[{"@context":"https:\/\/schema.org\/","@type":"Article","@id":"https:\/\/share-dev.upmc.com\/2025\/04\/linear-accelerator\/#Article","mainEntityOfPage":"https:\/\/share-dev.upmc.com\/2025\/04\/linear-accelerator\/","headline":"What Is a Linear Accelerator?","name":"What Is a Linear Accelerator?","description":"

Learn how radiation therapy using a LINAC precisely targets cancer. Discover its types, benefits, and how it helps destroy tumors while sparing healthy tissue.<\/p>","datePublished":"2025-04-29","dateModified":"2025-08-06","author":{"@type":"Organization","@id":"https:\/\/hillman.upmc.com\/","name":"UPMC Hillman Cancer Center","url":"https:\/\/hillman.upmc.com\/","sameAs":"https:\/\/share-dev.upmc.com\/upmc-hillman-cancer-center\/","parentOrganization":"UPMC"},"publisher":{"@type":"Organization","name":"UPMC HealthBeat","logo":{"@type":"ImageObject","@id":"https:\/\/share-dev.upmc.com\/wp-content\/uploads\/2019\/04\/UPMC-HealthBeat-Logo.png","url":"https:\/\/share-dev.upmc.com\/wp-content\/uploads\/2019\/04\/UPMC-HealthBeat-Logo.png","width":600,"height":60}},"image":{"@type":"ImageObject","@id":"https:\/\/share-dev.upmc.com\/wp-content\/uploads\/2025\/04\/GettyImages-498200652-e1745601046599.jpg","url":"https:\/\/share-dev.upmc.com\/wp-content\/uploads\/2025\/04\/GettyImages-498200652-e1745601046599.jpg","height":866,"width":2000},"url":"https:\/\/share-dev.upmc.com\/2025\/04\/linear-accelerator\/","about":["Cancer Care","Health Topics A-Z","Living and Wellness"],"wordCount":1332,"articleBody":"If you have cancer, your oncologist (cancer doctor) may recommend radiation therapy using a linear accelerator as part of your treatment plan. Here’s what that means.What Is a Linear Accelerator (LINAC)?A linear accelerator \u2014 LINAC for short \u2014 is a type of radiation machine. LINACs most often use high-energy x-rays, called photons, to treat cancer. Photons are painless but can travel deep into your body to kill cancer cells.LINAC machines can also use electrons to kill cancer. Electrons don’t travel as deep. They often target things like skin cancer or cancers close to the skin’s surface.Most LINAC machines today create radiation doses to conform to or match your tumor’s 3D shape and size. During treatment, the radiation targets the tumor, destroying cancer cells but sparing surrounding healthy tissue.What type of radiation therapy uses a LINAC?There are three main types of radiation therapy:External beam radiation therapy, or EBRT, which uses a machine outside the body to deliver radiation to tumors inside the body. Most people who need radiation therapy get EBRT, which doctors can use for many types of cancer.Internal radiation therapy (also called brachytherapy), in which radiation oncologists place a radiation source inside of your body, right on the tumor. The radiation source stays in for a short time. Brachytherapy limits the radiation to nearby body organs and tissues. It’s a common prostate cancer treatment.Systemic radiation therapy, which uses liquid drugs that include a radioactive substance. Doctors give you these radioactive drugs by mouth or through a vein. Systemic radiation travels through your entire body. Doctors use it for certain cancers that have spread to your bones or thyroid.LINAC machines deliver external beam radiation therapy. You lie under the LINAC machine on a special table during the treatment.Why Do You Need EBRT With LINAC?LINAC radiation machines are part of radiation therapy, also called radiotherapy. Cancer doctors use LINAC machines to treat cancer in any body site.Depending on your cancer type and stage, you may need external beam radiation therapy. Treatment with radiotherapy can help kill cancer cells. It can improve your chances of long-term survival and reduce your risk of cancer recurrence or cancer coming back.Who Oversees EBRT with LINAC?A specialized doctor called a radiation oncologist oversees radiotherapy. They work with other specialists to map out and deliver your care. Your LINAC radiotherapy care team may also include:Radiation dosimetrists, who use planning software to develop treatment plans. They help calculate the radiation needed to destroy cancer cells while sparing normal tissue. The radiation oncologist makes the final decision on radiation dosing.Medical physicists, who oversee the work of the radiation dosimetrist. They also develop and direct quality control and safety programs for LINAC machines and ensure their correct operation.Radiation oncology nurses, who care for you during your treatment. They see how you’re doing before and after each treatment. They also provide care to help you manage any side effects of radiation therapy.Radiation therapists, who use LINAC machines to deliver your radiation therapy treatment.Specialized EBRT and Other TechniquesRadiation oncologists can use LINACs for different types of external beam radiation therapy. At UPMC Hillman Cancer Center, we use different LINAC machines to provide different types of EBRT. This includes for:3D Conformal Radiation Therapy (CRT)With 3D CRT, doctors can direct radiation beams to conform to the shape of your tumor. The device delivers these beams from different directions, reducing radiation damage to nearby normal tissues.Image-Guided Radiation Therapy (IGRT)IGRT uses medical imaging to help plan and monitor cancer treatment. During