HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in JNM Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Pan, X.-B. Articles by Silverman, D. H.S. Search for Related Content PubMed PubMed Citation Articles by Pan, X.-B. Articles by Silverman, D. H.S.

Improving Influx Constant and Ratio Estimation in FDOPA Brain PET Analysis for Parkinson’s Disease

¹ Siemens Molecular Imaging, Oxford, United Kingdom
² Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, UCLA, Los Angeles, California

PET studies using L-3,4-dihydroxy-6-¹⁸F-fluorophenylalanine have been applied to assess the diminished functionality of the striatum in patients with suspected Parkinson’s disease. Two techniques for analyzing such studies are ratio methods and graphically computed influx constants. We propose a method for improving the consistency with which scans obtained by either of these techniques are analyzed. The method is based on a fully 3-dimensional analysis of the images. Methods: Fifty-one dynamically acquired datasets were corrected for motion before analysis. Regions of interest (ROIs) for the analysis were determined by manual affine registration to a standard template, using a separate transformation for each ROI. Indicator values for each ROI were computed by averaging the values of voxels having the highest activity within a specified proportion of the voxels in the ROI, to increase the robustness to perturbations in the ROI position. Sensitivity was analyzed by examining the variation in results obtained when the ROIs were translated by up to 6 mm. Results: We observed significant percentage differences in the computed influx constant before and after motion correction (mean variation ± SD, –0.75% ± 9.5% averaged over all regions of all patients). Our method was robust to placement of the cerebellum ROI, whereas a 2- dimensional analysis based on hand-drawn ROIs was associated with a 2- to 3-fold greater percentage variation in uptake for translations of 2 mm or more in ROI position. When we compared the 2 quantification techniques, our influx constants and ratios correlated at r² = 0.91, P < 0.0001. Conclusion: Motion correction is an important step for computing reliable results in dynamic studies. The robustness of the results can be increased further by using standard normalized volumetric ROIs and by using the average value of a specified proportion of the voxels with the highest activity in the ROI as an indicator for that ROI. Influx constant values computed using our analysis technique closely correlated to values computed with ratio methods using this general approach.

Key Words: FDOPA • Patlak graphical analysis • ratio method • Parkinson’s disease • PET

Related articles in JNM:

THIS MONTH IN JNM

JNM 2005 46: 8a-9a. [Full Text]