Rads' Gys confusion/discrepancy?

Logan51

An 11 year and 7 month Nasopharyngeal Survivor, unknown Primary, I have the final report from the Rad Dr. and her IMRT facts.

56 Gys from the chin up

60 Gys to top half of throat

68 Gys to bottome of throat

So, how does this relate to the number of places that get "zapped" with Rads/session? I had a co-worker get zapped only 3 times/session, and others on this Forum have said they had 10 places/session. Others say they didn't count, which tells me it might not have been comparable to what I got: 20 places/session. I would literally count down evey time I was clamped on the table, because you can hear the buzzing of the zaps. My last 3 sessions I only got zapped 4 times, so I reckon that was at the base of throat, but all the others were in 20 places.

Thus, the question is: how does the total Gys relate to the number of places One gets zapped/session? Or, did I get 60 Gys to every place in the top half of my throat, and 68 in the bottom half? If so, then the total amount of Rads the body received is dependent on an equation involving the number of places zapped/session.

My Chemo Dr. advised against getting my 3rd year PET/CT, saying I'd already had too much Radiation put into my body, which is part of my reason for wondering about this matter. Any definitive answers will be much appreciated.

johnsonbl

Your interpretation re: gys is right...

Your absorbed dose at the base of your throat is 68 gy, top of throat 60, chin up is 56.  How many times they turn the beam on during a session I don't think has really any relation to your dose.  They develop your treatment plan to minimize exposure of normal tissue and that means that they may turn the beam on and off multiple times from multiple angles depending on the area to be irradiated.

There are lifetime limits though I've yet to find an easy to read document outlining exactly what they are.

When I had my radiation I couldn't hear the beam turning on and off but I could hear the leaves inside the machine clicking and moving as they shaped the beam.  I could actually see them at certain points moving around in there.  It's pretty amazing technology.

Logan51

johnsonbl said:

Your interpretation re: gys is right...

Your absorbed dose at the base of your throat is 68 gy, top of throat 60, chin up is 56.  How many times they turn the beam on during a session I don't think has really any relation to your dose.  They develop your treatment plan to minimize exposure of normal tissue and that means that they may turn the beam on and off multiple times from multiple angles depending on the area to be irradiated.

There are lifetime limits though I've yet to find an easy to read document outlining exactly what they are.

When I had my radiation I couldn't hear the beam turning on and off but I could hear the leaves inside the machine clicking and moving as they shaped the beam.  I could actually see them at certain points moving around in there.  It's pretty amazing technology.

okay

I could hear the buzzzing, then it would stop and I'd hear the Rad arm moving and stop, then another buzzing- that's what I counted as 20 times. Another reason I wondered is because I'm now Feeding Tube dependent for the rest of my life due to scar tissue damage by the Rads to base of my throat around esophagus aperture- scar tissue grows. On a follow-up visit the Rad Dr. said they got a new machine that's better...