Addition of MRI for CT-based pancreatic tumor delineation: a feasibility study

Figures & data

Figure 1. Example slices of GTV delineated on 3DCT + MRI (a) or 3DCT-only [12] (b) and iGTV delineated on the Ave-IP using 4DCT + MRI (c) or 4DCT-only [12] (d). The MRI images (e–h) show the manually selected corresponding slice. The apparent diffusion coefficient map from the DWI acquisition is shown (h). T1W: T1-weighted; GE: gradient echo; CE: contrast enhanced; T2W: T2-weighted; TSE: turbo spin echo; DWI: diffusion-weighted imaging.

Table 1. Overview of the images.

	3DCT + MRI	3DCT-only^a	4DCT + MRI	4DCT-only^a
3DCT	X	X	+	+
4DCT Ave-IP	–	–	X	X
4DCT MIP	–	–	+	+
4DCT 10 phases	–	–	+	+
Diagnostic CTs	+	+	+	+
T1W GE	+	–	+	–
CE T1W GE	+	–	+	–
T2W TSE	+	–	+	–
DWI^b	+	–	+	–

X: images in main window, used for delineation; +: available in secondary window; Ave-IP: average intensity projection; MIP: maximum intensity projection; T1W GE: T1-weighted gradient echo; CE: contrast enhanced; T2W TSE: T2-weighted turbo spin echo; DWI: diffusion-weighted imaging.

^a These stages are from the CT-only study [12].

^b The apparent diffusion coefficient map of the DWI images was shown.

Table 2. Average volume, CI_gen, and overall observer variation.

	3DCT + MRI	3DCT-only^a	4DCT + MRI	4DCT-only^a
Average volume (cm^3)
Patient 1	13.3 (6.1–32.5)	36.7 (14.0–75.9)	19.3 (10.5–52.5)	41.8 (11.9–90.0)
Patient 2	9.1 (4.5–13.8)	20.3 (7.1–45.2)	18.5 (3.0–51.3)	20.6 (4.7–67.9)
Patient 3	5.7 (1.9–11.8)	10.4 (2.9–19.9)	11.0 (3.2–26.9)	32.4 (5.7–93.6)
Patient 4	53.4 (34.8–96.0)	52.3 (34.2–76.7)	59.8 (38.2–76.9)	65.5 (21.5–119.1)
Mean:	20.4	29.9	27.13	40.07
CIgen
Patient 1	0.31 (0.29–0.39)	0.34 (0.31–0.37)	0.25 (0.23–0.29)	0.29 (0.26–0.31)
Patient 2	0.34 (0.32–0.42)	0.22 (0.20–0.27)	0.17 (0.15–0.21)	0.20 (0.17–0.27)
Patient 3	0.23 (0.20–0.36)	0.34 (0.30–0.37)	0.20 (0.17–0.26)	0.16 (0.12–0.19)
Patient 4	0.56 (0.53–0.61)	0.59 (0.57–0.62)	0.61 (0.59–0.62)	0.45 (0.42–0.50)
Mean	0.36	0.37	0.31	0.27
Overall SD (cm)
Patient 1	0.43 (0.36–0.44)	0.70 (0.47–0.72)	0.57 (0.53–0.60)	0.71 (0.60–0.72)
Patient 2	0.40 (0.28–0.43)	0.84 (0.70–0.88)	1.11 (0.87–1.14)	0.90 (0.37–0.90)
Patient 3	0.40 (0.35–0.40)	0.48 (0.42–0.51)	0.62 (0.50–0.66)	0.89 (0.77–0.94)
Patient 4	0.43 (0.37–0.45)	0.43 (0.38–0.44)	0.39 (0.35–0.40)	0.68 (0.58–0.70)
Root-mean-square	0.41	0.63	0.73	0.80

SD: standard deviation (0: full agreement); CI_gen: generalized conformity index (0: no agreement, 1: full agreement).

Between brackets, range of volumes (average volume) and range of leave-one-out analyses (overall SD and CI_gen).

^a These results are from the CT-only study [12].

Figure 2. Scatter plots of the volume of the delineated iGTV on 3DCT + MRI (a), 4DCT + MRI (b), 3DCT-only (c) and 4DCT-only (d) per patient per observer. Median and interquartile ranges are indicated. Observer colors in the online article correspond to Figure 1(a–d). Graphs (c) and (d) are from Versteijne et al. [12].

Figure 3. The local observer variation (local SD) projected on the median surfaces of the iGTV for 3DCT + MRI (a), 3DCT-only (b), 4DCT + MRI (c) and 4DCT-only (d). Colors correlate to the local SD, with white (online: red) indicating local SD ≥9.4 mm. Volumes are viewed posterior of the patient (dummy). Note that for patient 2, the portocaval lymph node was included in b–d. Figures b and d are from Versteijne et al. [12].

Figure 4. For each patient, median surfaces for CT + MRI study (orange and light blue in the online version) and the CT-only study (red and dark blue in the online version) are shown.

Versteijne E, Gurney-Champion OJ, van der Horst A, et al. Considerable interobserver variation in delineation of pancreatic cancer on 3DCT and 4DCT: a multi-institutional study. Radiat Oncol. 2017;12:58.

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