Table 4. Intra-observer comparison of GTV volumes obtained with dual-modality image fusion (MRI/CT) and tri-modality (MRI/CT/PET) image fusion.

Observer	Patient	GTV with Dual-modality		GTV with Tri-modality
		Mean ± SD (cm3)	COV	Mean ± SD (cm3)	COV
Observer 1	Patient 1	21.52±1.48	0.07	17.15±0.68	0.04
	Patient 2	14.05±0.34	0.02	12.44±0.16	0.01
	Patient 3	2.64±0.29	0.11	1.87±0.02	0.01
Observer 2	Patient 1	22.52±1.00	0.04	19.76±0.31	0.02
	Patient 2	16.46±0.51	0.03	14.08±0.13	0.01
	Patient 3	2.79±0.12	0.04	1.94±0.02	0.01
Observer 3	Patient 1	20.28±0.96	0.05	17.55±0.47	0.03
	Patient 2	14.63±0.60	0.04	13.40±0.17	0.01
	Patient 3	1.99±0.16	0.08	1.66±0.02	0.01

GTV = gross tumor volume; COV = coefficient of variation; SD = standard deviation.