Standard radiation therapy emerged and improved for many years. It is an effective treatment for many types of cancer. However, radiation therapy has a side effect. The energy of primary photons and secondary electrons is released along the entire path of the beam, radiation affects healthy tissues both before the targeted tumor and beyond. Such an "exit dose" of radiation damages normal cells and can subsequently lead to health problems.
The advantage of proton therapy is that protons release most of their energy precisely at the site of the localization of a cancerous tumor. As they move through the body, the protons slow down, interact with electrons and release a maximum of radiation at the end of the path. The place where the greatest energy release occurs is called the Bragg peak. The doctor can calculate the Bragg peak in the patient's body in such a way that it coincides with the center of the cancerous tumor. The impact of protons exactly corresponds to the shape and depth of the neoplasm, while at the same time not affecting healthy tissues and organs.
The advantages of proton therapy
Minimal damage to healthy tissues and the resulting possibility of treating tumors near vital organs
Low risk of side effects during and after radiotherapy and faster recovery of patients after treatment
Lower risk of recurrence of malignant tumors due to precise focusing of proton therapy
How does it work?
To understand how proton therapy works, consider the physical processes taking place inside the proton accelerator, the cyclotron, and the beam transport system.
- The proton begins its movement in the ion source. For a fraction of a second, atoms of hydrogen are divided into negatively charged electrons and positively charged protons.
- Protons through a vacuum tube enter the linear accelerator, and in just a few microseconds their energy reaches 7 million electron / volts.
- Proton rays remain in the vacuum tube when entering the cyclotron, where acceleration increases their energy to values of 70 to 250 million electron / volts, sufficient to deliver them to any depth inside the patient's body.
- After leaving the cyclotron, the protons move through a system consisting of a series of magnets that form, focus and direct the proton beam to a special room where treatment will be performed.
- In the treatment room, a gantry system, which can rotate 360 degrees, is installed, allowing the beam to enter the patient's body from any angle. Accuracy of the beam targeting is calculated using powerful computers, doctors monitor the course of treatment on monitors. A multilevel safety system protects the patient and personnel from radiation exposure.
- At the exit from the nozzle, a special device (aperture) forms a beam of protons, and another special device (compensator) directs a three-dimensional beam to the depth of the tumor.
- At the maximum energy the proton beam moves at a speed equivalent to two thirds of the speed of light.
Pencil beam scanning
Pencil beam scanning (PBS) or a sharply pointed beam is the advanced method of using protons for the treatment of cancer, which is used so far in a few proton centers of the world. The MIBS proton therapy center team has mastered PBS technology.
The technology of "pencil" scanning is based on complex treatment planning systems and multiple magnets, which direct a narrow proton beam, effectively "painting" the dose of radiation layer by layer. A highly targeted beam of protons moves along the vertical and horizontal axes, like the tip of a pencil "painting" the entire tumor. In the process of beam movement, its intensity is modulated. Radiation of the maximum permissible intensity is delivered exactly into cancer cells without touching normal tissues.
- The treatment of cancer by a beam of protons is the vanguard of modern nuclear medicine in the world. But the technology itself was discovered a long time ago.
- 1946 - The idea to use protons in medicine was put forward in 1946 by the scientist-physicist Robert R. Wilson.
- 1950 - The first attempts to use proton radiation for the treatment of patients were made in 1950 in the USA in the research center of nuclear physics. But the energy of the accelerators at the time was not enough for the beam to penetrate deep into the body.
- 1970 - in the late 1970s, the widespread use of tomography, together with the development of high-tech computers and advanced accelerators, allowed the introduction of proton therapy into clinical practice.
- 2000 - The widespread use of proton therapy in the world began in the 2000s.
- Today throughout the world there are 57 centers of proton therapy located in the United States, Japan, Germany, the Czech Republic. It is expected that by 2018 their number will grow to 88.
To whom is the treatment indicated?
Proton therapy throughout the world is used for many types of oncological pathologies. And it is often the only solution for patients.
- First, treatment with a beam of protons does not require surgical intervention, which makes this method ideal for inoperable tumors. Treatment with a proton beam is suitable for patients who, for health reasons, cannot tolerate surgical intervention. Or for those who, for one reason or another, refuse to perform a cavitary operation.
- Secondly, the high accuracy of the destruction of cancer cells, together with the most sparing effect on healthy organs and normal tissues, make proton therapy an indispensable method when the tumor lies in dangerous proximity to such important organs as the brain, heart, spine.
- Thirdly, proton therapy provides excellent results for solid tumors with outlined boundaries, that is, in cases where the cancer has not spread to other parts of the body.
- Fourth, the sparing effect on healthy cells and the absence of side effects make it possible to consider proton therapy as the most appropriate method for treating children.
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