Linac Report FINAL

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CONTENTS INTRODUCTION ABOUT CANCER 1. 2. 3. Types of Cancer Causes of Cancer Treatment of Cancer

HISTORY LINEAR ACCELERATOR 1. 2. 3. Principle Major Components Description of Components


1. INTRODUCTUONA linear accelerator (LINAC) is the device most commonly used for external beam radiation treatments for patients with cancer. The linear accelerator is used to treat all parts/organs of the body. It delivers high-energy x-rays to the region of the patient's tumor. These x-ray treatments can be designed in such a way that they destroy the cancer cells while sparing the surrounding normal tissue. The LINAC is used to treat all body sites, using conventional techniques, Intensity-Modulated Radiation Therapy (IMRT), Image Guided Radiation Therapy (IGRT), Stereotactic Radiosurgery (SRS) and Stereotactic Body Radio Therapy (SBRT)

2. ABOUT CANCERCancer is a general term for a group of disease caused by the uncontrolled growth of abnormal cells. Cancer may occur in any region or any organ in the body. The DNA in each cell is responsible for programming that cells characteristics and growth. When this program derailed, cells lose the ability to grow and reproduce normally. As a rule, abnormal cells are detected by the defence system and eliminated. But when the body is no longer able to do this abnormal cell continue to multiply and can eventually form a tumor.


Types of tumor

Benign Tumors are not cancer. They often can be removed and in most cases, they do not come back. Cells in benign tumor do not spread to other parts of the body. More importantly, benign tumor are rarely life threatening. Malignant tumors are cancer. Cells in malignant tumors are abnormal and divide without control and order. These cancer cells can invade and destroy the tissue around them. In a process called metastatis, cancerous break away from the organs on which they are growing and travel to other parts of the body, where they continue to grow.

2.2 Types of CancerCancer is classified on the basis of tissue. They are of four types: CARCINOMAS: This type is mainly derived from epithelial cells. They breast, skin, brain, lung, stomach cancer etc. include cervical,

MELANOMAS: Cancerous growth of melanocyte (A type of skin cells) is called melanomas. SARCOMAS: These cancers are located in muscular tissue derived from mesoderm. Thus they include the cancer of bones, cartilage, tendons adipose tissue and muscles. i. ii. Cancer of bones is called Ostermas. Cancer of adipose tissue is known as lipomas.


They are rare in human about 1% of all tumors are sarcomas.

LEUKEMIAS and LYMPHOMAS: These are cancers of haematopoctic cells. Leukemias are commonly called blood cancer. The most common cancer in India is Mouth-Throat Cancer in men and uterine cervical cancer in women.

2.3 Causes of CancerChemical and physical agents that can cause cancer are called carcinogens and belong to these categories: ONCOGENIC TRANSFORMATION: They are agents or factors, which bring about changes in genetic materials. TUMORS PROMOTORS: They promote proliferation of cells, which has undergone oncogenic transformation. E.g. some growth factors are hormones. TUMORS VIRUSES: Some viruses are known to be connected with oncogenic transformations. RADITION: The X-rays, cosmic rays, UV-rays can cause cancer. PHYSICAL AGENTS: i. ii. iii. iv. Betel and tobacco chewing causes Oral cancer. Heavy smoking causes lung cancer and may also cause cancer of oral cavity, pharynx, and larynx. Jagged teeth may cause tongue cancer. Excessive exposure to sunlight may cause skin cancer.

CHEMICAL AGENTS: Several chemicals are known to cause cancer. These are caffeine, nicotine, products of combustion of coal and oil for pesticides, constant use of these substances can cause cancer. Some sex hormones, steroid if are given in large amount may cause cancer.

2.4 Detection and Diagnosis of Canceri. ii. iii. iv. Bone marrow lecopsy and abnormal count of WBC In leukaemia. Biopsy of tissue, direct or through endoscopy. Pap tests (cytological staining) used for detecting cancer of genetic tracts. X-rays (using dyes), CT scan, MRI scans, ultrasound, SPECT, PET, PET/CT of internal organs e.g. Kidney Pancreas. Mammography: it is a radiographic examination of breasts fir possible cancer.


Different Sites of Cancer

Some of the important sites of cancer are skin, mouth, oesophagus, stomach, colon, rectum, liver, gallbladder, blood, lymph, adipose tissue, lung, cervix, breast, brain, penis, prostate, muscle, thyroid, kidney and bone.


