Impact of subject head motion on quantitative brain (15)O PET and its correction by image-based registration algorithm.
OBJECTIVE
Subject head motion during sequential (15)O positron emission tomography (PET) scans can result in artifacts in cerebral blood flow (CBF) and oxygen metabolism maps. However, to our knowledge, there are no systematic studies examining this issue. Herein, we investigated the effect of head motion on quantification of CBF and oxygen metabolism, and proposed an image-based motion correction method dedicated to (15)O PET study, correcting for transmission-emission mismatch and inter-scan mismatch of emission scans.


METHODS
We analyzed (15)O PET data for patients with major arterial steno-occlusive disease (n = 130) to determine the occurrence frequency of head motion during (15)O PET examination. Image-based motion correction without and with realignment between transmission and emission scans, termed simple and 2-step method, respectively, was applied to the cases that showed severe inter-scan motion.


RESULTS
Severe inter-scan motion (>3 mm translation or >5° rotation) was observed in 27 of 520 adjacent scan pairs (5.2 %). In these cases, unrealistic values of oxygen extraction fraction (OEF) or cerebrovascular reactivity (CVR) were observed without motion correction. Motion correction eliminated these artifacts. The volume-of-interest (VOI) analysis demonstrated that the motion correction changed the OEF on the middle cerebral artery territory by 17.3 % at maximum. The inter-scan motion also affected CBV, CMRO2 and CBF, which were improved by the motion correction. A difference of VOI values between the simple and 2-step method was also observed.


CONCLUSIONS
These data suggest that image-based motion correction is useful for accurate measurement of CBF and oxygen metabolism by (15)O PET.
Department of Radiology and Nuclear Medicine, Research Institute of Brain and Blood Vessels Akita, 6-10 Senshu-Kubota-machi, Akita, 010-0874, Japan. matsubara@akita-noken.jp
Keisuke
K
Matsubara
Masanobu
M
Ibaraki
Kazuhiro
K
Nakamura
Hiroshi
H
Yamaguchi
Atsushi
A
Umetsu
Fumiko
F
Kinoshita
Toshibumi
T
Kinoshita
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D016477:Artifacts; D001783:Blood Flow Velocity; D002560:Cerebrovascular Circulation; D002561:Cerebrovascular Disorders / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D005260:Female; D019416:Head Movements; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D008297:Male; D008875:Middle Aged; D010092:Oximetry / Q000379:methods; D010100:Oxygen / Q000378:metabolism; D010101:Oxygen Consumption; D010104:Oxygen Radioisotopes / Q000493:pharmacokinetics*; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D055815:Young Adult
D010104:Oxygen Radioisotopes; D019275:Radiopharmaceuticals; D010100:Oxygen