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.