Assessment of central airways mechanics using Magnetic Resonance Imaging (MRI) and bronchoscopy: a comparison

Central airways mechanics in pediatric diseases is little known in vivo. Acute
and chronic airway inflammation can produce increase softness of the tracheal
and bronchial wall, with so resulting tracheobronchomalacia (TBM). For
instance, in a study with Cystic Fibrosis (CF) patients, TBM was diagnosed in
69% of the subjects. Differently, when airway inflammation heals by fibrosis,
this can result in airway stenosis. This type of healing process is common in
diseases such as relapsing polychondrithis, endobronchial tuberculosis or
prolonged intubation.

Central airways are mostly assessed with flexible bronchoscopy and CT.
Bronchoscopy is considered the gold standard modality, because it allows direct
visualization of the airway. However, bronchoscopy is an invasive technique,
limited to assessment during tidal breathing and requiring general anaesthesia.
Assessments of airway shapes and cross-sectional area (CSA) during bronchoscopy
are troublesome since they are influenced by anesthetic agents, intrathoracic
and airway pressures, gas-flow dynamics, and lung volume. Additionally,
objective airway dimension measurement is compromised during bronchoscopy due
to optical distortions caused by the fish eye shaped lens. For these reasons,
CT is combined with bronchoscopy. CT has high temporal and spatial resolutions
that allow direct and precise measurement of the central airway. Moreover CT
supplies additional information about the structures surrounding the airway and
about the lung parenchyma. One limitation of CT is the radiation exposure that
for pediatric patient is still matter of concern. To overcome this limitation
of CT, magnetic resonance imaging (MRI) has been introduced in airway imaging.
MRI is a free-radiation technique that enables repeated and dynamic
acquisition. Dynamic acquisitions (cine-MRI) are needed for better
understanding central airways mechanics, because they elicit the driving forces
that regulate inspiratory and expiratory changes. The diagnostic performance of
cine-MRI has never been compared to bronchoscopy. If MRI will prove to be as
good as bronchoscopy to diagnose central airways diseases, it will be possible
to reduce the number of invasive bronchoscopy. We developed a new MRI protocol
for airway imaging that proved to be feasible in pediatric patients.

We hypothesize that the new MRI protocol will be sensitive enough to detect a
diagnostic change of >= 50% change from the normal shaped trachea. The primary
objective of this study is to determine sensitivity, and specificity, of our
MRI protocol compared to flexible bronchoscopy, used as reference test

Prospective, observational study

Participation in the study will add an extra visit to Sophia Children*s
Hospital. Total visit time will be approx. 1.45 hours: 40 minutes MRI scanning,
55 minutes lung function testing, training and bronchodilator (including 10
minute break), and 10 minutes for consent and questionnaire. Early and safe
diagnosis of airway disease is beneficial in initiating appropriate treatment
such as earlier commencement of antibiotic treatment during winter months.
Finally, appropriateness of using bronchodilators for TBM symptoms, the most
common, but potentially least appropriate treatment of TBM symptoms, will be
assessed.