Evaluation of dynamic row-action maximum likelihood algorithm reconstruction for quantitative 15O brain PET.
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 (15)O 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 C(15)O, (15)O(2) 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 (CMRO(2)) 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 (15)O 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, CMRO(2) 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.


CONCLUSIONS
DRAMA reconstruction is applicable to quantitative (15)O PET study and is superior to conventional FBP in terms of image quality.
Ibaraki
Masanobu
M
Department of Radiology and Nuclear Medicine, Akita Research Institute of Brain and Blood Vessels, Akita 010-0874, Japan. iba@akita-noken.go.jp
Sato
Kaoru
K
Mizuta
Tetsuro
T
Kitamura
Keishi
K
Miura
Shuichi
S
Sugawara
Shigeki
S
Shinohara
Yuki
Y
Kinoshita
Toshibumi
T
D000368:Aged; D000465:Algorithms; D001921:Brain / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000378:metabolism; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods* / Q000592:standards; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000378:metabolism; D010104:Oxygen Radioisotopes; D049268:Positron-Emission Tomography / Q000379:methods* / Q000592:standards; D012015:Reference Standards
D010104:Oxygen Radioisotopes; D010100:Oxygen