Heavy ion beam: a new generation of "killers" to defeat cancer cells
【Technological frontier】
Editor's note
Recently, the 7 departments of the National Atomic Energy Agency, the Ministry of Science and Technology, the Ministry of Public Security, the Ministry of Ecology and Environment, the Ministry of Transport, the National Health Commission, the National Medical Security Administration, and the National Medical Products Administration issued in Beijing the "Medicine Isotope Medium and Long-term Development Plan (2021-2035). Year)", this is my country’s first policy document issued for the application of nuclear technology in the field of medical and health care.
Since last year, thanks to the efforts of our country's scientific and technological workers, nuclear technology has played an important role in the fight against the epidemic, and more and more industrial applications have played an important role in breaking the monopoly of foreign technology and protecting the lives of ordinary people. What's more rare is that my country's nuclear technology industry chain is completely independent and controllable, and a number of models from basic research to industrialized applications have emerged. In this issue, let’s take a look at the first domestic carbon ion therapy system with independent intellectual property rights developed by the Institute of Modern Physics, Chinese Academy of Sciences.
In recent years, the carbon ion therapy system with independent intellectual property rights issued by the Institute of Modern Physics of the Chinese Academy of Sciences has been successfully applied and has been widely praised by the society.
The domestic carbon ion therapy system has condensed the efforts of several generations of Chinese scientific researchers, and has embarked on a road of independent innovation in the entire industry chain of "basic research→technology research and development→product demonstration→industrial application", breaking the high-end radiotherapy market in my country and being foreign products. Monopoly situation.
This road from basic research to successful industrialization "promotion" has certain demonstrative and reference significance at present.
Nuclear technology is the "killer" against cancer cells
The carbon ion therapy system is a large-scale medical system with advanced technology that integrates related technologies such as accelerators, nuclear detection, and medical diagnosis and treatment.
How does it provide carbon ion beams for cancer treatment?
Cells are the basic unit of human body structure and physiological functions.
There are tens of trillions of cells in every human body. They "work" in an orderly manner every day, so that the human body can function normally.
But if the normal cells of the human body are diseased, this "sick" cell will become another face.
It no longer divides normally in a planned way, but becomes extremely predatory, frantically grabbing nutrients, reproducing malignantly, and growing out of control. This is cancer cell.
Therefore, once humans encounter cell cancer, they will often fall into a situation where they are out of control.
In the face of cancer cell’s “wild behavior”, human beings are not helpless.
Drug therapy, surgical resection and radiotherapy have become the three major means for humans to eliminate the "tumor king".
Radiation therapy is the most commonly used.
As a physical therapy method, radiotherapy has a history of more than 100 years.
In the "1.0 era" of radiotherapy, the most commonly used rays are X-rays, in addition to the familiar gamma rays, which are all called traditional radiotherapy rays (photon radiotherapy).
In fighting cancer cells, traditional rays are like a blindfolded "killer", unable to actively distinguish between normal cells and cancer cells, and perform indiscriminate killing after entering the human body.
For patients, the inherent properties of traditional rays are unavoidable side effects and even more serious complications.
Therefore, to a certain extent, the therapeutic effect is actually a "gambling".
The most frightening thing is that good cells often die first, but the vitality of cancer cells is particularly tenacious.
With the development of science and technology, radiation technology is also advancing. Researchers are constantly searching for, creating, and improving new methods that can be used, and finally found a new generation of "killers" who are more intelligent and capable than the traditional "blindfolded killer". ", its name is "heavy ion beam".
The emergence of the Chinese Academy of Sciences Institute of Modern Physics, a carbon ion therapy system with independent intellectual property rights, means that on the road to fighting cancer radiotherapy, China has officially entered the "2.0 era" of radiotherapy with a comprehensive upgrade and independent intellectual property rights.
The principle and future application prospects of heavy ion beam
Heavy ions are ions in which atoms with atomic numbers greater than 2 lose electrons.
