Pulmonary thromboembolism: a retrospective study on the examination of 991 patients by ventilation/perfusion SPECT using Technegas

Summary

Purpose: Conventional planar ventilation/perfusion (V/P)- imaging in those patients suspected of suffering from pulmonary thromboembolism (PTE) is of limited diagnostic value. It is the purpose of this retrospective study to determine whether the use of V/P- SPECT using Technegas might reduce the rate of those diagnostic uncertainties and might lead to better results. Methods: 991 patients (660 female, 331 male, age 18-90, mean 60), referred to our laboratory with suspected PTE, were examined as follows: patients inhaled 37 MBq of Technegas in the supine position and a SPECT-acquisition was started. Following SPECT-completion, 185 MBq 99mTc-MAA was injected intravenously. SPECT was then repeated. Coronal and transverse ventilation and perfusion SPECT-slices were reconstructed and compared section by section. 85 patients underwent control scans by the same technique at a mean interval of 22 months after the original scans. Results: As the SPECT images in almost all cases made a clear match/mismatch decision possible, we categorized all patients as embolic (PTE+) if there was at least one mismatching defect, and as non embolic (PTE-) if there were none. Our results were: PTE +: 178 patients (18%), PTE-: 808 patients (81%), uncertain: 5 patients (0.5%), if 34 triple-match defects are included: 39 patients (3.9%). 46 patients, categorized as PΪE+ underwent a control V/P scan after anticoagulant therapy. In 44 of these patients, PTE was confirmed by the controls. In a control group of 39 PTE- patients, control scans were unchanged in 38 cases. From these observations we can calculate a sensitivity of 96% and a specificity of 97%. Conclusion: We conclude that V/P imaging can be improved significantly by V/P SPECT using Technegas.

Zusammenfassung

Ziel: Bei der Fragestellung einer Lungenembolie ist die konventionelle planare Venlilations-/Perfusionsszinti-graphie (V/P-Szintigrafie) mit diagnostischen Unsicherheiten behaftet. Die vorliegende retrospektive Studie hat den Zweck, festzustellen, ob der Einsatz der SPECT-Technik unter Verwendung von Technegas die Rate dieser Unsicherheiten reduzieren kann. Methode: 991 Patienten (Pat., 660 weiblich, 331 männlich, Alter 18-90) mit der Verdachtsdiagnose einer Lungenembolie wurden in folgender Weise untersucht: Inhalation von 37 MBq Technegas in liegender Position mit anschließender SPECT-Akquisition. Im Anschluss i.v. Injektion von 185 MBq Tc99m-MAA, gefolgt von einer weiteren SPECT-Akquisition. Rekonstruktion koronaler und transversaler Ventilations- und Perfusionsschnitte und Schicht- für Schicht-Vergleich. Bei 85 Pat. fanden in gleicher Technik Kontrollszintigramme im mittleren Abstand von 22 Monaten statt. Ergebnisse: SPECT-Bilder erlauben in der Regel eine klare Einstufung, ob ein Match- oder ein Mismatch-Befund vorliegt. Wir haben alle Pat. als emboliebehaftet (PTE+) eingestuft, bei denen wenigstens ein Mismatch-Defekt nachzuweisen war, und ansonsten als emboliefrei (PTE-). Damit erhielten wir folgende Resultate: PTE+: 178 Pat. (18%), PTE-: 808 Pat. (81%), unsicher: 5 Pat. (0,5%), unter Hinzuziehung von 34 Pat. mit Triple-match-Befunden: 39 Pat. (3,9%). Bei 46 PTE+-Pat. bestätigte sich die Diagnose in den Verlaufskontrollen in 44 Fällen. Bei 39 PTE—Pat. zeigte sich nur in einem einzigen Fall in der Verlaufskontrolle eine Embolie. Daraus ergibt sich eine Sensitivität des Verfahrens von 96% und eine Spezifität von 97%. Schlussfolgerung: V/P-SPECT unter Verwendung von Technegas führt zu einer signifikanten Verbesserung der Aussagekraft der Lungenszintigraphie beim Verdachtsfall Lungenembolie.

Keywords

Pulmonary embolism - V/P-scanning - SPECT - Technegas

Schlüsselwörter

Lungenembolie - Ventilations-/Perfusionsszintigraphie - SPECT - Technegas

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