radio-imaging effectiveness :: essays research papers

Radiation can be used in both diagnosis and therapeutic manners. The radiation emitted from radioisotopes can destroy tissue and in the therapeutic use: the destruction of cancerous and other dangerous tissues. And with diagnosis the gamma particle pass through the body tissues with minimal damage to a gamma camera. To evaluate the effectiveness of PET, SPECT, MRI and X-rays, we first need some basic knowledge on how each of them work. PET stands for positron emission tomography and works by an instrument collecting radiation emitted from a radioisotope injected the patient’ body. The strengths of emission are recorded by a gamma camera, which has a series of scintillation crystals, each connected to a photomultiplier tube. The crystals convert the gamma rays, emitted from the patient, to photons of light, and the photomultiplier tubes convert and amplify the photons to electrical signals. These electrical signals are then processed by a computer to generate images. The table is then moved, and the process is repeated, resulting in a series of thin slice images of the body over the region of interest (e.g. brain, breast, liver). These thin slice images can be assembled into a three dimensional representation of the patient's body Nowadays, PET scanning devices are most often used in conjunction with CT scanners, so that a more accurate image can be observed by the doctor for easier diagnosis of diseases or disorders. SPECT (Single Photon Emission Computed Tomography) works in a way much the same to PET. But the radioactive substances used in SPECT (Xenon-133, Technetium-99, Iodine-123) have longer decay times than those used in PET, and emit single instead of double gamma rays MRI has a more complex principle for its function; it works by creating a magnetic field so strong that the hydrogen protons in the body are forced into alignment with the magnetic field. Short bursts of radio waves are sent from the scanner into your body. The radio waves knock the protons from their position. When the burst of radio waves stops, the protons go back into position. They realign back to being in parallel with the magnetic field. As the protons realign, in a process known as relaxation, they emit tiny radio signals. A receiving device in the scanner detects these signals. The type of tissue can be interpreted from the strength of the signal emitted. Most of the hydrogen atoms in the body are in water molecules.