In 1903, British physicists William Henry Bragg (William Henry Bragg) and Kleeman (Kleeman) observed in experiments that after a beam of charged particles entered matter, it would form a dose peak at a certain depth. The scientific community said It is called "Bragg Peak", which is translated as "Bragg Peak" in Chinese.
This "magic" phenomenon has attracted the attention of scientists.
In 1946, the American Wilson first proposed to use Bragg Peak for tumor radiotherapy. He believed that after entering the human body, the charged particle beam would not continuously release energy along the way like traditional rays, but would be released at a certain depth (that is, the tumor site). Almost all the energy.
This means that charged particle beams have advantages over X-rays and gamma rays used in traditional radiotherapy.
Also in the United States, in 1975 Lawrence Berkeley Laboratory (LBNL) practiced the first case of using heavy ion beams to treat tumors.
Since then, Japan, Germany, and China have successively carried out research on the treatment of tumors with heavy ion beams.
So, what skills has this new generation of "killers" called heavy ion beams upgraded in the face of tumors?
Accurately distinguish between friend and foe.
This skill is called unique depth dose distribution.
When the heavy ion beam travels through biological tissues, the deposited dose is small (flat area), which means that during the penetration process, the heavy ion beam just passes by and does not inflict damage. In this way, normal cells can finally no longer lie down. The gun is good for protecting normal tissues and key organs; when it reaches the cancer cells, it starts to zoom in and kill the enemy. The so-called dose is mainly deposited at the end of the range (peak area). This phenomenon is the "Bragg Peak" mentioned above. .
Therefore, by adjusting the energy of heavy ions, the Bragg peak can be accurately killed at the tumor, and healthy tissues can be cared for at the same time.
It is worth pointing out that the Bragg peak phenomenon is an attribute of the heavy ion beam itself, and it is simply an "angel" in the ray world.
The treatment cycle is shorter.
This skill is called Relative Biological Effect (RBE) high.
After the heavy ion beam enters the biological tissues, in the "peak area", where the cancer cells gather, the deposited energy density is high. High energy density represents a strong lethality, which will cause the cancer cell DNA to produce double-strand breaks. The proportion is higher.
The double bond is broken, and it is very difficult for cancer cells to reproduce malignantly...
How high is the relative biological effect of heavy ions?
The relative biological effects of heavy ions are about 3 times higher than that of conventional photon rays.
Therefore, the heavy ion beam has greater "killing power" on cancer cells, and the number of treatments is reduced accordingly, thereby shortening the treatment cycle.
Less dependent on oxygen, more sensitive.
This skill is called oxygen increase ratio (OER).
A large amount of evidence shows that tumors grow in a unique abnormal blood supply system, which leads to insufficient oxygen and nutrients for tumor cells, which are called hypoxic cells.
However, conventional radiation is not sensitive to these hypoxic cells. How to improve the radiosensitivity of hypoxic cells in tumors is also an important issue in tumor radiotherapy.
Unlike conventional photon radiotherapy, the killing of tumor cells by heavy ion beams does not depend on the presence of oxygen.
Because heavy ions are mainly used to kill cancer cells by breaking DNA double bonds through the ionization of high-density secondary electrons formed by ionization, heavy ions have a small oxygen increase ratio and can be used to treat hypoxic tumors with insufficient blood supply.
The imaging can be seen, and the accuracy of cancer treatment is high.
This skill is called PET online dose verification.
After the heavy ion beam interacts with the nucleus of biological tissues, positron emitters are generated. The positron emitter layer technology (PET) is used for external imaging and compared with the CT images of the treatment plan. The heavy ion beam can be irradiated into the body The tumor dose distribution is verified online to ensure the safety of treatment.
It is precisely the above four skills that control the heavy ion beam within the millimeter range, accurately and effectively kill tumor cells, and minimize the damage to the surrounding healthy tissue, especially for those that are not suitable for surgery, are not sensitive to conventional rays, and are not sensitive to conventional rays. Some tumors that recur after treatment can be treated with heavy ion beams.
