Quantitative parameters in novel spectral computed tomography: Assessment of Ki-67 expression in patients with gastric adenocarcinoma

Table 1 Inter-reader agreement of spectral parameters measurement

Parameters	ICC (95%CI)
	AP	VP
Zefflesion	0.88 (0.71, 0.95)	0.86 (0.69, 0.94)
Zeffaorta	0.94 (0.85, 0.97)	0.95 (0.88, 0.98)
IClesion (mg/mL)	0.86 (0.56, 0.95)	0.87 (0.73, 0.95)
ICaorta (mg/mL)	0.98 (0.94, 0.99)	0.95 (0.86, 0.98)
CT40 kev (HU)	0.95 (0.88, 0.98)	0.96 (0.79, 0.99)
CT70 kev (HU)	0.92 (0.78, 0.97)	0.91 (0.50, 0.98)
CT100 kev (HU)	0.86 (0.69, 0.94)	0.89 (0.70, 0.96)

ICC: Intraclass correlation coefficient; Z^eff_lesion and Z^eff_aorta: The effective atomic number of lesion and aorta; CT_{40 kev,} CT_{70 kev} and CT_{100 kev}: The computed tomography attenuation value of 40 kilo electron volt (kev), 70 kev and 100 kev monochromatic images; IC_lesion and IC_aorta: The iodine concentration of lesion and aorta; HU: Hounsfield unit; AP: Arterial phase; VP: Venous phase; 95%CI: 95% confidence interval.

Table 2 Correlation between spectral parameters and Ki-67 status

Parameters		Ki-67 status
		r (95%CI)	P value
AP	CT40 kev	-0.162 (-0.362, 0.043)	0.093
	CT70 kev	-0.097 (-0.290, 0.102)	0.316
	CT100 kev	-0.074 (-0.277, 0.117)	0.449
	λHU	-0.137 (-0.328, 0.056)	0.156
	Zeff	-0.427 (-0.606, -0.208)	< 0.001
	nZeff	-0.487 (-0.649, -0.318)	< 0.001
	IC	0.409 (0.228, 0.567)	< 0.001
	nIC	0.449 (0.288, 0.598)	< 0.001
VP	CT40 kev	-0.213 (-0.397, -0.005)	0.027
	CT70 kev	-0.216 (-0.407, -0.004)	0.025
	CT100 kev	-0.266 (-0.438, -0.096)	0.005
	λHU	-0.090 (-0.278, 0.093)	0.354
	Zeff	-0.455 (-0.647, -0.215)	< 0.001
	nZeff	-0.555 (-0.692, -0.403)	< 0.001
	IC	0.405 (0.223, 0.571)	< 0.001
	nIC	0.502 (0.355, 0.651)	< 0.001

Z^eff_AP and Z^eff_VP: The effective atomic number in the arterial and venous phase; nZ^eff_AP and nZ^eff_VP: The normalized effective atomic number in the arterial and venous phase; IC_AP and IC_VP: The iodine concentration in the arterial and venous phase; nIC_AP and nIC_AP: The normalized iodine concentration in the arterial and venous phase; CT_{40 kev,} CT_{70 kev} and CT_{100 kev}: The computed tomography attenuation value of 40 kilo electron volt (kev), 70 kev and 100 kev monochromatic images; λ_HU: The slope of the spectral curve; HU: Hounsfield unit; AP: Arterial phase; VP: Venous phase; 95%CI: 95% confidence interval.

Table 3 Comparison of dual-layer spectral detector computed tomography-derived parameters between low and high Ki-67 expression status

