Phase-Contrast Magnetic Resonance Imaging Measurements of Cerebral Autoregulation With a Breath-Hold Challenge

Abstract

Background and Purpose-Vasomotor reactivity (VMR) testing can identify patients with hemodynamically critical cerebrovascular disease. The use of VMR has been limited by the invasiveness of most of the available methods and of acetazolamide as VMR stimulus. In the present study, we evaluated a completely noninvasive VMR approach by combining quantitative phase-contrast magnetic resonance imaging (MRI) with a breath-hold challenge. Methods-Volume flow rates in the right and left internal carotid artery (ICA), basilar artery (BA), superior sagittal sinus, and sinus rectus were measured on 2-dimensional phase-contrast MR angiograms (MRAs) with a temporal resolution of 4.3 seconds. In 20 healthy control subjects, the VMR was assessed during 2 consecutive 30-second periods of breath-holding. Results-A flow increase on breath-holding of 66% was found for the left ICA (240Ϯ54 mL/min to 398Ϯ120 mL/min; PϽ0.01), 59% for the right ICA (253Ϯ98 mL/min to 402Ϯ159 mL/min; PϽ0.01), 71% for the BA (107Ϯ48 mL/min to 184Ϯ79 mL/min; PϽ0.01), 62% for the superior sagittal sinus (232Ϯ75 mL/min to 375Ϯ130 mL/min; PϽ0.01), and 65% for the sinus rectus (77Ϯ30 mL/min to 127Ϯ38 mL/min; PϽ0.01). The coefficient of variation for the total volume flow increase in the brain feeding arteries (ICAs and BA) between the first and the second breath-holds was 18%. Conclusion-The combination of MRA phase-contrast volume flow measurements and a breath-holding challenge allows for a fast, completely noninvasive, and reproducible assessment of VMR.

Hypercapnia-Induced Cerebral Hyperperfusion: An Underrecognized Clinical Entity

“…33 Animal and human studies have both demonstrated significant CBF increases in response to hypercapnia. [5][6][7]12,13,[16][17][18][33][34][35][36][37][38][39] This reaction has been exploited with tests such as the hypercapnia challenge to evaluate cerebrovascular reserve. 2,7,8 Previous human studies demonstrated up to a 200% increase in CBF as pCO 2 was raised experimentally.…”

“…[1][2][3][4][5][6] Gas mixtures with elevated concentrations of carbon dioxide (CO 2 ) are commonly used in both the research and clinical settings to evaluate cerebrovascular reserve, most frequently in patients with stenotic or occlusive cerebrovascular disease before extracranial-to-intracranial bypass. 2,7,8 Even small increases in the partial pressure of CO 2 (pCO 2 ) on the order of 5 to 6 mm Hg are capable of generating appreciable changes on perfusion imaging. 3,4,[7][8][9][10][11][12][13] Techniques such as transcranial Doppler, nuclear medicine positronemission tomography (PET) and single-photon emission CT, angiography, phase-contrast MR imaging, and arterial spinlabeled (ASL) MR perfusion have been used to evaluate the experimental hypercapnic effect on cerebral perfusion.…”

“…3,4,[7][8][9][10][11][12][13] Techniques such as transcranial Doppler, nuclear medicine positronemission tomography (PET) and single-photon emission CT, angiography, phase-contrast MR imaging, and arterial spinlabeled (ASL) MR perfusion have been used to evaluate the experimental hypercapnic effect on cerebral perfusion. 4,7,[11][12][13][14][15][16][17][18][19][20][21][22][23] It is not uncommon that hospitalized patients can have marked increases in pCO 2 in excess of 30 mm Hg from baseline, both on an acute or on a chronic basis. In a similar fashion, hyperventilation may produce marked hypocapnia.…”

The Influence of Carbon Dioxide on Brain Activity and Metabolism in Conscious Humans

“…The potential effect of CO 2 inhalation on neural activity is not clear. Existing literature mostly presumes that altering CO 2 partial pressure has no effect on brain tissue and the use of CO 2 inhalation or the carbonic anhydrase inhibitor acetazolamide can be considered a purely vascular challenge to assess cerebrovascular reserve (de Boorder et al, 2004) or to calibrate functional magnetic resonance imaging (fMRI) signal (Chiarelli et al, 2007;Davis et al, 1998;Kim and Ugurbil, 1997).…”

Regional Cerebral Blood Flow Using Quantitative MR Angiography

“…1,2 qMRA has been used to determine the total cerebral blood flow (CBF), [3][4][5] the effect of age and sex on the total CBF, 6 distribution of CBF in the circle of Willis, 7 and cerebral autoregulation, 8 as well as to evaluate various cerebrovascular disorders. [9][10][11][12][13][14][15][16] The range of blood flow for a healthy individual vessel in the brain, however, can be quite diverse because of inherent vascular anatomy and/or anatomic variations in the circle of Willis.…”