If you can summarize it in one sentence, it is that heavy ion radiotherapy has high precision, short treatment course, good curative effect, and low side effects.
Therefore, due to its unique physical and biological characteristics, heavy ion beams are considered to be the most ideal radiation therapy in the 21st century, and carbon ion beams are usually selected as heavy ion radiation therapy.
Heavy ion beam therapy: from basic research to industrialization
Modern basic research to industrial applications often involve multi-disciplinary crossovers and require advanced scientific equipment, which requires years of hard work and experimental investment by scientific research teams.
It is very difficult to achieve heavy ion beam therapy.
It requires a solid research foundation, involving nuclear physics and its interdisciplinary research, as well as advanced experimental devices, large accelerator devices that can generate huge energy ion beams.
It is not difficult to understand why the domestic carbon ion therapy system was born in the Institute of Modern Physics, Chinese Academy of Sciences.
Many years ago, the Institute of Modern Physics of the Chinese Academy of Sciences devoted itself to the basic research of nuclear physics and related applied research. It gathered a large number of scientific research talents, and the experimental conditions were very good, and many generations of large-scale heavy ion accelerator devices were built.
On the basis of these devices, the basic research work of the Institute of Modern Physics of the Chinese Academy of Sciences is very solid. Many teams have carried out a large number of cell experiments, animal experiments, and pre-clinical studies to find out the basic principles of heavy ion beam killing tumor cells and master The construction of the key core technology of medical heavy ion accelerator has laid a solid foundation for the development of my country's heavy ion cancer treatment.
With a firm foundation for basic research, applied research will be smoother.
They began to explore the accelerator manufacturing industry and founded a new technology company. With years of accumulation, they became an important bridge for heavy ion cancer treatment from the laboratory to the market. They developed and built my country’s first medical heavy ion accelerator with independent intellectual property rights—— China carbon ion therapy system.
The Chinese carbon ion therapy system consists of an ECR ion source, a cyclotron, a synchrotron, a treatment terminal and a beam transmission line. It has more than 60 patents, two of which have won the China Patent Excellence Award. It uses a combination of cyclotron injection and synchronous main acceleration. The unique design of route and charge stripping injection, compact synchrotron, multiple treatment modes and personalized treatment room layout not only breaks through the technical barriers of similar foreign products, but also improves cost performance, reduces operation and maintenance costs, and realizes domestic heavy ion Zero breakthrough in radiotherapy equipment.
According to international and domestic research data on heavy ion therapy for cancer, for some tumors, heavy ion beam radiotherapy is currently the least harmful and effective method, such as lung cancer, liver cancer, melanoma, skull base malignant tumor, chordoma, bone and soft tissue Tumors and other solid tumors that are relatively insensitive to conventional radiotherapy.
According to clinical trials, heavy ion radiotherapy can effectively control tumors distributed in the head, neck, chest, abdomen and pelvis.
The domestic carbon ion therapy system has condensed the efforts of several generations of scientific researchers, and has practiced a road of independent innovation in the entire industry chain from "basic research → technology research and development → product demonstration → industrial application", breaking the monopoly of my country's high-end radiotherapy market by foreign products Situation.
At present, there are 11 heavy ion hospitals in operation in the world, distributed in Japan, Germany, Austria, Italy and China; there are also 5 accelerators dedicated to cancer treatment under construction.
Globally, heavy ion hospitals have treated approximately 30,000 cancer patients.
The carbon ion therapy system is just one of the many research results of the Institute of Modern Physics of the Chinese Academy of Sciences and the Lanzhou Heavy Ion Accelerator Laboratory.
Relying on the Lanzhou Heavy Ion Accelerator, the Institute of Modern Physics of the Chinese Academy of Sciences has formed a discipline group centered on heavy ion science and technology, which can explore major basic scientific issues such as the origin of elements in the universe, and promote technological changes in energy, materials, and biomedicine. , And achieved a large number of original innovation results.
(Our reporter Yuan Yufei Our correspondent Yuan Haibo Gao Jingyi)