Collateral ventilation in a canine model with bronchial obstruction: assessment with xenon-enhanced dual-energy CT

Purpose: To determine the feasibility of the use of xenon-enhanced dynamic dual-energy computed tomography (CT) for visualization and quantitative assessment of collateral ventilation in a canine model with bronchial obstruction.

Materials and methods: This study was approved by the institutional animal care and use committee. One segmental bronchus was occluded in nine dogs (weight range, 20-25 kg). Dynamic dual-energy CT scanning was performed by using dual-source CT during the wash-in-washout study of xenon inhalation via mechanical ventilation. Imaging parameters were 14 x 1.2-mm collimation, 40 mAs (effective) at 140 kV and 170 mAs (effective) at 80 kV, pitch of 0.45, and 0.33-second rotation time. By using dual-energy software, CT images and xenon maps were reconstructed. CT attenuation values were measured in the airways proximal to obstruction (AW(PROX)) and airways distal to obstruction (AW(DIST)) and at the parenchyma with patent airways (P(PATE)) and parenchyma with obstructed airways (P(OBST)). CT attenuation values on dynamic xenon maps were plotted with exponential function; ventilation parameters, including velocity of ventilation (K value), magnitude of ventilation (A value), and time of arrival (TOA), were calculated on the basis of the Kety model.

Results: In all animals, delayed and weaker xenon enhancement was identified at the airway and parenchyma distal to obstruction. For the A value, in the wash-in study, the differences between AW(PROX) and AW(DIST) and between P(PATE) and P(OBST) were significant (71.80 and 57.64, P = .05; 51.86 and 37.52 HU, P = .02). The K value of P(OBST) was lower than that of P(PATE) in the wash-in study (0.006 and 0 .010, P = .06). Mean and standard deviation for TOA were observed in the following increasing order: AW(PROX) ([3.50 +/- 7.70] x 10(-6) sec), P(PATE) (4.58 +/- 2.83), AW(DIST) (9.20 +/- 6.87), and P(OBST) (21.00 +/- 13.44).

Conclusion: Collateral ventilation in a canine model with bronchial obstruction can be quantitatively assessed by using xenon-enhanced dynamic dual-energy CT.