Normal lung attenuation distribution and lung volume on computed tomography in a Chinese population

Figures & data

Figure 1 Flow chart for subject screening in the derivation group (A) and external validation group (B).

Table 1 Demographic characteristics of participants in the derivation and external validation groups

Characteristics	Median [IQR]
Groups	Derivation group	External validation group
Male/total	240/564	1066/1787
Height (cm)	163 [158–170]	-
Age (years)	58 [48–64]	60 [53–67]
Lung volume (mL)	4,423 [3,614–5,294]	4586 [3873–5524]
Weight (kg)	64. [57.-71.]
Body mass index (kg/m^2)	24 [22–26]
FEV1 (L)	2.56 [2.13–3.19]
FEV1% FVC	86.5 [81.29–92.49]
FVC (L)	2.95 [2.49–3.65]
TLC-SB (L)	5.12 [4.345–5.92]
RV%TLC-SB	40.54 [35.97–45.29]
DLCO SB (mmol/min/kPa)	7.43 [6.605–8.435]
DLCO/VA (mmol/min/kPa/L)	1.5 [1.405–1.66]
FVC%pred	94.3 [88.-101.2]
FEV1%pred	99.2 [92.4–106.9]
TLC-SB%pred	90.75 [85.1–97.]
DLCO SB%pred	88.05 [83.8–94.45]
DLCO/VA%pred	99.7 [93.58–109.5]

Abbreviations: IQR, interquartile range; RV, residual volume; TLC, total lung capacity; SB, single-breath; DLCO, diffusing capacity of the lung for carbon monoxide; pred, predicted.

Table 2 Description of lung attenuation distribution and lung volume from computed tomography (CT) in the derivation and external validation groups

Percentile	Group	2.5	25	50	75	95	97.5	99
Lung volume (mL)	Derivation	2169	3614	4423	5294	6680	6973	7845
	Validation	2344	3873	4586	5524	6649	7121	7494
LAA%(-960 HU)	Derivation	0	0	0.09	0.26	0.85	1.28	2.10
	Validation	0	0	0.07	0.25	0.69	1.05	1.84
LAA%(-950 HU)	derivation	0	0.03	0.19	0.43	1.2	2.17	3.05
	Validation	0	0.01	0.17	0.41	1.12	1.52	2.73
LAA%(-930 HU)	Derivation	0	0.22	0.56	1.42	5.22	7.59	13.32
	Validation	0	0.2	0.54	1.39	5.21	7.83	11.8
LAA%(-910 HU)	Derivation	0	0.81	2.41	7.84	22.84	29.87	38.79
	Validation	0	0.76	2.67	8.21	22.46	28.37	35.01
LAA%(-850 HU)	Derivation	0.82	25.66	46.86	62.72	73.86	76.61	78.93
	Validation	1.86	30.61	50.57	63.71	73.64	75.91	78.5
Perc 15 (HU)	Derivation	−921	−899	−884	−863	−810	−784	−768
	Validation	−921	−901	−887	−868	−829	−806	−783
V%(-950–700 HU)	Derivation	47.44	81.5	85.67	87.68	89.25	89.71	90.01
	Validation	59.66	82.94	86.06	87.68	89.25	89.62	90.06
V%(-800–500 HU)	Derivation	10.22	14.45	20.14	32.75	64.59	73.19	77.5
	Validation	10.41	14.01	18.39	28.1	55.13	66.51	75.37
V%(-700–500 HU)	Derivation	4.71	6.01	7.34	10.18	25.1	34.19	37.69
	Validation	4.81	5.87	7.01	8.98	18.91	25.76	34.05
V%(-1,000–900 HU)	Derivation	0.07	1.53	5.26	15.06	34.49	42.6	50.3
	Validation	0.04	1.63	6.33	16.14	34.46	40.79	48.18
V%(-900–500 HU)	Derivation	51.57	77.96	86.04	89.41	91.62	91.9	92.44
	Validation	53.71	77.46	85.96	89.81	91.96	92.44	92.79
V%(above-500 HU)	Derivation	4.91	6	6.75	8.23	13.62	18.1	23.05
	Validation	5.06	5.99	6.63	7.74	11.5	13.9	16.72
V(-950–700 HU)(mL)	Derivation	1066	2957	3798	4588	5938	6189	6939
	Validation	1462	3233	3937	4796	5880	6319	6628
V(-700–500 HU)(mL)	Derivation	246	292	348	417	648	746	833
	Validation	231	295	340	398	583	715	874

Abbreviations: LAA%, percentage of lung volume occupied by low attenuation areas; Perc 15, the 15th percentile of the histogram of attenuation values; V (given range), volume of lung with the CT attenuation within the given range; V% (given range), the ratio of V (given range) to the lung volume.

