Study On Dyskinetic Disorder And Ageing Using Quantitative Susceptibility Mapping

Quantitative susceptibility mapping(QSM)can deconvolve the GRE phase data to determine tissue magnetic susceptibility distribution.In this thesis,QSM was used to investigate dyskinetic disorder and ageing.The main contents are as follows:1.3D texture analyses within the substantia nigra of Parkinson’s disease patients on quantitative susceptibility maps and R2~*mapsIron accumulation in the substantia nigra(SN)is spatially heterogeneous,yet no study has quantitatively evaluated how the texture of quantitative susceptibility maps and R2~*might evolve with Parkinson’s disease(PD)and healthy controls(HC).The aim of this study was to discriminate between patients with PD and HC using texture analysis in the SN from QSM and R2~*maps.After correction for multiple comparisons,for the first-order analysis,the susceptibility of SN from patients with PD was significantly greater(p=0.017)compared with the SN from HC.For the second-order texture analysis,angular second moment,entropy,and sum of entropy showed significant differences in QSM(p<0.001)and R2~*maps(p<0.01).In addition,correlation,contrast,sum of variance and difference of variance,significantly separated the subject groups in QSM maps(p<0.05)but not in R2~*images.Receiver operating characteristic analysis showed that entropy and sum of entropy of the QSM maps in the SN yielded the highest performance for differentiating PD patients from HC(area under the curve=0.89).In conclusion,most first-and second-order QSM texture features successfully distinguished PD patients from HC and significantly outperformed R2~*texture analysis.The second-order texture features were more accurate and sensitive than first-order texture features for classifying PD patients.2.Measurement of metal accumulation in the deep gray matter nuclei of patients with Wilson’s disease on quantitative susceptibility maps at 3TWilson’s disease(WD)is a rare,autosomal recessive disorder characterized by excessive copper and iron accumulation in the brain,which can lead to neurologic and psychiatric problems.Currently,no study has evaluated potential differences in quantitative susceptibility maps(QSM)and R2~*between WD and healthy controls(HC)at 3T.In this study,we measured changes in magnetic susceptibility and R2~*values in deep gray matter nuclei to discriminate patients with WD from healthy controls,and to evaluate their sensitivities in diagnosing WD.Differences in magnetic susceptibility and R2~*values between WD patients and HC were compared using the Mann-Whitney U test.Receiver operating characteristic(ROC)curves were used to assess the ability of QSM and R2~*maps to discriminate WD from HC.The susceptibility and R2~*values in patients with WD were significantly higher than in healthy controls in multiple deep gray matter regions.For the second-order texture analysis,correlation and contrast showed significant differences in QSM(p<0.001)in all deep gray matter nuclei.The ROC curves showed that the QSM had the highest area under the curve(AUC=0.888)in the substantia nigra.In addition,some patients with WD had signal abnormalities in the basal ganglia in QSM maps but not in conventional MRI images(T1-weighted,T2-weighted,T2-FLAIR).In conclusion,QSM is a more sensitive quantitative technique to detect a significant increase of paramagnetic mineral deposition in WD patients than R2~*and conventional MRI images.3.Measurement of iron concentration in deep gray matter nuclei over the lifespan using quantitative susceptibility mappingThe aim of this study is to investigate the correlation of non-heme iron content in deep gray matter nuclei as a function of age using quantitative susceptibility mapping.We studied a group of 240 normal subjects ranging from 14 to 70 years old and measured the magnetic susceptibility of six subcortical gray matter nuclei.A strong age-susceptibility correlation was found in the caudate nucleus(r=0.570),putamen(r=0.712),and red nucleus(r=0.515).Different non-linear age-susceptibility trends were found in different deep gray matter.Results of sex analysis showed that male played a major role in the age-susceptibility correlation.Overall,we conclude that the age-susceptibility correlation can serve as a quantitative magnetic susceptibility baseline as a function of age for monitoring abnormal regional iron deposition.A regional analysis has shown a tighter age related behavior,providing a reliable and sensitive reference for normal iron content for studies of iron-related diseases.