Hi John,
After my Radiation treatments, my voice was just a whisper. My voice has come back to normal, it took awhile. I don't remember how long it was, people would tell me I sounded just like I did before.
It was about a month after the treatment that I started to get some more energy daily. But I was told that the Radiation would effect me for roughly 1 year. I did have days that I felt good for 3 or 4 days and then bang, felt weak for about a day or so.
Each person is different. Take Care.