Dual-Energy CT zur postoperativen Langzeitkontrolle nach endovaskulär therapierten abdominellen Aortenaneurysmen

Zusammenfassung

Ziel: Ziel dieser Studie war es, zu ermitteln, ob in der postoperativen CT-Nachsorge nach endovaskulär therapierten abdominellen Aortenaneurysmen (EVAR) die Strahlenexposition durch virtuelle Nativbilder aus der Dual Energy CT reduziert werden kann. Darüber hinaus sollte untersucht werden, ob die Darstellung von Endolecks aufgrund der relativen Kontrastanhebung bei niedrigen Röhrenspannungen in der venösen Phase ähnlich gut gelingt wie in der arteriellen Phase.

Material und Methoden: Zwischen Februar 2009 und März 2010 wurden bei 47 Patienten 51 CT-Untersuchungen durchgeführt, bestehend aus Nativscan und arterieller und venöser Phase im Dual-Energy-Verfahren (Protokoll A, Referenzstandard). Aus den Datensätzen der venösen Phase wurden virtuelle Bilder rekonstruiert. In Protokoll B wurden reelle Nativbilder durch virtuelle ersetzt, Protokoll C beinhaltete virtuelle Nativbilder und 80kV-Bilder der venösen Phase. Alle Daten wurden anonymisiert und von zwei unabhängigen Radiologen ausgewertet. Sensitivität, Spezifität, negativ und positiv prädiktiver Wert wurden für Protokoll C berechnet. Für jeden Scan wurde die effektive Dosis ermittelt.

Ergebnisse: Alle in Protokoll A identifizierten Endolecks wurden auch in Protokoll B und C erkannt. Für Protokoll C lagen Sensitivität und negativ prädiktiver Wert bei 100 %, Spezifität bei 94,1 % und positiv prädiktiver Wert bei 89,5 %. Protokoll C führte zu einer Reduktion der Strahlenexposition um 62,45 %.

Schlussfolgerung: Ein Scanprotokoll aus virtuellen Nativbildern und 80kV-Bildern der venösen Phase stellt eine zuverlässige Alternative zur Diagnose von Endolecks nach EVAR dar, bei einer Strahlenreduktion gegenüber dem Standardverfahren um 62,45 %.

Abstract

Purpose: This study investigates the dual-energy procedure for postoperative CT follow-up scans after endovascularly treated abdominal aortic aneurysms. The procedure is analyzed with respect to its sensitivity and specificity as well as the associated radiation exposure.

Materials and Methods: 51 examinations were carried out on 47 patients between February 2009 and March 2010. For each patient, a non-enhanced, an arterial and a venous scan were conducted, the latter two using the dual-energy technology. Virtual images for the non-enhanced phase were reconstructed from the data taken in the venous phase. Protocol A, the reference standard, consisted of non-enhanced images and images of the arterial and venous phase. In protocol B, standard non-enhanced images were replaced by the reconstructed virtual non-enhanced images. Protocol C consisted only of virtual non-enhanced and 80 kV images taken during the venous phase. All data was anonymized and evaluated by two independent radiologists. For protocol C, sensitivity, specificity, negative and positive predictive values were computed. The effective radiation dosage was determined for each scan.

Results: All endoleaks identified in protocol A were found using protocols B and C. For protocol C, the sensitivity and negative predictive value were 100 %, the specificity was 94.1 %, and the positive predictive value was 89.5 %. Compared to protocol A, protocol C reduces the radiation exposure by 62.45 %.

Conclusion: A scan protocol consisting of virtual non-enhanced images as well as 80 kV images taken during the venous phase was found to be a reliable alternative method for diagnosing endoleaks, while reducing the radiation exposure by 62.45 %.

Key words

aorta - CT angiography - aneurysm

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