Imaging the airways in 2006.

Imaging has traditionally been separated into two distinct disciplines: functional imaging and structural imaging. Functional imaging encompasses applications such as nuclear medicine (single photon emission computed tomography [SPECT] and positron emission tomography [PET]), autoradiography, magnetic resonance spectroscopy (MRS) and magneto-encephalography (MEG), while structural, or anatomical, imaging includes planar radiography, x-ray computed tomography (CT), and magnetic resonance imaging (MRI). However, today, the distinctions between these are blurring due to advances in software fusion and the development of multi-modality (SPECT/CT, PET/CT) scanners. New techniques such as MRI using hyperpolarized gases (3H and 129Xe) and xenon K-edge synchrotron x-ray subtraction imaging are also being developed to provide the researcher with a variety of ways to probe the airways, and the distribution of pharmaceuticals and subsequent uptake and bio-distribution. This paper reviews advances in imaging to present a contemporary view of the tools available.