Applicability of emission-based attenuation map for rapid CBF, OEF, and CMRO2 measurements using gaseous 15O-labeled compounds

Abstract

BackgroundCerebral blood flow (CBF), oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO2) images have facilitated understanding of the pathophysiological basis of cerebrovascular disorders. Such parametric images can be rapidly, measured within around 15 min, using positron emission tomography (PET) with sequentially administered 15O-labeled oxygen and water. For further shortening, one option is to eliminate the transmission scan by applying an emission-based attenuation correction.MethodsThe validity of the present method was tested by comparing parametric values with emission-based attenuation correction to those with transmission-based correction. This was applied to 27 subjects who were diagnosed with or without cerebrovascular disorders. All subjects received the rapid CBF/OEF/CMRO2 PET measurements. An emission-based attenuation map was generated by estimating the edge of the brain tissue contour on an obtained sinogram and by assuming the uniform tissue coefficient to be 0.1 cm−1. Then images were reconstructed, and parametric images were computed.ResultsNo difference was apparent between the emission- and transmission-based methods. Paired t-test showed no significant differences in CBF, OEF, or CMRO2 values between the emission- and transmission-based methods, except in the parietal and occipital and cerebellum and occipital regions, and the differences were less than 10%. The regression analysis showed a close correlation of r = 0.89 to 0.99.ConclusionsThe present study revealed that the attenuation correction can be performed by the emission-based estimation method and clinical PET duration can be shortened for the CBF, OEF, and CMRO2 gas study.

Quantification of brain oxygen extraction and metabolism with [15O]-gas PET: A technical review in the era of PET/MRI

“…In-plane spatial resolution ranged from 11.7 mm ( Mintun et al, 1984 ) to 16 mm ( Pantano et al, 1985 ), with slice separation between 14.4 mm ( Herscovitch et al, 1985 ) and 19 mm ( Lebrun-Grandie et al, 1983 ), ( Pantano et al, 1985 ). Later scanners enabled 2D [ 15 O]-PET with extended coverage and higher spatial resolution: for instance, 35 slices with 4.6–5.7 mm in-plane resolution and 4.0–5.3 mm slice thickness on the GE ADVANCE system (GE Medical System, Milwaukee) ( Okazawa et al, 2001a ); or 47 slices with 5.8 × 5.8 × 5.0 mm 3 resolution on the ECAT EXACT system (CTI Inc., Knoxville) ( Maeda et al, 2015 ). These high-resolution images are smoothed during reconstruction using a Gaussian or Hanning filter with 5.5–7.0 mm full-width half maximum to improve SNR.…”

“…In contrast, bolus inhalation of [ 15 O]-oxygen has become more prevalent in recent decades. In this paradigm, [ 15 O]-oxygen is delivered through a short inhalation of up to 1 min ( Mintun et al, 1984 ; Maeda et al, 2015 ; Shidahara et al, 2002 ), or through a single deep breath ( Meyer et al, 1987 ; Ohta et al, 1992 ), e.g. with a 10-s breath hold.…”

Impact of Attenuation Correction on Quantification Accuracy in Preclinical Whole-Body PET Images

“…As the skull itself was not visible in the FDG rat images, it was not feasible to include bone material into the segmented images and thus leading to an underestimation of brain FDG uptake. A previous study suggests a careful evaluation of EM-AC in applications where a uniform structure cannot be assumed [26].…”

Reconstruction of input functions from a dynamic PET image with sequential administration of 15O2 and H215O for noninvasive and ultra-rapid measurement of CBF, OEF, and CMRO2

“…The rapid PET protocol for CBF, OEF, and CMRO 2 was applied, 9,10 as was described in our previous article. 16 Briefly, PET acquisition was carried out in 2-D mode using a PET scanner (ECAT HR+, Siemens-CTI, Knoxville, TN, USA). Two tracers, 15 O 2 (3000 MBq, 60 s duration) and C 15 O 2 (3000 MBq, 60 s duration), were administrated in sequence, with a 11-min interval during the single PET scan with a total exposure of 780 s (6 × 10 s, 6 × 20 s, 3 × 30 s, 3 × 120 s, 12 × 5 s, and 9 × 10 s).…”