Hi, to find out where cancer cells are located, doctors injects you radioactive dye which is made of sugar. Cancer cells love sugar and they process it much more than normal cells. Thats why they are visible on PET scan. But what makes processing sugar visible on PET scan?
If you take a look on PET scan images, some organs are always visible like a brain. How do doctors distinquish what is cancer on brain and what is brain itself?
Thank you.
In: 2
PET scans detect a specific type of radiation called positron radiation (or beta + radiation). This means they can track a radioactive material which produces postitron radiation.
It is possible to make drugs which go to specific parts of the body and add positron producing radioactive isotopes to the drug. This allows doctors to see where the drug goes with a PET scanner.
A common drug is a variant of sugar. The body normally uses sugar for fuel if it is available. The specific drug looks like sugar to the body and the organs extract it from the blood. However, this drug doesn’t burn like sugar does and it gets part way through the burning process and then gets stuck in the organs.
This drug therefore acts like a meter to show how much sugar organs are tying to burn. By making it positron emitting, a PET scanner can trace it in the body and see which bits of thr body are using sugar and how much sugar they are trying to use.
Doctors have tables and example scans so that when they examine a PET scan they can tell if part of an organ is taking more sugar than it should be. Many types of cancer tend to take a lot of sugar, because energy is needed to grow, and cancers tend to grow quickly. So when a doctor is looking for cancer, they look for areas where lots of sugar is being taken where it wouldn’t normally be.
This isn’t always reliable. Some tumors grow slowly and use little energy, so don’t use much sugar and so don’t show up on the PET scan. Some organs take a ton of Energy normally, like the brain. Brain tumours aren’t reliably detected, because the tumor takes the same amount of sugar as the brain, so you can’t really see the tumour – it just blurs into the normal brain.
PET scan can track any drug which has a positron emitting radioactive isotope. This means different drugs can be used for different diseases. Brain tumours can be tracked on PET scan with a drug based on a specific amino acid – although usually other scans like MRI scan are better and cheaper.
Other drugs can be used to check bone health, or heart health or dementia. However, the process is the same. The radioactive isotope is tracked, and the doctor compares the pattern of where it had gone with tables and examples of what normally happens. Often there is some computer processing to calculate statistics to make the comparison more reliable.
Latest Answers