rine-18-fluorodeoxyglucose (FDG) single-photon imaging with 20'Tl (1 1—13). To improve detection of reversible ischemia, 24-hr delayed imaging (14—16)or reinjection 20'Tlimaging (17—20) hasbeensuggested. However, little is known about the metabolic activity of these segments. This study is undertaken to compare 20'Tl findings after reinjection with FDG-NH3 PET findings. METHODS Patient Populations The reinjection 20'Tl study was performed in 75 consecutive patients who showed initial perfusion abnormalities on stress 20'Tlimaging.Of these,18patientswererandomlyselected for the PET study. Therefore, this study includes 18 patients who underwentboth reinjection20'Tlimagingand PET imaging.Their agesrangedfrom 50 to 65 yr with a mean valueof 56.6. Fourteen patients had prior myocardial infarction, including 12 Q-wave and 2 non-Q-wave lesions.The interval from the onsetof infarc tion ranged from 2 mo to 8 yr. Coronary angiogramsshowed single-vessel disease in eight, two-vessel disease in five, and three vesseldiseasein fivepatients.Nine vesselsshowed100%occlu sion of the coronary artery. Elevenpatientshad coronary artery bypasssurgeryafter the radionuclidestudy. Thallium-201 Imaging The procedurefor performingstressredistribution and reinjec tion SPECT 20'Tl scanshasbeen fully describedelsewhere(19— 22). Briefly,all patients underwent graded bicycle exercise starting at a 25-watt workload with 25 watt increments every 3 mm. Approximately100MBq (2.7mCi)of20'Tlwereinjectedatpeak exerciseand the exercisecontinued for another minute. Stress 20'Tlimagingbeganwithin10mmafterthetracerinjection.The patientswereaskedto remain sedentaryand refrain from eating anycarbohydratemealsfor the 3-hr interval betweentheir initial and delayedthallium scans.Immediately after the delayedscan, 40 MBq (1.1 mCi) of 201T1 werereinjectedatrest.Tenminutes later, reinjection 20111 imageswererecorded. Single-photonemission computed tomography (SPECT) was recorded using a General Electric 400AC/T model camera equippedwithalow-energy general-purpose collimator,collecting 32projection imagesfor 30 seceachover 180° (19—22). A series Reinjection of thallium-201 after recording the 3-hr delayed scanoftendemonstratesimprovementin areas of persistent abnormalities. To determine the metabolic activity of these areas, the changes seen on stress/redistribution/reinjection thalliumSPECT were comparedwith PET usingfluorine-i8- fluorodeoxyglucose (FDG)in18 patientswithcoronaryartery disease. Of 48 segments showing no redistribution on the delayed scan, the reinjection scan identified new fill-in in 20 segments(42%),all of which demonstratedFDGuptake.In contrast,only 7 of the 28 segments(25%) showingno fill-in after reinjectionwere PET viable(p < 0.01). Elevenpatients had coronary bypass graft surgery after the radionudide study. The majorityof the segments showingredistribution (87%) and new fill-inafter reinjection(65%) improvedinwall motion, whereas only eight segments (25%) without new fill in improvedafter surgery.Of those without new fill-in, two segments showing PET ischemiaimprovedin wall motion, whereas the remainingsix segmentsshowingPET scar did not improveafter surgery.Thus,the segmentsshowingnew fill-in after reinjection are PET viable myocardium. However, reinjection thallium imaging still underestimates the extent of tissue viability compared to PET imaging. J NucI Med 1991; 32:673-678 tress-thallium-201 (20')Tl myocardial imaging hasbeen widely used for detection and characterization of ischemic heart disease (1—5). Although it is valuable to differentiate reversibleischemicmyocardium from irreversiblemyocar dial scar (6—8),it has limited value when the initially hypoperfused areas fail to show definite redistribution on the delayed scan (9,10). Persistent glucose utilization has been observed in some of these areas in a comparative study of positron emission tomography (PET) using fluo Received Aug. 13, 1990; revision accepted Nov. 16, 1990. For reprints contact: NagaraTamaki, MD, Department of Nuclear Medicine, Kyoto University Faculty of Medicine, Shogoin, Sakyo-ku, Kyoto, 606 Japan. 673 . Thallium Reinjection andFOG-PET • Tamaki etal Metabolic Activity in the Areas of New Fill-in After Thaffium-201 Reinjection: Comparison with Positron Emission Tomography Using Fluorine- 18-Deoxyglucose Nagara Tamaki, Hiroshi Ohtani, Keiji Yamashita, Yasuhiro Magata, Yoshiharu Yonekura, Ryuji Nohara, Hirofumi Kambara, Chuichi Kawai, Kazuo Hirata, Toshihiko Ban, and Junji Konishi Department ofRadiology and Nuclear Medicine, Third Division, Department ofinternal Medicine, and Department of CardiovascularSurgery, Kyoto University Faculty ofMedicine, Kyoto, Japan by on January 15, 2016. For personal use only. jnm.snmjournals.org Downloaded from