Linear Accelerator: What is it? How does it work? Cancer Radiation Therapy and Acquisition Tips

Linear accelerator machines create high-energy radiation that can be directed to the exact location of a tumor or injury.

Linear accelerator machines have proven to be a safe and effective treatment option for patients with inoperable brain tumors in dangerous locations, such as the optic nerve and brainstem.

The machine moves on a 360 degree gantry around the head to provide carefully calculated treatments by the neurosurgeon on the computer.

The linear throttle’s range of motion allows the medical team to focus on very specific targets that come in a variety of shapes and sizes.

If you are receiving multiple treatments, allow at least an hour for your first treatment. Treatment time will vary, depending on factors, including your diagnosis. The first medical linear accelerator in the Western Hemisphere was developed at Stanford, and the first patient was treated in 1956.

In 1994, Jefferson University Hospitals became the first hospital in the world to possess a linear acceleration machine used exclusively for stereotactic radiosurgery of the brain.

Currently, Jefferson is proud to be the fourth institution to offer this cutting-edge technology in the country. With continuous technological advancements, linear accelerators maintain their status as one of the most advanced radiation technologies available today.

The machines produce and deliver radiation with millimeter precision that was previously unavailable.

Increasingly, linear accelerators are also used to treat deep arteriovenous malformations (AVMs), sometimes in conjunction with other neurosurgical procedures that reduce arteriovenous malformations.

How a linear accelerator works

Linear accelerators use microwave technology to accelerate electrons in a waveguide, allowing electronic devices to collide with a heavy metal target, generating high-energy X-ray photons that adapt to the shape of the tumor and they destroy cancerous tissues.

Role of the linear accelerator in radiation therapy for cancer

Radiation therapy or radiotherapy (RT) describes the clinical process that uses ionizing radiation to kill cancer cells. It is one of the main medical modalities used in the treatment of cancer.

Other widely used cancer treatment modalities are surgery and chemotherapy. In fact, more than half of all cancer patients receive radiation therapy, either alone or in combination with surgery or chemotherapy.

The power of radiation therapy is its ability to ionize atoms and molecules within the nuclei of biological cells in the tissue to which the radiation is applied, thereby killing cancer cells by damaging their DNA.

The radiation therapy machine uses the linear accelerator (LINAC) as the source of ionizing radiation, which can be high-energy electron beams or X-rays (photon beams).

In radiation therapy, most treatments use X-rays and a smaller number use the electron beam or a combination of both therapies. Electron beams are used especially for superficial tumors (less than 5 cm deep).

For this reason, many of the linear accelerator-based radiation therapy machines provide the option of using photon beams and electron beams for cancer treatments.

In X-ray therapy, they can produce photon beams in the range of: 4 to 25 MV, and in electron therapy, the treatment electron beam can cover the range of: 6 to 25 MeV.

The length of the linear accelerator depends on the kinetic energy of the final electron, and ranges from ~ 30 cm for 4 to 6 MeV linear accelerators to ~ 150 cm for 25 MeV linear accelerators.

There are two basic settings for the radiation therapy machine. In one configuration, the linear accelerator is mounted on the gantry of the machine perpendicular to the patient.

This is the simplest setup for a radiation therapy machine. Eliminates the need for an intricate beam transport system. This is typically used in phototherapy to treat photon energies between 4 and 6 MV.

On the other hand, in higher energy machines, the linear accelerators, which are longer, are located in the gantry of the machine parallel to the axis of rotation of the gantry. An intricate beam transport system is then used to transport the electron beam from the accelerator to the treatment head.

This configuration is generally used in radiotherapy machines that emit X-ray or electron beams and with multiple energies up to 25 MeV.

Used in the most advanced radiation treatments

Linear accelerators can interact with computers to create targeted and advanced radiation therapy treatments, such as intensity-modulated radiation therapy (IMRT) and intraoperative radiation therapy (IORT).

These cutting-edge treatments are changing the landscape of cancer treatment, making radiation therapy an option for many more patients than ever before.

What Happens During Treatment?

Technicians use digitized imaging studies to precisely trace the tumor and provide highly specific radiation therapy. Patients are assigned a digital file containing their individual tumor target and radiation therapy information.

Because linear accelerators are so precise, it is important that the patient remains very still during the treatment, which usually lasts about 10 minutes.

Traditional linear accelerators revolve around the patient. The patient’s tumor is positioned in the center of this rotation. The process is repeated for several arches, all entering the patient through different angles to avoid exposing the surrounding healthy tissue to too much radiation.

With each arc, the tumor is caught in the X-ray crossfire, giving it a lethal dose. In the last two decades, technologies have evolved and certain linear accelerators are now equipped with a device called a multi-blade collimator.

Tumors are rarely perfectly round, so the multilayer collimator was developed to accurately shape the tumor so that the maximum radiation dose can be delivered evenly to the entire tumor, rather than joining many spherical overlapping doses .

During treatment, the shape of the tumor changes from the point of view of the radiation beam as the linear accelerator rotates around the patient. Multi-blade collimators continuously change the shape of the treatment beam to match the shape of the tumor from any angle.

The traditional way of securing the patient’s head in stereotactic radiosurgery is by attaching an invasive head frame to the skull with pointed screws.

Although the head frame is effective in keeping patients immobile during treatment, some patients find the head frame placement inconvenient and sometimes painful.

