A Patient Is Treated on a 6-MV Machine at 100

Multiple Choice

A patient is treated on a 6-MV machine at 100 cm SSD.The collimator setting is 15 × 15.There is no blocking used for this treatment.The prescription states that a dose of 3000 cGy is to be delivered to a depth of 3 cm in 10 fractions using a posterior treatment field using the nonisocentric method of calculation.The patient central axis separation is 20 cm.What is the MU setting for the treatment? Reference dose rate (RDR) for a 15 cm equivalent square is 0.993 cGy/MU.

A) 315
B) 321
C) 319
D) 317