{"entity":{"id":"c-arm-linac","kind":"technology","name":"C-arm medical linear accelerators (TrueBeam, Versa HD and others)","aka":[],"tldr":"The standard radiotherapy machine: an electron accelerator in a rotating arm that makes high-energy X-rays or electron beams, shapes them with moving metal leaves, and takes a CT of the patient before each dose. Most people who have radiotherapy are treated on one.","summary":"A medical linac fires electrons down a copper waveguide driven by microwaves until they reach several million electronvolts, bends them through a magnet and either slams them into a tungsten target to make photons or scatters them directly as an electron beam. The head carries a multileaf collimator whose tungsten leaves shape the field and modulate its intensity, and the whole assembly rotates on a C-shaped gantry around a couch that moves in six degrees of freedom. A kilovoltage imager on a side arm takes radiographs and cone-beam CT for image guidance, and surface cameras or breath-hold systems handle motion. The first clinical linac treated a patient in London in 1953; today Varian's TrueBeam and Edge and Elekta's Versa HD, Infinity and Harmony are the dominant models, with Chinese and Indian makers offering lower-cost units.\n\nThe C-arm is versatile: photons at several energies, electrons for skin and superficial targets, non-coplanar beams for brain radiosurgery, and every technique from palliative fields to VMAT and SBRT. Its limits are cost, a shielded bunker, a workforce of physicists and therapists, and mechanical tolerances that require daily quality assurance. Ring-gantry, helical and robotic designs trade some of that flexibility for speed, integrated imaging or steeper dose fall-off.","status":"standard-of-care","asOf":"2026-09-17","wikipedia":"https://en.wikipedia.org/wiki/Linear_particle_accelerator","links":[{"label":"Varian: TrueBeam","url":"https://www.varian.com/products/radiotherapy/treatment-delivery/truebeam"},{"label":"Elekta: linear accelerators","url":"https://www.elekta.com/products/radiation-therapy/"}],"tags":["machines-wave"],"related":["ring-gantry-linac","tomotherapy","cyberknife","cobalt-60-teletherapy","radiotherapy-access-gap"],"cancers":["breast-cancer","prostate","nsclc","head-and-neck","cervical","colorectal","glioblastoma","esophageal"],"sections":["radiation","devices"],"technologies":["imrt-igrt","vmat","sbrt","surface-guided-radiotherapy","respiratory-motion-management"],"targets":[],"drugs":[],"companies":["varian","elekta"],"institutions":[],"pathways":[],"terms":["imrt-term","organs-at-risk"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"principle":"Microwave-driven acceleration of electrons produces megavoltage X-rays or electron beams; a rotating gantry, multileaf collimator and on-board kilovoltage imaging shape and aim the dose to the target seen on the day.","strengths":["Treats almost every site and technique on one machine","Photon and electron beams at several energies","Integrated cone-beam CT and surface guidance"],"limitations":["Needs a shielded bunker and skilled staff","Daily quality assurance of mechanical tolerances","Throughput limited by set-up and imaging time"],"since":1953},"route":"/technologies/c-arm-linac/","neighbours":{"technology":[{"id":"cobalt-60-teletherapy","kind":"technology","name":"Cobalt-60 teletherapy","route":"/technologies/cobalt-60-teletherapy/"},{"id":"cyberknife","kind":"technology","name":"CyberKnife robotic radiosurgery","route":"/technologies/cyberknife/"},{"id":"electron-beam-therapy-systems","kind":"technology","name":"Electron beam therapy systems (linac electrons, total skin electron units, mobile electron