Placing the frame carries the risk of bleeding and infection, as well as requiring medication to be taken beforehand. The frame must remain in place for several hours, sometimes a whole day, until the treatment is complete.

With technologies such as Image Guided Radiation Therapy (IGRT), “frameless” radiosurgery has become a popular alternative to invasive skull frames for radiosurgery.

Image-guided radiation therapy uses imaging technology during radiosurgery: X-rays, computed tomography (CT), both to monitor the position and to adjust the position of the patient and / or radiation beams so that the staining is specifically directed at the tumor at all times.

Frameless radiosurgery is administered using a non-invasive mask system. The mask is made of thermoplastic sheets that become soft when heated in water.

Once formed in the patient, they cool down in minutes and become hard again. The process is completely painless and generally does not require anesthesia. Before radiation, the mask is fitted to the patient and then attached to the special treatment table, keeping the patient immobile during treatment.

The process is similar to how a frame-based treatment is delivered with the added benefit that no screws are placed in the skull, offering greater patient comfort.

There are different mask systems that use different techniques to ensure precision and control any movement of the patient during radiation treatment.

Internal Anatomy Tracking – Full frameless masks utilize the internal anatomy of the patient to ensure precision, control and account for any movement of the patient during radiation treatment.

Optical Surface Matching : Frameless open masks use the surface of the patient’s face as a surrogate for internal anatomy; however, skin change, facial hair, skin color, and other factors can affect accuracy.

The external surfaces are not as rigid as the internal anatomy and the skin moves and stretches, so these surfaces are not necessarily as reliable as to indicate the location of a tumor within the brain.

Optical outer surface tracking technology can be quite compatible with certain types of radiation treatments such as breast cancer and, in fact, most research studies on surface matching precision are based on cancer of the mother.

However, it is a widely held belief that the precision of “submillimeter” treatment is critical when treating brain cancers. In treating brain tumors, physicians have the most exacting spatial tolerances of any site within the body.

To accommodate the more limited precision of optical surface matching, clinicians may consider adding a “margin of error” around the tumor being treated.

However, the goal of any physician is to minimize margins, as expanding the area to be treated is equivalent to knowingly treating healthy brain tissue. A “margin of error” can significantly increase the total volume of the brain that is receiving a high dose of radiation.

Patients should understand that this could include vital structures that affect vision, hearing, or balance. For example, adding a margin around the tumor edge of just 2mm doubles the treatment volume for a brain metastasis just 15mm wide.

Patient position monitoring technology

Monitoring the patient’s position helps maintain the accuracy of the procedure and ensures that the treatment dose is delivered as prescribed by the cancer treatment team.

Different delivery techniques offer different types of patient positioning and monitoring technologies. Using a headframe approach, clinicians rely on various accessories and steps to align the tumor with the focal point of the radiation.

When using a non-invasive mask, two low-dose X-ray images are captured from two different angles. They are compared and combined with simulated radiographs taken directly from the 3D computed tomography data used for treatment planning.

The robotic treatment table can adjust the position of the patient with sub-millimeter movements. When you add image and micro-movement adjustments to the thermoplastic mask, you can achieve the same level of precision as a frame-based system without the hassle of placing the frame.

Ask your doctor about the different types of technologies and techniques to determine which procedure is best for you.

Tips for buying a linear accelerator

Buying a linear accelerator requires planning, experience, and a commitment to quality. These three key components can work to your advantage when you buy your next linear accelerator.

When you begin researching your linear accelerator, it is important that you take into account a variety of considerations, from the overall cost of the linear accelerator to your practice budget and clinical goals.

These machines are essential for any radiation oncology department that wants to provide comprehensive patient care and treatment plans, but they tend to be expensive and complicated.

Buying a used or refurbished linear accelerator machine is a great option for those looking for a more affordable solution.

Contact a professional such as Radiation Oncology Systems for one-on-one advice. Consider planning things like building constraints, room dimensions, water supply, power supply, etc.

Create a timeline to determine when you need your equipment to be fully installed. Develop a budget. Consider how long you intend to maintain the machine. Decide which manufacturers you prefer. Determine if you want to add updates or accessories.

Buying a used or new linear accelerator?

Determining whether or not to buy your used or brand new linear accelerator machine comes down to the specific needs and budget constraints of your facility.

The linear accelerator equipment used is appropriate for practices that treat relatively few patients (less than 8 or 10 per day) or those who live in a country where reimbursement rates are low and must generate profits.

Additionally, second-hand linear accelerators are a smart choice for veterinary, research, non-medical and industrial uses.

Top Reasons to Buy a Refurbished Linear Accelerator

Grow Your Practice – Treat more patients and grow your practice with a refurbished linear accelerator.

Whether you’re opening a new center, adding a new treatment room, or just want to improve your practice, the costs can be daunting. Refurbished purchase frees up budget money to increase the size of your practice

Flexibility – Backup your existing system with a redundant beam-compatible system. If a problem develops on one of your machines, you will be able to transfer patients to another linear accelerator.

Enhancements – Freeing up money from the budget also allows you to increase the quantity and quality of patient care you provide. Improving your practice improves the lives of the patients you treat. Add new updates, technologies, or more staff. Your patients will appreciate it.

Empower : With the uncertainty of impending refund cuts, it’s important to manage expenses to ensure you can navigate through any unexpected turbulence. Using reconditioned solutions reduces risk and strengthens your practice.