Radiopharmaceutical Localization Flashcards
Which portion of the radiopharmaceutical is primarily responsible for localization?
pharmaceutical but in newer RP, the radionuclide as well
what is the difference between radionuclides that are TAGGED RP and ESSENTIAL RP?
tagged is when uptake is completely dependent on the pharmaceutical
essential is describing when the radionuclide is needed or else localization of the pharmaceutical would not occur
what is biodistribution? what else is it called?
aka biorouting
it describes the organs where the rp collects
what is “high first pass extraction efficiency” describing?
wanting the uptake in the organ of interest to be fast; wanting the uptake the first time blood circulates through the organ of interest
what is compartmental localization?
when the RP is introduced to an enclosed compartment and is to remain there during imaging
what can be assessed with compartmental localization?
- uniform distribution
- leakage in compartment
- flow/movement in compartment
what is the difference between active transport and diffusion across a cell membrane?
active requires ATP due to the movement of ions from lower to higher concentrations
what are the three types of diffusion?
- simple
- filtration
- facilitated
describe simple diffusion.
movement of ions solely on concentration gradient and the characteristics of the rp
what type of molecules diffuse the easiest across membranes?
lipophilic + small molecules
describe filtration diffusion.
passive movement dependent on pressure gradient
describe facilitated diffusion.
the use of carrier or transport proteins to help with the movement of SELECTIVE molecules across membranes
does facilitated diffusion require energy?
no.
how is active transport similar to facilitated diffusion?
they both require transport proteins to move SELECTIVE substances across membranes
when active transport is used to move a substance out of an organ, what is that called?
secretion
what is an example of active transport in thyroid glands?
iodine is needed to create thyroid hormones T3/T4
therefore, with the use of radioiodine and 99mTcO4-, they get actively transported into the thyroid gland
what is an example of active transport in the liver?
99mTc IDA agents are treated like toxins which allows it to get actively transported into the hepatocytes to be secreted in bile
what is an example of active transport in kidneys?
99mTc-MAG3 gets excreted through tubular secretion
what is an example of active transport in the heart?
use of Tl-201 so it can be moved into the myocardial cells by the sodium/potassium pump
what organs are part of the RES (reticuloendothelial system)?
- liver
- spleen
- bone marrow
what causes colloid shift?
immunosuppression that causes less uptake in the liver and more in bone marrow and spleen than expected
smaller particles show more uptake in which res organ?
bone marrow
larger particles show more uptake in which res organ?
liver/spleen
what is the expected size of MAA particles?
10-90 um
what can happen if RP particles are too large?
it’ll cause a large embolus
what can happen if RP particles are too small?
no blockage in capillaries which results in uptake in res
what can happen if there is too many RP particles?
it can cause pulmonary hypertension
what can happen if there is too few particles?
it’ll result in patchy uptake and possibly a false positive (cold spots)
what is chemisorption?
binding of a substance to a solid surface
what is the lock and key type mechanism?
describes receptor binding which means that some rps are binding to specific cell receptors
what is chemotaxis?
chemical signals that WBCs are attracted to
what are types of RP localization?
- compartmental localization
- active transport and diffusion
- phagocytosis
- capillary blockage (blockade)
- chemisorption
- receptor binding
- cell migration (chemotaxis)
what RP is used for chemotaxis?
tc-99m or In-111 labelled wbcs
what are iatrogenic effects?
things caused by the diagnosis, manner, or treatment by a physician
for RPs, what does iatrogenic effects mean?
alteration in biodistribution due to medications the patient is taking
