3D Variation in delineation of head and neck organs at risk

Radiation Oncology

Table 1 Mean volume, coefficient of variance, and mean OAR ratio per observer and organ at risk

OAR	Mean volume	CV	Mean OAR ratio*
	[cm³] (SE)		obs. 1	obs. 2	obs. 3	obs. 4	obs. 5
Spinal cord	17.6 (1.1)	16%	0.98	0.98	0.91	0.92	1.17
Parotid gland left	28.4 (2.6)	15%	0.92	0.85	1.10	1.08	1.03
Parotid gland right	29.6 (3.9)	12%	0.88	0.90	1.06	1.04	1.02
Submandibular gland left	10.6 (0.9)	16%	1.06	0.86	1.12	1.06	0.95
Submandibular gland right	10.4 (0.9)	16%	1.09	0.88	1.06	1.03	0.90
Thyroid cartilage	11.4 (1.5)	14%	0.96	1.11	1.11	0.97	0.93
Glottic larynx	10.3 (2.8)	56%	0.45	0.60	1.13	1.38	1.66

OAR = organ at risk, SE = standard error of the mean, CV = coefficient of variance, obs. = observer
SE and CV were determined by the results of ANOVA, the CV represents variability due to observers
*OAR ratio = the volume of the OAR as determined by each observer divided by the mean volume of all five observers

ISSN: 1748-717X