Radiation therapy involves using radiation for curing difficult diseases such as cancer. Radiation therapy involves high energy radiation used to destroy cancer cells. It is effective for treating small tumors where surgery is not required to cure. It is also used in combination with surgery. After surgery, radiation therapy is used to destroy if any cancer cells left in oral cavity. Radiation therapy destroys both normal and cancer cells but normal cells gets repaired by themselves.
Prior to the radiation treatment, CT scanning is done to:
- Measure the size of tumor to decide the dose of radiation required for treatment.
- Give the exact position of the the tumor where radiation therapy is needed.
In radiation therapy, the complete dose of radiation is break down into small segments and given in regular intervals. This gives the time to repair normal cells and also prevents discomfort to patient.
Types of radiation therapy
Radiation therapy are classified into following types.
1. Based on the type of radiation given:
- X-Ray radiation
- Gamma radiation
2. Based on the position of radiation:
- Internal radiation
- External radiation
In this technique, the source of radiation is X-rays. X-rays are the first form of radiation source. The equipment that produce X-rays as radiations are linear accelerator and betatron. Depending on the amount of energy produced, X-ray radiation is used to destroy cancer tumors. The more energy produced, the deeper will be the penetration of X-rays. This has fewer side effects as the radiation is limited to particular area.
The effect of this radiation is same as x-ray radiation but here gamma rays are used as a source of radiation. In this gamma rays gives radiation spontaneously as they decompose.
Internal radiation is also called brachytherapy. It uses radio active materials to deliver radiation directly to the cancer cells. Radio active materials includes tubes or seeds. Radioactive substances are passed into these tubes. In some cases radio active pellets are placed directly on cancer cell. These can be removed after completion of radio therapy.
Prior to this radiation general anesthesia is given to prevent discomfort to patient. Then x-rays are taken to ensure that they are placed in a appropriate position. The advantage of internal radiotherapy is it has less effect on other parts of body as it directly given to tumor.
In this, a beam of radiation is delivered from machine to cancer cells from outside of the body. This is similar to taking x-ray but patient exposed to high radiation. Now a days advanced techniques in external radiations used are 3 dimensional radiation therapy (3-D CRT) and intensity modulated radiation therapy (IMRT).
Prior to these techniques, CT scanning or MRI scanning was done to locate the cancer position. Then, radiation is sent from various angles to the cancer site. This lowers the effect of radiation on other parts of the body.
Radiation therapy is used alone if the tumor is small and can be cured where surgery is not required. Radiation therapy in combination with surgery to destroy if any cancer cells left out after surgery.