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Usefulness of reinjection image for evaluating viable myocardium in the infarcted zone on exercise thallium-201 SPECT
S Tomiguchi1, M Takahashi, O Shimomura
1Department of Radiology, Kumamoto University School of Medicine, Japan.
Insights
Reinjection imaging using thallium-201 SPECT better assesses myocardial viability in patients with infarction. This technique reveals more viable myocardium compared to delayed imaging, especially when initial scans show limited redistribution.
Area of Science:
- Nuclear Medicine
- Cardiology
- Medical Imaging
Background:
- Myocardial infarction (MI) assessment relies on imaging to identify viable heart muscle.
- Standard thallium-201 SPECT (TSPECT) with delayed imaging can underestimate myocardial viability.
Purpose of the Study:
- To evaluate the efficacy of reinjection TSPECT for assessing myocardial viability in patients post-MI.
- To compare the redistribution index (RI) between 4-hour delayed and reinjection TSPECT images.
Main Methods:
- 23 patients with MI underwent exercise TSPECT with immediate, 4-hour delayed, and reinjection thallium-201 imaging.
- A redistribution index (RI) was calculated from perfusion defect changes on polar maps.
- Comparison of RI between delayed and reinjection imaging was performed.
Main Results:
- Reinjection imaging showed a significantly greater RI (46%) than 4-hour delayed imaging (26%) in MI patients (p<0.01).
- Four out of nine patients (44%) with no significant redistribution on delayed images showed significant redistribution after reinjection.
- Improved redistribution on reinjection correlated with less coronary artery disease and better collateral development.
Conclusions:
- Reinjection TSPECT improves the assessment of viable myocardium in the infarcted zone compared to standard delayed imaging.
- The technique is particularly recommended for patients with no or partial redistribution on 4-hour delayed images.
- Reinjection imaging may reflect collateral function in the resting state, aiding viability assessment.
Abstract:
Reinjection images were obtained in 23 patients with myocardial infarction by the additional injection of 37 MBq of thallium-201 after obtaining 4 hour delayed images on exercise thallium-201 SPECT (TSPECT). A redistribution index (RI) was derived of the changes in perfusion defects between immediate and 4 hour delayed images as well as immediate and reinjection images on polar bull's eye maps. The RI of reinjection images (46 +/- 27%) was significantly greater than that of 4 hour delayed images (26 +/- 26%) in patients with myocardial infarction (p less than 0.01). Significant redistribution after reinjection occurred in 4 of 9 patients (44%) without significant redistribution on 4 hour delayed images. Improvement in redistribution on reinjection images correlated significantly to the small extent of coronary artery disease and collateral development. The appearance of redistribution from 4 hour delayed imaging to reinjection imaging also might reflect the function of collateral development in the resting state in patients without significant redistribution on 4 hour delayed images. It has been demonstrated that underestimated viable myocardium on 4 hour delayed images in the infarcted zone can be better assessed on reinjection images. This reinjection technique is recommended in patients with no or partial redistribution on 4 hour delayed images.