The change in cerebrovascular reactivity between 3 T and 7 T measured using graded hypercapnia

Ian Driver,Nicholas Blockley,Joseph Fisher,Susan Francis,Penny Gowland

doi:10.1016/j.neuroimage.2009.12.113

Abstract

Mapping cerebrovascular reactivity (CVR) to hypercapnia is important both clinically and for improved understanding of the haemodynamic properties of the BOLD effect. In this work, BOLD/R2⁎ CVR was investigated by using a device which provided small, repeatable and stable steps in PETCO2, whilst maintaining a steady PETO2 level. Significant CVR was observed in both grey and white matter at both 3 and 7 T, whilst an approximately linear relationship found between R2⁎ CVR and field strength has implications for BOLD models and calibration. Grey matter R2⁎ CVR was 0.066±0.004 s−1 mm Hg−1 at 3 T and 0.141±0.008 s−1 mm Hg−1 at 7 T. White matter R2⁎ CVR was 0.021±0.003 s−1 mm Hg−1 at 3 T and 0.040±0.007 s−1 mm Hg−1 at 7 T.

Highlights

The ability of the body to modulate cerebral blood flow (CBF) is important both clinically and in understanding the haemodynamic response to neuronal activation
The BOLD Cerebrovascular reactivity (CVR) is of particular interest since it is used in calibrated BOLD: either the functional BOLD response to a task is divided by the BOLD response to mild hypercapnia on a voxel-byvoxel basis, or alternatively the functional BOLD response to a task is used to estimate δCMRO2 based on the model of Davis et al(Davis et al 1998)
The technique to control blood gases used in this study allowed independent control of PETCO2 and PETO2, to provide transitions to and between stable PETCO2 levels, whilst maintaining PETO2 at a constant level (Slessarev et al 2007)

Summary

Introduction

The ability of the body to modulate cerebral blood flow (CBF) is important both clinically and in understanding the haemodynamic response to neuronal activation. Cerebrovascular reactivity (CVR) as measured by BOLD MRI is defined as the change in BOLD signal in response to a change in PaCO2 and provides a measure of the capacity of vessels to react to a stimulus. This technique has been applied to map the regional distribution of CVR in cerebrovascular disease such as stroke and carotid artery stenosis and occlusion (van der Zande et al 2005; Mandell et al 2008). The BOLD CVR is of particular interest since it is used in calibrated BOLD: either the functional BOLD response to a task is divided by the BOLD response to mild hypercapnia on a voxel-byvoxel basis, or alternatively the functional BOLD response to a task is used to estimate δCMRO2 based on the model of Davis et al(Davis et al 1998)

Objectives

Methods

Results

Conclusion