Here is the challenge: Every 250 milliseconds, reconfigure a machine with 300,000 potential settings so that it pulls particles from one of three ion sources, tickles each of 500 quadrupole magnets to boost the particles (moving as fast as 80 percent of light speed) to within 0.1 percent of a precise energy, then hurl them down one of four delivery paths so they irradiate exactly the millimeter-sized volume of a tumor buried deep in a patient’s brain.
That’s the problem that confronted CERN engineer Johannes Gutleber as he built the controls for the MedAustron cancer therapy facility now under construction in Wiener Neustadt, an Austrian city of 42,000 people about 60 km south of Vienna—and 1,000 km away from CERN's Large Hadron Collider.
Particle beam therapy isn’t new or altogether uncommon, and the jury is still out on its overall effectiveness. Though most of the ion beam treatment facilities have been built in this century, the first opened in Moscow in 1969. Today, according to the Particle Therapy Cooperative Group, there are about 40 particle therapy facilities in operation, with another 30 (including MedAustron) in the construction or planning phases. Three quarters of the existing particle beam centers, though, have been built since 2000. Carbon-ion treatment is more recent. Only five installations--two installations in Japan and one each in Italy, Germany and China—currently deliver carbon beams. As of the end of 2012, about 10,000 patients worldwide had been treated with the technique.
Attaining this sort of high-speed precision with flexible, reconfigurable embedded I/O controllers and field-programmable gate array (FPGA) devices earned Gutleber triple honors at this year’s National Instruments Graphic Design System Achievement Awards: the Advanced Research Design Achievement Award, the Intel Intelligent Systems Award, and the Humanitarian Award.
The MedAustron installation does present special measurement and control problems. When it starts treating patients in 2015, the €150-million hadron accelerator will deliver proton and carbon ion beams, driven by a synchrotron to energies as high as 800 mega-electron-volts (MeV). Advocates say that hadron beams have a distinct advantage over traditional X-rays for destroying tissues deep in the body. X-rays deliver most of their energy at the surface, and continue to deliver energy to tissues all along their path, weakening considerably by the time they reach deep tissues.
Heavy particles like protons and carbon nuclei, by contrast, penetrate tissues with relatively little interaction until they reach a critical depth (a function of their initial energy). At that point—called the Bragg peak—they surrender almost all of their energy in just a few millimeters. Heavier particles, like carbon nuclei, demonstrate sharper Bragg peaks than lighter protons, allowing for tighter localization.
The Austrian facility will have four delivery beams—three patient-treatment rooms and a non-clinical research room. At its opening, it will delivery both proton and carbon-ion beams, at energies ranging from 60 to 800 MeV; plans call for adding the ability to deliver helium, oxygen, neon, and other ions later.
By sweeping the beam, raster-fashion, and minutely varying the beam energy, clinicians can use an ion beam to irradiate a region a few millimeters on a side while minimizing damage to tissue along the beam path and around the lesion—all while using about a third of the energy X-ray therapy would require. (For more, see a 2012 overview of the MedAustron project and a 2011 preview of the control design requirements.)
But this is possible only with the tightest possible synchronization and control. Beam energies have to be controlled to within about 0.1 MeV over the full 60-to-800 MeV range, and be synchronized to the millisecond. And the device needs to be reconfigured every 250 milliseconds to deliver the next pulse—to adjust the depth setting to continue treating the patient in Room 1, or to tee up a pulse for a different patient in Room 2 or Room 3.
Images: Johannes Gutleber/CERN