{"entity":{"id":"linac-machines-roadmap","kind":"roadmap","name":"Linear accelerator machines: from Clinac to AI-imaging linacs, rings and radiosurgery units","aka":[],"tldr":"The machine that gives most radiotherapy has been rebuilt every decade or so: sharper beams, then built-in scanners, then rings that treat faster, and now imaging good enough to replan on the spot. This is the chain of models, dated from the regulator's records.","summary":"Each generation of the medical linear accelerator fixed a limit of the one before. The record of FDA 510(k) clearances dates the steps: Varian's Clinac 20 in 1977; Trilogy in 2003 and Elekta Synergy in 2003, which put a kilovoltage imager on the gantry; TrueBeam in 2011, with energies from 4 MV and later 4D cone-beam CT and motion management; the radiosurgery-focused TrueBeam STx and Edge; Elekta's Versa HD and Infinity under a 2018 clearance; and Harmony in 2021. Halcyon in 2017 enclosed the linac in a fast ring, with mandatory imaging, and Varian claims it uses up to 70 per cent less power and roughly 65 per cent less concrete than a C-arm linac. Ethos in 2020 added same-session adaptive replanning, and the latest generation competes on image quality: HyperSight cone-beam CT on Halcyon, Ethos and TrueBeam, and Elekta Evo, cleared in January 2026, which uses machine-learning scatter correction and iterative reconstruction.\n\nAlongside the general-purpose linac run the specialised designs: CyberKnife on a robot (1999), helical TomoTherapy (2002) and its successor Radixact (2016), the Gamma Knife from Model B (1995 in the FDA record) to Perfexion (2006), Icon (2015) and Esprit (2022), the self-shielded ZAP-X (2017), and makers outside the two large vendors, including United Imaging's CT-integrated uRT-linac 506c (in clinical use since 2019), Our United's TaiChi family, Panacea's Siddharth-II and the Theratron Equinox cobalt unit. The pace is set less by physics than by staffing, bunkers and price, which is why lower-cost and self-shielded designs matter most where machines are scarce.","asOf":"2026-11-04","links":[{"label":"FDA 510(k) K771358: Clinac 20 (16 August 1977)","url":"https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm?ID=K771358"},{"label":"FDA 510(k) K033343: Trilogy (23 December 2003)","url":"https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm?ID=K033343"},{"label":"FDA 510(k) K032996: Elekta Synergy (23 October 2003)","url":"https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm?ID=K032996"},{"label":"FDA 510(k) K111106: TrueBeam (18 August 2011)","url":"https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm?ID=K111106"},{"label":"FDA 510(k) K140528: TrueBeam, TrueBeam STx, Edge (5 September 2014)","url":"https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm?ID=K140528"},{"label":"FDA 510(k) K182138: Synergy, Infinity, Versa HD (5 September 2018)","url":"https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm?ID=K182138"},{"label":"FDA 510(k) K210500: Elekta Harmony (11 June 2021)","url":"https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm?ID=K210500"},{"label":"FDA 510(k) K170817: Halcyon (27 June 2017)","url":"https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm?ID=K170817"},{"label":"FDA 510(k) K192377: Ethos (10 February 2020)","url":"https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm?ID=K192377"},{"label":"FDA 510(k) K252188: Elekta Evo and Harmony Pro (15 January 2026)","url":"https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm?ID=K252188"},{"label":"Elekta receives FDA 510(k) clearance for the Elekta Evo linear accelerator (January 2026)","url":"https://mfn.se/a/elekta/elekta-receives-fda-510-k-clearance-for-elekta-evo-linear-accelerator"},{"label":"Varian: