Differentiation of the Mu-opioid ligand GSK1521498 from naltrexone using [11C]carfentanil PET and fMRI. - John D. Beaver; Edward T. Bullmore; Graham E. Searle; Christopher J. Long; Samuel P. Hill; Jonathan Howard; Pradeep J. Nathan; Paul M. Matthews; Roger N. Gunn; Eugenii A. Rabiner (NeuroImage, 2010)