Motion correction in simultaneous PET/MR brain imaging using sparsely sampled MR navigators: a clinically feasible tool.
BACKGROUND
We present a study performing motion correction (MC) of PET using MR navigators sampled between other protocolled MR sequences during simultaneous PET/MR brain scanning with the purpose of evaluating its clinical feasibility and the potential improvement of image quality.


RESULTS
Twenty-nine human subjects had a 30-min [(11)C]-PiB PET scan with simultaneous MR including 3D navigators sampled at six time points, which were used to correct the PET image for rigid head motion. Five subjects with motion greater than 4 mm were reconstructed into six frames (one for each navigator) which were averaged to one image after MC. The average maximum motion magnitude observed was 3.9 ± 2.4 mm (1 to 11 mm). Visual evaluation by a nuclear medicine physician of the five subjects' motion corrected rated three of the five images blurred before motion correction, while no images were rated blurred after. The image quality was scored on a scale of 1-5, 5 being best. The score changed from an average of 3.4 before motion correction to 4.0 after. There was no correlation between maximum motion magnitude and rating. Quantitative SUVr scoring did not change markedly with motion correction.


CONCLUSIONS
Sparsely sampled navigators can be used for characterization and correction of head motion. A slight, overall decrease in blurring and an increase in image quality with MC was found, but without impact on clinical interpretation. In future studies with noteworthy motion artifacts, our method is an important and simple-to-use tool to have available for motion correction.
3982 Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, DK-2100, Copenhagen, Denmark. sune@pet.rh.dk.
Sune H
SH
Keller
3982 Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, DK-2100, Copenhagen, Denmark. casper.hanzen@gmail.com.
Casper
C
Hansen
3982 Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, DK-2100, Copenhagen, Denmark. christian.hanzen@gmail.com.
Christian
C
Hansen
3982 Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, DK-2100, Copenhagen, Denmark. flemming.andersen@regionh.dk.
Flemming L
FL
Andersen
3982 Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, DK-2100, Copenhagen, Denmark. claes.noehr.ladefoged@regionh.dk.
Claes
C
Ladefoged
6931 Neurobiology Research Unit, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, DK-2100, Copenhagen, Denmark. claus.svarer@nru.dk.
Claus
C
Svarer
3982 Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, DK-2100, Copenhagen, Denmark. andreas.kjaer@regionh.dk.
Andreas
A
Kjær
3982 Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, DK-2100, Copenhagen, Denmark. liselotte.hoejgaard@regionh.dk.
Liselotte
L
Højgaard
3982 Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, DK-2100, Copenhagen, Denmark. ilaw@petnet.rh.dk.
Ian
I
Law
3982 Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, DK-2100, Copenhagen, Denmark. otto.moelby.henriksen.01@regionh.dk.
Otto M
OM
Henriksen
3982 Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, DK-2100, Copenhagen, Denmark. adam.espe.hansen@regionh.dk.
Adam E
AE
Hansen
Clinical tools; Motion correction; Motion quality control; Navigators; PET/MR; Rigid head motion