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Pet scans works by the tech injecting a known amount of radioactive isotopes that binds with a known amount of glucose into the blood stream. They let that tagged glucose circulate. Cancer cells feed only on glucose and uses a large amount when activity growing. If a cell takes up a large amount of tagged glucose it is gathering fuel to grow. These cells light up as "hot" or very red and are labeled carcinogenic.
So the cells might not shrink up it won't light up with the same intensity, The SUV will decrease. It will use a lot less energy.
Here is an example of a growing tumor (notice "increased activity; maximum SUV of approximately 3,3 compared to approximately 2,9 on" previous scan.
Increased activity in the anterior aspect of the proximal right femur has a maximum SUV of approximately 3.3, compared to approximately 2.9 on 5/18/2016. Corresponding mixed lytic and sclerotic lesion on CT.
no where in the description does it say shrinking or growing. But you can tell it is an active tumor and is growing. The SUV (Standard Uptake Value= how much radioactivity tagged glucose was taken in for cell energy use) indicates size of tumor and growth rate. . It grew from 2.9 to 3.3 cm.
An example of a decreasing tumor: Increased activity in the posterior left acetabulum has a maximum
SUV of approximately 2.5, compared with approximately 3.4 on 5/18/2016. Corresponding predominantly lytic lesion on CT.
The SUV on previous scan was 3.4 and now 2.5. This means there was a significant difference in tagged glucose taken into the cells. Still an active tumor but only about 1/2 as active as previously noted. This is another way of saying "SHRINKING". It is smaller but still active.
Here is a tumor that isn't any bigger or smaller. It maintained the same growth rate as previous: Focal increased activity in the posterior aspect of the right
inferior pubic ramus has a maximum SUV of approximately 2.3, compared with approximately 2.3 on 5/18/2016.
Hope all this helps. Get copies of you scan reports and compare new scans with previous ones. What does the report say about a specific area and the SUV figures. Are they more or less then the previous scans?
Another important part of the scan report is the impression. Overall what does it look like. Are advances being made against tumor growth? It there new growth? etc. For the report where I took the 3 examples (all were from the same scan) the impression was:
Mixed response to treatment. New foci of increased activity in the right clavicle and the left second rib, without definite corresponding abnormalities on CT, suspicious for new osseous metastases. Interval increase in the activity associated with the metastases in the left L3 vertebral body and the right iliac bone/acetabulum. Interval decrease in the activity associated with the metastasis in the left sacrum. Multiple additional osseous metastases are not significantly changed from 5/18/2016.
Let me know if you understand this or did I make it more confusing? Let me know the results of the next scan and we can figure out what they are saying without trying to tell you anything. It is a big game. They hide results behind fancy language so they can charge you big bucks to explain it in a simple language. lol. It is all in code.
take GOoD care