Apr 26, 2012
In brief: research round-up
Mini magnetometer measures brain activity
A miniature magnetic sensor developed by the National Institute of Standards and Technology (NIST) in Boulder, CO, has successfully measured human brain activity. In experiments performed at the Physikalisch-Technische Bundesanstalt in Germany, the sensor was used for magnetoencephalography (MEG) to measure alpha waves associated with a subject opening and closing their eyes, and signals resulting from hand stimulation. Results were verified by comparison with signals recorded by a superconducting quantum interference device (SQUID), the most widely used MEG sensor (Biomed. Opt. Express 3 981).
The mini-sensor consists of a container of about 100 billion gaseous rubidium atoms. Light from a low-power infrared laser interacts with the atoms, which absorb more light as the magnetic field increases, and is transmitted through a fibre-optic cable to register the field strength. The sensor measured magnetic signals of about 1 picotesla, and the NIST scientists expect to boost its performance tenfold by increasing the amount of light detected. An enhanced sensor may match the sensitivity of SQUIDs, offering the potential for comparable performance with size, portability and cost advantages.
HIFU reduces side effects of prostate cancer treatment
Using high-intensity focused ultrasound (HIFU) to deliver focal treatment of prostate cancer may result in significantly fewer side effects than traditional treatments that treat the whole prostate, according to a study from University College London, UK. In the prospective study, 42 patients received focal HIFU delivered to clinically significant cancer lesions. Twelve months after treatment, urinary and erectile function returned to pre-treatment levels (Lancet Oncology doi: 10.1016/S1470-2045(12)70121-3).
Early evidence on cancer control was also encouraging. No evidence of cancer was identified in treated regions in 30 of 39 men who were biopsied at six months. After re-treatment in four men, 39 patients had no evidence of disease at 12 months. "We followed the HIFU treated patients for 12 months, evaluating the ability of this therapy to avoid side-effects such as incontinence and erectile dysfunction," said author Hashim Ahmed. "The results are very encouraging and warrant further study. We also need to test the medium and long term cancer control in multicentre comparative trials."
Adaptive optics optimizes 3D tissue imaging
Researchers at the University of Illinois (Urbana, IL) are employing adaptive optics to correct aberrations in three-dimensional, high-resolution tissue microscopy. Instead of using hardware-based adaptive optics to correct a light profile before it enters the lens, a complicated and expensive process, the team uses computer software to find and correct aberrations after the image is taken. "Computational techniques allow you to go beyond what the optical system can do alone, to ultimately get the best quality images," said researcher Steven Adie. "This would be very useful for real-time imaging applications such as image-guided surgery."
The researchers demonstrated the technique in gel-based phantoms laced with microparticles, as well as in rat lung tissue. They scanned the sample with an interferometric microscope, then computer-corrected the images at all depths within the volume. Blurry streaks became sharp points and features emerged from noise. They note that the method can be used with any type of interferometric imaging, such as optical coherence tomography, and can be performed using a standard desktop computer (PNAS doi: 10.1073/pnas.1121193109).
PET may detect Alzheimer's marker earlier
PET imaging with the tracer florbetaben can reliably detect beta-amyloid plaques in the living brain and may help doctors diagnose Alzheimer's disease earlier, concluded research presented this week at the American Academy of Neurology's 64th Annual Meeting in New Orleans, LA. Currently, Alzheimer's disease can only be definitively confirmed by detecting amyloid plaques and/or tangles in the brain during autopsy or via a brain tissue biopsy. This latest study compared in vivo brain PET with florbetaben to post-mortem analysis of the brain tissue.
More than 200 participants underwent MRI and florbetaben PET scanning. The amount of plaque found in 31 participants who reached autopsy was then compared to the scan results. Florbetaben PET could detect beta-amyloid with a sensitivity of 77% and a specificity of 94%. Comparing the visual assessment method proposed for clinical practice with post mortem diagnosis revealed a sensitivity of 100% and a specificity of 92%. "These results confirm that florbetaben is able to detect beta-amyloid plaques in the brain during life with great accuracy and is a suitable biomarker," said study author Marwan Sabbagh, director of Banner Sun Health Research Institute (Sun City, AZ).
Nanobubbles enable single-cell drug targeting
US researchers are developing methods to inject drugs and genetic payloads directly into cancer cells, using light-harvesting nanoparticles that convert laser energy into plasmonic nanobubbles. The nanobubbles are tiny pockets of air and water vapour created when laser light strikes a cluster of nanoparticles targeted to bind to cancer cells. The bubbles form just below the surface of cancer cells and as they expand and burst, briefly open small holes in the surface of the cells and allow cancer drugs to rush inside.
In tests on drug-resistant cancer cells, delivering chemotherapy drugs with nanobubbles proved up to 30 times more deadly to the cells than traditional drug treatment and required less than one-tenth the clinical dose. "We are delivering cancer drugs or other genetic cargo at the single-cell level," said Dmitri Lapotko from Rice University (Houston, TX). "By avoiding healthy cells and delivering the drugs directly inside cancer cells, we can simultaneously increase drug efficacy while lowering the dosage." The nanobubble technique is the subject of four recent peer-reviewed studies (Biomaterials doi: 10.1016/j.biomaterials.2012.03.077; Biomaterials 33 1821; Advanced Materials doi: 10.1002/adma.201103550; PLoS ONE 7 e34537).
About the author
Tami Freeman is editor of medicalphysicsweb.