IORT)","route":"/technologies/electron-beam-therapy-systems/"},{"id":"flash-research-accelerators","kind":"technology","name":"FLASH research accelerators (Oriatron, Mobetron FLASH, ProBeam FLASH)","route":"/technologies/flash-research-accelerators/"},{"id":"imrt-igrt","kind":"technology","name":"IMRT / IGRT (modern external beam)","route":"/technologies/imrt-igrt/"},{"id":"oncology-information-systems","kind":"technology","name":"Oncology information and record-and-verify systems (ARIA, MOSAIQ)","route":"/technologies/oncology-information-systems/"},{"id":"patient-positioning-surface-guidance-systems","kind":"technology","name":"Patient positioning and surface guidance systems (AlignRT, Catalyst, ExacTrac Dynamic)","route":"/technologies/patient-positioning-surface-guidance-systems/"},{"id":"proton-therapy-systems","kind":"technology","name":"Proton therapy machines: cyclotrons, synchrotrons and single-room systems","route":"/technologies/proton-therapy-systems/"},{"id":"radiotherapy-access-gap","kind":"technology","name":"Radiotherapy access and the global machine gap","route":"/technologies/radiotherapy-access-gap/"},{"id":"radiotherapy-qa-phantoms-dosimeters","kind":"technology","name":"Radiotherapy QA phantoms and dosimeters (Sun Nuclear, IBA Dosimetry, PTW)","route":"/technologies/radiotherapy-qa-phantoms-dosimeters/"},{"id":"respiratory-motion-management","kind":"technology","name":"Respiratory motion management (4D-CT, gating, breath-hold, tracking)","route":"/technologies/respiratory-motion-management/"},{"id":"ring-gantry-linac","kind":"technology","name":"Ring-gantry linacs (Halcyon, Ethos)","route":"/technologies/ring-gantry-linac/"},{"id":"sbrt","kind":"technology","name":"SBRT / SABR (stereotactic radiotherapy)","route":"/technologies/sbrt/"},{"id":"surface-guided-radiotherapy","kind":"technology","name":"Surface-guided radiotherapy (SGRT)","route":"/technologies/surface-guided-radiotherapy/"},{"id":"tomotherapy","kind":"technology","name":"TomoTherapy and Radixact (helical radiotherapy)","route":"/technologies/tomotherapy/"},{"id":"vmat","kind":"technology","name":"Volumetric modulated arc therapy (VMAT)","route":"/technologies/vmat/"},{"id":"zap-x","kind":"technology","name":"ZAP-X gyroscopic radiosurgery","route":"/technologies/zap-x/"}],"cancer":[{"id":"breast-cancer","kind":"cancer","name":"Breast cancer (all types)","route":"/cancers/breast-cancer/"},{"id":"cervical","kind":"cancer","name":"Cervical cancer","route":"/cancers/cervical/"},{"id":"colorectal","kind":"cancer","name":"Colorectal cancer","route":"/cancers/colorectal/"},{"id":"glioblastoma","kind":"cancer","name":"Glioma & glioblastoma","route":"/cancers/glioblastoma/"},{"id":"head-and-neck","kind":"cancer","name":"Head and neck squamous cell carcinoma","route":"/cancers/head-and-neck/"},{"id":"nsclc","kind":"cancer","name":"Non-small-cell lung cancer","route":"/cancers/nsclc/"},{"id":"esophageal","kind":"cancer","name":"Oesophageal cancer","route":"/cancers/esophageal/"},{"id":"prostate","kind":"cancer","name":"Prostate cancer","route":"/cancers/prostate/"}],"section":[{"id":"devices","kind":"section","name":"Devices & Physical Therapies","route":"/fronts/devices/"},{"id":"radiation","kind":"section","name":"Radiation Therapy","route":"/fronts/radiation/"}],"company":[{"id":"elekta","kind":"company","name":"Elekta","route":"/companies/elekta/"},{"id":"varian","kind":"company","name":"Varian (Siemens Healthineers)","route":"/companies/varian/"}],"term":[{"id":"imrt-term","kind":"term","name":"IMRT / IGRT / VMAT (modern external beam radiotherapy)","route":"/terms/imrt-term/"},{"id":"organs-at-risk","kind":"term","name":"Organs at risk and dose constraints","route":"/terms/organs-at-risk/"}]}}