Motion tracking / correction in PET-MRI
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Attenuation correction in PET-MRI using WASPI
One of the biggest hurdles of PET-MR is the accurate attenuation correction especially for the bone. The standard approach is to segment an MR image volume into different tissue classes and then assign the corresponding attenuation coefficients to them. Due to the lack of signal from solid bone in normal MR sequences, accurate attenuation correction in regions within or near bone is still an open problem. Investigators have proposed atlas-based technique and ultrashort echo time (UTE) pulse sequence based segmentation technique. These approaches might not fully capture the intra- and inter-subject bone density variation, which will inevitably lead to bias in reconstructed PET images.
We investigated using the Water- And fat-Suppressed Proton projection Imaging (WASPI) sequence to obtain accurate and continuous attenuation for the bones which accounts for intra- and inter-subject bone attenuation variations. Using data acquired from a phantom, it was shown that attenuation based on WASPI sequence is more accurate and precise comparing to conventional MR attenuation correction and UTE based segmentation approaches.