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 How cancer metastasis happens: Researchers reveal a key mechanism
19.01.2018 | Weill Cornell Medicine

nachricht Researchers identify new way to unmask melanoma cells to the immune system
17.01.2018 | Duke University Medical Center

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: Artificial agent designs quantum experiments

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.

We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Let the good tubes roll

19.01.2018 | Materials Sciences

How cancer metastasis happens: Researchers reveal a key mechanism

19.01.2018 | Health and Medicine

Meteoritic stardust unlocks timing of supernova dust formation

19.01.2018 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>