Medical physics question (1 Viewer)

[Squirrel]

Why is technechium 99 used between 2 to 5 hours? (its half-life is 6 hours).

i have no idea why you would use it between 2 to 5 hours

can someone help me out please

 

[sammie]

I think that question is talking about how it is best to be used between that period as it is down 75% etc. This then is not as threatning to other patients and people yet can stillbe detected. That is what i think!

 

[clever angel]

Tc-99m has a half life of 6hrs....which means it begins to decay after 6 hrs...so it shud be used b/w 2-5 hrs so that the whole amount of Tc-99m can be used.......

hope this helps...

 

[Inhuman]

It doesn't 'begin to decay' after six hrs, it's decaying the whole time. 6 hrs is the time for only half to be left, hence the term half life

 

[helper]

With any nuclear medicine you want the radiosotope to be present for the minimum time period possible.

Because the operation takes between 1 and 5 hours you do the operation, so that the radioisotope within that time.

The isotope dosage is adjusted so that within the time period of the use, the radisotope has a large enough dose to be detected. By the 5 hour mark, when the procedure is over the dosage will be reduced to the minimum level of usage that can still provide an effective image.

After the test is finished you want as low a value of isotope present as possible.

The determining factor for using the isotope is the biological half life. The time it takes the body to remove the radio-isotope. For liver and heart this is down near 1 hour for the procedure, so 2 hours for the body to remove it. Bone scans take 4 hours, so 5-6 to remove it.

 

[underthesun]

2 hour = wait til the isotope actually gets in the patient's organs?

5 hours = too weak?