QUANTITATIVE I-123 IMP AND TC-99M HMPAO IMAGING IN THE DOG FOLLOWING COCAINE ADMINISTRATION

SPECT and associated imaging procedures were used in beagle dogs to (1 ) evaluate the uptake, distribution, and clearance properties of i.v.- injected I-123 IMp (IMP) and Tc-99m HMPAO (HMPAO) in the brain, lungs, liver, and kidneys; (2) quantify the acute effects (after 15 sec) of very low doses (0.5 or 1.0 mg/kg) cocaine on the kinetics and localiza tion properties of IMP and HMPAO; and (3) evaluate comparative imaging properties of IMP and HMPAO for measuring regional cerebral blood flo w (rCBF), Regional and global uptake and localization of IMP or HMPAO were evaluated in control studies using dynamic planar (0-30 min) and SPECT imaging (at 35 min). The regional distribution properties of IMP and HMPAO in the brain were estimated from regions of interest (ROIs) drawn around anatomic structures on MR slices and manually registered with corresponding SPECT slices. Cocaine significantly reduced the 30 -min IMP uptake in the brain and lungs by similar to 15%, but only sli ghtly changed HMPAO uptake in the brain and other organs. In the contr ol studies, the respective uptakes of LMP in the brain and lungs were 9 and 39% greater (P < 0.01) than those of HMPAO. In control SPECT stu dies, the highest uptake of IMP was observed in the thalamus and progr essively less activity was observed in the parietal lobe, frontal lobe , cerebellum, occipital lobe, and entire brain; activity in the olfact ory bulb was lower than in all other regions, Cocaine reduced IMP upta ke in the cerebellum (p < 0.01), occipital lobe (p < 0.01), and entire brain (p < 0.05). IMP uptake (cpm/pixel-mCi) in the different brain r egions was 1.3 to 2.1 times greater than that of HMPAO (p < 0.001), HM PAO uptake was more homogeneous throughout the gray matter of the brai n; no significant uptake differences were observed among flagged regio ns. Results indicate that single, acute doses of cocaine, 0.5 and 1.0 mg/kg, significantly altered the uptake and localization properties of LMP in the dog's brain, lungs, liver, and kidneys, Variations in regi onal uptake of IMP in the parietal, frontal, and occipital lobes, cere bellum, and thalamus were greater than with HMPAO.