The ultrasound of the future will expand into new fields
The development of ultrasound as a medical aid started in Lund. And the technology is still being developed here as well as all over the rest of the developed world.
One of the researchers on this front is Tomas Jansson. After a career at LTH and the Department of Measurement Technology and Industrial Electrical Engineering, where he also led the Lund Alliance for Biomedical Imaging and Bioengineering, he has just moved over to the Faculty of Medicine. He is now senior lecturer in biomedical engineering and is working in fairly new premises next to the old hospital restaurant.
“But my task is to continue to link LTH and healthcare within Skåne University Hospitals, (SUS)”, he assures. This is why he is still assistant programme director of the Master’s programme in Biomedical Engineering.
We asked him to tell us what is hot on the research front within ultrasound technology these days.
“One example is the blood vessel characterisation that Magnus Cinthio at LTH is working on. He has discovered that blood vessels don’t only move across pulse pressure but also along it. We still don’t really know why and what exactly causes the movement. Research is being done to find out whether differences in the movement can be used to show a risk of cardio-vascular disease. Åsa Rydén-Ahlgren is the leading medical researcher in the field.”
“In general, the measurement of tissue movement is currently the big thing at specialist conferences. It is both about investigating the heart and looking for tumours”, explains Tomas.
Tumours often have stiffer tissue than the surrounding area. The classic method is to feel for lumps, as in the breast, for example. The new method, elastography, entails directing short sound impulses towards such tissue. The greater stiffness of the tumours means that the sound waves move in a different way, a new and elegant way of searching for tumours. The method is now used clinically in breast cancer cases and is being tested for prostate cancer.
Another important trend is to use a contrast agent in ultrasound. This could be extremely small gas bubbles (as small as red blood cells), which provide a clear echo, in the blood, which is harmless and can clearly show where the blood flows and where other tissue takes over. With Doppler technology and contrast agents, it is possible to see and measure the blood flow in the vessels.
“We’re also talking a lot about molecular imaging at the moment. Antibodies or other receptors on the contrasting particles stick to tumorous tissue for example, making it possible to discover very small tumours. Research is underway to use the technology for cardio-vascular and neurological diseases as well. Outside the bloodstream, much smaller contrasting particles are needed”, he continues. “We are now working with nanoparticles of magnetic iron oxide. When the particles get stuck in the tumour, we can see the tumour vibrate as we rapidly switch a magnet on and off”.
Tomas shows an image of a rat which has had nanoparticles injected into its paw. They end up in a lymph node and are clearly visible thanks to colour coding of measured vibrations.
The idea is to find lymph nodes that are affected by tumours. In the case of breast cancer operations, physicians add a colouring agent and see which lymph node in the armpit is coloured. There the risk of metastasis is greatest and the lymph node is usually removed for examination under a microscope. In the case of melanoma (skin cancer) the number of possible lymph nodes is so large that similar investigations are hard to carry out.
“Our idea is that magnetic nanoparticles with tumour-searching particles could replace excisions. And with nanoparticles, one could even look for the first lymph node in the case of melanoma.”
The research is a cooperation with Lund-based company Genovis. At last, since two weeks ago, Genovis has received funding from Vinnova to proceed with this. (See separate article.)
The nano project has also been selected as an Advanced Study Group at the Pufendorf Institute. The aim is to draw up an inventory of potential users at Lund University of technologies in which nanoparticles can be used as contrast agents, not only for ultrasound but also for PET, SPECT, MR and optical technologies.
A third hot trend is photoacoustics which uses lasers with ultrasound. With light pulses lasting nanoseconds, laser light is absorbed, warming and expanding tissue which causes it to produce an (ultra)sound. Blood absorbs best, particularly if it is oxygenated, which can also indicate the presence of a tumour. Nanoparticles that absorb a lot of heat, such as gold, can be used as contrast agents. The size of the particles determines what wavelength they absorb. This is a very hot area in which a device for commercial use now exists. It is used on laboratory animals but not yet on humans.
“Both the nano-based methods are very suitable for molecular imaging, which reveals the process of a disease. Perhaps the diagnosis of heart disorders could take place a whole decade earlier!? An incredibly hot area, where work is ongoing on many fronts,” says Tomas.
“A few years ago at a minor conference there was a sense that much had already been done in the field. But the new clues have strongly revived the impetus in research. Besides, you can blame the funding system, but it has contributed to the focus on medically relevant issues”, adds Tomas Jansson. However, sometimes technology-driven development is also positive. When the Doppler machine was developed by Japanese researcher Satemura, for example, he had no idea what it could be used for. Others came up with applications after he announced his innovation in a journal. You don’t always know what you might need!
Text and images: MATS NYGREN