نهمین کنگره نقشه برداری مغز

نمایش مقاله

Title:

Multimodal Evaluation of fMRI Activation Using Magnitude, Phase, and Magnetic Susceptibility Information

Subject:

Advanced Techniques in Signal Acquisition and Image Processing

Presenter Author:
Name:	Amir Kazemi

Author:
Name 1:	Amir Kazemi - Presenter
Affiliation 1:	Department of Radiation in Medicine, Shahid Beheshti University, Tehran, Iran

Name 2:	Mohamad Mohamadzadeh²* - Corresponding
Affiliation 2:	Department of Radiation in Medicine, Shahid Beheshti University, Tehran, Iran

Name 3:	Mehdi Panahi²
Affiliation 3:	Department of Radiation in Medicine, Shahid Beheshti University, Tehran, Iran

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Abstract

Original Research

introduction :

Functional magnetic resonance imaging (fMRI) plays a central role in noninvasive brain mapping, primarily relying on magnitude-based blood oxygenation level–dependent (BOLD) contrast to identify task-related neural activity. Despite its widespread use, magnitude-only analysis may not fully exploit the rich information embedded in phase and magnetic susceptibility variations induced by neuronal activation. Recent methodological advances suggest that incorporating these complementary signal components could improve the sensitivity and spatial specificity of functional localization. This study investigates the feasibility of a multimodal fMRI framework that integrates magnitude, phase, and susceptibility information within a unified analytical approach.

Methods:

fMRI data were acquired from a single healthy subject performing a toe movement task on a 3T MRI scanner. Standard preprocessing steps, including motion correction, spatial normalization, and statistical inference, were carried out using the FSL software package. Beyond conventional analysis, a BOLD perturbation model was implemented in MATLAB to exploit phase-related signal variations. Tissue magnetic susceptibility maps were reconstructed through an inverse modeling technique applied to the processed fMRI data. Activation patterns derived from susceptibility mapping were systematically compared with magnitude-based BOLD results. Quantitative evaluation was performed using signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), Dice similarity coefficient, and temporal correlation metrics to assess spatial accuracy, contrast enhancement, and network-level dynamics.

Results:

The susceptibility-based activation maps exhibited superior contrast and delineation of task-related regions compared to magnitude- and phase-derived maps. Quantitative analysis demonstrated higher SNR and CNR values for susceptibility information, alongside improved spatial agreement with the MNI-152 standard brain atlas, as indicated by elevated Dice similarity coefficients. Temporal correlation analysis further revealed complex interaction patterns among motor-related brain regions, including both cooperative and opposing dynamics during task execution. Notably, activation maps generated using the BOLD perturbation framework showed enhanced clarity and robustness relative to conventional magnitude-only approaches.

Conclusion:

This exploratory study demonstrates that integrating magnetic susceptibility information into fMRI analysis is both feasible and advantageous. The proposed multimodal framework provides more precise functional localization and captures additional physiological information beyond standard BOLD magnitude analysis. Such an approach holds promise for advanced brain mapping applications, particularly in pre-surgical planning and the investigation of functional brain networks.

Keywords:

fMRI, BOLD perturbation model, multimodal analysis, Dice similarity coefficient