Should caution be exercised with regard to the use of cardiac magnetic resonance?

Researchers at the GIGA-Cardiovascular Sciences laboratory of the University of Liege are advising caution with regard to repeated use of cardiac magnetic resonance, a commonly-used radiological examination. They showed that this examination induced signals that mimic DNA double-strand breaks in T lymphocytes, but that this effect, which is slight and temporary, disappears after one year. However, they still need to demonstrate the presence of such DNA double-strand breaks. If their results are confirmed, they will suggest a prudent approach to the use of this technology.

IRMIn the area of medical imaging technology. Cardiac Magnetic Resonance  (cardiac MRI) is a radiological examination that is increasingly used for diagnosing and monitoring heart conditions. "This technology makes possible not only to study the structure of the heart but also to provide information on heart function and eventual disease, it is a very particular examination in extremely high definition. In comparison with chest radiography, scanners or scintigraphy, it has the advantage of being a non-ionizing technique", explains Professor Patrizio Lancellotti, a cardiologist and director of GIGA-cardiovascular  (ULg).

In use for about twenty years, CMR has always been considered to be a harmless examination due to the fact that it does not emit ionizing radiation. However, some years ago, in vivo  and studies showed that there were possible alterations to cellular DNA and, particularly, to T lymphocytes. He continues, "As a cardiologist, I considered that it was essential to verify, support and complete these studies because this technique is more and more being used. This is a very important issue because if the results of the study are wrong it means that the technology is so harmless that it can be used a lot more in view of the fact that it provides very interesting information".

The GIGA-cardiovascular team, headed by Professor Lancellotti, Dr. Cécile Oury, biologist and researcher at the FNRS, and Dr. Alain Nchimi, radiologist, evaluated the early and late biological response of blood cells to CMR. (1)

These scientists enrolled 20 healthy males, with an average age of 20 who were asked not to practice intense sports activities and from whom they took blood samples before and after (1-2 hours, 2 days, 1 month and 1 year) a CMR examination. The number of blood cells (lymphocytes, monocytes, neutrophils, platelets...) and their activation status, as well as apoptosis were measured. They used a marker, a variant of phosphorylated histone, gamma-H2AX, considered to be the best marker of DNA damage induced by ionizing radiation: an increase in the levels of gamma-H2AX in circulating T lymphocytes, for example, very accurately reflects the induction of DNA double-strand breaks by ionizing radiation.  

The double-strand breaks signals return to baseline levels after one year

So what were the results? Professor Lancellotti and his colleagues were able to observe a slight but significant increase in the level of gamma-H2AX after 2 days and 1 month post-CMR. This DNA damage did not, however, induce the apoptosis of the T lymphocytes and activation of the T lymphocytes was not observed.

"We analysed the different sub-populations of lymphocytes: none of them was more marked than another. But the T lymphocytes are the most important in this case because these are the longest-lasting blood cells. Therefore if DNA damage accumulates in these T lymphocytes, that can have a real impact in the long term. This is why we have advised caution if the examinations are to be repeated several times in the same month", comments Cécile Oury

1 Biological Effects of Cardiac Magnetic Resonance on Human Blood Cells, Circ Cardiovascular Imaging 2015; 8:e003697

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