Jan 16, 2013
In brief: research round-up
Focused radiation keeps control of drug-resistant regions
Targeted cancer drugs such as crizotinib and erlotinib are highly effective for patients whose tumours depend on the basic mutations that these drugs exploit. However, if pockets of the cancer mutate again, moving away from the original, targeted mutation, the drugs can eventually cease to work. A study at the University of Colorado Cancer Center has shown that when such pockets of resistant cancer develop, it is possible to target them with focused radiation while continuing drug therapy to maintain control of the majority of the disease (J. Thoracic Oncol. 7 1807).
The study of 65 patients showed that continuing either crizotinib or erlotinib after irradiation of resistant pockets was associated with more than half a year of additional cancer control. The benefit was especially robust when the metastatic lung cancer progressed in the brain. "In nearly half of patients, when these drugs stop working, they stop working only in a limited number of sites," explained senior clinical fellow Andrew Weickhardt. "Given how well these people tolerate the medication, it made sense to us to treat these isolated spots with radiation, and continue the same drug, which was obviously working elsewhere."
Liquid nitrogen cooled MEG advances brain research
Magnetoencephalography (MEG) is an important tool for brain research and diagnostics, but MEG systems can be prohibitively expensive. Researchers from Chalmers University of Technology and the University of Gothenburg in Sweden are now working to develop a MEG system that's simple and cheap enough to be available at every hospital. Current MEG sensors require liquid helium cooling to –269 °C. In contrast, the new "Focal MEG" technology is based on sensors that work at –196 °C and can be cooled with liquid nitrogen. This means that less insulation is required between the sensors and the subject's head, allowing closer placement to the brain and higher-resolution recording of brain activity (Appl. Phys. Lett. 100 132601).
The researchers have used two of their Focal MEG sensors to successfully record spontaneous brain activity – a feat never before achieved with liquid-nitrogen cooled sensors. The team also made an unexpected finding, recording an uncharacteristically strong brain wave, the theta rhythm, from the back of the brain. "This is quite exciting," said Mikael Elam, professor in clinical neurophysiology at the University of Gothenburg. "It may be an as-yet undetected type of brain signal that can only be found when one measures as close to the head as we do."
Additive manufacturing eases collimator creation
Production of complex multi-pinhole SPECT collimators can be labour intensive, expensive or sometimes impossible using current techniques. Researchers in the Medical Imaging and Signal Processing (MEDISIP) group at Ghent University in Belgium have examined a rapid collimator construction technique called metal additive manufacturing. The process involves building up the collimator in layers, using selective laser melting of tungsten powders at locations defined by the CAD design file as solid material (Med. Phys. 40 012501).
The team designed and produced a 16 mm thick collimator with 20 loftholes with 500 µm pinhole opening. Production accuracy ranged from –260 to +650 µm. Aperture positions had a mean deviation of 5 µm, and the mean aperture diameter was 464 ± 19 µm. Point source measurements performed with the collimator mounted on a SPECT detector showed that calculated and measured values of sensitivity and resolution agreed well. Tests with the collimator positioned in a 7T MRI scanner showed no influence of the magnetic field on the collimator and minimal distortion on the MR scan of a uniform phantom.
Radionuclide production ramps up to industrial scale
Scientists at the National Centre for Nuclear Research (NCBJ) in Poland have developed technologies for producing 90Y and 177Lu radionuclides, as precursors for innovative radiopharmaceuticals. The researchers have shown that both radioisotopes (to date produced only on a small scale) in combination with peptides and monoclonal antibodies may form effective cancer treatments. The 90Y (Itrapol) and 177Lu (Lutapol) preparations feature high specific activity, as well as high chemical and radiological purity.
A dedicated production line for these radioisotopes has been developed at NCBJ's Radioisotope Centre POLATOM, with work in progress to begin pilot production. The first batches, along with a complete analytical and technological validation, will be used to apply for formal registration of the radionuclides as radiopharmaceutical precursors. "The technological solutions that we have developed may be used to produce both radionuclides at an industrial scale," said POLATOM's Renata Mikołajczak. "Increased supply of radioisotopes to the market should increase availability of the derivative radiopharmaceuticals and help to disseminate new forms of internal radiotherapy."
Compact X-ray source targets hand-held scanners
A University of Missouri engineering team has invented a compact radiation source that could be used to create low-cost, portable X-ray scanners for medical and dental applications. The device uses a piezoelectric crystal (lithium niobate) to produce more than 100,000 V of electricity from only 10 V of electrical input. Such low power consumption could allow the crystal to be fuelled by batteries (IEEE Trans. Plasma Sci. 41 106).
"Currently, X-ray machines are huge and require tremendous amounts of electricity," said Scott Kovaleski, associate professor of electrical and computer engineering at MU. "In approximately three years, we could have a prototype hand-held X-ray scanner using our invention. The cell-phone-sized device could improve medial services in remote and impoverished regions and reduce healthcare expenses everywhere. We have never really had the ability to design devices around a radioisotope with an on-off switch. The potential for innovation is very exciting."
About the author
Tami Freeman is editor of medicalphysicsweb.