Linear Accelerator

Everything you want to know about a linear accelerator 

A linear accelerator is a mechanical device that is essential for many purposes in different settings. In the medical world, it is called the medical linear accelerator (LINAC). This device is suitable to use for patients undergoing radiation therapy because of cancer. The linear accelerator customizes high energy x-rays and electrons that change to the shape of the tumor, in turn, to kill the cancer cells while sparing the unaffected surrounding cells and tissue. The linear accelerator modality is the only modality that treats cancer without an invasive procedure. The therapy is painless and does not irritate the patient at all. Most clients find the medication to be very comfortable and not at all scary. A team of medical doctors designs the procedures for a radiation dosimetrist, medical physicist, and radiation oncologist, depending on the client's condition. All treatment plans are double checked before the process. This procedure is performed by the radiation oncologist, who ensures each medication's quality is exactly as the previous one given. This modality has proven to be an essential part of cancer treatment at almost any given site in the body. 

History of linear accelerators

For years now, linear accelerators have been an essential part of medical technology. These instruments proved helpful in battling various lethal diseases. They have evolved into the modern-day version being used today. In 1937 the first clinical based medication called the Van de Graaff generator carried out at Harvard Medical school. In 1947 the first linear accelerator was built at Stanford by William Hansen and the Varian brothers. Then, in 1953, Dr. Henry Kaplan, along with a physicist named Edward Ginzton, were the first individuals in the western hemisphere to develop the first medical linear accelerator. The 6MV unit was then installed in San Francisco and Stanford-Lane hospital. By 1956 seven medical linear accelerators were functioning worldwide. The first invented device could only rotate to 110 degrees in either direction, and by 1960, the first fully rotational accelerator was introduced by the Varian clinic. Dr. Kaplan and Dr. Saul Rosenberg initiated this device's use for chemotherapy sessions in Hodgkin's disease in 1962. 

The first accelerometer was retired in 1972 to the Smithsonian Institute. In 1972 Dr. Peter Fessenden began developing a new linear accelerometer to combat the tumor cells with two different radiations. This research took place at Stanford, and the team was able to create the first accelerator that uses both x-ray and electron treatment combined. Between 1972-1988 many different manufacturers came out with variations of the same modality. In 1994 a linear accelerator was developed, one that could continually track tumors and display them in real-time. The use of the device was on its first client in the same year. For the first time, four-dimensional radiotherapy was implemented in 2004. In the modern-day millions of accelerators are used in clinical settings worldwide and have been effective in treating millions of various lethal diseases. Research is ongoing to improve the effectiveness of the modality to better the prognosis in cancer treatment. 

Indications to use

This modality's primary use is to find and treat tumors that have caused the client to develop cancer. The linear accelerator uses the energy of electrons and ultrasound waves to emit radiation into the site with carcinoma. The rays strike the tumor and only the tumor without harming the healthy tissue surrounding. Radiation therapy using LINAC can treat multiple types of cancers, such as:

  • Brain tumors 
  • Spine Tumors 
  • Cancers of the head and neck
  • Lung cancer 
  • Breast cancer 
  • Esophageal cancer 
  • Stomach cancer 
  • Rectum/uterus cancer 
  • Prostate/bladder cancer 
  • Bone carcinoma 

The use of this modality is on its own, or the health care professionals can combine it with other medications as per need, such as cancer surgery or chemotherapy. Quality assurance of the modality is a critical point that must be accurate and checked properly. Every day, before a patient goes through the surgery, the radiation therapist must check the modality to ensure it functions correctly. The main important things are radiation intensity, uniformity, and if it is emitting correctly or not. More in-depth and more detailed checks must be made every month following annual inspections as well. Before building the linear accelerator, the installation of software happens to check itself according to the treatment plan and will only turn on if all requirements are met. There are numerous steps involved in the initiation of the procedure, and all must be followed accordingly.

How a linear accelerator works

The steps to the procedure are:

Step 1: The client must be asked by the professional to change into a gown and remove all metal objects.

Step 2: The radiation therapist brings the patient into the therapy room, and the patient lies on the modality's therapy couch. 

