Dose/volume-based evaluation of the accuracy of deformable image registration for the rectum and bladder

Figures & data

Table I. The Vmanual and the Vprop volumes [population median (range)]. The p-value refers to a Wilcoxon signed-rank test.

Volumes (cm^3)	Rectum	Bladder
Vmanual	82.5 (50.2–120)	130 (73.0–240)
Vprop	99.5 (51.3–121)	126 (76.5–251)
Vprop/Vmanual	1.02 (0.97–1.53)	1.07 (0.70–1.30)
p	0.31	0.17

Table II. Patient averages (range), given for one of the quantitative measures (DSC) and the qualitative measure.

Patient No.	Rectum		Bladder
	DSC	Qualitative	DSC	Qualitative
1	0.85 (0.76–0.98)	0.10 (0.02–0.19)	0.92 (0.88–0.95)	0.06 (0.00–0.31)
2	0.83 (0.76–0.87)	0.22 (0.05–0.44)	0.84 (0.71–0.93)	0.41 (0.17–0.68)
3	0.84 (0.79–0.87)	0.07 (0.02–0.27)	0.80 (0.67–0.93)	0.43 (0.21–0.59)
4	0.72 (0.66–0.80)	0.43 (0.32–0.57)	0.87 (0.84–0.91)	0.12 (0.00–0.23)
5	0.75 (0.69–0.79)	0.33 (0.13–0.52)	0.88 (0.82–0.93)	0.24 (0.00–0.64)
6	0.77 (0.74–0.83)	0.26 (0.14–0.42)	0.85 (0.76–0.92)	0.43 (0.06–0.67)
7	0.8l (0.80–0.83)	0.02 (0.00–0.11)	0.94 (0.90–0.95)	0.04 (0.00–0.13)
8	0.80 (0.76–0.85)	0.25 (0.00–0.40)	0.80 (0.76–0.85)	0.08 (0.00–0.16)
9	0.79 (0.69–0.86)	0.22 (0.00–0.65)	0.94 (0.87–0.95)	0.10 (0.00–0.52)

Table III. The investigated dose/volume-based measures [population median (range)] assessed for the Vmanual and the Vprop volumes.

Dose/volume measures	Rectum			Bladder
	Vmanual	Vprop	p	Vmanual	Vprop	p
gEUD (Gy)	58.3 (56.3–60.3)	58.8 (55.8–60.3)	0.37	59.9 (52.9–67.2)	59.4 (53.3–66.9)	0.26
V70Gy (%)	6.2 (3.7–9.0)	6.8 (3.5–9.7)	0.51	12.5 (4.7–29.1)	11.2 (4.9–27.5)	0.11
Dmean (Gy)	19.1 (9.4–27.2)	18.4 (7.7–24.2)	0.14	12.8 (2.6–45.3)	11.0 (2.5–44.1)	0.14

Figure 1. The linear correlation between two of the dose/volume-based measures (Rectum: DVHdiff; Bladder: gEUDdiff) and the volume variations related to the DIR quality (|Vprop-Vmanual|/Vmanual) or the actual volume variation (|Vmanual-VpCT|/VpCT) for the rectum (left) and the bladder (right).

Figure 2. An illustration of the association between the quality of the DIR and the resulting differences in the DVH for the bladder. Referring to the upper right plot in Figure 1, the two patients shown here are the patients with the largest (left), respectively the smallest (right) DIR quality related volume variations (|Vprop-Vmanual|/Vmanual = 0.30 and 0.01, respectively) and gEUDdiff (gEUDdiff = 1.94 and 0.47). For both patients, the scan shown is the scan with values of the DIR quality related volume variations closest to the median.

Table IV. Linear correlations (R²) between the dose/volume-based measures and the quantitative and qualitative measures. *p ≤ 0.05.

	Rectum				Bladder
R^2	DSC	|Vprop-Vmanual|/Vmanual	|Vmanual-VpCT|/VpCT	Qualitative	DSC	|Vprop-Vmanual|/Vmanual	|Vmanual-VpCT|/VpCT	Qualitative
gEUDdiff (Gy)	0.49*	0.15	0.11	0.47*	0.23	0.83*	0.61*	0.58*
V70diff (%)	0.45*	0.13	0.09	0.32	0.22	0.62*	0.32	0.56*
Dmeandiff (Gy)	0.46*	0.63*	0.76*	0.48	0.14	0.32	0.08	0.46*
DVHdiff (%)	0.79*	0.83*	0.85*	0.70*	0.39	0.81*	0.59*	0.74*