Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Medical imaging relaxes to brighten up

09.04.2002


Protein packaging may enhance MRI contrast.



Images of body tissues and organs could soon be brighter and sharper thanks to a technique developed by Italian chemists. They have made the chemical contrast agents used in magnetic resonance imaging (MRI) produce a stronger signal by trapping them in protein cages just 12 millionths of a millimetre (nanometres) or so widesup>1.

Such improvements increase the contrast of the images, so they should reveal more detailed information, enabling doctors to better discriminate between different tissue types. The researchers, Silvio Aime and co-workers at the University of Turin, hope to persuade their protein cages to latch onto particular cells, as this would help them to pinpoint diseased tissues.


One of the best MRI contrast agents is a molecule containing atoms of the element gadolinium. Injected into the bloodstream, the gadolinium compound accumulates in abnormal tissues such as scar tissue and tumours, so they become brighter in MRI scans. The agent is ultimately passed out of the body in urine.

Making gadolinium contrast agents brighter is a subtle business. Gadolinium enhances MRI contrast because it helps water molecules to relax. The MRI signal comes from water molecules that have been stimulated into an excited state by radio waves. The quicker the water molecules return to their normal state, the stronger the signal. Gadolinium assists in this process.

How well gadolinium does its job depends on the molecules around it. Proteins can amplify the relaxation induced by gadolinium because chemicals on their surface interact with water molecules. Aime’s team found they got better MRI contrast by keeping standard gadolinium contrast agents close to proteins.

Nature provided them with a ready-made protein cage in the form of ferritin, a shell of 24 protein molecules with a cavity about 7.5 nanometres across. Liver cells store iron inside ferritin, packing up to 4,500 iron atoms into its hollow interior.

The Italian team used a stripped-down version of ferritin known as apoferritin. They trapped the gadolinium contrast agent inside the cavity by first splitting the capsule open in acid and then reforming it in neutral solution containing the gadolinium compound. Each apoferritin compartment holds about ten of these gadolinium molecules.

Crucially, apoferritin’s walls are riddled with channels that are wide enough to let water in and out but too narrow to let gadolinium through. This exchange of water between the inside and the outside is essential for increasing its relaxation rate. Apoferritin seems to enhance gadolinium’s relaxation about 20-fold, the team reports.

They haven’t yet discovered how this translates into changes in MRI contrast, however. The clinical usefulness of the new approach will depend on many other factors, such as how efficiently apoferritin-bound gadolinium can be transported round the body, and how easily it can be cleared from the bloodstream.

References
  1. Aime, S., Frullano, L. & Crich, S.G. Compartmentalization of a gadolinium complex in the apoferritin cavity: a route to obtain high relaxivity contrast agents for mangetic resonance imaging. Angewandte Chemie International Edition, 41, 1017 - 1019, (2002).


PHILIP BALL | © Nature News Service

More articles from Health and Medicine:

nachricht Satellites, airport visibility readings shed light on troops' exposure to air pollution
09.12.2016 | Veterans Affairs Research Communications

nachricht Oxygen can wake up dormant bacteria for antibiotic attacks
08.12.2016 | Penn State

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>