A new fast algorithm for the evaluation of regions of interest and statistical uncertainty in computed tomography

A new algorithm for region of interest evaluation in computed tomography has been developed. Region of interest evaluation is a technique used to improve quantitation of the tomographic imaging process by summing (or averaging) the reconstructed quantity throughout a volume of particular significance. An important application of this procedure arises in the analysis of dynamic emission computed tomographic data, wherein the uptake and clearance of radiotracers are used to determine the blood flow and/or physiologic function of tissue within the significant volume. The new algorithm replaces the conventional technique of repeated image reconstructions with one in which projected regions are convolved and then used to form multiple vector inner products with the raw tomographic data sets. Quantitation of regions of interest is made without the need for reconstruction of tomographic images. The computational advantage of the new algorithm over conventional methods is between a factor of 20 and a factor of 500 for typical application encountered in medical science studies. The greatest benefit of the new algorithm (and the motivation for its development) is the case with which the statistical uncertainty of the result is computed. The entire covariance matrix for the regions of interest can be calculated with relativelymore » few operations. Knowledge of the statistical uncertainties and correlations of the regions of interest results in a more efficient estimation of model parameters in the subsequent analysis of physiologic function from dynamic data.« less