Introduction: Nuclear medicine is a specialty medicine system that uses radioactive isotopes for the diagnosis and treatment of diseases. Here small amounts of radioactive isotopes are injected into the body and it is taken up by the target organ to measure its activity. The common radioactive isotopes used are Iodine -123, Iodine -131,Techneti um-99, Gal I i um-67 and Thallium-201 etc.Radionucleotides are also combined with other chemical compounds to form radiopharmaceuticals which are administrated to the patients to localize specific organs. Then the nuclear medicine system will count the radioactive decay from isotopes to measure whether the target organ is working well or not. It can be done by comparing with the standard values of radioactive decay. The end result of nuclear medicine process is a ‘dataset’ comprising one or more images. The radiation doses delivered to a patient in nuclear medicine system present a small risk of inducing cancer. It is one of the major disadvantages of nuclear medicine system.
Operation: A nuclear medicine system mainly consists of following components.
- Detector collimator
- Analyzer and recorder
Patient is injected with a radioactive element at the specific target organ. The nuclear isotope radiation is to be analyzed by the detector collimator. A scanner motor assembly connected to the detector collimator helps to scan back and forth in a linear fashion. A detector collimator uses sodium-iodine crystal to detect the radiation collimated to its surface. Collimators help to shape the beam of radiation emerging from the machine. The photomultiplier tube intensifies the signal after which it is linearly amplified using a linear amplifier. Its pulse is analyzed for comparison between successive events using a pulse height analyzer. Number of pulses per unit time is important and there are some standard values for each organ .The dot scan recorder produces a map of dots on a paper representing the distribution of radioactivity. A graph of radioactivity can be thus drawn indicating the amount of radioactive isotope taken up by the target organ. Improper amounts indicate organ malfunction.