Are three computed tomography lung sections comparable with the whole lung?

Computed tomography (CT) has been shown to provide accurate measurements of lung tissue mass and volume. However, besides the risk of moving the patient from intensive care to CT scan and the high costs, the high radiological exposure to X-rays may limit the possibility for relatively frequent CT acquisition. One chest CT scan corresponds to 400 chest X-rays [1]. A possible solution to reduce the X-ray exposure could to be perform only three lung sections compared with the whole lung.

The aim of this study was to investigate the difference between the three CT slices technique versus the whole lung in acquiring clinical relevant data (i.e. hyperinflated, normally, poorly and not inflated lung zones).

Thirty-four intubated sedated paralyzed patients with ALI/ARDS (mean age 56.2 ± 18.2 years, BMI 23.7 ± 3.6 kg/m², PEEP 11.2 ± 2.8 cmH₂O, PaO₂/FiO₂ 195 ± 81) were enrolled. Spiral CT scan of the lung was acquired at 120 kV and 250 mA during an end expiratory pause at 5 and 15 cmH₂O PEEP. The lung CT regions of interest were manually delineated on each image by dedicated software (Maluna; University of Maanheim, Germany). The three CT lung sections were selected at the apex, hilum and base.

The Bland–Altman analysis showed a bias of 0.001% with an interval limits for agreement of 7.2% at 5 cmH₂O PEEP and of 0.00001% with 98% at 15 cmH₂O PEEP.

These data showed that the three CT scan technique provides an adequate measure of the distribution of lung compartments while strongly reducing X-ray exposure.

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