Varian Medical Systems International AG v Elekta Ltd & Anor

A patent must disclose a workable prototype capable of performing the claimed invention without an undue burden. The work may involve substantial research and lengthy routine experimentation where that is normal in the relevant technology. The skilled team is assessed against the complexity of the art, and the fact that a particular embodiment is difficult or has not previously been built does not establish insufficiency.

For patent construction, “real time during treatment” referred to responsive control over a treatment fraction, not merely while the beam was switched on. Controlling radiation intensity could mean controlling fluence over the fraction, and respiratory gating could control both spatial distribution and intensity. A claim amendment may broaden coverage without adding matter, but it adds matter if the amended patent discloses a new technical teaching absent from the application.

The claimant owned the Green patent, concerning a radiotherapy machine combined with magnetic resonance imaging. The defendants’ Crawley MR-Linac used MRI images and automated gating to pause and restart the radiation beam when a tumour moved.

The claimant alleged infringement of claims 1 and 4. The defendants challenged validity on insufficiency, obviousness over Van Vaals and Shepherd, and added matter. The court had to construe the claims, determine infringement, and decide whether the patent disclosed the invention sufficiently and without unlawful amendment.

1. Construction and infringement. Claim 1 did not require control based on detecting irradiation products such as free radicals. The MRI imaging information itself could provide the control input. “Treatment” meant a treatment fraction, and real-time control required a degree of immediacy but did not require control only while the beam was on. “Intensity” was construed in the context of radiotherapy and could refer to fluence, namely the total radiation delivered over the fraction. Spatial distribution concerned the distribution of the applied radiation, not necessarily movement or reshaping of the beam. Respiratory gating could control both spatial distribution and intensity. The Crawley MR-Linac infringed claim 1.
2. “Spaced segments” in claim 4 referred to spacing which allowed the beam axis to pass between the coil segments. The claim was not limited to separate casings, cryostats or Faraday cages. Claim 4 was infringed.
3. Insufficiency. Under section 72 of the Patents Act 1977 and article 83 of the EPC, the required result was a workable prototype technically suitable for radiotherapy on a human patient. The skilled team could use ordinary trial and error, even though the project involved complex engineering and substantial work. The patent was sufficient. The alleged difficulty of retrofitting an existing Linac did not establish insufficiency because retrofitting was not required. Magnetic and RF shielding, an increased source-axis distance, and treatment-planning adjustments could be achieved without undue burden.
4. Obviousness. The skilled radiotherapy and MRI team would read Van Vaals with interest and would arrive at the combined MRI-Linac concept because accurate targeting and respiratory gating were important problems. The relevant claims were obvious over it. The two proposed Shepherd scenarios did not establish obviousness: the first did not provide sufficiently immediate real-time control, and the second did not point towards imaging during treatment.
5. Added matter. Although the amendments concerning spatial distribution and intensity broadened claim coverage, they did not alone add matter. However, claim 1 disclosed control using MRI images without detecting irradiation effects, whereas that teaching was absent from the application as filed. Claim 1 therefore contravened sections 72(1)(d) and 76 of the Patents Act 1977.
6. The patent was invalid for obviousness and added matter. It was sufficient and would have been infringed if valid. The judgment was handed down after settlement because the public interest in the validity and scope of the patent outweighed the parties’ private interests.