Table 1. Protocols proposed for the reduction of either dose exposure or operator workload for quantitative or semi-quantitative lung aeration assessment in ARDS.

Method	Description	Irradiated portion of the chest	Number of slices used in the analysis	Validation	Estimated dose reduction	Limitations
Retrospective extrapolation of slices (25)	Extrapolation of 10 equally spaced slices	Whole chest	10	Retrospective (157 critically ill patients, 41 ponies, 23 pigs, 11 sheep)	NA	No dose reduction
Low dose spiral CT (26)	Spiral scans at 60 and 30 mAs	Whole chest	30–40, 5 mm-slices	Prospective (45 patients with ARDS at two PEEP levels, 14 sheep)	−70% with 30 mAs	No reduction of number of slices
Visual assessment (21)	Visual estimation of recruited lung tissue at two PEEP levels	Whole chest	30–40, 5 mm-slices	Retrospective (50 patients with ARDS, scans performed at two PEEP levels)	NA	No dose reduction
Ultra-low dose sequential CT (27)	Thin-slice sequential scan performed with 180 and 50 mAs	1 mm portions interleaved by 20 mm of non-irradiated chest	10–12, 1 mm-slices	Prospective (12 pigs), retrospective (32 critically ill patients)	−97% with 50 mAs	Longer acquisition time

ARDS, acute respiratory distress syndrome; PEEP, positive end-expiratory pressure; CT, computed tomography; NA, not applicable.