Elekta Unity MR-Linac

Manufacturer: Elekta · Modality: MR-Linac

First commercially deployed clinical MR-Linac (FDA cleared 2018). Combines a 1.5 Tesla MRI with a 7 MV flattening-filter-free linear accelerator, enabling real-time MRI visualization of target + organs at risk during radiotherapy delivery. The MRI is between the patient and the linac beam — the RF / X-ray physics of that geometry is what made Unity an engineering accomplishment.

Clinical significance

MR-Linac enables adaptive radiotherapy — the treatment plan is adjusted each day based on that day's anatomy, not the CT simulation scan from weeks ago. Particularly valuable for moving / changing targets (pancreas, liver, bladder-influenced prostate, lung). Clinical outcomes data still maturing.

Specs

1.5 T MRI (Philips magnet, integrated by Elekta)
7 MV FFF linac
Agility MLC (160 leaves)
In-beam MRI geometry (magnet rings around the patient; linac rotates around the magnet)
Real-time cine imaging during delivery
Monaco TPS with adaptive planning workflow

Install reality

Install complexity is extreme — combines RT vault shielding, MRI RF shielding (Faraday cage inside the vault), helium management (cold head, quench pipe), 5-gauss-line containment. Multi-month site prep; install cost in the eight figures. Competes for a very small number of buyer sites annually.

Dosimetry considerations

The 1.5 T magnetic field changes electron transport (electron return effect). TPS must account for it. Commissioning is different from a conventional linac — Elekta + the medical physicist do the ground-truth beam data together.