how are radioactice isotopes metabolised by the body? (1 Viewer)

[bally24]

ive looked in all the textbooks i could find but none seem to describe this dot point...some don't even mention the word metabolise. im quite confused about it, does anyone have a summary for this bit or could explain it to me? thanks.

 

[Mountain.Dew]

radioactive isotopes are metabolised by the body because these isotopes are attached to certain substances that are naturally metabolised by the body. take for example glucose - it is readily absorbed and used by the brain. by attaching a radioactive isotope to the glucose (i think you are using carbon isotopes...?), that isotope would reach the brain and is released from metabolism.

this is very brief, but its essentially what happens.

hope this helps, M.D.

 

[Irskin]

Metabolism describes all of the chemical processes that occur inside the body. Radioactive isotopes such as Iodine-131, Fluorine-18, Technetium-99m, Oxygen-15 etc are attached to molecules that the body uses to maintain metabolic and physiological function. For example, the body needs to metabolise oxygen and glucose in cellular respiration so by attaching these radioactive isotopes to these naturally occuring molecules, they will also metaboilise the attached isotopes. This is called 'tagging' the normal molecules with radioisotopes to produce radiopharmacueticals. The body then uses these tagged molecules the same way they would use the normal molecules and thus, the radioisotopes are administered into the body. This is done by either injection or inhilation.

 

[moeydalati88]

The actual radioisotope is not metabolised by the body. To understand this concept we can use an example of how Oxygen-18 is metabolised by the brain to be used in PET. THe radioisotope is tagged to a molecule which is metabolised by the region of the body to be examined, in this case Oxygen-18 is tagged to a glucose molecule which is metabolised by the brain. Hence, the radioisotope ends up in the region to be viewed. Here, the radioisotope begins to decay through positron emission. Thus, it is not the radiisotope that is being metabolised but the molecule that it is attached to which takes it to the viewing region. If you wanted to view the kidney you would attach a radioisotope to a molecule that is metabolised by the kidney.

Hope that answers your query. Cheers!!

 

[acullen]

Metabolism describes all of the chemical processes that occur inside the body. Radioactive isotopes such as Iodine-131, Fluorine-18, Technetium-99m, Oxygen-15 etc are attached to molecules that the body uses to maintain metabolic and physiological function.

This isn't true when irradiating thyroid gland tissue. As the thyroid requires a regular uptake of Iodine in order to synthesise thyroid hormones (due to T₃ being composed of 2x tyrosine and 3x iodine and T₄ being composed of 2x tyrosine and 4x iodine). Conveniently, ¹³¹I is a short-lived radioactive isotope of Iodine (half life of around 8 days) which produces both beta and gamma radiation (however the beta radiation is the workhorse emission here).

This intrinsic requirement of iodine by the thyroid means that ¹³¹I is an effective treatment of thyroid gland tumors and hyperthyroidism by unsealed source radiotherapy.