A comparison of the sensitivity of PET and NMR for in vivo quantitative metabolic imaging

Using positron emission tomography (PET) in combination with compounds labelled with positron-emitting radionuclides like ¹¹C, ¹³N and ¹⁵O, it is possible to study metabolism in vivo in a non-invasive way. Nuclear magnetic resonance (NMR) imaging takes advantage of the spin of protons in water molecules to measure both their number and relaxation times in vivo, but is, in principle, not limited to protons and can also be used for other nuclei with a non-zero spin, e.g. ¹³C and ³¹P. The use of ¹³C opens the possibility of studying the metabolism of a large number of compounds. In order to choose the appropriate methodology for metabolic imaging, i.e. PET or NMR, it is important to know the sensitivity of each modality. The present study outlines the sensitivity of both techniques.