Shorter Examination Method for the Diagnosis of Misery Perfusion with Count-Based Oxygen Extraction Fraction Elevation in 15O-Gas PET
Masato Kobayashi 1,
Takashi Kudo 1,
Tetsuya Tsujikawa 1,
Makoto Isozaki 2,
Yoshikazu Arai 2,
Yasuhisa Fujibayashi 1,
and
Hidehiko Okazawa 1*
1 Biomedical Imaging Research Center, University of Fukui, Fukui, Japan
2 Department of Neurosurgery, Faculty of Medical Sciences, University of Fukui, Fukui, Japan
* To whom correspondence should be addressed. E-mail: okazawa{at}u-fukui.ac.jp.
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Abstract |
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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
