• The Korean Journal of Nuclear Medicine
• /
• v.30 no.1
• /
• pp.95-103
• /
• 1996

Reverse redistribution(RRD) refers to a perfusion defect that develops or becomes more evident on rest imaging compared with the stress imaging. This phenomenon was not uncommonly noted on myocardial perfusion single photon emission computed tomography (SPECT). However, the clinical significance and pathophysiological mechanism of RRD were unclear. The aim of this study was to evaluate the incidence and clinical significance of RRD on either dipyridamole T1-201 or Tc-99m MIBI myocardial perfusion SPECT. RRD was defined as ${\geq}10%$ decrease in relative T1-201 and Tc-99m MIBI uptakes on rest images compared to the stress images or as an appearance of new perfusion defects on rest images. It was observed in both T1-201 (44/463, 9.5%) and Tc-99m MIBI (124/999, 12.4%) myocardial SPECTs similarly, with an overall incidence of 11.5%(168/1462). Many apparent)y unrelated disease groups showed the finding: post-revascularization(53.9%), coronary artery disease(24.6%), myocardial infarction(12.3%), and those with normal coro-nary arteries (9.2%). Clinical and angiographic characteristics of 65 consecutive patients who underwent coronary arteriography in 168 patients who had RRD on myocardial perfusion SPECT were reviewed. Tc-99m MIBI was used in 44 patients, and T1-201 was used in 21 patients. Of the 81 myocardial segments analyzed which showed RRD, 32 segments(39.5%) were in septum, 24(29.5%) in inferior wallL, 12(14.8%) in anterior wall, 7(8.7%) in apex and 6(7.4%) in lateral wall. There was no clear association between RRD and coronary arterial stenosis or Presence of collateral circulations. Ventriculographical wall motion was evaluated in 27 regions with RRD; it was normal in 12 regions, hypokinetic in 12 regions and dyskinetic in 3 regions. In 14 of 21 patients who showed RRD on T1-201 myocardial SPECT, T1-201 reinjection was performed immediately after the 3-4 hour redistribution studies. Ten of 14 (71.4%) showed enhanced T1-201 activity(${\geq}10%$ increased) after reinjection. We conclude that RRD is not related to mode of stress or radiopharmaceuticals. RRD might represent many inhomogeneous pathophysiological processes.

• The Korean Journal of Nuclear Medicine
• /
• v.37 no.4
• /
• pp.219-228
• /
• 2003

Purpose: The amount of salvaged myocardium is an important prognostic factor in patients with acute myocardial infarction (MI). We investigated if early Tl-201 SPECT imaging could be used to predict the salvaged myocardium and functional recovery in acute MI after primary PTCA. Materials and Methods: In 36 patients with first acute MI treated with primary PTCA, serial echocardiography and Tl-201 SPECT imaging ($5.8{\pm}2.1$ days after PTDA) were performed. Regional wall motion and perfusion were quantified with on 16-segment myocardial model with 5-point and 4-point scaling system, respectively. Results: Wall motion was improved in 78 of the 212 dyssynergic segments on 1 month follow-up echocardiography and 97 on 7 months follow-up echocardiography, which were proved to be salvaged myocardium. The areas under receiver operating characteristic curves of Tl-201 perfusion score for detecting salvaged myocardial segments were 0.79 for 1 month follow-up and 0.83 for 7 months follow-up. The sensitivity and specificity of Tl-201 redistribution images with optimum cutoff of 40% of peak thallium activity for detecting salvaged myocardium were 84.6% and 55.2% for 1 month follow-up, and 87.6% and 64.3% for 7 months follow-up, respectively. There was a linear relationship between the percentage of peak thallium activity on early redistribution imaging and the likelihood of segmental functional improvement 7 months after reperfusion. Conclusion: Tl-201 myocardial perfusion SPECT imaging performed early within 10 days after reperfusion can be used to predict the salvaged myocardium and functional recovery with high sensitivity during the 7 months following primary PTCA in patients with acute MI.

• The Korean Journal of Nuclear Medicine
• /
• v.4 no.1
• /
• pp.19-26
• /
• 1970

1. Sixteen normal healthy subjects free from occult blood in the stool were selected and administered with their $^{51}Cr$ labeled own blood via duodenal tube and the recovery rate of radioactivity in feces and urine was measured. The average fecal recovery rate was 90.7 per cent ($85.7{\sim}97.7%$) of the administered radioactivity, and the average urinary excretion rate was 0.8 per cent ($0.5{\sim}1.5%$) 2. There was a close correlation between the amount of blood administered and the recovery rate from the feces; the more the blood administered, the higher the recovery rate was. It was also found that the administration of the tagged blood in the amount exceeding 15ml was suitable for measuring the radioactivity in the stools. 3. In five normal healthy subjects whose circulating erythrocytes had been tagged with $^{51}Cr$, there was little fecal excretion of radioactivity (average 0.9 ml of blood per day). This excretion is not related to hemorrhage and the main route of excretion of such an negligible radioactivity was postulated as gastric juice and bile. 4. A comparison of the radioactivity in the blood and feces of the patients with $^{51}Cr$ labeled erythrocytes seems to be a valid way of estimating intestinal blood loss.