Maximum sound pressure levels at 7 Tesla – what’s all this fuss about?

Introduction The acoustic noise during image acquisition is a well-known problem in MRI, which is especially pronounced during fast imaging with high gradient slew rates and at high field strengths. Patients can be exposed to sound pressure levels (SPL) as high as 130 dB [1] and more on clinical 3 Tesla MR systems. As the SPL increases linearly with gradient amplitude [2] the SPL of a 7T System approximates 140 dB, which is far beyond the human pain threshold. In this work the acoustic resonances of a 7 T system were examined and the linear dependency of the sound pressure on the gradient amplitude were verified. Moreover the protocols of three different, fast imaging sequences were adjusted on the scanners resonances so that they generate a maximum SPL. The sequence’s SPL values were measured and compared to a theoretical maximum value.