Treating cancers
    Most cancerous tissues consist 
    of rapidly dividing cells, which 
    can be seriously affected by ionising 
    radiation that damages their DNA. 
    DNA damage may result
    in cellular destruction during cell 
    division. 
    Though cells have a mechanism to
    repair the damaged DNA, cells which 
    are dividing rapidly have much less 
    time to have their DNA repaired, 
    thus resulting in preferential                  a patient with cancer being prepared for treatment 
    destruction of cancer cells.There are 
    several types of radiation therapy:

    Brachytherapy:  putting radioactive
    sources into the tumor or close to it. 

    Cancers can be treated by inserting 
    hollow needles (made of iridium-
    platinum alloy), with radioactive 
    radium sulphate inside, in a suitable
    pattern, as to give a uniform dosage 
    to the tumor. A permanent implantation
    of a radioactive source is also used to treat cancer. Gold-198 (with a half-life of 65 hours) 
    or iodine-125 (with a half-life of 60 days) are packed in some very tiny cylinders and 
    implanted in the cancerous area. These short-lived [radionuclides]deliver the dose to the 
    tumor and then promptly decay away.

    High-intensity X-rays treatment

      This is used for tumors deep inside the body or tumors in inoperable areas. The X-rays are
      concentrated on the cancerous area to kill the cancer cells.

      However, this sort of treatment can also kill normal cells which divide rapidly, such as the
      hair cells, skin cells and blood cells. These cells are severely affected by radiation, this 
      explains why cancer patients taking these therapies suffer from hair loss. Since radiation 
      can cause so much harm to normal cells, these therapies are usually fractionated to allow 
      time for the damaged normal cells to repair.


   Tracers
    Tracers are weak [radioisotopes], which are injected into a system and can be traced through
    the system with a detector.

     It can be used to:

• estimate the blood volume of a patient
• view the structure of the blood vessels of the patient
• locate the blood clots inside the body-by injecting sodium-24 into the blood stream and finding out where the flow stops

     In addition, tracers are used for organ imaging. Certain organs in our body concentrate 
     certain types of chemicals, by injecting radioactive isotopes into the bloodstream, tumors 
     in a particular area can be detected and will be affected if that area concentrates that 
     radioactive isotope. 
     On the other hand, this can be used to obtain images of organs with a gamma camera. 
     The following table shows the corresponding location in which a particular chemical is 
     concentrated.

  Cancerous tissue

     Therapy

                        A person receiving radiotherapy to treat cancer. 
The illuminated disks indicate the areas that are to receive radiation.

       Administration of radioactive iodine can be used to treat thyrotoxicosis (overactivity of the 
       thyroid gland). Since the thyroid gland concentrates the iodine, excess tissue of the thyroid 
       gland can be destroyed by beta emission. The dose is orally taken in a solution of sodium 
       iodide.

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