A Novel Approach to CT, MR, and PET Examination of Patients with Infections Requiring Stringent Airborne Precautions.

PURPOSE: To investigate the feasibility of using a modified portable isolation chamber, which conforms to Centers for Disease Control and Prevention (CDC) isolation requirements, in the imaging of infectious patients.

MATERIALS AND METHODS: This study was approved by the ethics committee, and all participants gave written informed consent. In this prospective study, the isolation chamber was assessed for computed tomographic (CT), magnetic resonance (MR), and positron emission tomographic (PET) image uniformity and noise by using uniform phantoms. For each modality, equivalent phantom examinations were performed without the isolation chamber. Paired analyses of the differences from these baseline values were conducted by finding the mean difference in the matched sections for each image quality parameter. A potential increase in CT patient dose was assessed, and MR radiofrequency (RF) interference was monitored. Eight participants with active pulmonary tuberculosis (mean age, 48.1 years; age range, 26-88 years; five men, three women) were then examined within a hybrid PET/MR imager. The 95% confidence intervals for the difference in the two matched population means were determined by using the two-sided t distribution for each of the phantom study imaging modalities.

RESULTS: Phantom images were evaluated for image uniformity and noise. Increased image noise can affect low contrast resolution, which has the potential to mimic or mask abnormalities when the differences between healthy and diseased tissues are small; clinically, CT image noise is maintained at a constant level with dose modulation. Increased attenuation of annihilation photons, when not corrected for, could lead to photopenic areas on the PET image; PET image nonuniformity complied with guidelines. Artifacts on the MR image due to RF noise spikes could mask abnormalities; paired analysis of variations in MR imaging mean signal-to-noise ratio and uniformity from baseline were within 5% for both gradient-echo and spin-echo sequences. In the eight participants who underwent imaging, the increased radiation dose for the attenuation of the isolation chamber would have resulted in a mean increase in patient size-specific dose estimate of 0.32 mGy ± 0.04 (standard deviation). The RF noise assessment revealed no prominent increase at any frequency band. The eight participants were examined within the isolation chamber without incident. CONCLUSION A modified portable isolation chamber, which conforms to CDC infection control guidelines, was found to be feasible within the confines of CT, MR imaging, and PET environments.