[Introduction of Scientific and Technological Achievements] Fast Wild Multi-leaf Grating

Today, Xiao Bian brings you another scientific and technological achievement of our hospital in the field of biomedical manufacturing and general health-the rapid growth of wild multi-leaf gratings.

The rapid field multi-leaf grating is developed by the military-civilian integration intelligent equipment technology research center of our hospital, and is a key functional component of high-end rotating radiotherapy equipment. Please come with Xiaobian to know more about it ~

 

science and technology research and development]

Tumor radiotherapy is a local treatment method that uses radiation to treat tumors. Radiation includes alpha, beta, gamma rays produced by radioisotopes and x-rays, electron beams, proton beams and other particle beams produced by various x-ray treatment machines or accelerators. The role and status of radiotherapy in tumor treatment is becoming more and more prominent, and it has become one of the main means of treating malignant tumors.

With the help of the development of CT imaging technology and computer technology, the current radiotherapy technology has developed from two-dimensional radiotherapy to three-dimensional radiotherapy and four-dimensional radiotherapy technology, and radiotherapy dose distribution has also developed from point dose to volume dose distribution, and dose intensity modulation in volume dose distribution. Multi-leaf grating is a key functional component for ray conformal intensity modulation and precise dose control in high-end rotary radiotherapy equipment.

Multi-leaf collimator (multi-leaf grating)

Multi Leaf Collimator (Multi Leaf Collimator-MLC) is a mechanical moving part used to produce conformal radiation field, also known as multi-leaf grating, multi-leaf diaphragm and so on. The initial application of MLC replaces the traditional block to form the desired field shape and carry out classical conformal radiotherapy. Compared with the field block, MLC conformal has significant advantages: it can greatly improve the efficiency of conformal treatment, easy to operate, and does not produce harmful gases or dust. However, the application of MLC is not limited to the conformal field. It is also widely used in rotating irradiation: in the process of rotating the radiation source, the shape of the radiation field is adjusted to follow the projection shape of the target area; in intensity modulated radiation therapy: by controlling the movement of MLC leaves, the desired dose distribution is achieved.

Working principle of multi-leaf grating

Throughout its historical development, the multi-leaf collimator is mainly around to improve the shape, reduce the transmission penumbra, reduce leakage, adapt to dynamic and dynamic wedge plate and other advanced functions.

The width of the blade directly determines the geometric fitness (conformability) of the irregular field formed by the multi-leaf collimator and the shape of the planned target volume (PTV); the thinner the blade, the better the conformability, but the processing is also more difficult, the more and more complex the drive motor and other mechanisms, the corresponding increase in cost, so a reasonable compromise must be made between conformability and cost.

The height of the blade must be able to reduce the intensity of the original rays and radiation to less than 5% of the point. Due to the need to maintain the relative dynamic movement of low resistance between the blades, there are often some leakage rays between the blades, which will reduce the shielding effect of the blades on the original rays. The height of the blades needs to be appropriately thickened, generally not less than 5cm thick tungsten alloy. If the leakage radiation dose is reduced to less than 2%, a tungsten alloy thickness of 7.5cm is usually required.

 

science and technology innovation]

Based on the research of spiral radiotherapy and precise radiation control technology, the Research Center for Military-civilian Integration Intelligent Equipment Technology of our hospital has developed a fast field-forming multi-leaf grating (F-MLC,Fast Multi Leaf Collimator) with a self-developed micro-linear motor as the driving element. Rapid field-forming multi-leaf grating is the key functional component of ray conformal intensity adjustment and precise dose control in high-end rotary radiotherapy equipment, ensuring maximum killing of tumor cells and reducing radiation to normal tissues, and is the enabling component of high-end precision radiotherapy, and its performance index directly determines the quality of treatment.

Main functions

1. Through the F-MLC fan beam, the precise control of the shape and dose of the ray is realized, and the radiotherapy of the tumor segments is divided into sectors to meet the radiotherapy needs of complex tumors.

2. Through the F-MLC fan beam, the precise control of the shape and dose size of the ray is realized, and the radiotherapy of the tumor segments is divided into sectors to meet the radiotherapy needs of complex tumors.

