Determination of optimal tracheal stent size using measurements derived from computed tomography

To devise a reliable method of predicting postplacement tracheal stent length using measurements from CT and to compare predicted versus actual stent length in a cohort of dogs undergoing stent placement for tracheal collapse grades I to III.

Retrospective analysis of 11 dogs undergoing tracheal stenting for tracheal collapse grades I to III.

Measurements of tracheal diameter were determined from stored CT images. Tracheal diameter was calculated from the square root of the product of the major and minor axes at 4 locations: 1 cm caudal to the larynx, the thoracic inlet, the midthoracic trachea, and 1 cm cranial to the carina. Values were averaged to determine predicted stent diameter in situ. The predicted length of the stent placed in each dog was calculated with regression formulas derived from the manufacturer's information regarding stent diameter and length. Actual stent length following deployment was determined from stored fluoroscopic images. Predicted stent lengths were compared to actual stent lengths, and the percent error was determined for each patient.

Appropriate images were available for 11 dogs. Differences in predicted length ranged from 0% to 5.5%, with a median of 2.32%. In 10 of 11 dogs, the error was < 5%.

Tracheal diameter can be reliably determined from CT imaging with the use of 4 specific locations in dogs with tracheal collapse grades I to III, allowing for accurate prediction of stent length after placement. This study will assist with appropriate stent size selection for dogs with tracheal collapse and is expected to improve procedural efficiency and efficacy.