radiotherapy, your tumor’s size and shape as well as your anatomy can change. IGRT uses advances in medical imaging to track these changes throughout all stages of radiotherapy.As your tumor shrinks, doctors can see whether they need to make any changes to your treatment plan. Doctors often use IGRT to treat tumors in areas that tend to move, such as the lungs, pancreas, liver, and prostate gland.IGRT LINAC machines may include the following built-in imaging capabilities to track these changes:Computed tomography, also called CT-LINAC.Magnetic resonance imaging, also called MRI-LINAC.Ultrasound \u2014 probes and wands attached to LINACs for additional imaging.Intensity-Modulated Radiation Therapy (IMRT)Like 3D CRT, IMRT shapes the radiation beams to your tumor and delivers radiation from different directions. With IMRT LINAC, however, doctors can increase the strength or intensity of the beam in certain areas.IMRT allows doctors to deliver higher and more effective radiation doses safely and with fewer side effects than conventional radiotherapy techniques. However, it’s a more complex technique that often involves more planning and longer total daily treatment times.Volumetric modulated arc therapy, or VMAT, is a type of IMRT. VMAT-LINAC delivers radiation in an arc while the machine rotates around your body. With VMAT, you can get a complete radiation treatment in just one or two treatments.Stereotactic Radiosurgery (SRS)Stereotactic radiosurgery, or SRS, is an ultra-precise, nonsurgical form of radiotherapy that doesn’t involve incisions or cutting. Doctors use SRS to treat abnormalities and tumors in the brain and spine.Stereotactic body radiotherapy, or SBRT, treats tumors in hard-to-reach areas of the body.Both can deliver targeted radiation in fewer higher-dose treatments.SRS and SBRT are usually single-day treatments. However, some people may require two to five treatments, which doctors call fractionated SRS or SBRT.What is FFF in LINAC?Standard LINACs use flattening filters to deliver uniform radiation beams to the target site. These beams can’t conform or reshape to the tumor shape.Advanced LINAC machines include a flattening filter-free (FFF) mode. With FFF, the LINAC can shape the beam to the tumor. This concentrates the beam, delivering a higher dose in a shorter amount of time with less radiation scatter.LINAC radiation therapy systemsTo provide the EBRT listed above, UPMC Hillman offers several LINAC radiation therapy systems:Halcyon\u2122 \u2014 This radiotherapy system delivers image-guided IMRT or VMAT. It delivers radiotherapy up to four times faster than traditional EBRT.RapidArc\u00ae\u00a0\u2014 This is a very fast and precise form of image-guided IMRT. It delivers your daily radiation dose with a single 360-degree rotation of the LINAC around you, which takes less than two minutes.Trilogy \u2014 This is an advanced LINAC and stereotactic radiosurgery system.TrueBeam STx\u00a0\u2014 This advanced LINAC and SRS system allows doctors to target hard-to-reach tumors. It uses innovative technology, ExacTrac\u00ae, to image your tumor, even when it moves during your natural breathing. The system uses these images to confirm that radiation beams target your tumor.Doctors can use Halcyon and RapidArc to treat a wide variety of cancers and tumors.Doctors may use Trilogy and TrueBeam STx to treat cancer and benign tumors in highly sensitive or hard-to-treat areas. This includes the brain, spine, head and neck, liver, lung, pancreas, and prostate. We may also use these systems to treat cancers that return or are inoperable.UPMC Hillman also offers\u00a0Gamma Knife,\u00a0a radiosurgery system that kills cancer cells using gamma rays instead of photon beams. Its most common uses are for treating brain cancer and tumors.Your radiation oncologist will review which external beam radiotherapy and LINAC make sense for your cancer treatment.Editor's Note: This article was originally published on April 29, 2025, and was last reviewed on August 6, 2025.SourcesRadiological Society of North America. Linear Accelerator. LinkRadiological Society of North America. Radiation Therapy for Pain Relief. Link Radiological Society of North America. Professions in Radiation Therapy. Link American Cancer Society. Getting External Beam Radiation Therapy. LinkRadiological Society of North America. Intensity-Modulated Radiation Therapy. LinkRadiological Society of North America. Image-guided Radiation Therapy. Link Radiological Society of North America. Stereotactic Radiosurgery (SRS) and Stereotactic Body Radiotherapy (SBRT). LinkAmerican Cancer Society. Getting Oral or Systemic Radiation Therapy. LinkJournal of Biomedical & Physics Engineering. Enhancement of the Dose on 12 MV Linac with Free Flattening Filter Mode. LinkJournal of Applied Clinical Medical Physics. Linac primary barrier transmission: Flattening filter free and field size dependence. Link"},{"@context":"https:\/\/schema.org\/","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"2025","item":"https:\/\/share-dev.upmc.com\/2025\/#breadcrumbitem"},{"@type":"ListItem","position":2,"name":"04","item":"https:\/\/share-dev.upmc.com\/2025\/\/04\/#breadcrumbitem"},{"@type":"ListItem","position":3,"name":"What Is a Linear Accelerator?","item":"https:\/\/share-dev.upmc.com\/2025\/04\/linear-accelerator\/#breadcrumbitem"}]}]