What Are the Different Physics Careers?

Physicists are very, very important members of tumor radiotherapy. It is no exaggeration to say that without a physicist, radiotherapy cannot be carried out. Especially with the rapid development of tumor radiotherapy equipment and technology in recent years, the role of physicists in ensuring radiation safety, improving the level of treatment technology, and providing high-quality services to patients has become increasingly important. In the tumor radiotherapy department of European and American national hospitals, physicists have a long history as a profession. The number of physicist occupations has also increased due to the development of equipment and precise radiotherapy technology. At the same time, their responsibilities have become increasingly heavy. .

Physicist

Right!

Physicists are very, very important members of tumor radiotherapy. It is no exaggeration to say that without a physicist, radiotherapy cannot be carried out. Especially with the rapid development of tumor radiotherapy equipment and technology in recent years, the role of physicists in ensuring radiation safety, improving the level of treatment technology, and providing high-quality services to patients has become increasingly important. In the tumor radiotherapy department of European and American national hospitals, physicists have a long history as a profession. The number of physicist occupations has also increased due to the development of equipment and precise radiotherapy technology. At the same time, their responsibilities have become increasingly heavy. .

Chinese name

Physicist

Nature

Occupation name

Belongs to

Tumor radiotherapy

Function

Ensure radiation safety

In tumor

1. Work on radiotherapy equipment

Modern radiotherapy equipment includes long-range irradiation equipment, brachytherapy equipment and simulators, etc. Considering the rapid development of radiotherapy equipment, the types of diseases targeted and the relatively expensive price, it is the responsibility of the physicist to choose the performance-price ratio of the radiotherapy equipment that the unit needs to purchase, and to make his own suggestions on how to carry out the treatment project, and Put forward the indicators and conditions that manufacturers' equipment needs to meet. This not only requires physicists to constantly understand the latest radiotherapy technologies, but also to understand the scope and limitations of various technologies and methods, and to understand the complexity of the implementation process of these technologies.

The installation of radiation therapy equipment is generally done by the manufacturer, but then the acceptance test and machine data measurement of the equipment are the work of a medical physicist. For each radiotherapy device, a formal acceptance inspection entry can be listed. The guiding principle is that any device used for the patient must be tested to ensure that it meets the requirements for use and safety standards. For example, for linear accelerators, the following tests are required: radiation protection measurement, inspection of the symmetry of the independent collimator, whether the central axis of each part is consistent, the influence of the rotation of the frame and the head on the position of the center point, Detection of X-ray energy, emission field flatness and emission field symmetry, detection of electron beam energy, emission field flatness and emission field symmetry, monitoring of ionization chamber stability and linearity detection, etc. Each test has different content, steps and indicators, which can be completed in a form of one by one.

Part of the radiotherapy equipment that can pass the acceptance test can be used directly in clinical use, but some cannot be used directly. More data is needed. For example, before the linear accelerator is used clinically, it must be calibrated and measured to obtain all the data required by the treatment planning system. Beam parameters and machine parameters and input them into the treatment planning system, and then verify that the dose distribution calculated by the treatment planning system is consistent with the actual measurement results, these are the work of a physicist. Only machines authorized by a physicist can be used to treat patients.

The quality assurance (QA) of radiotherapy equipment is a necessary condition for a clinical institution to perform high-quality radiotherapy services. Every radiotherapy equipment needs to have the quality assurance content that should be done every day, the quality assurance content that should be done every month, and the quality assurance content that should be done every year, and list it in the document, and arrange the personnel one by one according to the time. Some regular quality assurance tasks can be performed by either a physicist or a dosimeter, but the physicist must establish quality assurance content items and steps to guide the entire process and check the final results.

2. Work on radiation treatment planning

First, the acceptance inspection, data measurement, and daily system and data maintenance of the radiation treatment planning system hardware and software need to be completed by a physicist. The inspection of the hardware system includes the accuracy and linearity of the digital input and output equipment. The inspection of the software system is to select a series of treatment conditions and check the accuracy of the calculated data compared to the measured data under these conditions, such as in three dimensions. Comparison of various calculations and measurement data that can be performed in the water tank. Another important aspect is the testing of various algorithms in the treatment planning system, such as their accuracy, constraints and characteristics. The role of the medical physicist here is to ensure that the treatment planning system is used correctly.

Secondly, the radiation treatment planning process must involve the participation of a physicist. Although the patient's treatment plan is fully under the responsibility of the radiation oncologist, the specific treatment plan is jointly completed by the radiation oncologist and the physicist, because the design and optimization of many plans during the treatment planning process involves complex physical concepts. The general model is: The radiation oncologist decides whether to perform a CT or MR examination, or both, according to the patient's condition, and determines the positioning mode and location of the CT simulation; The physicist combines the CT image data and MR Image data is input into the treatment planning system; If there is MR image data, the physicist first fuses the CT image and the MR image, and then outlines the outer contour and the outline of important organs on the CT image; Radiation Oncology The doctor outlines the target area, discusses with the physicist how to set the shooting field, and outlines the shape of the stop in the shooting field on the DRR image. At this time, after understanding the doctor's treatment plan, the physicist considers the actual physical conditions and equipment conditions and proposes himself The physicist sets the parameters and dose calculations, and constantly improves and optimizes the plan to achieve the doctor's treatment plan as much as possible; Finally, the doctor decides whether the treatment plan is acceptable, and signs the medical record for approval. Throughout the process, radiation oncologists and physicists should work closely together. In many treatment centers, the general treatment plan is completed by the dosimeter. The above steps also need to be followed. The physicist mainly plays the role of supervision and guidance. When it comes to complex treatment plans, the physicist completes it.

