A CT-, PET- and MR-imaging-compatible hyperbaric pressure chamber for baromedical research

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.

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.

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.

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.