MR-Based Attenuation Mapping of the Pelvis Using 3D UTE DIXON at 3T

Christian Stehning¹, Michael Helle², Stefanie Remmele³, Melanie Kotys-Traughber⁴

MR-based radiation therapy planning (RTP) and hybrid PET/MR systems require a complete segmentation of bone, soft tissue, and air for attenuation correction. Conventional MRI sequences cannot reliably differentiate between air and bone. While promising results for cortical bone were obtained with 3D ultrashort echo time imaging (UTE) in the knee and head, UTE bone imaging in the pelvis is more demanding due to the significantly larger FOV. A UTE Dixon sequence and reconstruction workflow is presented, which provides good in vivo image quality and reliable bone segmentation over a 400mm FOV. This is an integral component of emerging application such as MR-based therapy planning, and hybrid PET/MR systems.