It's a concept that has interested scientists for years - what if you could use stem cells in the heart after a heart attack to help re-build damaged tissue? It may be a good idea, but researchers have had trouble measuring if and how well the heart might respond. Now, new technology may change that. Scientists are putting a tiny, high-tech tattoo on the heart to see just how well this new approach is working.

When someone has a heart attack, unless treatment is almost immediate, damage will be permanent. Scientists say that might change if they can somehow transplant fresh stem cells into the heart to help rebuild it. The problem is no one has been able to tell how or why the stem cells work - until now - thanks to tiny sensors that are essentially tattooed onto the heart.

"They give a signal - a magnetic resonance signal - and this signal will give information about the oxygen concentration surrounding the crystal in this," says Periannan Kuppusamy, PhD, at Ohio State University Medical Center.

Kuppusamy says this technology is the first to non-invasively measure how much oxygen is getting to an organ inside the body. In a recent study, it showed higher oxygen levels and better function after stem cells were transplanted into a damaged heart. It's a therapy that could someday help patients like Nelson Smith.

"The doctors said I had less than 4 days to live and less than a 5% chance of making it," says Smith.

Thanks to a heart transplant, Nelson did make it. Thanks to this new tattoo technology, doctors may someday be able to monitor cases like his, by tracking oxygen levels of transplanted organs. For now, it's only being tested in the lab, but given its promise, it could make a difference in a lot of diseases.

"Not only for stem cell therapy, the technology can be used for measuring oxygen concentration in a variety of other applications - for example, cancer treatment," says Kuppusamy.

In any situation, oxygen is essential to help the body heal and this technology allows doctors to monitor its levels inside the body like never before. The next step for researchers includes building a machine large enough for people that will read the data from the tattoo on the heart - so oxygen levels can be read in a clinical setting and not just in a lab.

* American Heart Association, Statistical Fact Sheet & Heart Attack and Angina Statistics, 2007,

Ohio State University