Quantitative analysis of rotating gamma camera thallium-201 scintigrams of myocardium.

Detection of defects in myocardial uptake of thallium-201 has been investigated by tomography with a rotating gamma camera. Twenty patients, 17 of whom had symptoms suggestive but not diagnostic of angina, and three with definite angina, underwent exercise ECG testing. Thallium-201 was injected at peak stress, followed by tomographic imaging with 180 degree data collection. A repeat study 4 h later showed the resting blood flow (redistribution) pattern. Transverse, coronal and sagittal sections were reconstructed and stress and redistribution studies compared. Quantitative comparison of T1-201 uptake in the stress and redistribution sections was investigated using profile analysis. These results were compared with a visual assessment. Tomographic images clearly showed defects in myocardial uptake and enabled scans to be classified definitely as normal, ischaemic or showing previous myocardial infarction. Results agreed with those from exercise ECG where ECG findings were definite, and gave a clear diagnosis in cases with equivocal ECG results. Significant differences were demonstrated between stress and resting uptake profiles for all segments judged ischaemic on stress from the images alone. A 'normal' profile was obtained to permit identification of infarcted regions. While quantitative analysis enabled the tomograms to be classified objectively, qualitative assessment was equally effective in nearly every case, possibly due to the clear and unconfusing image presentation.