ASSIGNMENT

ON

Medical applications of Accelerators-Cancer Therapy

BY

MD ALI RAZA

(2K14/NSE/03)

DEPARTMENT OFAPPLIED PHYSICS

DELHI TECHNOLOGICAL UNIVERSITY

SHAHBAD DAULATPUR, DELHI-110042

MARCH-2015

Medical applications of Accelerators-Cancer Therapy

1. INTRODUCTION

There are many applications of particle accelerators in various fields. This assignment deals with application of particle accelerators in medical fields concentrating on the area cancer therapy.

A particle accelerator is a device that uses electromagnetic fields to propel charged particles to

high speeds and to contain them in well-defined beams. Large accelerators are best known for

their use in particle physics as colliders (e.g. the LHC at CERN, RHI at Brookhaven National Laboratory, and Tevatron at Fermi lab). Other kinds of particle accelerators are used in a large variety of applications, including particle therapy for oncological purposes, and as synchrotron light sources for the study of condensed matter physics. There are currently more than 30,000 accelerators in operation around the world

1.2. Accelerators for Health and Medicine

The most direct way that particle accelerators impact most of our lives will be through their applications in medicine. With the advancement of accelerator science, new techniques for the treatment of cancer and diagnosis of various diseases have contributed significantly to major steps forward in the last decades.

3D scanner built using linear accelerator

1.3. Cancer

It’s a disease caused by an uncontrolled division of abnormal cells in a part of the body. Not all tumors are cancerous; benign tumors do not spread to other parts of the body. Possible signs and symptoms include: a new lump, abnormal bleeding, a prolonged cough,unexplained weight loss, and a change in bowel movements, among others. While these symptoms may indicate cancer, they may also occur due to other issues. There are over 100 different known cancers that affect humans.

1.3.1 Signs and symptoms

When cancer begins, it invariably produces no symptoms. Signs and symptoms only appear as the mass continues to grow or ulcerates. The findings that result depend on the type and location of the cancer. Few symptoms are specific, with many of them also frequently occurring in individuals who have other conditions. Cancer is the new "great imitator". Thus, it is not uncommon for people diagnosed with cancer to have been treated for other diseases, which were assumed to be causing their symptoms

2. Treating Cancer

One of the most important of all applications of particle accelerators is their application in the treatment of cancer. Cancer takes on many forms, so the treatment for cancer must also take on many forms. The main types of cancer treatment are

Surgery, where the cancerous tissue is surgically removed.

Chemotherapy, where powerful cancer-killing medicine is given to the patient.

Radiotherapy, where the cancer is destroyed by energy deposited by radiation.

2.1. Surgery

Surgery can be used to diagnose, treat, or even help prevent cancer in some cases. Most people with cancer will have some type of surgery. It often offers the greatest chance for cure, especially if the cancer has not spread to other parts of the body.

2.2. Chemotherapy

Chemotherapy (chemo) is the use of medicines or drugs to treat cancer. The thought of having chemotherapy frightens many people. But knowing what chemotherapy is, how it works, and what to expect can often help calm your fears. It can also give you a better sense of control over your cancer treatment.

2.3. Radiotherapy

Radiation therapy uses high-energy particles or waves to destroy or damage cancer cells. It is one of the most common treatments for cancer, either by itself or along with other forms of treatment.

Accelerator based treatments fall into the category of radiation therapy. Presently about 50% of all patients with cancer will undergo radiation therapy often in conjunction with other treatments such as chemotherapy or surgery. The most common form of radiation therapy is external beam radiotherapy where a beam of radiation is fired into the body by a particle accelerator.

3. X Ray Therapy

X-ray therapy is the most common form of radiotherapy. High energy X-rays - generated by firing electrons at a material like tungsten - are directed into a cancerous tumour. The radiation damages the DNA of the cancerous cells which ‘kills’ the cells. A high dose in the tumour is essential in the curing process by radiation. Unfortunately the X-ray radiation doesn’t only harm the cancerous cells; it also damages healthy cells at locations in the patient’s body that cannot be avoided by the X-ray beam. This can lead to unpleasant side effects for the patient such as pneumonitis, dry mouth due to loss of saliva production and damage to the skin. The aim of all new techniques in radiotherapy is to deliver a high dose of radiation to the tumour (to get a high cure rate) whilst reducing the radiation dose in healthy tissue (to reduce side effects).

