You figure this out because in the region of interest that you draw around the heart, the one with the lowest radioactive counts is systole and with the highest, diastole.
The way the test is done is different to how all the other nuc tests are done. Namely, with nucs you do the one injection of the radiotracer. However, the MUGA is like Augmentin - i.e. there's two components.
So, firstly you inject a chemical called stannous into the person- this is basically tin! This drifts into the red blood cells and they do stuff to it - "reduce it" - so that it doesn't poison them. This also traps the stannous inside the red blood cells. You have to wait about 20 minutes for all of this to happen.
Then you suck out some blood into a syringe that already has Pertechnetate in it (it'll be the syringe with the lead shield on it), and it gets bound to the reduced stannous that is inside the cells. This all takes about another 20 minutes and then you inject the Tc-labelled RBC's back into the patient. So, now you can see the cells with a gamma camera! You record only those frames that fall into the R-R window that you have set. This is why it takes forever to record AF or multiple ectopics.
The three views that you use are:
1. LAO Caudal/Cranial tilt
- you see the septum, apex, and the inferolateral and true lateral walls. Everything else is superimposed, so need to do some other pictures:
2. Left lateral right decubitus (i.e. patient lying on their right side and you are taking a mug-shot of the heart from the left) to see the anterior and inferior walls, and the apex.
3. RAO to see the anterolateral wall and a mix of the inferoseptal and inferior walls.
In an anterior view, one sees the anterolateral, inferoseptal and apical segments.
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