Noninvasive Quantification of the Cerebral Metabolic Rate for Glucose Using Positron Emission Tomography, ¹⁸F-Fluoro-2-Deoxyglucose, the Patlak Method, and an Image-Derived Input Function

Abstract

The authors developed and tested a method for the noninvasive quantification of the cerebral metabolic rate for glucose (CMRglc) using positron emission tomography (PET), 18F-fluoro-2-deoxyglucose, the Patlak method, and an image-derived input function. Dynamic PET data acquired 12 to 48 seconds after rapid tracer injection were summed to identify carotid artery regions of interest (ROIs). The input function then was generated from the carotid artery ROIs. To correct spillover, the early summed image was superimposed over the last PET frame, a tissue ROI was drawn around the carotid arteries, and a tissue time activity curve (TAC) was generated. Three venous samples were drawn from the tracer injection site at a later time and used for the spillover and partial volume correction by non-negative least squares method. Twenty-six patient data sets were studied. It was found that the image-derived input function was comparable in shape and magnitude to the one obtained by arterial blood sampling. Moreover, no significant difference was found between CMRglc estimated by the Patlak method using either the arterial blood sampling data or the image-derived input function.

An input function estimation method for FDG-PET human brain studies

“…The within subject variation of K is comparable whether calculated using u p or u e . The results are comparable to those presented in [9], in which analysis of CMRglc for one subject yields R 2 .9997, slope 1.0018, and intercept −0.031.…”

“…The curve associated with the image data from CA-ROIs is obtained from the PET frames using the same protocol, and code as used in [9]. The initial time frames up to time 2 minutes are summed so as to emphasize those voxels which show the tracer in the CA-ROIs, typically 3 to 5 slices in the lower portion of the brain (for FDG-PET data acquired with the 951/31 EC AT scanner), and from which whole blood time activity curves for each observed CA-ROI can be calculated.…”

“…To provide a comparison with the method presented in [9], the recovered input for each subject is used in Patlak analysis for each cluster TTAC. The data of the last three frames, i.e.…”

“…These include obtaining arterialized venous plasma samples, [2], using population-based input functions, [3], [4], [5] estimating the rate constants using a multichannel blind identification without input function, [6], and simultaneously estimating (SIME) both the input and the kinetic parameters for a limited number of brain regions, [7], [8]. Other methodologies include constructing an image-derived input function, possibly combined with limited plasma sampling and/or the SIME approach, [9], [10], [11], [12]. Noting the risks and discomfort associated with any kind of plasma sampling, the PET Neuroimaging Working Group [1] has recommended that, where possible, PET studies be accomplished through use of a completely image-derived input function.…”

“…Noting the risks and discomfort associated with any kind of plasma sampling, the PET Neuroimaging Working Group [1] has recommended that, where possible, PET studies be accomplished through use of a completely image-derived input function. We make further progress toward this end by proposing a new functional model for the input function of FDG-PET which is then used to extend an existing image-derived approach [9].…”