Semi-quantitative cerebral blood flow parameters derived from non-invasive [¹⁵O]H₂O PET studies

Abstract

Quantification of regional cerebral blood flow (CBF) using [15 O]H 2 O positron emission tomography (PET) requires the use of an arterial input function. Arterial sampling, however, is not always possible, for example in ill-conditioned or paediatric patients. Therefore, it is of interest to explore the use of non-invasive methods for the quantification of CBF. For validation of non-invasive methods, test-retest normal and hypercapnia data from 15 healthy volunteers were used. For each subject, the data consisted of up to five dynamic [15 O]H 2 O brain PET studies of 10 min and including arterial sampling. A measure of CBF was estimated using several non-invasive methods earlier reported in literature. In addition, various parameters were derived from the time-activity curve (TAC). Performance of these methods was assessed by comparison with full kinetic analysis using correlation and agreement analysis. The analysis was repeated with normalization to the whole brain grey matter value, providing relative CBF distributions. A reliable, absolute quantitative estimate of CBF could not be obtained with the reported non-invasive methods. Relative (normalized) CBF was best estimated using the double integration method.

Simultaneous phase‐contrast MRI and PET for noninvasive quantification of cerebral blood flow and reactivity in healthy subjects and patients with cerebrovascular disease

“…In addition, it has inherent limitations, with the delay and dispersion of the tracer as it travels to the brain because arterial blood is typically sampled from the radial artery at the wrist . Although several quantitative H 2 15 O‐PET methods without arterial blood sampling such as population‐based input functions have been designed, these approaches have the drawback of ignoring individual AIF variation . Image‐derived input function (IDIF) methods that identify brain feeding arteries in the PET field of view by time‐of‐flight (TOF) magnetic resonance imaging (MRI) have also been proposed.…”

High Intravascular Signal Arterial Transit Time Artifacts Have Negligible Effects on Cerebral Blood Flow and Cerebrovascular Reserve Capacity Measurement Using Single Postlabel Delay Arterial Spin-Labeling in Patients with Moyamoya Disease

“…This feature is an important limitation with 15 O-water PET; quantitative studies require an arterial input function most reliably acquired through continuous arterial sampling. 32,33 Arterial sampling may not be feasible in patients in poor condition and is not feasible in children with MMD. 33 However, several noninvasive methods can estimate relative CBF in the absence of existing arterial blood sampling.…”

“…32,33 Arterial sampling may not be feasible in patients in poor condition and is not feasible in children with MMD. 33 However, several noninvasive methods can estimate relative CBF in the absence of existing arterial blood sampling. 33,34 ASL is, by definition, fully noninvasive, with no radiation exposure and greater availability than cyclotron-dependent 15 O-water PET.…”

“…33 However, several noninvasive methods can estimate relative CBF in the absence of existing arterial blood sampling. 33,34 ASL is, by definition, fully noninvasive, with no radiation exposure and greater availability than cyclotron-dependent 15 O-water PET. As concluded by other authors, ASLderived CBF/CVRC has potential in pre-/postoperative assessment in patients with MMD.…”

Evaluation of Arterial Spin Labeling MRI—Comparison with 15O-Water PET on an Integrated PET/MR Scanner

“…Although MRI-based attenuation correction methods are still under investigation, zero-echo time (ZTE)-based attenuation correction has recently been demonstrated to be an adequate method for brain PET/MR applications [ 12 , 13 , 14 ]. Third, 15 O-water PET is considered the gold standard for measuring CBF when using a kinetic modeling approach with an arterial input function (AIF) based on arterial sampling [ 1 , 15 , 16 ]. Although several studies compared CBF measurements with 15 O-water PET and ASL, none of them fulfilled all three requirements.…”