B L Knittel | Search PubMed

PubMed1986

Methodologic factors affecting PET measurements of cerebral glucose metabolism.

Measurements of cerebral glucose utilization rates in similar populations of human subjects under similar conditions vary considerably because of methods used in data collection and analysis. Using data acquired in two patients, we evaluated the effects of time schedule of data collection, region of interest size, method of attenuation correction, and input function shape on LCMRglu determined by dynamic positron emission tomographic scanning and calculation of rate constants. These different strategies of data acquisition and analysis produced variations of 3 to 14% in calculated LCMRglu. These factors, in conjunction with the well described effects of instrument resolution and sensitivity may account for data discrepancies in the literature.

Brain↗

PubMedDate not supplied

Dynamic PET data analysis.

A general method for estimating the precision of parameters resulting from the use of various experimental designs (rate of injection and rate of tomographic data collection) in emission tomography studies is proposed. The sensitivity matrix of the study model and an estimate of the statistical uncertainty of the tomographic data are used to compute the covariance matrix of the parameters. The determinant of this covariance matrix (proportional to the total volume of uncertainty of the model parameters) serves as a criterion to be minimized. The method is applied to a three-compartment, three-transfer rate constant for glucose metabolism using dynamic positron emission tomography, and a comparison of various current protocols is made with simulated data. The results show that higher rates of injection and higher rates of tomographic data collection at early times lead to smaller statistical uncertainties for the estimates of rate constants. However, for the range of rate constants encountered in practice, differences are insignificant when an initial scan duration less than 30 s is used, without regarding the injection duration.

Deoxyglucose↗