In addition, the physicist has an important task, which is to ensure the quality of the treatment plan. After the treatment plan is approved by the doctor, it needs to be output to the computer that controls the treatment equipment to control the actual treatment process. On the other hand, it needs to be output to the patient's medical record. Both outputs need to be very accurate. Physical The teacher needs to check each item to ensure that the data of the plan output, control output, and patient's medical records are consistent; in addition, because radiotherapy generally requires fractional treatment, in order to check whether each treatment is performed as planned The therapist needs to fill in the daily treatment situation according to the form, such as the date, the actual dose output when each field is treated, and so on, while the physicist checks these records every other week or so and finds that the problem is corrected in time. In order not to make mistakes, the above inspections generally require double inspections by two physics divisions.

If the patient's treatment plan is an intensity-modulated radiation therapy plan (IMRT), then a special quality assurance process is required for it. Each radiotherapy department can formulate the quality assurance content of IMRT according to the equipment conditions of the department. For an IMRT treatment plan, you can apply the treatment plan to a solid water phantom, and calculate the isodose distribution of each shooting field in this phantom; meanwhile, use Mapcheck to actually measure the isodose of each shooting field. Distribution, where each shooting field consists of dozens or even hundreds of subfields. The calculated value is compared with the measured value. If the dose error of 80% of the points is less than 5%, then the plan will be passed and the next treatment can be carried out. Or use a small cavity ionization chamber to measure the absolute dose at a certain point, and use an EDR2 film to measure the equal dose distribution on a plane, and then compare it with the calculated result. If a radiotherapy department has IMRT treatment planning systems from two different manufacturers, quality assurance can be performed using a method called hybrid plan validation. The specific method is to apply the IMRT plan generated by a system to a solid water phantom, and calculate the equal dose distribution of each shooting field in this phantom; at the same time, use the same beam condition in another treatment planning system Calculate the dose distribution in the solid water phantom and compare the calculated results of the two systems. The difference between the calculated results of the isocenter dose should be less than 5%. This method is similar to the method of QA verification using an independent dose calculation system.

3 Training and research

Due to the complexity and rapid development of radiotherapy technology, each radiotherapy department not only requires a team of physicists who can meet clinical tasks, but also continuous training of its personnel is very important. These trainings include not only routine clinical training, but also step-by-step mastery of new technologies and treatments. First of all, for those who are new to the field of medical physics and engaged in the work of physicists, there must be a reasonable period of clinical training, and many practical operations in clinical work must have a familiar process; second, a new treatment method is introduced Go to a radiotherapy department, such as whole body irradiation, electron beam irradiation, 3D conformal radiation therapy, intensity modulated radiation therapy, stereotactic radiosurgery, low-energy source implanted internal irradiation, high-dose rate internal irradiation, etc. On the one hand, it is necessary to master the treatment technology itself, and on the other hand, to understand the treatment equipment that carries out the treatment technology, and to formulate corresponding operating procedures and quality assurance plans for this treatment device, and comprehensively develop the various functions of the device. Therefore, the professional training of medical physicists should be a long-term continuous education and self-training process. This can ensure that the treatment equipment is in good working condition and provide the best technical support for the diagnosis and treatment of patients. In addition, the physicist has the responsibility to train the dosimeter and therapist of the unit in their physical knowledge.

The rapid development of various high-tech, sophisticated technologies in modern society is also concentrated in the development and application of modern radiotherapy equipment, such as electronic technology, precision instruments, computer networks, graphic image processing, and automatic control technology. Medical physicists have played an important role in improving radiotherapy technology and developing new treatment equipment, especially in their design and clinical applications. The research work related to all aspects of medical physics is the source of promoting the continuous development of radiotherapy technology. Improving radiation therapy technology itself is also one of the duties of medical physicists. Physical support in the process of tumor radiotherapy is not necessarily completed by a physicist himself. Some of the specific technical work can be done by a dosimeter and checked by a physicist. In this way, the physicist can have some time to carry out some research work, improve the level of treatment technology, and develop new treatment methods.

The role and responsibilities of each medical physicist in tumor radiotherapy depends very strongly on the type of equipment and the treatment project that he or she is in, and also the number of physicists in the department. Related, other physics teachers also have to bear some teaching and management tasks, so it is difficult to summarize them in detail. However, their common goals are to assist oncologists to accurately and effectively prescribe the prescribed dose to the target area of the lesion, improve and develop clinical treatment technology, and provide patients with high-standard treatment services.