Journal of Vision - Beyond BOLD: Expanding the role of fMRI in low vision rehabilitation, by Glielmi, Hu, & Schuchard

Volume 7, Number 9, Abstract 769, Page 769a

doi:10.1167/7.9.769

http://journalofvision.org/7/9/769/

ISSN 1534-7362

Beyond BOLD: Expanding the role of fMRI in low vision rehabilitation

Christopher B Glielmi	Department of Biomedical Engineering, Emory University / Georgia Institute of Technology, Atlanta, Georgia
Xiaoping P. Hu	Department of Biomedical Engineering, Emory University / Georgia Institute of Technology, Atlanta, Georgia
Ronald A Schuchard	Rehabilitation Research & Development Center, VA Medical Center, Atlanta, Georgia

Abstract

Purpose: Retinitis Pigmentosa (RP) is a common cause of peripheral first and then central visual field loss [1]. Virtually all fMRI studies of visual field loss utilize BOLD contrast despite longitudinal and inter-subject variability [2]. However, recent studies in animals and healthy humans demonstrate cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO₂) measures are more consistent over time within subjects and also between subjects [2-4]. The current study provides the first MRI application of CBF and CMRO₂estimation in the low vision population providing a platform for future rehabilitation and cortical reorganization studies.

Methods: Two RP patients (age 34,45, visual acuity 20/90,110, central visual field 15, 5 deg.) participated in a monocular study. Four flashing stimuli (rings at two eccentricities and checkerboards at two resolutions) were used as subjects fixated on a central target. Anatomical and functional (simultaneous CBF and BOLD images) were acquired with a Siemens 3T Trio [5]. Data were analyzed using Matlab with SPM2 functionality, estimating CMRO₂using a highly respected model [6].

Results: Activation maps demonstrate CBF’s improved spatial specificity relative to BOLD. Furthermore, % ΔCMRO₂ estimates, % ΔCBF and absolute CBF results agree with previous studies that showed closer association with neuronal activity than BOLD alone.

Conclusions: The current work demonstrates for the first time that fMRI can be used to measure absolute and relative CBF and estimate relative CMRO₂ in people with visual field loss. Integration of these techniques into future studies will demonstrate their benefit in rehabilitation intervention and cortical reorganization studies.

References: [1] National Advisory Eye Council. Bethesda: Natl. Inst.Health, MD; DHHS Publ. No. 93-3186. [2] Tjandra TI. NeuroImage 2005. 27:393-401. [3] Wong EC. Functional MRI 1999. 63-9. [4] Sicard KM. NeuroImage 2005. 25:850-8. [5] Alsop DC. Radiology 1998. 208:410-416. [6] Davis TL. Proc Natl Acad Sci USA 1998. 95:1834-9.

Supported by VA Rehabilitation R&D Service and NIH RO1 EB002009.


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