Computed Tomography known as CT scan use the X rays to get the axial films. This differs from normal X-ray films because it can give more details about the tissue. The X-ray is passed from one side and the sensor will catch the rays from the opposite side. This will happen around the body. The probes can move in a circle and the 360 degree expose will help to get the clear images. The computer will calculate and give the view of the tissue according to the radiation. In CT the radiation is given from outside by X rays.
PET scan is the shorten form of Positron Emission Tomography. Positron is emitted during nuclear reactions. Positron is like an electron in weight but positively charged. The isotopes (the atoms can divide and emit the rays) used in the PET scan. Usually FDG (Fluro deoxy glucose) is used. This will emit the positrons. Usually the radioactive FDA is taken by the active tissue. FDA is like glucose. Glucose is the fuel for energy to the tissue. So Glucose will be taken up by the active tissue. Same way FDG is also taken by the metabolically active tissue. So the radioactive substance [example: isotopes with short half lives such as carbon-11 (~20 min), nitrogen-13 (~10 min), oxygen-15 (~2 min), and fluorine-18 (~110 min)] will attach to the glucose. When the glucose is taken by the tissue the radioactive substance is also taken inside the tissue. The amount of uptake will help us to identify the activity of the tissue. According to the amount taken by the tissue, the emission amount varies. The positrons will react with the electrons in the tissue. Electron is a negative charged particle and positron is a positive charged particle. This reaction will be calculated by the computer and the final image will be given by the computer. PET scan is useful to find out the spread of the cancer. The cancer tissue usually divides very quickly, in other words they are ACTIVE. So they will take more glucose from the blood.
PET scan need more time than a CT scan. Because, there is a waiting time from the time of injection and the tissues take the glucose. Usually the time gap is nearly one hour.
PET scan can be combined with CT scan or MRI scan.
› CT and PET scan are imaging techniques used by the medical professionals.
› Both are helpful to find out the spread of the cancer.
› Both can increase the risk of cancer as they are using RADIATION.
› PET scan is superior to CT as it will give the metabolic activity of the tissue.
› PET scan need more time compared with the plain CT.
› PET scan uses RADIO ACTIVE isotopes, which emits radiation, but CT uses X-rays.
› CT is comparatively simple procedure than PET scan