# MR-linacs and biology-guided radiotherapy: from a cobalt MRI machine to PET-guided beams

Source: https://onco.cc/roadmaps/mr-and-biology-guided-radiotherapy-roadmap/  
OnCo record `mr-and-biology-guided-radiotherapy-roadmap` (Roadmap). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Machines that watch the tumour while treating it: first with MRI inside the treatment machine, then with a PET scanner that steers the beam from the tumour's own signal. Dated from the FDA records.

## Summary

ViewRay's first system, cleared in May 2012 (K111862), combined MRI with three cobalt-60 sources. The MRIdian Linac replaced cobalt with a linac in 2017 (K162393) and was redesigned in 2021 (K212958). Elekta Unity, a 7 MV linac rotating around a 1.5 tesla MRI, was cleared in December 2018 (K182076) with MRIdian as predicate. ViewRay filed for Chapter 11 in July 2023; ViewRay Systems, established in February 2024 after acquiring its assets, sells the MRIdian A3i. RefleXion's X1 was cleared in 2020 (K190978) and its PET-guided SCINTIX therapy by De Novo in February 2023 (DEN220014) for lung and bone tumours, and the X2 (K252071, December 2025) widened the PET field of view from 5.3 to 21.5 cm.

## Fields

- Kind: Roadmap
- Last checked: 2026-11-04
- Tags: machines-wave3

## Sources

- FDA 510(k) K111862: ViewRay System (22 May 2012): https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm?ID=K111862
- FDA 510(k) K162393: MRIdian Linac System (24 February 2017): https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm?ID=K162393
- FDA 510(k) K212958: MRIdian Linac System (14 December 2021): https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm?ID=K212958
- FDA 510(k) K182076: Elekta Unity (4 December 2018): https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm?ID=K182076
- FDA 510(k) K190978: RefleXion Medical Radiotherapy System (12 March 2020): https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm?ID=K190978
- FDA De Novo DEN220014: fludeoxyglucose F18-guided radiation therapy system (RefleXion): https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/denovo.cfm?id=DEN220014
- FDA 510(k) K252071: RefleXion X2 (18 December 2025): https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpmn/pmn.cfm?ID=K252071
- ViewRay Systems: investors page (assets of ViewRay, Inc. acquired; company established 6 February 2024): https://viewraysystems.com/investors/

## Connected records

- roadmaps: [Linear accelerator machines: from Clinac to AI-imaging linacs, rings and radiosurgery units](https://onco.cc/roadmaps/linac-machines-roadmap/), [Radiotherapy roadmap: X-rays → shaped beams → fewer fractions, particles and FLASH](https://onco.cc/roadmaps/radiation-roadmap/)
- ideas: [Coverage-with-evidence registries for MR-guided and adaptive radiotherapy](https://onco.cc/ideas/idea-fund-adaptive-radiotherapy-evidence/)
- fronts: [Devices & Physical Therapies](https://onco.cc/fronts/devices/), [Radiation Therapy](https://onco.cc/fronts/radiation/)
- technologies: [Adaptive radiotherapy (online replanning)](https://onco.cc/technologies/adaptive-radiotherapy/), [Biology-guided radiotherapy (RefleXion X1, SCINTIX)](https://onco.cc/technologies/biology-guided-radiotherapy/), [Cobalt-60 teletherapy](https://onco.cc/technologies/cobalt-60-teletherapy/), [MR-guided adaptive radiotherapy](https://onco.cc/technologies/mr-linac/), [PET/CT](https://onco.cc/technologies/pet-ct/), [Respiratory gating and tumour tracking systems (RPM, ABC, Calypso, Synchrony)](https://onco.cc/technologies/respiratory-gating-tumour-tracking-systems/)
- companies: [Elekta](https://onco.cc/companies/elekta/), [RefleXion Medical](https://onco.cc/companies/reflexion/), [ViewRay (MRIdian)](https://onco.cc/companies/viewray/)
- bottlenecks: [Surgery and radiotherapy cure most, get least](https://onco.cc/bottlenecks/b-surgery-radiation-innovation/)

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