Evaluation of a reduced dose protocol for respiratory gated lung computed tomography in an animal model

We sought to evaluate and validate a low-dose protocol for respiratory-gated multislice computed tomography (CT) for volume calculations in small ventilated neonatal animals as a model for the ventilated human neonatal lung.

Five mechanically ventilated newborn piglets were imaged in a multislice CT scanner (0.5-mm slice thickness, 4:16 pitch, 0.5 seconds rotation time, 120 kV) using a normal (100 mAs) and a reduced (10 mAs) dose protocol. All animals were scanned twice (at 100 and 10 mAs) at each of 3 different ventilator settings. Complete volume datasets were reconstructed throughout the respiratory cycle in increments of 10% using retrospective half-scan reconstruction. End-inspiratory volumes and volumes during maximal expiration (functional residual capacity) were calculated by a customized software and values for normal and reduced dose protocols were compared using Kolmogorov-Smirnov test and Bland-Altman plots.

Two volume datasets (one normal and one reduced dose protocol) showed artifacts on the axial images, which could not be analyzed by the software. Those values were determined after manual segmentation and excluded from final analysis. The mean (+/-SD) end-inspiratory volumes and functional residual capacity were 34.3 +/- 10.1 mL and 25.3 +/- 8.0 mL for the normal-dose protocol versus 33.1 +/- 10.0 mL and 24.7 +/- 8.1 mL for the reduced-dose protocol, respectively. There was no statistically significant difference between normal and reduced dose protocol (KS-Test: D = 0.14 < Dmax).

Lung volume calculation in ventilated newborn piglets (end-inspiratory volumes and functional residual capacity) can be performed using respiratory-gated multislice CT even at a substantially reduced dose (eg, to 10 mAs). This makes the technique a candidate for future pediatric use.