	Parameters	Low Ki-67 status	High Ki-67 status	t value	P value
AP	CT40 kev	177.3 ± 43.9	162.3 ± 37.8	1.85	0.068
	CT70 kev	90.9 ± 20.1	85.5 ± 16.6	1.48	0.141
	CT100 kev	63.8 ± 12.7	61.7 ± 12.6	0.81	0.422
	λHU	2.88 ± 1.04	2.56 ± 0.98	1.58	0.118
	Zeff	8.30 ± 0.19	8.21 ± 0.10	2.87	0.006
	nZeff	0.78 ± 0.04	0.74 ± 0.03	5.33	< 0.001
	IC (mg/mL)	1.61 ± 0.15	1.73 ± 0.19	-3.53	0.001
	nIC	0.15 ± 0.02	0.19 ± 0.04	-5.88	< 0.001
VP	CT40 kev	265.9 ± 61.4	237.3 ± 45.8	2.50	0.016
	CT70 kev	126.5 ± 33.4	108.0 ± 20.9	3.07	0.003
	CT100 kev	84.3 ± 18.7	73.9 ± 17.2	3.71	0.005
	λHU	4.65 ± 1.43	4.31 ± 1.15	1.33	0.185
	Zeff	8.75 ± 0.24	8.62 ± 0.15	3.04	0.004
	nZeff	0.87 ± 0.04	0.83 ± 0.03	6.59	< 0.001
	IC (mg/mL)	2.62 ± 0.17	2.75 ± 0.21	-3.40	0.001
	nIC	0.41 ± 0.04	0.46 ± 0.06	-5.87	< 0.001

CT_{40 kev}, CT_{70 kev} and CT_{100 kev}: The computed tomography attenuation values of at 40 kilo electron volt (kev), 70 kev and 100 kev respectively; λ_HU: The slope of the spectral curve; Z^eff: Effective atomic number; nZ^eff: The normalized effective atomic number; IC: Iodine concentration; nIC: Normalized iodine concentration; AP: Arterial phase; VP: Venous phase.

Table 4 Receiver operator characteristic analysis of spectral parameters in differentiating Ki-67 low expression status from high expression status

		AUC (95%CI)	TV	YI	Sen (%)	Spe (%)	PPV (%)	NPV (%)	Acc (%)
AP	Zeff	0.759 (0.668, 0.836)	≤ 8.27	0.67	85.92	81.08	92.96	37.84	71.30
	nZeff	0.796 (0.707, 0.867)	≤ 0.74	0.67	80.28	86.49	85.92	54.05	75.00
	IC	0.752 (0.660, 0.830)	> 1.63	0.60	78.87	81.08	88.73	21.62	65.74
	nIC	0.773 (0.683, 0.848)	> 0.16	0.61	74.65	86.49	81.69	48.65	70.37
VP	CT40 kev	0.630 (0.531, 0.721)	≤ 271.2	0.26	80.28	45.95	95.77	24.32	71.30
	CT70 kev	0.631 (0.533, 0.722)	≤ 138.8	0.31	92.96	37.84	94.37	32.43	73.15
	CT100 kev	0.662 (0.565, 0.750)	≤ 89.3	0.28	81.69	45.95	87.32	32.43	68.52
	Zeff	0.777 (0.687, 0.851)	≤ 8.75	0.73	88.73	83.78	92.96	29.73	74.07
	nZeff	0.835 (0.751, 0.899)	≤ 0.83	0.68	78.87	89.19	85.92	51.35	74.07
	IC	0.747 (0.654, 0.826)	> 2.65	0.63	84.51	78.38	85.92	27.03	65.74
	nIC	0.805 (0.718, 0.875)	> 0.43	0.71	78.87	91.89	85.92	37.84	69.44
Multi-parameters		0.967 (0.913, 0.992)	-	0.88	95.77	91.89	97.18	86.49	93.52

AUC: Area under the curve; TV: Threshold value; YI: Youden index; Sen: Sensitivity; Spe: Specificity; NPV: Negative predictive value; PPV: Positive predictive value; Acc: Accuracy; Z^eff_AP and Z^eff_VP: The effective atomic number in the arterial and venous phase; nZ^eff_AP and nZ^eff_VP: The normalized effective atomic number in the arterial and venus phase; IC_AP and IC_VP: The iodine concentration in the arterial and venous phase; nIC_AP and nIC_AP: The normalized iodine concentration in the arterial and venous phase; CT_{40 kev}, CT_{70 kev} and CT_{100 kev}: The computed tomography attenuation values of at 40 kilo electron volt (kev), 70 kev and 100 kev respectively.