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

Abstract

15 O-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 15 O 2 gas inhalation. Methods: Twenty-five patients (66 6 13 [mean 6 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 15 O 2 inhalation at a constant flow rate (740 MBq/min). Each subject also underwent C 15 O and H 2 15 O PET with the bolus administration method. To evaluate the effects of different scan start times and durations during 15 O 2 inhalation, we extracted and summed individual 15 O 2 PET data from the dynamic 15 O 2 dataset. Count-based OEF (cbOEF) images were calculated from 15 O 2 and H 2 15 O 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 15 O 2 images at 2-3 min after 15 O 2 inhalation. Conclusion: The cbOEF obtained by 15 O 2 imaging from 4 min after 15 O 2 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. Oxygen-15-gas brain PET is the most reliable examination technique for evaluating misery perfusion, defined as impaired hemodynamics with a regional increase in the oxygen extraction fraction (OEF), in imaging modalities. Patients with this condition have a higher risk of stroke recurrence than patients with normal OEF (1-4). Several PET methods have been developed and used to calculate quantitative OEF (qOEF) for the diagnosis of misery perfusion (5-9). However, these methods require arterial blood sampling during the PET examination, which necessitates a long examination time and introduces the risk of bleeding from the arterial line.Count-based OEF (cbOEF) methods can noninvasively evaluate asymmetric increases in OEF with a simple calculation as a substitution for qOEF measurements (3,(10)(11)(12)(13). In a previous study, we evaluated whether the asymmetry index (AI) of cbOEF (cbOEF-AI) could appropriately d...

Clinical impact of hemodynamic parameter measurement for cerebrovascular disease using positron emission tomography and 15O-labeled tracers

“…A normalized method using cerebellar counts showed poor agreement with quantitative OEF elevation [72]. However, another study employing a simplified AI comparison method using count-based ratio images showed good accordance with the AI of quantitative OEF in CVD patients [73,74]. The advantage of these simplified methods is that the scanning protocol is simple and the operation is non-invasive without arterial blood sampling.…”

Evaluation of utility of asymmetric index for count-based oxygen extraction fraction on dual-tracer autoradiographic method for chronic unilateral brain infarction

“…Kobayashi et al [25] reported the cbOEF-AI can be successfully used to diagnose misery perfusion if one uses 4-7 min of the summation time for continuous inhalation of 15 15 O data. Hence, the total study time for their study should be longer than 10 min.…”

“…By the cbOEF image, one can non-invasively evaluate asymmetric increase in OEF value with a simple calculation [6,21,22,24]. Recently, Kobayashi et al investigated the optimal scan protocol for computing cbOEF to diagnose misery perfusion [25]. They concluded the cbOEF could appropriately diagnose misery perfusion when they used 15 2 15 O was utilized for the administration of tracers.…”

Optimal scan time of oxygen-15-labeled gas inhalation autoradiographic method for measurement of cerebral oxygen extraction fraction and cerebral oxygen metabolic rate

“…Kobayashi et al [21] examined relationship between count-based OEF and scan duration. They used quantitative OEF as a standard to evaluate optimal scan duration.…”