title: A CT-, PET- and MR-imaging-compatible hyperbaric pressure chamber for baromedical research.
abstract: OBJECTIVE
  We describe the development of a novel preclinical rodent-sized pressure chamber system compatible with computed tomography (CT), positron emission tomography (PET) and magnetic resonance imaging (MRI) that allows continuous uncompromised and minimally invasive data acquisition throughout hyperbaric exposures. The effect of various pressures on the acquired image intensity obtained with different CT, PET and MRI phantoms are characterised.
  
  
  METHODS
  Tissue-representative phantom models were examined with CT, PET or MRI at normobaric pressure and hyperbaric pressures up to 1.013 mPa. The relationships between the acquired image signals and pressure were evaluated by linear regression analysis for each phantom.
  
  
  RESULTS
  CT and PET showed no effect of pressure per se, except for CT of air, demonstrating an increase in Hounsfield units in proportion to the pressure. For MRI, pressurisation induced no effect on the longitudinal relaxation rate (R₁), whereas the transversal relaxation rate (R₂) changed slightly. The R₂ data further revealed an association between pressure and the concentration of the paramagnetic nuclei gadolinium, the contrast agent used to mimic different tissues in the MRI phantoms.
  
  
  CONCLUSIONS
  This study demonstrates a pressure chamber system compatible with CT, PET and MRI. We found that no correction in image intensity was required with pressurisation up to 1.013 mPa for any imaging modality. CT, PET or MRI can be used to obtain anatomical and physiological information from pressurised model animals in this chamber.
authors.affiliation: Institute for Clinical Medicine, Aarhus University, Aarhus N, Denmark, MR Research Centre, Aarhus University, Aarhus N, Denmark, Comparative Medicine Lab and Institute for Clinical Medicine, Palle Juul-Jensens Boulevard 99, DK-8200 Aarhus N, Denmark, E-mail: kasperhansen@clin.au.dk.
authors.forename: Kasper
authors.initials: K
authors.lastname: Hansen
authors.affiliation: Institute for Clinical Medicine, Aarhus University, Aarhus N, Denmark, MR Research Centre, Aarhus University, Aarhus N, Denmark, Danish Diabetes Academy, Odense, Denmark.
authors.forename: Esben Ss
authors.initials: ES
authors.lastname: Hansen
authors.affiliation: Department of Nuclear Medicine and PET-Center, Aarhus University Hospital, Aarhus N, Denmark.
authors.forename: Lars P
authors.initials: LP
authors.lastname: Tolbod
authors.affiliation: Department of Procurement and Clinical Engineering, Central Denmark Region, Aarhus N, Denmark.
authors.forename: Martin C
authors.initials: MC
authors.lastname: Kristensen
authors.affiliation: Institute for Clinical Medicine, Aarhus University, Aarhus N, Denmark, MR Research Centre, Aarhus University, Aarhus N, Denmark.
authors.forename: Steffen
authors.initials: S
authors.lastname: Ringgaard
authors.affiliation: Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Alf O
authors.initials: AO
authors.lastname: Brubakk
authors.affiliation: Institute for Clinical Medicine, Aarhus University, Aarhus N, Denmark, Comparative Medicine Lab, Aarhus University, Aarhus N, Denmark.
authors.forename: Michael
authors.initials: M
authors.lastname: Pedersen
mesh_terms: D004867:Equipment Design / Q000379:methods; D006931:Hyperbaric Oxygenation / Q000295:instrumentation* / Q000379:methods; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000379:methods*; D011312:Pressure; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: Pressure chambers; animal model; equipment; hyperbaric research; pressure; radiological imaging