The fast field-forming multi-leaf grating is based on the micro-special linear motor drive technology developed by independent innovation, which has the advantages of continuous and binary blade drive of current mainstream products, and can improve the ray utilization rate. The research and development F-MLC supports volume-fault intensity modulation mode, which can improve radiotherapy efficiency and reduce radiotherapy side effects. Based on F-MLC, errors caused by tumor motion can be compensated, thus improving radiotherapy accuracy.

The emergence of fast-growing multi-leaf gratings fills the domestic gap, and the dynamic performance indicators such as blade speed and acceleration have reached the international leading level.

First principle prototype

 

Product test prototype

What are the advantages of fast field multi-leaf gratings compared to multi-leaf gratings? Let's look down together ~

Advantages of fast field-forming multi-leaf grating

Combining the advantages of continuous and switched multi-leaf gratings, it can not only realize the precise conformal control of blade stroke, but also realize the binary dynamic control of high speed and high acceleration.

2. Compared with the binary pneumatic grating of the helical tomography radiotherapy system (TOMO), it can reduce noise, improve the ray utilization and efficiency of the linear accelerator, and increase the life of the magnetron, which can replace the TOMO grating and reduce the cost.

3. Compared with regular electric multi-leaf grating, it has fast speed, high efficiency, low noise and long life.

 

Specific parameters of fast field-forming multi-leaf grating

 

Independent research and development of linear motor

 

 

The first generation 4-axis drive, the second generation 16-axis drive, the third generation 8-axis drive

 

bus multi-axis controller

Quick Chengye Multi-leaf Grating has developed a 3-type principle prototype, obtained 10 national invention patents, and applied for 5 new invention patents. It was at the 23rd National Invention Exhibition · One Belt One Road and BRICS Skills Development and Technology Won the Gold Award for the Innovation Competition.

NDRC 2018-2019 "National Quality Investment Project" Award

 

Gold Award of the 23rd National Invention Exhibition in 2019

 

application value]

The multi-leaf grating is the core enabling functional component of the rotating radiotherapy equipment and the key to the completion of the treatment plan. The speed, acceleration and other technical indicators of multi-leaf grating play a vital role in the accuracy and efficiency of radiotherapy. The products of the project have important clinical value in 4D radiotherapy technology and beam modulation intensity efficiency.

clinical value

1. Higher treatment accuracy

The same isocenter height and the same multi-leaf grating position, the thinner the blade thickness, the higher the theoretical modulation resolution. High speed and high acceleration of blades can improve the accuracy of ray conformal and dose dynamic control.

2. High treatment efficiency and dynamic response performance

High-speed, high-acceleration follow-up performance allows the frame to rotate faster, which is conducive to improving treatment efficiency.

3. High ray utilization rate

Compared with VMAT intensity-modulated MLC: high speed and high acceleration can obtain better dose distribution modulation ability. Compared with TOMO binary pneumatic MLC: greater ray utilization can be obtained.

4. Tumor motion tracking

In the process of radiotherapy, the tumor movement caused by respiration is an important factor to produce the deviation between the planned dose and the actual dose. The respiratory motion error of the tumor in the abdominal cavity and chest cavity can reach 12~75mm. High-speed multi-leaf grating can achieve better tracking of respiratory motion.

5. Innovative treatment

Based on the fast field multi-leaf grating, the innovative envelope tomography treatment method is proposed. The envelope fault algorithm is comparable in accuracy to the TomoTherapy using fault intensity adjustment, and in efficiency to the VMAT technology and Varian's RapidArc technology using volume rotation intensity adjustment.

In the industrial process, some technical products will be applied in cooperation with radiotherapy equipment enterprises, which will directly generate economic benefits. In addition, the core technologies such as the developed micro-special linear motor and its servo drive, multi-axis motion control based on high-speed bus and real-time data acquisition system will respectively form characteristic and competitive products to meet the needs of intelligent manufacturing, robots, high-end manufacturing equipment and other industries, have a wide range of market demand, and generate direct economic benefits through the market.

 

Technical docking and business negotiation

Contact: Mr. Ye

Fixed line: 010-62773269

E-mail: yepq@tsinghua.edu.cn

 

Source | Military-civilian Integration Intelligent Equipment Technology Research Center

Editor | Zhang Shu

The final interpretation right of the above related technologies belongs to the civil-military integration intelligent equipment technology research center.