Quantitation of Local Cerebral Blood Flow and Partition Coefficient without Arterial Sampling: Theory and Validation

Abstract

A new technique that requires neither arterial blood sampling nor prior knowledge of the indicator's tissue-blood partition coefficient has been developed for quantitation of local CBF. This technique arises from an existing method that uses the inert, freely diffusible gaseous tracer [18F]methyl fluoride (CH3(18)F) and positron computed tomography. The shape of the arterial blood curve is derived from continuous sampling of expired air. The concentration of CH3(18)F in the arterial blood is assumed to be proportional to the expired gas curve interpolated between end-tidal values. The absolute scale of the blood curve is determined by fitting a series of venous blood samples to a multicompartment model. Four validation studies were performed to compare values derived using the venous scaled expired breath input function with those derived using direct arterial samples. The proposed method gave higher flow values than the standard arterial sampling method by an average of 4.4%. These validation studies and data from both normal and patient scans suggest that the method provides the quantitation necessary for interstudy comparisons yet avoids the trauma of an arterial puncture.

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

“…Mintun et al [27] proposed a three-step method which includes 15 15 O-water PET were also proposed and the three-step method was improved. Several methods for image calculation and correction were also proposed and simulated to improve the image quality and calculation time [44][45][46][47][48][49][50][51][52][53][54][55][56][57]. A two-compartment (one-tissue compartment) model analysis increased the accuracy of CBF values by separating the vascular component from the blood flow value as shown in Fig.…”

Parametrically defined cerebral blood vessels as non-invasive blood input functions for brain PET studies

“…A number of alternatives to arterial blood sampling have been investigated, such as arterialized venous blood sampling (Phelps et al 1979), continuous sampling of expired air (Koeppe et al 1985, use of an external lung monitor (Nelson et al 1993), continuous infusion of the radiotracer (Carson et al 1993), population-based input functions (Takikawa et al 1993), and reference tissue input models (Lammertsma et al 1996, Di Bella et al 1999. A promising method that circumvents many of the problems related to arterial blood sampling consists of drawing regions of interest (ROI) in the blood pools visible on the PET images.…”

PET Measurement of rCBF in the presence of a neurochemical tracer

“…Tissue:blood partition coefficients for body, lung, and brain were fixed at a value measured for human brain using [ 18 F]fluoromethane and PET with arterial sampling (Koeppe et al, 1985),…”