Step 3: The radiation therapist carefully positions the patient using alignment lasers. An imaging test is performed by the health care professionals on the patient to verify the accuracy of the patient setup for therapy.

Step 4: Once the patient is set securely on the treatment plane, the therapist makes sure the patient is comfortable and is then advised to leave the room.

Step 5: The device is then switched on, and beams emerge from one or more than one direction. 

Step 6: The modality can be on standby for several minutes in each field. 

Step 7: Once the duration is completed, the machine is switched off.

Step 8: The therapist is to go back inside the treatment room and help the patient out of the modality. 

Step 9: The therapist is required to ask the patient if he/she is ok and escort them out. 

The whole process takes one hour or less each day, the first therapy being the longest and subsequent ones taking 15-30 minutes each. The procedure is customized per person based on the type of disease they have, the duration, and the delivery method. These therapies last for about 2-9 weeks. The medication itself is painless, but the client will hear clicking and buzzing noises or even an odd smell during the process. But other than this, the client should feel nothing out of the ordinary. During the process, the therapist can observe and hear the client through microphones attached to the therapy room, and the client can speak to the therapist if needed.

Complications 

Radiation therapy is a treatment that has surpassed all procedures in the study to treat cancer patients and the only modality that promises to minimize the damage to the surrounding cells. Although very helpful, like all medical treatments, it still has its side effects. It is a standard protocol to inform the client before the procedure about anything out of the normal, which has even the slightest chance to occur. 

The side effects the patient may experience are,  

  • Redness itching or peeling at the site of radiation
  • Fatigue 
  • Headaches 
  • Trouble swallowing 
  • Digestion problems 
  • Pain 
  • Nausea 

It is essential to inform and brief the clients on what to expect from the procedure and not just its side effects. The doctor has to counsel the client and make him/her ready for the medication. 

Some things the client should be told are:

  • All patients will go through a "stimulation," typically a CT scan performed in the treatment position. 
  • Some patients may require "markers" that will be placed in the body, that will allow the transponders to locate the tumor quickly. 
  • A custom-fit positioning device may be needed if the client does not stay still during the treatment procedure. 
  • All long-term risks must be informed before the treatment. 

 

General specifications

There are many different types of linear accelerators available in the market with advanced technology and new features, but consist of almost the same general specifications as the base model, such as:

  • Energy: 13.6GeV
  • Charge: 0.25nC
  • Bunch length: 8-10 micrometers
  • Laser energy: 20-150 micro J
  • Gun field at cathode: 115MV/m
  • Quantum efficiency: 0.7-7 10^5
  • Emittance: 0.7-1 micrometers
  • Peak current: 3kA

These specifications vary with different models and brands of the device. It is necessary to check all the specifications needed before using the modality so there may be no problem in use.

Market leaders 

As the demand for the linear accelerators is increasing day by day, the market is also growing and bringing out designs that are more modern and up to date. The global market for these devices has seen very high demand from the past few years. All companies are working tirelessly to make their device the most accurate and most popular one sold. The top ten market leaders so far trending in the manufacture of these modalities are,

  • Accuray Inc. USA 
  • BrainLab AG Germany 
  • Elekta AB Sweden 
  • GE Healthcare UK 
  • Hitachi America, LTD USA 
  • IBA Group Belgium
  • Nordion, INC. Canada
  • Philips Healthcare USA 
  • RaySearch Lab AB Sweden 
  • Sumitomo Heavy Industries Ltd. Japan

Conclusion

These linear accelerators have become a common practice and have proven positive results in various disease treatments, but they can be very costly. The modality itself is very expensive to buy; a new device costs roughly between $300,000-$500,000 cheapest being the general base model. Furthermore, it is very costly to repair and keep up to date with the maintenance of these life-saving machines. Despite all these cons, the devices are deemed essential in every hospital setting, especially in the oncology units of all hospitals. As cancer is one of the deadliest diseases globally, this device is a godsend for all patients suffering from this condition. Almost more than half of the diseased patients receive radiotherapy by this modality and recover. Since the invention day of this device to date, this has become a promising procedure that produces excellent results and positive feedback. Researchers are still working to improve and evolve the machinery to provide even more accurate results than it is now. Without this invention, treatment for various lethal diseases would be complicated.

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