Re: radiation half-life

[Guest guest]

Hi, Rich 7 Zippy,

>Glowing in the dark isn't a problem, but nuclear medicine procedures

>do give the patient some radiation dose. I don't know the doses for

>the blood volume measurements, but generally speaking the shorter the

>half-life, the lower the dose for substances that are injected. So

>technetium-99m (half-life=6 hours) will give a lower dose than

>chromium-51 (half-life=27 days) or iodine-125 (half-life=59.4 days).

It should be noted that the dose received depends not just on the

radioactive half-life (quoted by Rich above), but by the biological

half-life also (the time that it takes for the body to eliminate half of the

material - same for radioactive & non-radioactive isotopes.)

For example, radioactive iodinated albumin would have a biological half-life

shorter than 59.4 days, because the free albumin is broken down; the

iodinated amino acid or peptide that is left from this breakdown cannot be

reused and is excreted in the urine. In this case the effective biological

half-life is a matter of a couple of days. Most of the radioactivity gets

excreted before the radioactive decay.

Jerry

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[Guest guest]

> Hi, Rich 7 Zippy,

>

> >Glowing in the dark isn't a problem, but nuclear medicine procedures

> >do give the patient some radiation dose. I don't know the doses for

> >the blood volume measurements, but generally speaking the shorter the

> >half-life, the lower the dose for substances that are injected. So

> >technetium-99m (half-life=6 hours) will give a lower dose than

> >chromium-51 (half-life=27 days) or iodine-125 (half-life=59.4 days).

>

> It should be noted that the dose received depends not just on the

> radioactive half-life (quoted by Rich above), but by the biological

> half-life also (the time that it takes for the body to eliminate half of the

> material - same for radioactive & non-radioactive isotopes.)

>

> For example, radioactive iodinated albumin would have a biological half-life

> shorter than 59.4 days, because the free albumin is broken down; the

> iodinated amino acid or peptide that is left from this breakdown cannot be

> reused and is excreted in the urine. In this case the effective biological

> half-life is a matter of a couple of days. Most of the radioactivity gets

> excreted before the radioactive decay.

>

> Jerry

Thanks, Jerry. Good point. I did find an abstract that said that evenso the

decrease in dose in going to technetium as compared with chromium was about a

factor of thirty.

Rich