Ultrashort Echo Time Imaging of Phosphorus in Man
The 31P nucleus is NMR-visible and exists throughout the human body. The MRI/MRS community has principally focused on the 31P in the high-energy metabolites, which have relatively long T2s. However, using short echo time (TE) methods, it is possible to obtain signal from the short P that is present in the hydroxyapatite of the bone matrix. This article discusses how the signal from these fast-relaxing components can be observed and what we find when imaging them. It is shown that it is possible to collect images of the cortical bone from humans in vivo in clinically practical imaging times. The measured T1 ( ∼ 10 s) and T2* ( ∼ 200 µs) restrict the available signal-to-noise ratio, and at the present time it remains difficult to get high-resolution images, but the technique may offer useful insights into bone disease.