Ultra-short echo time (UTE) magnetic resonance imaging (MRI) allows for visualization of tissues with very short T2 relaxation times. This tissues, which include collagen-rich tisuses such as tendons, ligaments and menisci, as well as calcifications, myelin, periosteum and cortical bone, are normally invisible with conventional MRI techniques.
Long-T2 species suppression is required for many UTE applications to improve the contrast of short-T2 species. We have developed new long-T2 RF suppression pulses. This page provides descriptions and Matlab files for designing these pulses, as well as providing some sample pulses.
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| Normal UTE brain image | Long-T2 suppression with a 16 ms TBW = 2.4 single-band pulse |
These pulses contain a single spectral band for suppressing long-T2 species at the water proton resonance. They can be easily designed using the SLR pulse design algorithm as maximum-phase saturation pulses, as described in Pauly et al, Parameter relations for the Shinnar-Le Roux selective excitation pulse design algorithm (NMR imaging) IEEE Transactions on Medical Imaging 10:53-63 (1991).
The rf_tools Matlab toolbox for SLR RF pulse design is available at Stanford Radiological Science Laboratory Software. With this package, single-band pulses are designed with the command: rf = dzrf(Npoints, TBW, 'sat', 'max'); The pulses can be scaled to various lengths depending on the bandwidth required and/or T2 suppression desired.
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| Normal UTE knee image | UTE knee images using a dual-band long-T2 suppression pulse | |
These pulses contain two spectral bands for suppressing long-T2 species at both the fat and water proton resonances. They are created using the complex Parks-McClellan filter design algorithm.
Bloch Equation Simulator by Brian Hargreaves
Stanford Radiological Science Laboratory Software (includes rf_tools package)