Radiaton measurement during IMRT/IGRT tidbit

I work several radiologist, and digital radiograph so I was a little concern on the out of field radiation when I undergo radiotherapy. I know the radiotherapy is well collimated, but there will still be out of field emission. Additionally there are quite a few papers on secondary cancers caused by radiotherapy, some of which remote from the prostate area which I would assume be caused by out of field radiation. (Disclaimer, it is hard to prove or not prove these cancers are directly caused by radiotherapy or by idiopathic causes.)

So todays session I brought my digital Geiger counter to measure the amount of radiation I received during the cone beam CT imaging (CBCT), and during the radiotherapy session (1.8 Gray or 1,800,000 microsieverts).

I placed the probe over my heart, during the CBCT imaging I received 7 microsieverts, and during the actual radiotherapy I received 70 microsieverts. I was surprised that it was a lot lower then I had expected.

For reference 7 microsieverts is about the amount of radiation from a set of dental x-rays. And 70 microsieverts is a little less than the average dose to people living within 16 km of Three Mile Island.

Lapilot,

Have you been spending time with "The Wizard" in Rochester? It sure sounds like it. :)
Interesting info you gathered!

As a side note, recently learned from "The Wizard", stay away from the old red/orange radioactive Fiesta Ware! :)

MsWorryWart,

I have a couple of antique Vaseline glass objects that has uranium oxide to impart the greenish look of the glass. a bowl and a dog. Both glow under a ultraviolet light and both are radioactive, the dog being more radioactive than the bowl.

lapilot said...
MsWorryWart,

I have a couple of antique Vaseline glass objects that has uranium oxide to impart the greenish look of the glass. a bowl and a dog. Both glow under a ultraviolet light and both are radioactive, the dog being more radioactive than the bowl.

Yes, he had samples of some of those pieces as well. I thought it was all quite fascinating, however, I see no reason to keep any around in my house. :)

MsWorryWart said...

Redwing57 said...


Here's a link to my Youtube video. It's not really visually dynamic, but it is a 1st person POV of a real IGRT session with overlaid comments about what's happening at any time. Some have found it helpful when contemplating IGRT:

/www.youtube.com/watch?v=AMEEBZDQSNo&feature=youtu.be

I noticed you said you had this in your shirt pocket.... were you breathing? The video is so still! Actually, I think this should be somewhere on a sticky so newcomers could get an idea of what to expect.

That's kind of funny, really; never thought about it but you're right. I tried so hard not to move at all during treatment. Not a muscle, very shallow breathing, all trying to not move after the targeting xrays, not to move *at all*. Having that prodigious x-ray machine pointed at my personal self, with planning volumes defined to the millimeter, was very motivating!