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Shorter Examination Method for the Diagnosis of Misery Perfusion with Count-Based Oxygen Extraction Fraction Elevation in ¹⁵O-Gas PET

¹ Biomedical Imaging Research Center, University of Fukui, Fukui, Japan; and ² Department of Neurosurgery, Faculty of Medical Sciences, University of Fukui, Fukui, Japan

Correspondence: For correspondence or reprints contact: Hidehiko Okazawa, MD, PhD, Biomedical Imaging Research Center, University of Fukui, 23-3 Matsuoka-Shimoaizuki, Eiheiji-cho, Fukui 910-1193, Japan. E-mail: okazawa{at}u-fukui.ac.jp

¹⁵O-Gas PET is useful for evaluating hemodynamic status in patients with ischemic cerebrovascular disease. To reduce examination time and exposure to radioactive gas, we assessed a count-based method with shorter continuous ¹⁵O₂ gas inhalation. Methods: Twenty-five patients (66 ± 13 [mean ± SD] y old) with unilateral cerebrovascular stenoocclusive disease were examined by use of measurements of asymmetric oxygen extraction fraction (OEF) elevation. Dynamic PET scans of 1 min per frame were obtained starting 2 min after the beginning of ¹⁵O₂ inhalation at a constant flow rate (740 MBq/min). Each subject also underwent C¹⁵O and H₂¹⁵O PET with the bolus administration method. To evaluate the effects of different scan start times and durations during ¹⁵O₂ inhalation, we extracted and summed individual ¹⁵O₂ PET data from the dynamic ¹⁵O₂ dataset. Count-based OEF (cbOEF) images were calculated from ¹⁵O₂ and H₂¹⁵O PET images. The asymmetric indices (AI) of cbOEF (cbOEF-AI) were obtained from regions of interest drawn on territories of the bilateral middle cerebral artery. These AI were compared with the AI of quantitative OEF (qOEF-AI). Results: The slopes of the regression lines and the coefficients of correlation between qOEF-AI and cbOEF-AI were close to 1.00 and greater than 0.79, respectively, regardless of different scan start times and durations. The cbOEF-AI obtained with a longer scan duration were closer to the qOEF-AI than those obtained with a shorter scan duration. Longer scan durations also provided better coefficients of correlation between cbOEF-AI and qOEF-AI regardless of scan start times. The coefficients of correlation between cbOEF-AI and qOEF-AI were greater than 0.90, except for cbOEF-AI obtained from ¹⁵O₂ images at 2–3 min after ¹⁵O₂ inhalation. Conclusion: The cbOEF obtained by ¹⁵O₂ imaging from 4 min after ¹⁵O₂ inhalation to 7 min or longer can correctly diagnose misery perfusion. The less invasive count-based PET method used in this study will be able to reduce examination time, exposure time, and stress for patients with ischemic cerebrovascular disease.

Key Words: ischemic cerebrovascular disease • misery perfusion • oxygen extraction fraction • ¹⁵O-gas PET

COPYRIGHT © 2008 by the Society of Nuclear Medicine, Inc.

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