Table 4.

Coefficients of determination (R²) of between each dosimetric value (V90 and V50) and ratio of an OAR’s volume overlapping with PTV to the whole organ volume (V_overlap/V_whole).vb

Institutions	Organs	Dosimetric Parameters	Coefficients of determination (R2) in the quadratic regression curves
			DVH for registered plans	Upper limit of ED	Lower limit of ED
A	Rectum	V90	0.601	0.996	0.994
		V50	0.488	0.864	0.877
	Bladder	V90	0.865	0.998	0.997
		V50	0.781	0.852	0.903
B	Rectum	V90	0.254	0.133	0.011
		V50	0.293	0.158	0.138
	Bladder	V90	0.845	0.935	0.911
		V50	0.695	0.679	0.698
C	Rectum	V90	0.666	0.967	0.961
		V50	0.592	0.826	0.839
	Bladder	V90	0.885	0.931	0.962
		V50	0.620	0.594	0.649
D	Rectum	V90	0.529	0.997	0.995
		V50	0.485	0.494	0.519
	Bladder	V90	0.987	0.999	0.999
		V50	0.515	0.544	0.578
E	Rectum	V90	0.626	0.944	0.946
		V50	0.169	0.334	0.435
	Bladder	V90	0.971	0.994	0.994
		V50	0.804	0.849	0.866

Abbreviations: DVH dose volume histogram, ED estimated dose, V90 the volume ratio of receiving 90% of the prescribed dose, V50 the volume ratio of receiving 50% of the prescribed dose