a multicenter transversal study was carried out in a large cohort of PD patients going from the early to the late stage of the disease and matched controls.
Background: Several postmortem studies have shown an accumulation of iron in the substantia nigra (SN) in Parkinson’s disease (PD). The iron concentration can be estimated by the MRI-R2* mapping.
Method: Images acquired at 3T in 12 clinical centers were registered, then normalized to the MNI space using DARTEL approach for level group analyses. R2* values were measured in different subcortical regions of interest (ROI) segmented from an automatic atlas. In this study, the observed inter-subject variability was significantly higher than the disease effect. For this reason, an original strategy (intrasubject subcortical quantitative referencing, ISQR) was developed using the measurement of R2* in the red nucleus (RN) as an intra-subject reference. This structure is not directly involved in the PD circuit but exhibits non-specific variability equivalent to that presented in the ROI. ISQR is based on the calculation of the difference between a structure of interest and the RN: R2*(ISQR) (ROI,subject)=R2*(ROI,subject)-R2*(RN,subject)
Results: An increased R2* value was only achieved in the SN of PD patients compared to controls (Pleft-SN<0.001, Pright-SN=0.001). After stratification of patients into 4 subgroups according to the disease duration (G1<5 years; G2, between 5 and 10 years; G3, between 10 and 15 years and G4>15 years), no significant difference for R2* was found between PD subgroups, for all ROI (figure1). These results can be explained by the high inter-subject variability in all subcortical regions of R2*. By applying our ISQR strategy, increased R2*(ISQR) values were obtained in the SN when comparing; PD patients to controls (Pright-SN, Pleft-SN<10-4), each PD subgroup to controls (Pright-SN, Pleft-SN<10-3), and between PD subgroups (Pright-SN=0.03, Pleft-SN=0.01) with an overall increase of R2*(ISQR) magnitude values (figure2). A significant difference was found when compared G3 to G1 (Pleft-SN=0.04, Pright-SN=0.02) and G4 to G1 (Pleft-SN=0.006, Pright-SN<0.001) (figure3).
Conclusion: Our results support the use of ISQR to reduce variations not directly related to PD. These findings demonstrate that our original ISQR strategy is useful for PD progression.
To cite this abstract in AMA style:
L. Khedher, JM. Bonny, F. Durif. Intrasubject subcortical quantitative referencing to make quantitative MRI sensitive to Parkinson’s disease [abstract]. Mov Disord. 2021; 36 (suppl 1). https://www.mdsabstracts.org/abstract/intrasubject-subcortical-quantitative-referencing-to-make-quantitative-mri-sensitive-to-parkinsons-disease/. Accessed September 7, 2024.« Back to MDS Virtual Congress 2021
MDS Abstracts - https://www.mdsabstracts.org/abstract/intrasubject-subcortical-quantitative-referencing-to-make-quantitative-mri-sensitive-to-parkinsons-disease/