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Technetium-99m tetrofosmin has been used as a tumor-imaging agent in cases of lung cancer. The authors present a case showing a lung tumor that concentrated Tl-201 distinctly more than Tc-99m tetrofosmin during a dual-isotope cardiac examination. A brief review of the literature is provided and possible explanations for this difference in tracer uptake are discussed.

The prognostic value of symptom-limited treadmill exercise electrocardiography, exercise thallium myocardial perfusion scintigraphy and rest and exercise radionuclide ventriculography was compared in 117 men, aged 54 +/- 9 years, tested 3 weeks after a clinically uncomplicated acute myocardial infarction (MI). During a mean follow-up period of 11.6 months, 8 men experienced "hard" medical events (cardiac death, nonfatal ventricular fibrillation or recurrent MI) and 14 were hospitalized for unstable angina pectoris, congestive heart failure or coronary bypass surgery (total of 22 combined events). By multivariate analysis (Cox proportional hazards model), peak treadmill work load and the change in left ventricular ejection fraction (EF) during exercise were significant (p less than 0.01) predictors of hard medical events; these 2 risk factors and recurrent ischemic chest pain in the coronary care unit were also significantly predictive (p less than 0.001) for combined events. A peak treadmill work load of 4 METs or less or a decrease in EF of 5% or more below the value at rest during submaximal effort distinguished 22 high-risk patients (20% of the study population) from 89 low-risk patients. The rate of hard medical events within 12 months was 23% (5 of 22 patients), vs 2% (2 of 89 patients) in the high- and low-risk patient subsets, respectively (p less than 0.001). Thus, in patients who underwent evaluation 3 weeks after a clinically uncomplicated MI, exercise radionuclide ventriculography contributed independent prognostic information to that provided by symptom-limited treadmill testing and was superior to exercise thallium scintigraphy for this purpose.

A method for background subtraction is presented. The data are digitized scintigraphic images, stored in 64 X 64 frames. Within this array a rectangular area surrounding the target is defined. All data points outside of this area are set equal to zero. From each data point within the area, the computer subtracts a background value equal to the average of the two intersecting linear interpolations between the values at the edges of the rectangular area having the ordinate and abscissa values of the point of interest. The rationale for this approach is discussed and its application in myocardial perfusion studies is illustrated.

Thallium-201 myocardial imaging was performed in seven long-term cardiac transplant survivors who were undergoing selective coronary arteriography as a screening test for immune mediated coronary atherosclerosis. The radionuclide studies showed fixed defects in all patients, though none was known to have had a myocardial infarction. Such abnormalities may be due to previous rejection episodes. Reversible ('ischaemic') defects were present in two patients with triple vessel disease, and were also seen in three subjects with minor (less than 50% luminal diameter) stenosis. Ischaemic thallium-201 defects in cardiac transplant recipients indicate the presence of coronary artery disease, though the stenosis may be of a degree which would normally be considered haemodynamically non-significant. The possible role of small vessel disease in producing these defects is discussed.

A method is presented for the quantitative interpretation of thallium-201 myocardial perfusion studies. The data are planar images collected immediately following the stress injection, and 4 to 6 hours later. Data analysis consists of preprocessing, including thresholding of the original data, and data reduction using a variant of the circumferential profile methods. The profiles are subdivided into segments, and for each segment the difference between the norm and the actual data is computed. This difference is a quantitative symptom, whose size is assumed to be related to the probability of having the disease. The relationship between the size of the symptom in each of nine segments (three segments/view in three views) and the probability of disease is expressed in a table in which for 30 diseases (combinations of vascular lesions) the sensitivity for each of the nine symptoms is described as a Gaussian function whose average and standard deviation are computed from previous validated cases. Using an arbitrary prevalence, the post-testing probability can then be computed using Bayes' formula sequentially. The sensitivities, however, are not expressed as a binary function of the presence or absence of a symptom, but as a distribution function defined by experience. The method is sensitive for the detection of isolated left anterior descending disease (100%) and triple vessel disease (96%). When specific combinations of vascular lesions are recognized the specificity increases from 79% (when unspecified abnormalities are recognized) to 87% when left anterior descending disease or triple vessel disease is recognized.(ABSTRACT TRUNCATED AT 250 WORDS)

Seventy-six thallium-201 myocardial perfusion studies were performed on twenty-five patients to assess their reproducibility and the effect ofvarying the level of exercise on the results of imaging. Each patient had a thallium-201 study at rest. Fourteen patients had studies on two occasions at maximum exercise, and twelve patients had studies both at light and at maximum exercise. Of 70 segments in the 14 patients assessed on each of two maximum exercise tests, 64 (91%) were reproducible. Only 53% (16/30) of the ischemic defects present at maximum exercise were seen in the light exercise study in the 12 patients assessed at two levels of exercise. Correlation of perfusion defects with arteriographically proven significant coronary stenosis was good for the left anterior descending and right coronary arteries, but not as good for circumflex artery disease. Thallium-201 myocardial imaging at maximum exercise is reproducible within acceptable limits, but careful attention to exercise technique is essential for valid comparative studies.

Using the angiographic findings as the standard, we have examined the sensitivity and specificity of ECG-gated static thallium-201 myocardial images in 54 patients undergoing selective coronary arteriography. Gated and nongated images, each in anterior, 45 degrees LAO, and 65 degrees LAO projections, were processed by interpolative background subtraction. They were then analyzed separately by four independent observers who were unaware of patient identity, the results of coronary arteriography, and which studies were gated or nongated. No significant differences were observed between the gated and nongated images regarding sensitivity or specificity, the detection rate for reversible myocardial ischemia, the accuracy of prediction of arteriographic extent of disease, or the degree of inter- or intraobserver variability. We conclude that ECG-gated acquisition of T1-201 images does not produce any significant advantages, at least when interpolative background subtraction is used.