Halcyon","url":"https://www.varian.com/products/radiotherapy/treatment-delivery/halcyon"},{"label":"Yu et al., commissioning a fully integrated CT-linac, the uRT-linac 506c (J Appl Clin Med Phys 2021)","url":"https://doi.org/10.1002/acm2.13313"}],"tags":["machines-wave3"],"related":["radiation-roadmap","mr-and-biology-guided-radiotherapy-roadmap","idea-acc-open-hardware-linac","idea-acc-linac-uptime-contracts"],"cancers":[],"sections":["radiation","devices"],"technologies":["c-arm-linac","ring-gantry-linac","tomotherapy","cyberknife","gamma-knife","zap-x","rotating-gamma-radiosurgery-systems","cobalt-60-teletherapy","imrt-igrt","adaptive-radiotherapy","in-room-imaging-systems"],"targets":[],"drugs":[],"companies":["varian","elekta","accuray","zap-surgical-systems","united-imaging","our-united","panacea-medical-technologies","best-theratronics"],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":["b-surgery-radiation-innovation","b-global-access","b-workforce"],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"provenance":{"editedBy":"OnCo machines inventory (openFDA, accessdata.fda.gov, ClinicalTrials.gov v2, Europe PMC, maker pages)","editedOn":"2026-11-04"},"steps":[{"era":"1953-1990s","title":"Megavoltage linacs replace cobalt","description":"The first clinical linac treated a patient in London in 1953, and through the following decades linacs replaced cobalt-60 units in high-income countries. In the FDA database the Varian Clinac 20 was cleared in August 1977 (K771358) and the Clinac C series in 1986. Cobalt units stayed in service where power and servicing were unreliable; the Theratron Equinox, cleared in 2006, is still sold.","refs":["c-arm-linac","cobalt-60-teletherapy","varian","best-theratronics"],"status":"historic"},{"era":"2003-2010","title":"Imaging on the gantry","description":"Varian Trilogy (K033343, December 2003) and Elekta Synergy (K032996, October 2003) mounted a kilovoltage imager on the treatment machine so the patient could be imaged in the treatment position before each dose. Image guidance made intensity-modulated and stereotactic treatment practical outside academic centres.","refs":["varian","elekta","imrt-igrt","in-room-imaging-systems"],"status":"historic"},{"era":"2011-2018","title":"TrueBeam, Versa HD and radiosurgery-grade linacs","description":"TrueBeam (K111106, August 2011) extended the energy range down to 4 MV and added collision detection; its next clearance (K123291, 2012) brought a six-degree-of-freedom couch, 4D cone-beam CT and a motion management interface. TrueBeam STx and Edge were cleared for radiosurgery indications in 2014 (K140528, which states the device itself was unchanged), and VitalBeam in 2015 as a configuration based on TrueBeam. Elekta's Versa HD and Infinity first appear by name in a 2018 clearance (K182138); Elekta says Versa HD with its high-dose-rate mode delivers stereotactic treatment in a standard 15-minute slot.","refs":["c-arm-linac","radiosurgery-srs","sbrt","varian","elekta"],"status":"historic"},{"era":"2017-2020","title":"Rings and adaptive replanning","description":"Halcyon (K170817, June 2017) put a single-energy 6 MV linac in an enclosed ring with mandatory imaging every fraction; Varian states it uses up to 70 per cent less power and roughly 65 per cent less concrete than a C-arm linac. Ethos (K192377, February 2020) used the same ring for same-session adaptive replanning with automated contouring. Elekta answered with the compact Harmony C-arm (K210500, June 2021).","refs":["ring-gantry-linac","adaptive-radiotherapy","auto-contouring-ai","varian","elekta"],"status":"historic"},{"era":"2023-2026","title":"CT-quality imaging on the treatment machine","description":"HyperSight cone-beam CT on Halcyon and Ethos (first named in K232113, November 