Do 4-hour reinjection thallium images and 24-hour thallium images provide equivalent information?

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Niel F. Starksen, Vu Ying of California, San Francisco,

CA

In patients with fixed TM01 myocardial perfusion defects at 4 hours, 24-hour delayed images improve the assessment of injection with Tl-201 myocardial redistribution and viability. redistribution. Fortyprior to 4-hour imaging appears to enhan seven consecutive patients with recognized 4-hour defects on screening planar images were reinjected witb I-1.SmCi of TI-201 and underwent SPECT thereafter (4 hours) and at 24 hours; 36 patients were men, I1 were women. Their mean age was 66 yrs. Stress was dynamic in 31 patients and pharmacologic in 16. Twenty-one patients had a history of prior infarction. In 41/47 patients (87%). 24.hour redistribution SPECT images showed no further redistribution beyond /I-hour postreinjection (PR) SPECT images. However, the 24-hour image in 6/47 patients revealed limited further redistribution in the same coronary beds identified at 4 hours PR. The findings were not likely to be clinically significant. lo l/47 patients there was redistribution at 24 hours in vascular regions that appeared to have fixed perfusion defects at 4 hours PR. This was likely of clinical significance. This patient and 4 of the 6 other patients with discordant 4-hour PR and 24-hour findings presented with acute or chronic rest pain, suggestin ischemia at the time of reinjection. In most patients, 4-hour post-r the same information that appears in 24-hour redistribution images. Patients with acute or unstable pain syndromes may benefit from additional delayed imaging even after 4-hour reinjection.

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