Shifting from giant accelerators 26 km (16 miles) across to brain surgery theaters, a particle detector first developed by physicists at CERN is being used by scientists in Germany to treat brain tumors with greater precision and safety.
Destroying head and neck tumors is relatively simple. You dose them with the right chemicals or blast them with powerful enough radiation, and job done. The problem is figuring out how to kill the cancer cells without killing the patient.
One effective way of treating such tumors is by using ion beams. Accelerating charged particles to three quarters of the speed of light, they can penetrate as far as a foot into living tissue. To protect healthy cells, the conventional technique is to move the ion projector in a curve with the tumor centered at the focus. This way, the tumor is continually bombarded while the healthy tissue is only slightly exposed.
It's a simple and effective method, but it's far from perfect, especially when the tumor is in the brain. In such a situation, there's a real danger of exposing neighboring healthy cells to secondary radiation caused by the ion beam hitting tissues, which can result in memory loss, damage to the optic nerve, and other problems.
To minimize this, X-ray computed tomography (CT) scans can precisely map the location of the tumor to guide the surgeon in setting up the treatment. Unfortunately, a scan taken before the operation may be inaccurate because the brain has shifted about in the skull since then.
To compensate for this, researchers from the German National Center for Tumor Diseases (NCT), the German Cancer Research Center (DKFZ), and the Heidelberg Ion Beam Therapy Center (HIT) at Heidelberg University Hospital used a new imaging device built by Czech company ADVACAM that incorporates the Timepix3 pixel detector developed at CERN.
Designed to work with both semiconductor detectors and gas-filled detectors, the Timepix3 is a general-purpose integrated circuit that can take sparse detection data and provide outputs with high resolution over a short time. This allows the ADVACAM to use the secondary radiation from the ion beam to update the tissue maps by using the radiation as a tracking beacon.
"Our cameras can register every charged particle of secondary radiation emitted from the patient's body," said Lukáš Marek from ADVACAM. "It's like watching balls scattered by a billiards shot. If the balls bounce as expected according to the CT image, we can be sure we are targeting correctly. Otherwise, it's clear that the 'map' no longer applies. Then it is necessary to replan the treatment."
The idea is that these updates will better target the tumor while reducing the amount of unwanted radiation the patient is exposed to while hitting the tumor with higher levels of radiation.
At the moment, the detector requires interrupting the treatment to allow for replanning. However, later phases of the program will include the ability to correct the beam path in real time.
"When we started developing pixel detectors for the LHC we had one target in mind – to detect and image each particle interaction and thereby help physicists to unravel the secrets of Nature at high energies," says Michael Campbell, Spokesperson of the Medipix Collaborations. "The Timepix detectors were developed by the multidisciplinary Medipix Collaborations whose aims are to take the same technology to new fields. Many of those fields were completely unforeseen at the beginning and this application is a brilliant example of that."
Source: CERN