2023) and on TrueBeam (K232870, December 2023) was cleared for simulation and planning; Varian says its Hounsfield accuracy rivals conventional CT so dose can be calculated on it. Elekta Evo, Harmony Pro and Versa HD gained a high-definition reconstruction with machine-learning scatter correction (K252188, January 2026). Imaging good enough to plan on is what makes daily adaptive treatment possible on a conventional linac.","refs":["c-arm-linac","ring-gantry-linac","adaptive-radiotherapy","in-room-imaging-systems","varian","elekta"],"status":"current"},{"era":"1995-2025","title":"Dedicated radiosurgery machines","description":"The Gamma Knife appears in the FDA record from Model B (K924849, 1995) to Perfexion (K061941, 2006), Icon (K151561, 2015), which added mask fixation, cone-beam CT and intrafraction motion monitoring, and Esprit (K222047, 2022). CyberKnife was cleared in 1999 (K984563), the M6 with a multileaf collimator in 2015 (K150873), and Accuray launched the S7 in 2020. ZAP-X (K171804, 2017) is self-shielded, which its maker says removes the need for a radiation bunker. Chinese rotating gamma and hybrid cobalt-linac designs (Our United TaiChi, MASEP Infini) are cleared alongside them.","refs":["gamma-knife","cyberknife","zap-x","rotating-gamma-radiosurgery-systems","elekta","accuray","zap-surgical-systems","our-united","masep"],"status":"current"},{"era":"2002-2025","title":"Helical delivery","description":"TomoTherapy Hi-Art (K013673, 2002) delivered radiotherapy helically from a CT-like ring. Its successor Radixact (K161146, 2016) added Synchrony motion tracking (K182687, 2018) and helical kilovoltage CT imaging, ClearRT (K202412, 2020). Accuray sells regional configurations: Helix for India and similar markets (CE-marked, 2024), Tomo C, approved by the NMPA in China in 2023, and Stellar for the US from 2025.","refs":["tomotherapy","accuray"],"status":"current"},{"era":"2019-2026","title":"Makers beyond the two large vendors","description":"United Imaging's uRT-linac 506c, which combines a C-arm linac with a diagnostic 16-slice CT, entered clinical use in China in 2019; no FDA clearance was found. Panacea's Siddharth-II from India was cleared by the FDA in 2021 (K210894) with Halcyon and TrueBeam as predicates, and Our United's TaiChiA linac in 2020. These matter for price and for countries building capacity.","refs":["united-imaging","panacea-medical-technologies","our-united","c-arm-linac","global-oncology-access"],"status":"current"},{"era":"Next","title":"Cheaper bunkers, fewer staff, daily adaptation by default","description":"The unmet needs named in the sources are cost, shielding and staffing: self-shielded radiosurgery, rings that need less concrete, and imaging that lets software replan every day. Proposals already in OnCo include an open-hardware linac designed for unreliable power and service contracts that pay for uptime rather than for the machine.","refs":["idea-acc-open-hardware-linac","idea-acc-linac-uptime-contracts","b-global-access","b-workforce"],"status":"emerging"}],"watch":[]},"route":"/roadmaps/linac-machines-roadmap/","neighbours":{"roadmap":[{"id":"mr-and-biology-guided-radiotherapy-roadmap","kind":"roadmap","name":"MR-linacs and biology-guided radiotherapy: from a cobalt MRI machine to PET-guided beams","route":"/roadmaps/mr-and-biology-guided-radiotherapy-roadmap/"},{"id":"radiation-roadmap","kind":"roadmap","name":"Radiotherapy roadmap: X-rays → shaped beams → fewer fractions, particles and FLASH","route":"/roadmaps/radiation-roadmap/"}],"idea":[{"id":"idea-acc-open-hardware-linac","kind":"idea","name":"An open-hardware radiotherapy machine built for unreliable power and dust","route":"/ideas/idea-acc-open-hardware-linac/"},{"id":"idea-acc-linac-uptime-contracts","kind":"idea","name":"Pay