I'm sorry you had the rectal coil. They used that a lot when all the MRIs were 1.5T, but now that 3Ts are prevalent, many believe them to be unnecessary. Did Dr Freeman know you had a rectal coil? The reason I ask is because the coil changes the shape of the rectum and prostate and makes it difficult to fuse the MRI image with the CT you will have after the fiducials are in.
Some ROs do use a rectal balloon during SBRT treatment, but most don't. It stabilizes the prostate during treatment. It pushes most of the rectum away from the prostate but pushes some of the rectum into the prostate. So the point dose - the highest dose received by the rectum - may be actually higher with it than without it. There is a randomized clinical trial now investigating whether there is any benefit to a balloon or a spacer compared to using nothing. There is no substitute for tight rectal margins and dose constraints, and checking for bowel distension.
Do NOT take cranberry! That will stimulate the kidneys to produce more urine -- the last thing you want to do when your urinary tract is irritated. For a few weeks cut down on acidic juices, coffee and drink only when thirsty. Otherwise you'll be getting up all night to pee.
Allen - not an MD
•PSA=7.3, prostate volume=55cc, 8/17 cores G6 5-35% involvement
•SBRT 9 yr onc. results
•SBRT 7 yr QOL results
•treated 10/2010 at age 57 at UCLA,PSA now: 0.1,no lasting urinary, rectal or sexual SEsmy PC blog