Quantitative susceptibility mapping to evaluate brain iron deposition and its correlation with physiological parameters in hypertensive patients

Lifestyle, biological, and genetic factors related to brain iron accumulation across adulthood

Iron is necessary for many neurobiological mechanisms, but its overaccumulation can be harmful. Factors triggering age-related brain iron accumulation remain largely unknown and longitudinal data are insufficient. We examined associations between brain iron load and accumulation and, blood markers of iron metabolism, cardiovascular health, lifestyle factors (smoking, alcohol use, physical activity, diet), and ApoE status using longitudinal data from the IronAge study (n = 208, age = 20-79, mean follow-up time = 2.75 years). Iron in cortex and basal ganglia was estimated with magnetic resonance imaging using quantitative susceptibility mapping (QSM). Our results showed that (1) higher peripheral iron levels (i.e., composite score of blood iron markers) were related to greater iron load in the basal ganglia; (2) healthier diet was related to higher iron levels in the cortex and basal ganglia, although for the latter the association was significant only in younger adults (age = 20-39); (3) worsening cardiovascular health was related to increased iron accumulation; (4) younger ApoE ε4 carriers accumulated more iron in basal ganglia than younger non-carriers. Our results demonstrate that modifiable factors, including lifestyle, cardiovascular, and physiological ones, are linked to age-related brain iron content and accumulation, contributing novel information on potential targets for interventions in preventing brain iron-overload.

Deep gray matters iron deposition is positively associated with white matter hyperintensity in hypertension

The association and underlying mechanisms between iron deposition and white matter hyperintensity (WMH) remain unclear. In this study, quantitative susceptibility mapping (QSM) was used to quantify deep gray matters iron deposition and to explore the association from both global and regional perspectives. A total of 84 patients with hypertension and 26 healthy controls underwent a strategically acquired gradient echo (STAGE) protocol, and the multi-echo data were used to reconstruct QSM images. The susceptibilities were used to describe iron content. Global region (RI) susceptibilities were measured in regions of interest, and age-related thresholds were used to determine high-iron content region (RII) susceptibilities. Compared with healthy controls, hypertension had higher total WMH scores and regional scores (all p = .001) and higher susceptibilities using the RI or RII analysis (all p < .05). In healthy controls, there was no significant association between susceptibilities and WMH scores. In hypertension, the susceptibilities of deep gray matters were positively correlated with WMH scores (RI analysis: right putamen; RII analysis: bilateral caudate nucleus head, putamen, red nucleus, substantia nigra, and dentate nucleus; age and education corrected p < .05). These findings suggest that iron deposition in deep gray matters was positively associated with WMH in hypertension, especially using the RII analysis.

Quantitative Susceptibility Mapping of Brain Iron Relating to Cognitive Impairment in Hypertension

BACKGROUND

Hypertension (HTN) might impair cognition. Brain iron deposition correlates with cognitive impairment. The relationship between brain iron and cognition in HTN patients is less clear.

PURPOSE

To measure brain susceptibility in HTN patients using quantitative susceptibility mapping (QSM) and to explore the relationship between brain iron and cognition.

STUDY TYPE

Retrospective cross-sectional study.

SUBJECTS

Sixty HTN patients (35 with mild cognitive impairment [MCI] and 25 without MCI) and 24 age, gender, and education matched controls.

FIELD STRENGTH/SEQUENCE

3 T; strategically acquired gradient echo (STAGE) imaging protocol for QSM analysis.

ASSESSMENT

All subjects underwent Montreal Cognitive Assessment (MoCA) scoring of visuospatial/executive, naming, attention, abstraction, language, delayed memory, and orientation functions. HTN patients were divided into two groups (with and without MCI) depending on the MoCA score. Regions of interest (ROIs) were manually demarcated on the STAGE images by three independent radiologists and susceptibility were determined for bilateral frontal white matter, parietal white matter, occipital white matter, caudate nucleus (CN), putamen (PU), globus pallidus (GP), thalamus (TH), red nucleus (RN), substantia nigra (SN), and dentate nucleus (DN).

STATISTICAL TESTS

Analysis of variance with post-hoc least significant difference (LSD) tests and Pearson correlation coefficients (r). A P-value <0.05 was considered to be statistically significant.

RESULTS

The susceptibility was significantly different in CN, PU, and DN among the three groups. The susceptibility of right CN and left PU were correlated with MoCA scores (r = -0.429 and r = -0.389, respectively). The susceptibility of left PU was also correlated with delayed memory scores (r = -0.664). The susceptibility of left and right GP were correlated with naming scores (r = -0.494 and r = -0.446, respectively) and the susceptibility of left DN were correlated with visuospatial/executive scores (r = 0.479).

DATA CONCLUSION

QSM measured brain iron was significantly higher in CN, PU, and DN in HTN patients. Cognitive impairment was correlated with regional brain iron deposition.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY: Stage 3.