Radiotherapy: The idea for radiation therapy was developed over 100 years ago. Today radiotherapy is the most common treatment for cancer

New radiotherapy techniques being developed that use particle accelerators, such as proton therapy, show clear signs of reducing side effects due to a reduction of the radiation dose in healthy tissues and for some types of cancer an increase in the possibility of curing the cancer; see section below on proton beam therapy.

4. Electron beam therapy

This technique uses the same type of accelerator that is used to generate X-rays, however the X-ray producing target is removed so that the electrons are fired directly into the tumour. Electron beam therapy is useful for treating tumours near the surface of the skin as the electrons quickly lose their energy when they interact with atoms in the body (see the graph below). Electron beam therapy causes far less damage to healthy tissue in the body as the beam does not pass all the way through the body.

5. Hadron beam therapy

A hadron is a type of particle made up of quarks. Hadron therapy falls into three categories:

proton therapy neutron therapy

ion (e.g. Carbon or Helium Ion) therapy.

The three types of hadron therapy differ in the type of particle beam that is used in the treatment. The dose deposition and its biological consequences depend on the particle type and its energy. The different therapies are used to treat different forms of cancer at different locations in the body as the particles penetrate and deposit their energy in different ways.

Gantry, the first and only compact scanning facility for the treatment of deep seated tumours using a scanned proton beam, has been operated at the Paul Scherrer Institute (PSI) in Switzerland. Patient treatments started at the facility in 1996.

The dose deposition of high energy neutrons is much like that of X-rays. The therapeutic difference is the stronger biological effect (cell killing per amount of deposited dose) of neutrons. For a limited amount of cancers and at certain locations in the body, this can be of an advantage.

The advantage of proton and ion-beam therapy over current X-ray radiotherapy is that the particles do not penetrate the whole body; they are fired into the body with a certain energy which dictates the range of the particles. The range is the depth that the protons or ions can penetrate into the body. Once protons or ions reach this depth they stop, whereas X-ray radiation passes through the whole body, thus also damaging cells on the way in and on the way out. Using protons or ions, this means that, for a certain dose in the tumour, the patient is exposed to less radiation in regions outside the tumour and therefore less healthy tissue is damaged in the treatment.

Ions such as carbon have a larger biological effect than protons. This can be exploited in certain cases. But to accelerate ions to sufficient energies, much larger accelerators, beam transport systems and gantries are needed than for protons. Until the 1990s proton therapy was performed in nuclear physics laboratories that were equipped with a particle accelerator and in this period most of the pioneering proton therapy research was performed and most of the dose delivery concepts were developed.

Above graph is Relationship between different kinds of particles (at a given energy) and their ability to penetrate inside the human body : In depth distribution of the absorbed dose, in the case of 20 MeV electrons, 8 MeV photons, 190 MeV protons: Electrons and photons mainly affect the first layers of tissue, while protons release most of the energy to a precise depth, variable with the beam energy. The green line shows the distribution of the dose received by the patient in the case of treatment of a tumor with a thickness of 6 cm and located between 18 and 24 cm depth, irradiated with proton beams with controlled different energies. The dose is concentrated along the lesion, with limited damage to the surrounding tissues.

6. Cancer research

Accelerator scientists are working on developing new techniques, such as a novel technique using synchrotron radiation from the ALICE accelerator at Daresbury Laboratory in the UK, to

detect certain cancers early, refine earlier techniques and improve accelerator technology so that treatments like proton therapy can become economically accessible for more hospitals around the world.

Due to the numerous forms that cancer can take and the many treatments cancer research is a large and extremely important area of medical research

7.Conclusions

In conclusion, an optimal use of the available modern linear accelerators, in particular conformation therapy, will improve the outcome of the radiotherapy treatments in some groups of patients. The side effects and complications will certainly be reduced. Optimization of the treatments with linear accelerators will be facilitated by further improvement in their technical performance and reliability. In addition, several companies have designed specific types of linear accelerators for specific purposes