Effectiveness of QSM over R2∗ in Assessment of Parkinson's Disease - A Systematic Review

The incidence and prevalence of Parkinson's (PD) are increasing rapidly in developing countries. PD is difficult to diagnose based on clinical assessment. Presently, magnetic resonance imaging (MRI) methods such as R2∗ and Quantitative Susceptibility Mapping (QSM) were found to be useful in diagnosing the PD based on the iron deposition in different regions of the brain. The objective of this review was to evaluate the efficacy of QSM over R2∗ in assessment of PD. A comprehensive literature search was made on PubMed-Medline, CINAHL, Science Direct, Scopus, Web of Science, and the Cochrane library databases for original research articles published between 2000 and 2018. Original articles that reported the efficacy of QSM and R2∗ in assessment of PD were included. A total of 327 studies were identified in the literature search. However, only ten studies were eligible for analysis. Of the ten studies, five studies compared the accuracy of QSM over R2∗ in measuring the iron deposition in different regions of brain in PD. Our review found that QSM has better accuracy in identifying iron deposition in PD patients compared to R2∗. However, there is discrepancy in the results between MRI Imaging methods and Postmortem studies. Additional longitudinal research studies are needed to provide a strong evidence base for the use of MRI imaging methods such as R2∗and QSM in accurately measuring iron deposition in different regions of brain and serve as biomarkers in PD.