Emphysema quantification on low-dose CT using percentage of low-attenuation volume and size distribution of low-attenuation lung regions: Effects of adaptive iterative dose reduction using 3D processing

Purpose To evaluate the effects of adaptive iterative dose reduction using 3D processing (AIDR 3D) for quantification of two measures of emphysema: percentage of low-attenuation volume (LAV%) and size distribution of low-attenuation lung regions.

Method and materials: Fifty-two patients who underwent standard-dose (SDCT) and low-dose CT (LDCT) were included. SDCT without AIDR 3D, LDCT without AIDR 3D, and LDCT with AIDR 3D were used for emphysema quantification. First, LAV% was computed at 10 thresholds from -990 to -900 HU. Next, at the same thresholds, linear regression on a log-log plot was used to compute the power law exponent (D) for the cumulative frequency-size distribution of low-attenuation lung regions. Bland-Altman analysis was used to assess whether AIDR 3D improved agreement between LDCT and SDCT for emphysema quantification of LAV% and D.

Results The mean relative differences in LAV% between LDCT without AIDR 3D and SDCT were 3.73%-88.18% and between LDCT with AIDR 3D and SDCT were -6.61% to 0.406%. The mean relative differences in D between LDCT without AIDR 3D and SDCT were 8.22%-19.11% and between LDCT with AIDR 3D and SDCT were 1.82%-4.79%. AIDR 3D improved agreement between LDCT and SDCT at thresholds from -930 to -990 HU for LAV% and at all thresholds for D.

Conclusion AIDR 3D improved the consistency between LDCT and SDCT for emphysema quantification of LAV% and D.