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How Radiation Therapy Works

What Radiation Therapy Is
Radiation therapy for cancer is the exposure of cancerous tissue to ionizing radiation. This is usually done by what is called "external" therapy, using electron, X-rays or gamma rays to treat the tissue. This therapy may occur either before or after surgery, or in the place of surgery.

Therac-25 was a 3rd generation radiation therapy machine for external radiation therapy. It used either electron beam or X-rays to treat tissue.

Why Radiation Therapy Works
Cancer cells usually multiply faster than most other cells in the body. Tissue composed of these quickly-dividing cells can be shrunken by disabling its genetic material. By doing this, ionizing radiation interferes with the cancerous tissue’s ability to grow.

Unfortunately, the radiation makes no distinction between cancerous cells and other rapidly dividing body tissues. Skin and hair are some of the most noticeably hurt tissues after treatment, and treatment may produce skin lesions and hair loss. These tissues have cells that rapidly divide and the radiation halts their development. But they are usually able to recover from this assault and return to normalcy. Nevertheless, skin lesions and hair loss are not an unusual side effect of radiation therapy.

What a Treatment Session is Like
Radiation therapy is usually done in a series of sessions occurring over several weeks, allowing the effect of the radiation to build up over time. The treating doctor will determine the specific number of treatments, the dosage at each treatment, and the schedule. During treatment, the doctor will usually see the patient once a week to check on general health, side effects, and the progress of the treatment.

Before the series of treatments occurs, a radiation therapy technician will outline the specific area to be treated with a marking pen, indelible ink or silver nitrate.

Depending on the body area to be treated, the patient would need to remove his or her clothing and put on a hospital gown. After going to the radiation therapy room, they would then either lie on a treatment table or sit in a special chair (Therac-25 had a table). The marks on the skin are used to guide the machine operator in locating the precise area to be treated. Once the machine is sset up, the operator leaves the room for a control room nearby. This protects the operator from prolonged exposure to low-level radiation that might scatter from the machine (an operator may treat as many as 30 patients in a day). From there, the operator will turn on the treatment machine while he/she watches. With the Therac-25, this was accomplished by means of a television camera and monitor. During radiation therapy, the treatment machine makes a buzzing noise. Treatments are typically brief and painless, normally lasting 1 to 5 minutes. Total time in the treatment room will usually be 5 to 15 minutes.