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12 Cards in this Set
- Front
- Back
- 3rd side (hint)
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99mTc pertechnetate ion is similar in size and charge(-1) to what other common ion, and what problems does that potentially create?
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Iodide ion
Since 99mTc ions behaves like the iodide ion its distribution in the body can be altered by the use of Potassium Iodide, Potassium Perchlorate or Lugol’s Solution. |
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What is important to consider if Tc99m is used to scan a pregnant woman?
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fetal dose must be considered as it can cross the placenta
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When Tc99m pertechnetate is injected intravenously where does it go initially?
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70-80% of it binds to serum proteins
what problem does that present in getting Tc99m into tissues? |
these proteins are too large to pass by diffusion into tissues and can only be distributed into cells of tissues via active transport
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Where does the unbound 99mTcO4 go?
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it can pass freely into the interstitial fluid space.
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After 30 minutes what will be the hottest organ on a scan with 99mTcO4?
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The stomach
Why is this? |
99mTcO4 – is absorbed by the acid producing cells of the stomach wall lining. 99mTcO4 – is then secreted with the stomach acids where it is reabsorbed by the same cells making an internal loop.
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Why are the kidneys and then the bladder seen on a 99mTcO4 scan?
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99mTcO4 – is removed from the vascular compartment by the kidneys. The kidney effectively removes free pertechnetate from the plasma proteins it is bound to. This explains the visualization of kidneys in a 99mTcO4 – scan.
What is the only time the bladder is not seen? |
When pts have renal failure
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Why does 99mTcO4 end up in the Thyroid gland?
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The thyroid gland traps 99mTcO4 – . This trapping is a form of active transport, a complex method of localization. The thyroid traps 99mTcO4 – because of its negative charge and its similarity in size, and molecular weight to the iodide ion. 99mTcO4 – cannot be organified like iodine and is eventually released into the blood stream.
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Does a pt have hot saliva when injected with TcO4?
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Yes
How does TcO4 get in saliva? |
Tech gets in interstitial fluiid of tthe salivaary glands where it iis taken up by the cells eventually being secreted into saliva
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Does the bowel play a part in eliiminating tech?
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Yes,pity diffusses into wall of am iintestine, where it eventually goes to fecces inn bowel, 30-40% gets excreted this way
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True or false: When99mTcO4 gets trapped in cells of choroid plexus tech is secreted into CSF
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False, even though there is uptake into cells of choroid plexusit is not secreted into spinal fluid
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Can sweat glands secrete hot perspiration after injecting a pt with tech?
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Only a very small fraction
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Name the 7 methods of mechanisms of localization and give an example of each one
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1. Active transport (cardiac scan with Tl201, which is an analog of potassium)
2. Phagocytosis (kupffer cells entrap SC in liver spleen scan) 3. Capillary blockade (maa in lung perfusion scan) 4. Cell sequestration (labeling, then damaging RBC's for spleen scan) 5. Simple diffusion (Xe133 in lung scan ) 6. Compartmental localization ( MUGA, Xe133-vent lung) 7. Chemisorption (PYP, HDP binds to bone; In111 tagged for certain tumors) |
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