Radiation - how much is too much?

As I understand things, no radiation from MRI but significant amount from CT.  How much is too much...that question is over my pay grade. Best of luck to you with the radiotherapy.    Hero

Since my IGRT treatment involves a CT scan each day prior to the radiation for alignment purposes, I wonder just how much extra radiation I am absorbing. If CT scans are so bad, it would seem I am really getting a lot of extra radiation, and not specifically targeted to the area of treatment. Hopefully I won't start glowing at the end of the 39 zaps!!!! Squid

subic, that's a good point.

during each of my 39 SRT zaps, they did 2 "snap-shot instant x-rays each and every day as part of the alignment process, so that would be another 78 xrays on top of the daily zap. geez.

If that is the case I'm in deep s**t with 5 CT scans in 3 months.

I read that a ct scan has a 1 in 4000 chance of causing cancer. When I consulted on adjuvent therapy,, they said there was a 1.5 % chance of radiation tumors fron the radiation.

We tend to kind of gloss over it sometimes.

Check Out - hps.org/hpspublications/articles/dosesfrommedicalradiation.html

Fogball

Post Edited By Moderator (James C.) : 6/15/2010 6:04:06 AM (GMT-6)

Interesting and important query BB.

First point to mention is that we all have about a one in forty chance of getting cancer in our lifetimes.

This site had a good list of comparisons of xray doses:
www.radiologyinfo.org/en/safety/index.cfm?pg=sfty_xray

and at this one you can input your own data to work out your totatl dose from all sorts of sources:
www.ans.org/pi/resources/dosechart/

During my RT 2 xrays at right angles were taken at regular intervals to check the position of things. This was done on day one, and then after every 5 sessions. At the beginning of the last week two additional xrays were taken after something was found to have moved by two millimetres.

The beep made by the machine when taking these xrays was very very short compared to the beep during each dose of RT, indicating that the dose was much smaller.

From what I have read the initial CT scan used for mapping the whole area gives a 3D image, that used for targetting before RT uses a 2D image. I was under the impression that the CT scan prior to RT was simply enough to locate certain specific reference points in the target area. Worth asking about it though I think. And again the time the CT scan takes is an indication of how big a dose you are receiving. (I cannot imagine anyone could be getting 35 big CTscans in a row)

Equivalence is also relevant. The dose given/absorbed must also be seen in terms of the percentage of your body (by weight) to which that dose is given. 20gy is a fatal dose for a human if given to the entire body thus when we get say 70Gy that is on the basis that the prostate/prostate bed is only a few ounces of a body that weighs many pounds.

This radiaton is at least trying to make us better. Radiation from things that are no benfit are much worse. I wanted to play a RT joke on folk by painting my belly with fluorescent make-up but that is no longer sold here as it gives off too much dose. And I remember using a Geiger-counter to test radioactive samples in a labm, and though we had to handle them with special gloves and tongs, the dials of our wrist-watches actually gave bigger readings.

I mustn't get too scientific about stuff I don't know a lot about. My RT team were happy to answer all questions I asked them, so ask the experts.

Alfred

The glowing part is a benefit as you do not need a nightlight to find the bathroom at night...

The balance would thus seem to be that the small extra bit of radiation that results from the mini-CT is off-set by the fact that because of the mini-Ct the actual RT is directed more accurately and less radiation damages surrounding healthy tissue.
Alf