Shashi Khandekar

The incidence of scintigraphically viable and nonviable tissue by rubidium-82 and fluorine-18-fluorodeoxyglucose positron emission tomographic imaging in patients with prior infarction and left ventricular dysfunction

BackgroundAlthough reversible perfusion defects, perfusion-metabolism mismatch and match patterns are important for differentiating viable from nonviable myocardium, the frequency of these scintigraphic patterns has not been reported. The study objective was to establish the incidence of these scintigraphic patterns to estimate the clinical need for metabolic positron emission tomography for evaluating tissue viability in patients with prior myocardial infarction (MI).Methods and Results82Rb perfusion images were interpreted to identify reversible or irreversible defects, followed by determination of their 18F-fluorodeoxyglucose (18F-FDG) uptake pattern. In 155 patients with prior MI, analysis of 613 abnormal segments showed reversible perfusion defects in 13%. The 87% irreversible defects, 18% showed perfusion-metabolism mismatch, whereas 69% showed the match pattern. Reversible perfusion defects and perfusion-metabolism mismatches were noted in 20% (31/155) and 29% (45/155) of patients, respectively, whereas the match pattern was noted in 51% (79/155) of patients.ConclusionIrreversible perfusion defects were common in our patients with prior MI, and distinction between viable and nonviable tissue was not possible by perfusion imaging alone. The identification of hibernating myocardium was possible only with the additional 18F-FDG imaging in about one third of patients. This indicates a significant clinical demand for 18F-FDG imaging that identifies patients who will benefit from revascularization.

Scintigraphic detection of post-pneumonectomy bronchopleural fistulae

Abstract. A total of 20 ventilation studies [16 with xenon-133 and four with technetium-99m diethylenetriamine pentaacetic acid (DTPA)] were performed in 11 patients with suspected post-pneumonectomy bronchopleural fistulae. The findings on the ventilation scan were correlated with bronchoscopy, taken as the gold standard for purposes of comparison. The sensitivity and specificity for 133Xe scans were 83% and 100% respectively, while the sensitivity for 99mTc-DTPA aerosol studies was poor at 0%. Special techniques for optimal visualization of the fistulae are enumerated.