Off-resonance binomial preparatory pulse technique for high sensitivity MRI of H2O17.
H2O17 is a freely diffusible tracer and naturally occurring isotope of O16 detectable by MRI and has been shown to be useful for assessing cerebral perfusion in animal studies using direct and indirect MR detection techniques. However, earlier MR techniques are either not sensitive to changes in small concentrations of tissue H2O17 or are not practical for use on clinical scanners. In this work, a novel method for detecting H2O17 with high sensitivity has been proposed that uses a short, intense, binomial preparatory spin lock pulse with resonance offsets for high sensitive rapid, multislice imaging of tissue H2O17. Two sets of phantom experiments were performed on the 1.5 T and repeated on 3.0 T to assess the feasibility of the proposed technique. The phantom was constructed using ovalbumin and doped with 0.4 atom% and 1.0 atom% H2O17. After obtaining initial parameters, the proposed technique was validated in an anesthetized primate model that was injected with 1.8 cc of 40 atom% H2O17. Phantom experiments showed that the proposed technique was able to detect H2O17 with relatively high sensitivity and high B1 amplitude (and small offsets) preparatory pulses produced similar results as low B1 amplitude (and larger offsets). Primate brain study showed a 42.97% difference in mean signal intensity between pre- and post-H2O17 injection. The proposed technique was successfully implemented on a clinical scanner and was able to detect H2O17 with relatively high sensitivity. Primate study has shown that such a technique can be successfully used for human imaging applications to investigate and assess cerebral perfusion.
Radiological Sciences Laboratory, Lucas MRI Center, Department of Radiology, Stanford University, Stanford, CA 94305, USA. rohit@s-word.stanford.edu
Rohit
R
Sood
D000818:Animals; D001921:Brain / Q000033:anatomy & histology*; D002560:Cerebrovascular Circulation; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D010103:Oxygen Isotopes; D019047:Phantoms, Imaging; D012453:Saimiri; D014867:Water
D010103:Oxygen Isotopes; D014867:Water