Vertical challenge

An ion beam — which its developers claim will be the highest-resolution instrument of its type in the world — could allow cancer care to be tailored for individual patients.

Capable of sending a single ion through a single cell, the vertical scanning nanobeam is to be built at the University of Surrey.

Ion beam research uses electrical fields to accelerate protons — hydrogen ions — to speeds of around 112million km/hr, then focus them to a point so they can be used to study minerals and biological materials.

Several types of information can be gathered by this method, by looking at how the protons are scattered from the target and the types of radiation the bombardment causes. This can show how the subject interacts with radiation and can provide information on the distribution of elements on both the surface and inside the material.

Focusing beams

Beams are generally described in terms of their energy — in the Surrey beam’s case, some 2MV — and their resolution. A millibeam will focus to a dot about a millimetre across, while a microbeam will focus to a few microns. The Surrey instrument will be a nanobeam, using an electrostatic lens to focus the beam to a point around 10nm across, said Surrey’s Ion Beam

Centre (IBC) director Roger Webb. The other remarkable thing about it is its orientation — firing protons straight down into a sample, rather than horizontally.

‘Traditionally, everything is done horizontally, because it is much easier to keep everything steady when you’re horizontal. You just bolt them across the floor,’ explained Webb.

‘If you do it vertically, you have to hang things from something to keep them secure, which makes it that bit harder. This beam is 10m long, so holding something rigid over 10m to avoid vibrations of a few nanometres is quite a challenge.’ Although considerable, the challenge is not quite as huge as it sounds, Webb admitted, as it is the beam that needs to be kept absolutely steady relative to the sample: some vibration in the beam-generating equipment is allowable.

The advantage of a vertical scanning beam over a horizontal one is that it allows ion beams to be used on liquids. Holding a liquid horizontal so that a beam of ions can be targeted through it is nigh impossible, but sending a beam vertically through a liquid target is much simpler.

It also makes it easier to scan the beam, again using electric fields to move the protons across the target. ‘There are other vertical beam instruments in the world, but none of them will be able to match the resolution or the scanning capability of ours,’ said Webb.

The centre is working with the Grey Cancer Institute in London to study how tumour cells respond to radiation. ‘We’ll literally shoot one ion at a time through particular cells,’ said Webb. ‘This allows us to look at the radiation effects and do elemental analysis, as well as looking at where the nutrients flow into the cell and how drug uptake happens. This is only possible by manipulating the beam. The Grey Institute is doing this sort of work with single protons, but they can’t scan — they can only move the cell to the beam.’

Radiation response

The data gathered will help the researchers determine why some cancer cells are more sensitive to radiation than others. ‘For a long time, everyone assumed that you can just give a tumour a dose of radiation at a particular level and see how many cells die, then repeat that at a different level and count the cells again, and extrapolate that back to provide a simple straight line showing the radiation response,’ said Webb. ‘But what’s been noticed now is that some cells die more easily if they are given a low dose. It would be interesting and valuable to know why, and to see whether treating the cells with certain drugs would make them more sensitive.’

Webb thinks the equipment could be valuable to determine how to treat unusual tumours. ‘For rare types, physicians and surgeons could take a biopsy, grow the cells in culture and send a sample to the IBC, and we could test their sensitivity in the environment of different drugs to find the best course of treatment.’

Total costs of the beam will be £1.2m: £800,000 is coming from a Wolfson Foundation grant, the rest from the university. It will be housed within a 13m-high tower, with vibration damping from the London clay on which it stands, plus a concrete base mounted on 13m-deep pilings. The beam equipment will be mounted on three pillars formed from 300mm-wide metal cylinders filled with sand, which will be vibrationally isolated from the building.

‘Most of the design of the lens and focusing system is in-house,’ said Webb. ‘We hope to have the beam functional in May or June next year, and should see the first results by September.’