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Characterization of the reinjection thallium image
P Pieri1, K A McKusick, A J Fischman
1Department of Radiology, Massachusetts General Hospital, Boston 02114.
Summary
Thallium-201 (201TI) reinjection imaging in cardiac stress tests reveals decreased myocardial activity in normal patients. In men, higher reinjection myocardial activity than initial activity suggests increased likelihood of coronary artery disease (CAD).
Area of Science:
- Nuclear Cardiology
- Cardiovascular Imaging
- Radiopharmaceutical Applications
Background:
- Planar 201Thallium (201TI) cardiac stress tests are standard for diagnosing coronary artery disease (CAD).
- The impact of reinjection imaging on myocardial uptake and its correlation with CAD requires further elucidation.
Purpose of the Study:
- To analyze 201TI myocardial activity after reinjection in patients undergoing cardiac stress tests.
- To determine the influence of reinjection on image characteristics and its association with CAD probability, particularly in male patients.
Main Methods:
- Analysis of stress and reinjection 201TI data from 204 patients; redistribution data from 63 patients.
- Measurement of maximum count densities in myocardium, lung, and liver; calculation of stress/redistribution and stress/reinjection ratios.
- Comparison of imaging findings between normal (<5% CAD probability) and abnormal (>5% CAD probability) groups, with subgroup analysis by sex.
Main Results:
- In normal patients, reinjection decreased myocardial activity (initial/reinjection ratio = 1.22).
- In male patients with >5% CAD probability, peak myocardial activity post-reinjection was influenced by interval, dose, and scan results (abnormal: initial/reinjection = 1.06).
- Myocardial activity post-reinjection correlated linearly with redistribution activity (r=0.82); no significant sex-based differences were observed in women.
Conclusions:
- Myocardial 201TI activity decreases after reinjection in normal individuals.
- Elevated 201TI myocardial activity on reinjection compared to the initial image increases the likelihood of underlying CAD in men undergoing stress tests.