A new method to validate thoracic CT-CT deformable image registration using auto-segmented 3D anatomical landmarks

Figures & data

Table I. The median bronchial branch point deviations following image registration.

Variable	Median (mm)	95% CI (mm)
Patient
1	1.4	(1.2; 1.5)
2	2.2	(1.9; 2.5)
3	1.8	(1.6; 2.0)
4	2.5	(2.2; 2.8)
5	2.0	(1.7; 2.3)
Algorithm
Demons	1.6	(1.4; 1.7)
B-spline	1.1	(1.0; 1.2)
Affine	4.2	(3.8; 4.7)
Branch position
Upper lung	1.7	(1.6; 1.9)
Middle lung	2.1	(1.9; 2.3)
Lower lung	2.0	(1.8; 2.2)

Figure 1. (A) Airway segmentation for a reference image (blue) with overlay of a registered image (red). Three superior-inferior positions for the bronchial bifurcations were defined as: upper, middle and lower lung positions. The bronchial branch point in the upper right and left lung segment were classified to the upper position. The right middle lung- and the ligulae segment in the left lung were classified as middle position and the right and left lower lung segment were classified to the lower position. (B) Bronchial segment following image registration where local deformations result in misaligned airway segment.

Table II. Centile distribution of the bronchial branch point deviation in (mm).

	Centile	5%	25%	50%	75%	95%	Max deviation
Demons	Combined	1	1	2	2	5	16
n = 108	Upper	1	1	1	2	4	7
n = 60	Middle	1	1	2	2	12	16
n = 71	Lower	1	1	2	2	3	6
B-spline	Combined	0	1	1	2	5	15
n = 105	Upper	0	1	1	2	3	15
n = 80	Middle	0	1	1	2	6	10
n = 86	Lower	0	1	1	2	8	9
Affine	Combined	1	3	5	6	10	13
n = 102	Upper	2	3	4	5	10	13
n = 56	Middle	1	3	4	6	10	13
n = 70	Lower	1	4	5	6	9	12

Bronchial branch point deviations (total n = 738) for all five patients divided into the three algorithms and superior/inferior position inside the lungs.

Table III. The body and lung DSC following image registration.

Dice coefficients	Body volume 95% CI	Lung volume 95% CI
Demons	0.99 (0.98; 0.99)	0.96 (0.96; 0.96)
B-spline	0.99 (0.99; 0.99)	0.97 (0.97; 0.98)
Affine	0.96 (0.96; 0.97)	0.91 (0.88; 0.95)

DSC calculated for all patients and scans separated into two volumes and the three algorithms.