Treatment of Cancer

All cancer treatments focus on destroying malignant cells. The most commonly used treatment, regimens consist of surgery, radiation therapy, chemotherapy, hormonal therapy, immunotherapy, either alone or in some combination. Because certain tumors respond best to specific treatments, there is no best treatment for all tumor types. Surgery Surgery is the oldest form of treatment for cancer. It also has an important role in diagnosis and staging (finding the extent) of cancer. Here the surgeon removes the cancerous tissue along with a sufficient margin of healthy tissue. Today more limited (less invasive) operations are often done to remove tumors while preserving as much normal function as possible. Surgery offers the greatest chance for cure for many types of cancer, especially those that have not yet spread to other parts of the body. Chemotherapy Chemotherapy is the term used to describe the treatment of cancer with drugs that can destroy cancer cells by stopping them from growing or multiplying healthy cells can also be harmed, especially those that multiply quickly. Normal body cells usually repair themselves after chemotherapy is completed. There are more than 100 different chemotherapeutic agents available today and can be administered as infusion, injections, pills or as ointment, depending upon the drugs chosen and the type of tumor to be treated, the chemotherapy drugs may be fixed together or given individually. Immune Therapy Immune therapies try to force the patients own immune systems to stop the growth of cancer cells. This can be accomplished by stimulating the immune systems to work harder, or by given the patient synthetic immune system proteins. Immune therapy is the most effective when used to treat small tumors, or when the patients cancer is not very advanced. Radiation Therapy Radiation therapy (sometimes called radiotherapy, x-ray therapy, or irradiation) is the treatment of the disease using penetrating beams of high energy waves or streams of particle called radiation. Radiation is used to treat cancer and other illness. The radiation used for cancer treatment comes from special machine or radioactive source. Radiation therapy equipment aims specific amount of the radiation at tumor or area of the body where there is a disease. Radiation in high doses kills cells or keeps them from growing and dividing. Because cancer cells grow and divide more rapidly than most of the normal cells around them, radiation therapy can successfully treat many kinds of cancer.

2.7 Treatment ObjectiveThe goals of any forms of cancer treatment is the destruction of the tumor and its spread into the neighbouring lymph system or the palliation (relieve) of symptoms when a cure is not attainable. These goals are realized by the delivering a precisely measured uniform lethal dose of radiation to the tumor while minimizing the potentially harmful irradiation of normal tissue.

2.7.1 ProceduresExternal beam therapy (EBT): External beam therapy is a method for delivering a beam of high energy x-rays to the location of the patients tumor. The beam is generated outside the patient (usually by a linear accelerator) and is targeted at the tumor site. This x-ray can destroy the cancer cells and careful treatment planning allows the surrounding normal tissue to be spared. No radioactive source is placed inside the patients body. Intensity -Modulated Radiation Therapy (IMRT):IMRT is an advance mode of high precision radiotherapy that utilizes computer controlled x-ray accelerator to deliver precise radiation doses to a malignant tumor or specific areas within the tumor. The radiation dose is designed to conform to the three dimensional(3-D) shape of the tumor by modulating or controlling the intensity of the radiation beam to focus a higher radiation dose to the tumor while minimizing radiation exposure of surrounding normal tissue. Treatment is carefully planned using 3-D CT images of the patient in conjunction with computerized dose calculations to determine the dose intensity pattern that will best conform the tumor shape. Because the ratio of normal tissue dose to tumor dose is reduced to a minimum with the IMRT approach, higher and more effective radiation doses can safely be delivered to tumor with fewer side effects as compared with conventional radiotherapy techniques. IMRT also has the potential to reduce treatment toxicity, even when doses are not increased. A medical linear accelerator generates the photon or x-rays used in IMRT. The machine is the size of a small room-approximately 10 feet high and 15 feet long. The intensity of each beams radiation dose is dynamically varied according to the treatment plan shrinking or eliminating tumors. Stereotactic Radiosurgery:Stereotactic radio-surgery is a highly precise form of radiation therapy used primarily to treat tumors and other abnormalities of the brain. Stereotactic radiosurgery is a non-surgical procedure that uses highly focused x-rays to treat certain types of tumors, inoperable lesions and as a post-operative treatment to eliminate any leftover tumor issue. The treatment involves the delivery of a single high dose or sometimes smaller, multiple do