Air Susceptibility Effects on Proton Resonance Frequency Temperature Mapping

Markus Nikola Streicher¹, Andreas Schfer¹, Dimo Ivanov¹, Robert Turner¹

MR thermometry is usually based on the temperature dependence of the proton resonance frequency (PRF), thus any magnetic field changes might be misinterpreted as temperature changes. Here we report on the effects of changes of susceptibility of surrounding air on the magnetic field inside an object. When the air was heated by 46 C, its susceptibility changed from χ _air = 3.610^-7 to χ _air = 2.710^-7, inducing an apparent additional temperature change of 1.9C inside the object. For a more realistic surrounding air temperature increase of 10C this could result in an error of 0.75C.