for radiotherapy machine uptime, not for the machine","route":"/ideas/idea-acc-linac-uptime-contracts/"}],"section":[{"id":"devices","kind":"section","name":"Devices & Physical Therapies","route":"/fronts/devices/"},{"id":"radiation","kind":"section","name":"Radiation Therapy","route":"/fronts/radiation/"}],"technology":[{"id":"adaptive-radiotherapy","kind":"technology","name":"Adaptive radiotherapy (online replanning)","route":"/technologies/adaptive-radiotherapy/"},{"id":"auto-contouring-ai","kind":"technology","name":"AI auto-contouring and adaptive planning","route":"/technologies/auto-contouring-ai/"},{"id":"c-arm-linac","kind":"technology","name":"C-arm medical linear accelerators (TrueBeam, Versa HD and others)","route":"/technologies/c-arm-linac/"},{"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":"gamma-knife","kind":"technology","name":"Gamma Knife","route":"/technologies/gamma-knife/"},{"id":"global-oncology-access","kind":"technology","name":"Global oncology and access in low- and middle-income countries","route":"/technologies/global-oncology-access/"},{"id":"imrt-igrt","kind":"technology","name":"IMRT / IGRT (modern external beam)","route":"/technologies/imrt-igrt/"},{"id":"in-room-imaging-systems","kind":"technology","name":"In-room imaging for radiotherapy (cone-beam CT, ExacTrac, CT-on-rails, HyperSight)","route":"/technologies/in-room-imaging-systems/"},{"id":"ring-gantry-linac","kind":"technology","name":"Ring-gantry linacs (Halcyon, Ethos)","route":"/technologies/ring-gantry-linac/"},{"id":"rotating-gamma-radiosurgery-systems","kind":"technology","name":"Rotating gamma and hybrid cobalt systems (Our United TaiChi, MASEP Infini, Akesis Galaxy, GammaPod)","route":"/technologies/rotating-gamma-radiosurgery-systems/"},{"id":"sbrt","kind":"technology","name":"SBRT / SABR (stereotactic radiotherapy)","route":"/technologies/sbrt/"},{"id":"radiosurgery-srs","kind":"technology","name":"Stereotactic radiosurgery (Gamma Knife, CyberKnife, linac SRS)","route":"/technologies/radiosurgery-srs/"},{"id":"tomotherapy","kind":"technology","name":"TomoTherapy and Radixact (helical radiotherapy)","route":"/technologies/tomotherapy/"},{"id":"zap-x","kind":"technology","name":"ZAP-X gyroscopic radiosurgery","route":"/technologies/zap-x/"}],"company":[{"id":"accuray","kind":"company","name":"Accuray","route":"/companies/accuray/"},{"id":"best-theratronics","kind":"company","name":"Best Theratronics","route":"/companies/best-theratronics/"},{"id":"elekta","kind":"company","name":"Elekta","route":"/companies/elekta/"},{"id":"masep","kind":"company","name":"MASEP Medical Science and Technology Development (Shenzhen)","route":"/companies/masep/"},{"id":"our-united","kind":"company","name":"Our United Corporation","route":"/companies/our-united/"},{"id":"panacea-medical-technologies","kind":"company","name":"Panacea Medical Technologies","route":"/companies/panacea-medical-technologies/"},{"id":"united-imaging","kind":"company","name":"United Imaging","route":"/companies/united-imaging/"},{"id":"varian","kind":"company","name":"Varian (Siemens Healthineers)","route":"/companies/varian/"},{"id":"zap-surgical-systems","kind":"company","name":"ZAP Surgical Systems","route":"/companies/zap-surgical-systems/"}],"bottleneck":[{"id":"b-global-access","kind":"bottleneck","name":"Most of the world has almost no cancer care","route":"/bottlenecks/b-global-access/"},{"id":"b-workforce","kind":"bottleneck","name":"Not enough oncologists, nurses, pathologists, physicists","route":"/bottlenecks/b-workforce/"},{"id":"b-surgery-radiation-innovation","kind":"bottleneck","name":"Surgery and radiotherapy cure most, get least","route":"/bottlenecks/b-surgery-radiation-innovation/"}]}}