Published in:
01-09-2009 | Original Article
Evaluation of dynamic row-action maximum likelihood algorithm reconstruction for quantitative 15O brain PET
Authors:
Masanobu Ibaraki, Kaoru Sato, Tetsuro Mizuta, Keishi Kitamura, Shuichi Miura, Shigeki Sugawara, Yuki Shinohara, Toshibumi Kinoshita
Published in:
Annals of Nuclear Medicine
|
Issue 7/2009
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Abstract
Objective
A modified version of row-action maximum likelihood algorithm (RAMLA) using a ‘subset-dependent’ relaxation parameter for noise suppression, or dynamic RAMLA (DRAMA), has been proposed. The aim of this study was to assess the capability of DRAMA reconstruction for quantitative 15O brain positron emission tomography (PET).
Methods
Seventeen healthy volunteers were studied using a 3D PET scanner. The PET study included 3 sequential PET scans for C15O, 15O2 and H
2
15
O. First, the number of main iterations (N
it) in DRAMA was optimized in relation to image convergence and statistical image noise. To estimate the statistical variance of reconstructed images on a pixel-by-pixel basis, a sinogram bootstrap method was applied using list-mode PET data. Once the optimal N
it was determined, statistical image noise and quantitative parameters, i.e., cerebral blood flow (CBF), cerebral blood volume (CBV), cerebral metabolic rate of oxygen (CMRO2) and oxygen extraction fraction (OEF) were compared between DRAMA and conventional FBP. DRAMA images were post-filtered so that their spatial resolutions were matched with FBP images with a 6-mm FWHM Gaussian filter.
Results
Based on the count recovery data, N
it = 3 was determined as an optimal parameter for 15O PET data. The sinogram bootstrap analysis revealed that DRAMA reconstruction resulted in less statistical noise, especially in a low-activity region compared to FBP. Agreement of quantitative values between FBP and DRAMA was excellent. For DRAMA images, average gray matter values of CBF, CBV, CMRO2 and OEF were 46.1 ± 4.5 (mL/100 mL/min), 3.35 ± 0.40 (mL/100 mL), 3.42 ± 0.35 (mL/100 mL/min) and 42.1 ± 3.8 (%), respectively. These values were comparable to corresponding values with FBP images: 46.6 ± 4.6 (mL/100 mL/min), 3.34 ± 0.39 (mL/100 mL), 3.48 ± 0.34 (mL/100 mL/min) and 42.4 ± 3.8 (%), respectively.
Conclusion
DRAMA reconstruction is applicable to quantitative 15O PET study and is superior to conventional FBP in terms of image quality.