title: Effect of patient arm motion in whole-body PET/CT.
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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: 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
authors.forename: Martin A
authors.initials: MA
authors.lastname: Lodge
authors.forename: Joyce C
authors.initials: JC
authors.lastname: Mhlanga
authors.forename: Steve Y
authors.initials: SY
authors.lastname: Cho
authors.forename: Richard L
authors.initials: RL
authors.lastname: Wahl
mesh_terms: D001132:Arm / Q000502:physiology*; D016477:Artifacts; D006801:Humans; D009068:Movement; D064847:Multimodal Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography; D012542:Scattering, Radiation; D014057:Tomography, X-Ray Computed; D051598:Whole Body Imaging / Q000379:methods*
references.citation: Eur J Nucl Med Mol Imaging. 2003 Apr;30(4):588-96
references.pmid: 12582813
references.citation: Phys Med Biol. 2004 Jun 21;49(12):2577-98
references.pmid: 15272675
references.citation: J Nucl Med. 2006 Dec;47(12):1960-7
references.pmid: 17138738
references.citation: Eur J Nucl Med Mol Imaging. 2010 Mar;37(3):505-16
references.pmid: 19789872
references.citation: AJR Am J Roentgenol. 2006 May;186(5):1458-67
references.pmid: 16632745
references.citation: J Nucl Med. 2010 Oct;51(10):1501-6
references.pmid: 20847169
references.citation: Phys Med Biol. 1976 May;21(3):390-8
references.pmid: 778862
references.citation: Phys Med Biol. 1996 Jan;41(1):153-76
references.pmid: 8685253
references.citation: Eur J Nucl Med Mol Imaging. 2010 Jan;37(1):181-200
references.pmid: 19915839
references.citation: Semin Nucl Med. 2008 May;38(3):167-76
references.pmid: 18396177
references.citation: J Comput Assist Tomogr. 1983 Feb;7(1):42-50
references.pmid: 6600755
references.citation: Eur J Nucl Med Mol Imaging. 2007 Sep;34(9):1447-54
references.pmid: 17318548
references.citation: Med Phys. 1998 Oct;25(10):2046-53
references.pmid: 9800714
references.citation: Phys Med Biol. 2008 Oct 21;53(20):5705-18
references.pmid: 18812649
references.citation: Nucl Med Commun. 2004 Mar;25(3):221-5
references.pmid: 15094438
references.citation: J Nucl Med. 2006 Dec;47(12):1936-44
references.pmid: 17138736
references.citation: J Nucl Med. 2006 Jan;47(1):91-9
references.pmid: 16391192
references.citation: J Nucl Med. 2005 Jun;46(6):1059-65
references.pmid: 15937320
references.citation: Eur J Nucl Med Mol Imaging. 2008 Feb;35(2):305-10
references.pmid: 17909791
references.citation: J Nucl Med. 2006 May;47(5):885-95
references.pmid: 16644760