Table 1.

The six treatment plans created to compare optimization structure and treatment technique

Treatment plan	Acronym	Hydrogel	Treatment technique	Structure
1	Pre_IMRT	No	IMRT	Rectum
2	CRW_IMRT	Yes	IMRT	Composite rectum
3	RW_IMRT	Yes	IMRT	Rectum
4	Pre_VMAT	No	VMAT	Rectum
5	CRW_VMAT	Yes	VMAT	Composite rectum
6	RW_VMAT	Yes	VMAT	Rectum

CRW: composite rectum wall; IMRT: intensity modulated radiotherapy; RW: rectal wall; VMAT: volumetric modulated arc therapy.