Table 1.

Quality categories for dynamic 4-D CT

Category	Criteria
Good - diagnostic	Successfully performed without motion or density artefact, i.e. all of these criteria: a) Included all the relevant anatomy/pathology. b) Clearly included an inspiratory and an expiratory phase (as determined by a clear motion of the airway in a craniocaudal direction and with clear change in the caliber of the airway in the axial plane). c) Not degraded by motion or density artefact.
Acceptable - diagnostic	Achieved with motion or density artefact but remained interpretable, i.e. all of these criteria: a) Included all the relevant anatomy/pathology. b) Included an inspiratory and an expiratory phase (as determined by a clear motion of the airway in a craniocaudal direction and with clear change in the caliber of the airway in the axial plane). c) Degraded by motion or density artefact that did not prevent evaluation and measurement of the airway collapsibility in the areas of interest.
Poor and nondiagnostic	Achieved incompletely, with motion or density artefact that made it uninterpretable, i.e. any of these criteria: a) Did not include all the relevant anatomy/pathology. b) Did not include an inspiratory and an expiratory phase (as determined by a clear motion of the airway in a craniocaudal direction and with clear change in the caliber of the airway in the axial plane). c) Significant artefact caused misregistration of structures during respiratory phases on reconstructions. d) Significant artefact caused obscuration of relevant pathology/anatomy. e) Significant artefact precluded evaluation and measurement of the airway collapsibility in the areas of interest.