Radiation therapy is a method of delaying or preventing the growth of malignant tissue or removing malignant tissue by damaging or destroying target tissue using high-energy waves such as X-rays or gamma rays, or high-energy particle rays such as electron rays or proton rays. Radiation therapy may be used to treat malignant tumors, medical diseases, and some skin diseases in addition to cancers. Radiosurgery using a large amount of radiation at one time instead of making an incision has recently been developed as a substitute for neurosurgery in which the cranium is cut.
Radiation therapy has become common, and about 60% or more of recent cancer patients receive radiation therapy. In addition to being used to treat tumors, radiation therapy may be used to treat large invasive tumors that are difficult to treat surgically or may be used, together with other surgical methods of treating an area of the body not removed by surgery, to reduce the size of tumors and make it easy to perform surgery, or may be used to destroy malignant cells remaining after surgery.
External radiation therapy devices configured to emit radiation from the outside of the body may be classified into low-energy X-ray therapy devices, radioisotope therapy devices, linear accelerators, particle accelerators, and so on, according to the methods of generating high-energy particles or radiation.
Although low-energy X-ray therapy devices had been used to treat skin diseases or deep parts of the body by using X-ray generators, the use of low-energy X-ray therapy devices is now rare.
Radioisotope therapy devices use gamma rays emitted from radioisotopes such as cobalt 60 (Co-60). Although radioisotope therapy devices use relatively high-energy gamma rays compared to low-energy X-ray therapy devices, the use of radioisotope therapy devices has been gradually reduced.
Linear accelerators, which are considered as standard radiation therapy devices, are capable of emitting X-ray beams and electron beams and transferring various forms of energy and have a high dose rate and a beam shape adjusting (beam-forming) function.
Particle accelerators, in which particles such as neutrons or protons are accelerated using a cyclotron accelerator, transferred through a beam transport tube, and ejected to a desired area through a nozzle, have a deeper Bragg peak than linear accelerators and are thus capable of concentrating energy only on a deep tumor while minimizing the dose in normal tissue.
In general, as the position of patients is intentionally changed or patients unconsciously move their bodies, the diagnosis accuracy or therapy effect of medical radiation devices decreases, and the dose of radiation absorbed in normal tissue around a lesion increases, thereby increasing the time and costs for treatment. Thus, medical radiation devices have been gradually advanced from a type in which a radiation head and a radiation detection unit face each other at fixed positions to a type in which a radiation head and a radiation detection unit are movable around a patient.
Recent medical radiation devices have been developed into a type in which a radiation head is attached to a gantry having an arm and a type using a ring-shaped gantry. Since a radiation source and a radiation detector are required to rotate around living body tissue in a state in which a radiation head and the radiation detector face each other with the living body, tissue being therebetween, a ring gantry structure or a C-arm gantry structure is mainly used.
The above-described background art is technical information that the inventors had or learned when or while inventing the present invention and may not be publicly known before the filing of the present patent application.