Table 3.

Summary statistics [median (interquartile range)] of image quality measures from the FDK the FIRST reconstruction methods. All metrics were computed using linear attenuation coefficients and not HU. RMSE, bias and percent difference in FWHM for microcalcifications were computed with respect to the reference FDK reconstruction. [FWHM: Full-Width at Half-Maximum]

Metric	FDK	FIRST	P-value
Signal-difference to noise ratio, SDNR	59.15 (49.23–62.20)	119.86 (117.41–145.36)	P<0.0001
Signal-difference (cm−1)	0.0657 (0.0563–0.0675)	0.0652 (0.0596–0.0692)	P=0.18
Variance within fibroglandular region ( × 10−4 cm−2)	1.03 (0.88–1.12)	0.25 (0.16–0.35)	P=0.0001
Variance within adipose region ( × 10−4 cm−2)	0.65 (0.57–0.90)	0.09 (0.05–0.17)	P<0.0001
% FWHM (x)	Reference	0 (0 – 0)	P=0.25
% FWHM (y)	Reference	0 (0 – −0.06)	P=0.125
RMSE ( × 10−6 cm−1)	Reference	3.52 (3.29–4.31)	NA
Bias ( × 10−4 cm−1)	Reference	58.64 (49.70–57.41)	NA