Mean volumes of bowel within the modified RTOG PTV were 19.5 cm ( 3 ) ( with 0 mm BEM ) , 17.4 cm ( 3 ) ( 1-mm BEM ) , 10.8 cm ( 3 ) ( 2-mm BEM ) , 6.9 cm ( 3 ) ( 3-mm BEM ) , 5.0 cm ( 3 ) ( 4-mm BEM ) , and 1.4 cm ( 3 ) ( 5-mm BEM ) in comparison with an overlap of 9.2 cm ( 3 ) seen using the RMH technique .