Figure 2 Distributions of LAA% and Perc n in subjects with normal lung function in males and females.

Abbreviations: LAA%, percentage of lung volume occupied by low attenuation areas; Perc n, percentile of the histogram of attenuation values.

Table 3 Reference equations and normal ranges for lung attenuation distribution and lung volume from computed tomography (CT) scans based on data from the derivation group

Indices	Normality of residual error	Reference equations and normal range
With height and weight
Lung volume (mL)	0.392	−1.015*10^4+605.3*Sex+92.61*Height-12.99*Weight±1766
LAA%(-950 HU)	0.098	[0.2027+0.05926 *Sex-4.111*10^-3*Weight+4.924*10^-3*Height+8.504*10^-4*Age]^7.341–0.05
		ULN: [0.2027 +0.05926 *Sex-4.111*10^-3*Weight+4.924*10^-3*Height+8.504*10^-4*Age+0.1993]^7.341–0.05
LAA%(-930 HU)	0.694	[0.1477 +0.06335 *Sex-3.957*10^-3*Weight+6.011*10^-3*Height+9.405*10^-4*Age]^10.63–0.05
		ULN: [0.1477 +0.06335 *Sex-3.957*10^-3*Weight+6.011*10^-3*Height+9.405*10^-4*Age+0.1741]^10.63–0.05
LAA%(-910 HU)	0.740	[-0.2288 +0.01058 *Height-6.500*10^-3*Weight+0.08544 *Sex]^8.201–0.05
		ULN: [-0.2288 +0.01058 *Height-6.500*10^-3*Weight+0.08544 *Sex+0.2991]^8.201–0.05
LAA%(-850 HU)	0.080	100-[4.436–0.01473 *Height+6.992*10^-3*Weight±0.1846]^4.405
Perc 15 (HU)	0.996	[-1.564*10^-3+1.391*10^-4*Sex+2.703*10^-5*Height-1.450*10^-5*Weight±8.607*10^-4]^-0.796–1024
V% (-950–700 HU)	0.079	100-(-0.02572–7.282*10^-5*Age+3.113*10^-4*Height-1.534*10^-4*Weight±9.114*10^-3)^-0.602
V% (-800–500 HU)	0.087	(-0.1977–3.777*10^-4*Age+2.925*10^-3*Height-1.345*10^-3*Weight±0.09071)^-1.742
V% (-700–500 HU)	0.101	(-0.1875–4.183*10^-4*Age+2.144*10^-3*Height-9.551*10^-4*Weight±0.06203)^-0.799
V% (-1,000–900 HU)	0.514	(-1.761+0.1724*Sex+0.02511*Height-0.01514*Weight±0.8356)^4.464
V% (-900 HU to -500 HU)	0.217	95-(1.145–0.03139*Sex-8.776*10^-4*Age-3.642*10^-3*Height+2.293*10^-3*Weight±0.168)^-4.878
V% (above -500 HU)	0.295	(-0.08562–2.522*10^-4*Age+1.059*10^-3*Height-5.596*10^-4*Weight±0.02495)^-0.59
V (-950–700 HU) (mL)	0.062	−9641+546.7*Sex-7.432*Age+89.43*Height-17.15*Weight±1911
V (-700 –500 HU) (mL)	0.022	(2.551*10^-4–1.441*10^-5*Sex-7.157*10^-7*Age-1.340*10^-6*Weight±8.117*10^-5)^-0.649
Without height and weight
Lung volume (mL)	0.566	4612+1495*Sex-13.99*Age±1960
LAA%(-950 HU)	0.283	[0.7894+0.06981*Sex]^7.341–0.05
		ULN: [0.7894+0.06981*Sex+0.2077]^7.341–0.05
LAA%(-930 HU)	0.481	[0.9218+0.08791*Sex]^10.63–0.05
		ULN: [0.9218+0.08791*Sex+0.1843]^10.63–0.05
LAA%(-910 HU)	0.490	[1.066+0.1406*Sex]^8.201–0.05
		ULN: [1.066+0.1406*Sex+0.3168]^8.201–0.05
LAA%(-850 HU)	0.048	100-[2.383–0.106*Sex+2.335*10^-3*Age±0.4393]^4.405
Perc 15 (HU)	0.836	[2.065*10^-3+2.882*10^-4*Sex-3.370*10^-6*Age±9.078*10^-4]^-0.796–1024
V% (-950–700 HU)	0.058	100-(0.01633+2.051*10^-3*Sex-1.033*10^-4*Age±9.647*10^-3)^-0.602
V% (-800–500 HU)	0.087	(0.2019+0.02202*Sex-6.541*10^-4*Age±0.09483)^-1.742
V% (-700–500 HU)	0.226	(0.1076+0.01595*Sex-6.243*10^-4*Age±0.06529)^-0.799
V% (-1,000–900 HU)	0.268	(1.33+0.3065*Sex±0.8855)^4.464
V% (-900–500 HU)	0.129	95-(0.6523–0.04607*Sex±0.1735)^-4.878
V% (above -500 HU)	0.629	(0.05517+6.497*10^-3*Sex-3.562*10^-4*Age±0.02734)^-0.59
V (-950–700 HU) (mL)	0.130	4094+1376*Sex-16.62*Age±2086
V (-700–500 HU) (mL)	0.060	(1.746*10^-4–2.861*10^-5*Sex-7.082*10^-7*Age±8.483*10^-5)^-0.649

