@bl2023: Thank you for you reply.

To all: Thanks for all your comments and advice.

Today my RAD treatment was at 8:15 am. I finished drinking 1 litre (32 oz) of water 30 mins prior appt time. I told the RAD tech that I had no bowel movement this morning. The last bowel was yesterday afternoon around 3pm. I had regular dinner last night. She said I should have a bowel before the treatment but she would scan to see if it is OK. She showed me the scan images on the screen. It came out that the bladder is 100% full and there were some contents in the rectum but they were higher up which did not interfere. After the treatment, I almost needed to run to the washroom right away. Thank God! I did not need to wait and re-prepare today's treatment. Mostly all of my appts are very early in the morning from 7:45 am - 8:15 am. I think I have some ideas how to fill up my bladder (thanks everyone). I hope I will have bowel movements in all the rest of the sessions. Anyhow, Three down, Seventeen more to go!