No woman's breast tissue is the same, so MRIs detecting and monitoring cancer should not treat them all the same. Without a way to prove that a new MRI technique is safe for all women, clinical MRIs haven't been able to keep pace with the latest advances in MRI research. 

More informative cancer detection is possible with stronger magnetic fields that also, unfortunately, increase the risk of tissue heating during a screening. Purdue University researchers have simulated how over 20 different breast tissue ratios respond to heat given off by MRIs at higher field strengths than available in hospitals today.

MRI screening

The simulations would allow cutting-edge MRI techniques to finally show that they meet safety limits, as defined by entities like the U.S. Food and Drug Administration, and start clinical trials for real-life use.

On the flip side, using knowledge about how much radiofrequency energy each breast tissue ratio can handle, new techniques could one day target the heat produced from an MRI at tumors to kill them.

Published findings are featured in the journal Magnetic Resonance in Medicine, and software code for the simulations is available open-access to the scientific community via Github.

The work aligns with Purdue's giant leaps celebration, acknowledging the university's global advancements made in health, space, artificial intelligence and sustainability as part of Purdue's 150th anniversary. Those are the four themes of the yearlong celebration's Ideas Festival, designed to showcase Purdue as an intellectual center solving real-world issues.

Despite the limitations of clinical field strengths, a yearly MRI screening is still recommended for women with higher than average risk of breast cancer because it's more sensitive than a standard mammogram.

"We are starting to develop techniques at high field strengths that could immediately monitor how tumors respond to treatment. So we don't want tissue heating concerns to stand in the way of improving such a powerful tool," said Joseph Rispoli, Purdue assistant professor of biomedical engineering and electrical and computer engineering.

How dense a woman's breast is determined by how much radiofrequency energy from an MRI the breast will absorb in the form of heat, defined as the specific absorption rate (SAR). The more fibroglandular tissue in the breast compared with fat tissue, the higher the breast density and SAR.

But not all women have the same ratio of fibroglandular to fat tissue. This makes it harder for researchers to show that a potentially life-saving MRI technique is safe for every woman, even though the risk of overheated tissue is generally low.

"In hospitals, MRI field strengths are currently up to 3 teslas, Tesla being the unit we use for measuring magnetic field strength," Rispoli said. "Many techniques would be far superior at 7 teslas. This would come at a fivefold increase in SAR, but also double the MRI sensitivity."