Session PC7.4

Partial Volume Correction of Small Animal PET Cardiac Dynamic Images Using Iterative Reconstruction: Effects on Glucose Metabolic Rate Measurement

D D'Ambrosio*, G Fiacchi, P Cilibrizzi, C Lamberti, G Baldazzi,
S Boschi, R Franchi, M Marengo, AE Spinelli

Scuola di Specializzazione in Fisica Sanitaria
Bologna, Italy

Introduction: Small animal positron emission tomography (PET) image quantitation is severely affected by partial volume effect (PVE) caused by the spatial resolution of PET tomographs. The aim of this work was to reduce the PVE using an iterative expectation maximization (EM) reconstruction algorithm based on the inclusion of the point spread function (PSF) into the system matrix. More precisely the goals of the method were to increase the accuracy of regions of interest (ROI) tracer concentration values in order to obtain an in vivo better estimate of physiological parameters such as for example the glucose metabolic rate (GMR).
Material and Methods: The performance of the proposed correction method was evaluated by calculating ROI (left ventricle and myocardium) mean value using simulated cardiac fluorodeoxyglucose (FDG) dynamic images (40 frames, 30min total scan time). The full width at half maximum (FWHM) of the system PSF was set to 1.5 mm to simulate the spatial resolution of a typical small animal PET scanner. Simulations were performed in order to compare the known metabolic rate with the one obtained from reconstructed images with and without PVE correction. ROI mean values of the uncorrected and PVE corrected mouse phantom images were then used to calculate the FDG metabolic rate using the Patlak graphical analysis. The PVE correction was also applied to true rat images and the improvement of spatial resolution was tested by drawing line profiles across the myocardium and left ventricle.
Results: The FDG GMR obtained without PVE correction was about 30% lower with respect to the true value while for PVC images the difference was about 10%. Both images where reconstructed using 100 iterations. Line profiles drawn across the uncorrected and PVC corrected images showed a significant improvement in the delineation of the myocardium and the left ventricle.
Conclusions: The proposed method PVE correction method shows a significant improvement with regard to GMR measurements using FDG. Future work will be focused on the effect of PVE correction on myocardium perfusion and cardiac output measurements using small animal PET.

(Abstract Control Number: 263)