Reduced inter-observer and intra-observer delineation variation in esophageal cancer radiotherapy by use of fiducial markers

Figures & data

Table 1. Patient, tumor, and fiducial marker characteristics.

Patient	Age	Sex	Tumor length (cm)	TNM	Histology	Tumor location	Tumor visibility on pCT	Cardia involvement	Marker type	Markers on tumor border?	No. of markers on pCT
1	73	M	4	T2N0M0	SCC	Proximal	Clear	No	HG	Yes	3
2	71	M	5	T4aN2M0	SCC	Distal	Clear	Yes	HG	Yes	5
3	84	M	7	T3N1M0	AD	Distal	Clear	No	HG	Yes	3
4	70	M	5	T2N1M0	SCC	Proximal	Poor	No	FM	1 cm below caudal border	3
5	65	F	5	T2N0M0	SCC	Middle	Poor	No	FM	0.5 cm below cranial border	3
6	45	M	4	T2N1M0	AD	Distal	Poor	Yes	FM	Yes	3
7	61	M	6	T3N2M0	AD	Distal	Poor	Yes	FM	Yes	3
8	63	M	10	T3N2M0	AD	Distal	Clear	Yes	FM	2 cm below caudal border	4
9	75	M	3	T3N1M0	SCC	Distal	Poor	No	SM	Yes	2
10	61	M	6	T3N1M0	AD	Distal	Clear	No	FM	1 cm above caudal border	3

Abbreviations: AD: adenocarcinoma; F: female; FM: flexible coil-shaped gold marker; HG: injectable radiopaque hydrogel; M: male; pCT: planning computed tomography; SCC: squamous cell carcinoma; SM: solid rigid gold marker.

Figure 1. Delineations of patient 5 on the planning computed tomography without (left) and with markers (right). The delineations of the individual observers are indicated in different colors. The colors match the same observer throughout this work. Red arrows indicate fiducial markers. Insert demonstrates transversal slice without delineations.

Figure 2. Anterior view of the local surface distance variation (SD) over the five observers projected on the median surface of the 10 patients in the series without and with markers. Column (a) the original series (b) the repeated series.

Table 2. Inter-observer overall SD as well as longitudinal and radial SDs of delineations on CTs without (left columns) and with (right columns) markers.

Patient	Overall SD [cm]				Longitudinal SD [cm]												Radial SD [cm]
					At cranial end				At caudal end				At both ends
	Without markers		With markers		Without markers		With markers		Without markers		With markers		Without markers		With markers		Without markers		With markers
With clearly visible tumor
1	0.35	0.25	0.24	0.27	0.62	0.25	0.21	0.47	0.67	0.83	0.47	0.36	0.64	0.62	0.37	0.42	0.28	0.19	0.21	0.21
2	0.54	0.39	0.34	0.24	0.74	0.35	0.14	0.20	0.72	0.38	0.50	0.56	0.73	0.37	0.37	0.42	0.78	0.45	0.42	0.28
3	1.24	1.19	0.12	0.12	2.33	2.25	0.15	0.25	2.01	2.38	0.11	0.21	2.18	2.32	0.13	0.23	0.10	0.13	0.13	0.12
8	0.19	0.23	0.40	0.35	0.90	1.04	0.43	0.18	0.25	0.24	1.12	0.99	0.66	0.75	0.85	0.71	0.15	0.18	0.17	0.19
10	0.26	0.26	0.10	0.15	0.80	0.29	0.35	0.57	0.67	0.90	0.12	0.29	0.74	0.67	0.26	0.45	0.10	0.15	0.09	0.09
RMS	0.62		0.26*		1.19		0.33**		1.14		0.58		1.17		0.47*		0.32		0.21
With poorly visible tumor
4	0.56	0.22	0.19	0.14	0.65	0.37	0.26	0.02	1.74	0.48	0.62	0.79	1.31	0.43	0.47	0.56	0.11	0.16	0.10	0.10
5	0.57	0.82	0.15	0.14	1.49	1.91	0.21	0.15	2.54	2.41	0.15	0.28	2.08	2.18	0.18	0.22	0.12	0.13	0.16	0.15
6	1.00	1.13	0.22	0.22	2.46	2.53	0.57	0.48	2.94	2.27	0.18	0.26	2.71	2.40	0.42	0.39	0.15	0.13	0.13	0.15
7	0.29	0.24	0.17	0.16	0.83	2.15	0.13	0.20	0.88	0.31	0.31	0.33	0.86	1.54	0.24	0.27	0.22	0.21	0.16	0.17
9	0.33	0.40	0.19	0.14	0.34	0.19	0.44	0.15	0.75	0.89	0.48	0.46	0.58	0.67	0.46	0.34	0.18	0.18	0.12	0.12
RMS	0.64		0.17**		1.56		0.31***		1.77		0.43**		1.67		0.38***		0.16		0.14
RMS (all)	0.63		0.22***		1.39		0.32***		1.49		0.51***		1.44		0.42***		0.26		0.18

