Differences in respiratory-induced pancreatic tumor motion between 4D treatment planning CT and daily cone beam CT, measured using intratumoral fiducials

Figures & data

Figure 1. Sum of pixel values over the ROI divided by the mean sum over all gantry angles (a, b) and the same signal after filtering out the change in attenuation and cardiac motion (c, d). The values on the vertical axes are given in arbitrary units (a.u.).

Figure 2. 4DCT (red solid lines) and CBCT data (boxplots) of respiratory-induced fiducial marker motion magnitude (MM) in (a) superior-inferior, (b) anterior-posterior and (c) left-right direction.

Table I. Tumor motion in superior-inferior direction, comparing 4DCT with daily CBCT.

Patient #	# of CBCTs	#(Δ ≥ 3 mm), (% of fractions)	#(Δ ≥ 5 mm), (% of fractions)	MM4DCT compared to mean MMCBCT (p-value)
1	25	1 (4%)	0 (0%)	0.0002
2	25	17 (68%)	2 (8%)	< 0.0001
3	25	2 (8%)	0 (0%)	0.69
4	25	0 (0%)	0 (0%)	0.35
5	25	12 (48%)	1 (4%)	< 0.0001
6	25	24 (96%)	22 (88%)	< 0.0001
7	25	0 (0%)	0 (0%)	0.0020
8	25	9 (36%)	1 (4%)	< 0.0001
9	17	0 (0%)	0 (0%)	0.0005
10	24	2 (8%)	0 (0%)	0.04
11	18	17 (94%)	9 (50%)	0.0002
12	25	23 (92%)	21 (84%)	< 0.0001
13	25	9 (36%)	1 (4%)	< 0.0001
14	10	0 (0%)	0 (0%)	0.08
15	25	7 (28%)	0 (0%)	0.57
16	27	2 (7%)	0 (0%)	0.001
17	15	10 (67%)	6 (40%)	0.0076
18	15	9 (60%)	4 (27%)	0.0026
All	401	144 (36%)	67 (17%)	NA

CBCT, cone beam computed tomography; MM_4DCT, tumor motion magnitude on 4DCT; MM_CBCT, tumor motion magnitude on CBCT; Δ, absolute difference between MM_4DCT and MM_CBCT; bold indicates p ≤ 0.01.

Figure 3. Marker motion in the superior-inferior direction during a CBCT, for 3 fractions (a–c). Circles indicate projections selected by the program to make end-inhale (open) and end-exhale (closed) phase reconstructions.

Figure 4. MM_CBCT values (closed symbols) in superior-inferior direction for patients 8 (a) and 15 (b), plotted as function of treatment day (day 0 is the day of planning CT). Lines are linear fits to the MM_CBCT data; slopes (mm/day) are indicated in the legends (*p < 0.05; **p < 0.01; ***p < 0.001). MM_4DCT values (open symbols) were not included in the fit.