How many DatScans is too many?

[redhawk1]

Just concluded the Prothena Pasadena clinical trial which required a DatScan at the beginning and end of the two year trial. Now considering taking part in the Neuraly clinical trial that requires two DatScans as well. At what point does the radiation inherent in each scan become a risk?

[park_bear]

Here is a link to the FDA label that specifies radiation dosage by organ for DatScan:

accessdata.fda.gov/drugsatf...

" The Effective Dose resulting from a DaTscan administration with an administered activity of 185 MBq (5 mCi) is 3.94 mSv in an adult"

Lifetime exposure to radiation from imaging investigations

ncbi.nlm.nih.gov/pmc/articl...

"Mean lifetime radiation exposure was 14.94 mSv. No patients had exceeded the lifetime occupational limit of 400 mSv; however, 4.4% of patients had exceeded the annual occupational exposure limit of 20 mSv at some point in their lives. Mean lifetime exposure of those with cancer was found to be significantly higher than exposure of those without cancer. This difference was due to the extra radiation exposure after the cancer was diagnosed; hence a causal relationship was not shown. Mean level of annualradiation exposure from diagnostic imaging has been slowly increasing since the 1960s"...

" While the relationship between low levels of radiation and adverse health effects is not entirely clear,4-6 many studies have shown that, in some patients, accumulated doses of low-level radiation can cause adverse health effects, such as leukemia and other cancers.7-10 Government agencies formulated guidelines for occupational exposures to regulate how much radiation people may be exposed to with negligible risk.11-15 Most guidelines are given as annual radiation limits, usually at 20 millisieverts (mSv/y). Some authors have suggested, however, that a lifetime maximum radiation limit of 400 mSv also is appropriate.14"

[Numbers refer to references linked to in the text]

So according to this document five DaTscans hits your annual exposure limit. You might want to check the references and decide for yourself how much exposure you want to have.

By the way, did you receive any benefit from the trial?

[redhawk1 in reply to park_bear]

Thanks for all that good info park-bear!! Really appreciate it! Not on any kind of meds yet after 3 years since diagnosed so I could still attempt to qualify for the Neuraly trial.

Very hard to say if and how much the Prothena medication helped since I did not notice any kind of dramatic improvement to any symptoms . . . and difficult to ascertain if the medication slowed the progression as one can’t compare . . . but I do know symptoms are still slowly progressing . . . seems like a little faster since I have finished the trial . . . but that could very simply be the natural progression of the disease.

[WinnieThePoo in reply to redhawk1]

Do you know at this stage which treatment arm you were in?

[redhawk1 in reply to WinnieThePoo]

Hi Winnie . . . not sure what you mean by “treatment arm”. Have been following your progress as well as I noted you were in the Biogen study.

[WinnieThePoo in reply to redhawk1]

Hi Redhawk. I meant do you know if you were on placebo, 1500 or 4500 dosage part 1, and 1500 or 4500 part 2. My next infusion will be part 2 of the modified spark protocol. It's still a bit surreal that nobody commenting on spark has noticed the trial protocol has changed

[redhawk1 in reply to WinnieThePoo]

Hey Winnie . . . never inquired as to the dosage . . . will make a point to do that!

[Xenos in reply to park_bear]

Right on ! Thanks, ParkBear.

[pvw2]

Another thing to consider is how close together the DATscans are because they give you a 100 to 120 mg dose of iodine each time to protect your thyroid. I'm not sure how far apart those need to be, but that's enough to cause a definite overdose if too close together. You should inform them when you had the last DATscan. Your body will eventually get rid of the excess iodine.

[redhawk1 in reply to pvw2]

Thanks pvw2 . . . my last scan was about 6 months ago. So, another scan so soon might be pushing it! Who knows?? Felt a little “brain fog after my last scan.

[pvw2 in reply to redhawk1]

My guess is 6 months is plenty of time to wait as long as you haven't been taking a high dose iodine supplement.

[WinnieThePoo in reply to redhawk1]

I fell asleep during my last datscan

[pvw2 in reply to redhawk1]

Never hear of brain fog being a sign of iodine overdose. Usually the first symptoms are sore gums, sore throat, and cold like symptoms.

[pvw2 in reply to redhawk1]

The recommended maximum dose for iodine is about 1 mg per day. So, if you got a dose of 120 mg, you should be clear in 4 months.

[SilentEchoes]

I think one is too much. My hair fell out and got very thin.