Notes: For all equations, age was measured in years; height was measured in cm; weight was measured in kg; and sex was coded as 1= male, 0= female.

Abbreviations: LAA%, percentage of lung volume occupied by low attenuation areas; Perc 15, the 15th percentile of the histogram of attenuation values; V (given range), volume of lung with the CT attenuation within the given range; V% (given range), the ratio of V (given range) to the lung volume; ULN, upper limit of normal range.

Table 4 Lung volume and attenuation distribution from different scanners and reconstruction kernels

Manufacturer	Scanner	Kernel	n	Lung volume (mL)	LAA%(-950 HU)	LAA%(-910 HU)	Perc 15 (HU)
GE	Discovery CT750 HD	STANDARD	24	4105±1254	0.07 [0~0.21]	0.47 [0.22~2.47]	−857 [-885~-837]
GE	LightSpeed VCT	STANDARD	62	4220± 1302	0.20 [0.05~0.39]	1.11 [0.47~3.37]	−870 [-889~-844]
GE	LightSpeed16	STANDARD	281	4504 ±1331	0.23 [0.06~0.47]	2.90 [0.94~8.64]	−886 [-901~-868]
SIEMENS	Perspective	I31	101	4540 ± 1137	0.09 [0~0.29]	2.45 [0.79~9.16]	−886 [-903~-867]
SIEMENS	Perspective	I41	69	4444 ± 1169	0.12 [0~0.38]	2.13 [0.82~8.25]	−884 [-899~-863]
SIEMENS	SOMATOM Definition Flash	B26f	27	4779 ± 1253	0.36 [0.01~0.80]	3.44 [1.59~11.85]	−891 [-905~-877]

Abbreviations: LAA%, percentage of lung volume occupied by low attenuation areas; Perc 15, the 15th percentile of the histogram of attenuation values.

Table 5 Comparison between observed value of derivation group and the predicted value from different reference equations for lung volume and extent of emphysema

Indices	Mean difference	Mean absolute difference	% Observed values over the ULN	% Observed values below the LLN
Lung volume (mL)
Present 1	−4	709	1.42%	3.01%
Present 2	0	792	1.77%	2.30%
Hoffman 1	298	783	NA	4.43%
Come 1	−1010	1101	NA	NA
Come 2	−246	736	NA	NA
LAA%(-950 HU)
Present 1	−0.05	0.26	5.32%	NA
Present 2	0.15	0.28	5.85%	NA
Hoffman 2	−0.98	1.07	0.35%	NA
Hoffman 3	−0.76	0.87	6.56%	NA
Hoffman 4	−0.61	0.74	0.71%	NA

Notes: Present 1: the reference equations of the present study including sex, age, height, and weight. Present 2: the reference equations of the present study including only sex and age. Come 1: the reference equation for the lung volume of NHW. Come 2: the reference equation for the lung volume of African American. Hoffman 1: the reference equation for the lung volume. Hoffman 2: the reference equation for LAA%(-950 HU) for former smokers and never-smokers. Hoffman 3: the reference equation for LAA%(-950 HU) for current smokers (about five cigarettes per day). Hoffman 4: the reference equation for LAA%(-950 HU) for current smokers (about 20 cigarettes per day).

Abbreviations: LAA%, percentage of lung volume occupied by low attenuation areas; ULN, upper limit of normal range; LLN, lower limit of normal range.

Figure 3 Consistency and difference between computed tomography (CT) lung volume vs single-breath (SB) lung volume. (A) Scatter plot between lung volume measured on CT and lung volume measured by SB gas dilution method (total lung capacity [TLC]-SB). (B) Scatter plot between lung volume (CT) - TLC (SB) and TLC (SB). (C) Scatter plot between lung volume (CT) - TLC (SB) and vital capacity on spirometry. (D) Scatter plot between lung volume (CT) - TLC (SB) and age. (E) Scatter plot between lung volume (CT) - TLC (SB) and height. (F) Scatter plot between lung volume (CT) - TLC (SB) and weight.