Ultra-Low Dose CT vs Standard-Dose to Quantify Emphysema

Ultra-low dose CT (ULDCT) with and without iterative reconstruction (IR) can substitute for standard-low dose (SDCT) when quantifying emphysema, according to a study published in the American Journal of Roentgenology.                                                  

Researchers from Japan performed a retrospective study to evaluate the agreement between SDCT and ULDCT findings among 50 patients diagnosed with emphysema, with respect to emphysema quantification. ULDCT images were reconstructed with and without IR. Adaptive iterative dose reduction with 3D processing was used for IR.

All patients underwent SDCT (tube current: 250 mA) and ULDCT (tube current: 10 mA) and ULDCT with IR was used for emphysema quantification. The low-attenuation volume percentage (LAV%) in the lungs at four thresholds (−970, −950, −930, and −910 HU), mean lung attenuation, and total lung volume were computed. Concordance correlation coefficients (CCC) were used to assess the agreement of emphysema quantification between SDCT and ULDCT.

The results showed that the LAV% CCC values were 0.310–0.789 between SDCT and ULDCT without IR and 0.934–0.966 between SDCT and ULDCT with IR. The agreement of LAV% improved when IR was used for ULDCT. The mean lung attenuation CCC value between SDCT and ULDCT without IR was substantial (0.957), whereas that between SDCT and ULDCT with IR was poor (0.890). The total lung volume CCC values were substantial (0.982 with IR, 0.983 without IR).

The researchers concluded that using ULDCT with and without IR can substitute for SDCT in emphysema quantification.