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J Nucl Med. 2011 Dec;52(12):1891-7. doi: 10.2967/jnumed.111.093583. Epub 2011 Nov 11.

Effect of patient arm motion in whole-body PET/CT.

Author information

1
Division of Nuclear Medicine, Russell H Morgan Department of Radiology and Radiological Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA. mlodge1@jhmi.edu

Abstract

Arm motion during whole-body PET/CT acquisition is not uncommon and can give rise to striking cold artifacts on PET images. We investigated the mechanisms that underlie these artifacts and proposed a potential solution.

METHODS:

A phantom experiment based on 5 clinical cases of suspected arm motion was designed. The experiment involved a central 20-cm-diameter (68)Ge/(68)Ga cylinder simulating the neck and 2 peripheral 10-cm-diameter (18)F cylinders simulating arms. After motion-free CT and PET on a whole-body PET/CT system, the position of the arms was altered so as to introduce different amounts of misalignment. Twenty sequential PET scans were acquired in this position, alternating between 2-dimensional (2D) and 3-dimensional (3D) acquisition, as the (18)F decayed. Decay of (18)F in the arms, while the activity in the (68)Ge/(68)Ga cylinder remained approximately constant, allowed the relative impact of scatter and attenuation-correction errors to be determined.

RESULTS:

Image artifacts were largely confined to the local region of motion in 2D but extended throughout the affected slices in 3D, where they manifested as a striking underestimation of radiotracer concentration that became more significant with increasing misalignment. For 3D, scatter-correction error depended on activity in the arms, but for typical activity concentrations scatter-correction error was more significant than attenuation-correction error. 3D image reconstruction without scatter correction substantially eliminated these artifacts in both phantom and patient images.

CONCLUSION:

Reconstruction artifacts due to patient arm motion can be substantial and should be recognized because they can affect both qualitative and quantitative assessment of PET.

PMID:
22080444
PMCID:
PMC4337880
DOI:
10.2967/jnumed.111.093583
[Indexed for MEDLINE]
Free PMC Article
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