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Horse Fracture Project (Bone Marrow (MRI (Dixon (Multi-echo for T2*…

- - - - STEAM has less J-coupling, reduces qualification errors when correcting for T2 decay and allows shorter TE for short T2 water component
      - Aim is for PDFF rather than signal-weighted FF
      - Beware chemical shift, can we use sLASER?
      - Robust peak fitting difficult (broad peaks in trabecularised regions) but has been reported
      - NEED MULTIPLE TEs to correct for T2 decay
      - In theory could separate different fat types, but challenging due to overlap with water - poor reproducibility
      - J-coupling in olefinic fat peak minimised for STEAM with TE=100 ms and TM=20 ms
      - MT also used previouslywith PRESS
  - - - Multi-echo for T2* correction, T1 correction (or small flip), multiple peaks in fat spectrum
- - - - General UTE approaches
        
        Dual echo UTE with echo subtraction uses long echo to subtract long T2 components
        
        UTE with rescaled echo subtraction uses scaled FID so that muscle and fat become negative and air hovers around zero
        
        Long T2 sat UTE saturates then crushes long T2 components, or slightly inverts then waits for null. Also subtracted
        
        UTE with off-res sat suppresses cortical bone signal, so subtract from standard UTE to give high contrast bone images
        
        SIR UTE uses single adiabatic IR to invert water and fat. Acquisition happens at a compromise point where water and fat are close to null, but residual signals removed by subtraction of previous image
        
        DIR UTE inverts both water and fat and allows imaging at null point for both
        
        UTE spectroscopic imaging (?)
        
        Phase images can also show good contrast
        
        PETRA and ZTE also mentioned for reduction of blurring
      - Quantitative UTE approaches
        
        T1 by SR or VFA
        
        T2* by multiple TEs but need efficient nulling of long T2 species
        
        Can do biexponentials for bound and free water quantification, but complicated BUT significant correlation with microCT porosity
        
        Direct imaging of bound and free water also possible but difficult
        
        MT also possible but needs specialised sequence