Simple approach for increasing SNR, reducing breast shading and improving fat suppression at 3T

Introduction Due to its exquisite sensitivity, breast MRI is becoming more and more popular for screening high-risk patients and for detecting high-grade ductal carcinoma in situ [1]. While 3T breast imaging yields clear benefits, such as increased SNR, allowing higher temporal or spatial resolution, it also comes with certain drawbacks. Most importantly, complaints about image shading and improper fat suppression emerged [2], slowing down the transition of breast MRI studies to 3T. Inhomogeneous B0, inhomogeneous B1, and inhomogeneous B1 were all blamed in the past as main sources of these problems [2]. Typical image post-processing approaches, used in the past for shading correction [3], cannot recover lost SNR due to improper local flip angle. While parallel transmit systems were suggested in the recent past as possible solutions [4], such systems are not the current clinical standard. Consequently, simpler solutions, capable to mitigate breast image artifacts in the thousands of existing 3T MRI scanners are needed. In this work, the origin of shading and improper fat suppression at 3T is investigated. It is found, through simulations and experimental data acquisitions, that a bimodal distribution of the excitation field is the main source of the artifacts. A simple solution, based on the addition of a tuned loop over the right breast mitigates image shading, improves fat suppression, and increases image SNR in all volunteers studied.