Optical coherence tomography:
Optical coherence tomography (OCT) is a very informative imaging
technique that uses infrared light to image tissue in a similar way to
ultrasound. Due to the wavelength of infrared light, it is able to
visualise mucosa and cartilage with extreme accuracy below 1 mm giving
comparable views to tissue histology.42,43 OCT
requires a special 1 mm dragonfly catheter (St Jude Medical, Abbott
U.S.) which is passed through an endotracheal tube on a monorail system
under fluoroscopy - it can then image the exact calibre of the bronchi
and trachea including the mucosa and cartilage, which appears as a black
acoustic shadow. This technology can accurately identify if the
cartilage rings are complete or almost complete (pseudo-complete ring),
the latter being potentially balloon dilatable and subject to
growth(figure 12). OCT is also able to identify scar tissue and may be
able to assess the degree of healing around the tracheal suture lines.
The combination of echocardiography,bronchoscopy,bronchography and CT
imaging provide excellent information to plan the surgical approach. It
is also worth mentioning that antenatal foetal echocardiography can
detect pulmonary artery sling.44 There are increasing
reports on the diagnostic value of antenatal MRI for detection of
vascular and cardiac abnormalities in utero.45
Finally a genetic workup is also useful to detect major chromosomal
abnormalities such as Down syndrome or VACTERL which may be associated
with LPAS, especially if spinal and vertebral abnormalities or
imperforate anus are present.