A compound having structure I: wherein xC is selected from the group consisting of 11C, 12C, and 13C; R is selected from the group consisting of —OH, —O−R4+ wherein R4 is selected from the group consisting of Na and K, —OR3 wherein R3 is selected from the group consisting of C1-8 alkyl and C1-8 alkenyl, —NH2, and NHR3; R′ is selected from the group consisting of —H, —Cl, —F, —Br, and —I; R″ is selected from the group consisting of —H, —Cl, —F, —Br, and —I; and R′″ is selected from the group consisting of —H, —Cl, —F, —Br, —I, 18F, 19F, 75Br, 76Br, 77Br, 123I, 124I, and 131I; provided, when xC is 12C, R′″ is selected from the group consisting of 18F, 19F, 75Br, 76Br, 77Br, 123I, 124I, and 131I. Also, a method of imaging in a mammal a medical condition, such as a cancer, lactic acidosis, or cardiac or cardiovascular function by administering to the mammal a composition comprising a compound having structure I and observing the distribution of the compound in the mammal by an imaging modality selected from the group consisting of positron emission tomography (PET) imaging, single photon emission computed tomography (SPECT), gamma camera devices, magnetic resonance imaging (MRI), and hand-held radiation detection probes. In addition, a method of treating a cancer in a mammal by administering to the mammal a composition comprising a compound having structure I.