Note. The two columns under the ‘without markers’ (and ‘with markers’) represent the original and repeated series. Bold numbers represent the significant differences in inter-observer variation between the series without and with marker. The significance code (*<.05, **<.01, ***<.001) is labeled next to the significantly smaller number.

RMS: root mean square; SD: standard deviation.

Table 3. Intra-observer overall SD as well as longitudinal and radial SDs of delineations on CTs without (left columns) and with (right columns) markers.

Patient	Observer	Overall SD [cm]		Longitudinal SD [cm]						Radial SD [cm]
				At cranial end		At caudal end		At both ends
		Without markers	With markers	Without markers	With markers	Without markers	With markers	Without markers	With markers	Without markers	With markers
With clearly visible tumor	1	0.66	0.25	2.16	0.32	1.41	0.45	1.82	0.39	0.22	0.12
	2	0.27	0.25	0.32	0.11	0.38	0.11	0.35	0.11	0.13	0.14
	3	0.36	0.29	0.55	0.80	0.59	0.33	0.57	0.61	0.38	0.13
	4	0.53	0.29	1.84	0.31	0.58	0.84	1.37	0.64	0.18	0.17
	5	0.30	0.29	0.42	0.27	0.48	0.53	0.46	0.42	0.31	0.25
	RMS	0.45	0.27	1.31	0.43*	0.78	0.51	1.08	0.47*	0.26	0.17*
With poorly visible tumor	1	0.76	0.22	0.72	0.17	2.44	0.31	1.80	0.25	0.23	0.15
	2	0.29	0.25	0.84	0.37	0.49	0.21	0.69	0.30	0.14	0.15
	3	0.32	0.26	0.86	0.21	0.98	0.63	0.92	0.47	0.14	0.10
	4	0.34	0.23	1.42	0.34	0.74	0.39	1.13	0.37	0.12	0.15
	5	0.32	0.21	0.42	0.11	0.79	0.21	0.63	0.17	0.23	0.13
	RMS	0.44	0.24*	0.91	0.26***	1.29	0.38*	1.12	0.33***	0.18	0.14
All patients	1	0.72	0.23	1.54	0.25	2.05	0.38	1.81	0.32	0.22	0.14
	2	0.28	0.25	0.64	0.27	0.44	0.17	0.55	0.23	0.14	0.14
	3	0.34	0.28	0.72	0.58	0.81	0.50	0.77	0.55	0.29	0.12
	4	0.44	0.26	1.64	0.33	0.66	0.66	1.25	0.52	0.15	0.16
	5	0.31	0.25	0.42	0.21	0.66	0.40	0.55	0.32	0.27	0.20
	RMS	0.45	0.26**	1.11	0.35***	1.09	0.45**	1.10	0.41***	0.22	0.15**

Note. The number in each observer is the RMS of the overall/longitudinal/radial SDs over the 10 patients. Bold numbers indicate the significant differences in intra-observer variation between series without and with marker. The significance code (*<.05, **<.01, ***<.001) is labeled next to the significantly smaller number.

RMS: root mean square; SD: standard deviation.