Day-to-day test-retest variability of CBF, CMRO2, and OEF measurements using dynamic 15O PET studies

Abstract

Purpose: We assessed test-retest variability of cerebral blood flow (CBF), cerebral blood volume (CBV), cerebral metabolic rate of oxygen (CMRO(2)), and oxygen extraction fraction (OEF) measurements derived from dynamic (15)O positron emission tomography (PET) scans.

Procedures: In seven healthy volunteers, complete test-retest (15)O PET studies were obtained; test-retest variability and left-to-right ratios of CBF, CBV, OEF, and CMRO(2) in arterial flow territories were calculated.

Results: Whole-brain test-retest coefficients of variation for CBF, CBV, CMRO(2), and OEF were 8.8%, 13.8%, 5.3%, and 9.3%, respectively. Test-retest variability of CBV left-to-right ratios was <7.4% across all territories. Corresponding values for CBF, CMRO(2), and OEF were better, i.e., <4.5%, <4.0%, and <1.4%, respectively.

Conclusions: The test-retest variability of CMRO(2) measurements derived from dynamic (15)O PET scans is comparable to within-session test-retest variability derived from steady-state (15)O PET scans. Excellent regional test-retest variability was observed for CBF, CMRO(2), and OEF. Variability of absolute CBF and OEF measurements is probably affected by physiological day-to-day variability of CBF.

Fig. 1

Typical warped whole-brain flow territory volumes of interest (maps). Territory of ACA, gray on left hemisphere. Territory of MCA, brown on left hemisphere. Territory of PCA, blue on left hemisphere.

Fig. 2

Typical CBF, OEF, and CMRO₂ parametric maps for a healthy volunteer in comparison with a patient who had recurrent TIAs associated with a left internal carotid artery occlusion. The PET study of the patient shows in the ipsilateral hemisphere a decreased CBF and increased OEF compared with the contralateral hemisphere.

Fig. 3

Relationship between test and retest measurements of gray matter CBF, CMRO₂, and OEF in seven healthy volunteers. Black circle test right hemisphere; black triangle test left hemisphere, black square test both hemispheres. Gray circle retest right hemisphere, gray triangle retest left hemisphere, gray square retest both hemispheres. ACA anterior cerebral artery, MCA middle cerebral artery, PCA posterior cerebral artery. Total brain included all flow territories.

Fig. 4

Relationship between test and retest left–right ratio measurements of CBF, CMRO₂, and OEF in seven healthy volunteers. Black indicates test data, gray indicates retest data. ACA anterior cerebral artery, MCA middle cerebral artery, PCA posterior cerebral artery.