Intracoronary Thallium-201 Assessment of Thrombolysis in Acute Myocardial Infarction Validation of the Method of Imaging Before and After Therapy

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Abstract
In order to study acute changes in perfusion with intracoronary thrombolytic therapy, 10 times the pretherapy intracoronary 201Tl dose was used for the posttherapy study. Because of the larger posttherapy dose, the posttherapy images had 10 times as many counts as the pretherapy images. Since the change in image quality between the pretherapy and posttherapy studies might affect interpretation, the effect of image statistics on interpretation of perfusion scintigraphy was studied. The pretherapy and posttherapy images were scored on a 4-point scale in 5 segments on each of 3 views. In 31 patients, Poisson-distributed pseudorandom noise was added to the posttherapy study in order to match the statistical accuracy of the pretherapy study. A blinded interpretation of the pretherapy and posttherapy noise-added images was performed in the same way as the initial unblinded interpretation. The mean difference between the unblinded pretherapy and posttherapy scores (the improvement in Tl distribution with therapy) was 2.5+/-0.8 compared with the difference between the blinded pretherapy and posttherapy noise-added scores which was 2.6+/-1.0. The correlation between readings of similar pairs of data was higher than the correlation between pretherapy and posttherapy studies. The difference in statistic quality of the pretherapy and posttherapy studies did not affect the interpretation of these studies. Therefore, the evaluation of pretherapy and posttherapy studies using a 10-fold increase in T-201 dosage is valid.