Dynamic CT Angiography after Abdominal Aortic Endovascular Aneurysm Repair: Differences in Contrast Agent Dynamics in the Aorta and Endoleaks-Preliminary Results
ABSTRACT To assess differences in aortic and endoleak enhancement in patients after endovascular aneurysm repair (EVAR) with dynamic computed tomography (CT) angiography.
Twenty-one consecutive patients (mean age, 74.5 y ± 6; range, 61-88 y) with endoleaks after EVAR of the abdominal aorta were examined on a second-generation dual-source CT unit with 10 unidirectional scan phases (temporal resolution, 5 s; 80 kV; 120 reference-mAs; z-axis field of view, 283 mm), followed by a venous scan phase. Enhancement was assessed in aorta and endoleaks for all phases by density measurements. The diagnostic reliability of endoleak detection was assessed on a five-point confidence scale.
In total, 26 endoleaks (type I, n = 1; type II, n = 25) were detected. The highest detection rate was found in phase 5 (22 s after threshold; P < .01 vs other dynamic phases). Mean peak aortic enhancement (560 HU ± 96) was present in an early arterial phase (phase 3, 12 s after threshold), whereas the mean peak endoleak enhancement (398 HU ± 174) for type II endoleaks was present later, in phase 4 (17 s after threshold). Despite perceived high diagnostic confidence in phases 1 and 2 (ie, typical arterial phase of biphasic CT protocol), only 23% and 62% of endoleaks were detected, respectively, whereas peak diagnostic confidence (phases 4 and 5) corresponded well with the maximum endoleak detection rate but decreased significantly in later phases (ie, 6-10).
Preliminary dynamic CT angiography results in post-EVAR follow-up revealed notably different peaks of endoleak and aortic enhancement, which are not covered sufficiently by conventional biphasic CT protocols. Phase 5 demonstrated the highest type II endoleak detection rate, with high diagnostic confidence.
[Show abstract] [Hide abstract]
ABSTRACT: Background: Vascular contrast-enhanced ultrasound (CEUS) is a special ultrasound application without the harmful side effects of nephrotoxicity and radiation exposure. CEUS can be used for advanced diagnosis of carotid stenosis and follow-up checks of endovascular repair of abdominal aortic aneurysms (EVAR). Low-flow phenomenon in peripheral vascular disease can easily be detected by enhanced colour-coded duplex sonography (CCDS). Methods: The technical requirements of CEUS are explained here for the aorta, carotid, and peripheral arteries. The benefits and risks compared to computed tomography (CT), magnetic resonance (MR) and angiography are evaluated. Based on a selective review of the literature and the authors' personal experiences, CEUS is recommended for routine surveillance after EVAR. Results: CEUS is a safe method using SonoVue® (Bracco) as the only approved agent for vascular examination. Special equipment and training is necessary. In prospective studies and meta-analyses the detection and characterisation of endoleaks is comparable to that of CT imaging. Neovascularisation as a sign of carotid plaques at risk can be seen without the need for invasive treatment. Imaging of crural vessels with enhanced CCDS is a promising but rarely needed option in diabetic and renally insufficient patients. Conclusion: CEUS in vascular medicine should be performed prior to other methods to avoid nephrotoxic contrast agents for the patients, especially in follow-up checks after EVAR. The time and effort required are still limiting its practical breakthrough.Zentralblatt für Chirurgie 12/2013; 139(5). DOI:10.1055/s-0033-1351028 · 1.19 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: Purpose:To determine the time course of enhancement patterns in the aorta and endoleaks at dynamic computed tomographic (CT) angiography as well as their effect on the endoleak detection rate in patients who have undergone abdominal aortic endovascular aneurysm repair (EVAR).Materials and Methods:This retrospective study was approved by the local ethics committee and compliant with the Declaration of Helsinki. All patients gave written informed consent for the scientific analysis of their data. Seventy-one patients (mean age, 72 years ± 8 [standard deviation]) were retrospectively included after EVAR of the abdominal aorta. All patients underwent dynamic CT angiography with 10 unidirectional scan phases, followed by a venous phase. Endoleaks were detected visually in all scan phases; the magnitude of enhancement was assessed by using region-of-interest measurements in the aorta and the detectable endoleaks. Statistical analysis was performed with the χ(2) test, the paired t test, and analysis of variance with repeated measurements.Results:The highest mean aortic enhancement was achieved 12 seconds after the bolus-tracking threshold, and the highest mean endoleak enhancement was achieved 22 seconds after the bolus-tracking threshold. In total, 44 endoleaks were detected. The detection rates differed significantly in between the dynamic CT angiography phases (minimum, seven endoleaks at 2 seconds after the bolus-tracking threshold; maximum, 44 endoleaks at 27 seconds after the bolus-tracking threshold; P = .001). The highest detection rate was achieved when the contrast between aortic and endoleak enhancement reached its maximum.Conclusion:Dynamic CT angiography revealed that the peak enhancement of endoleaks is significantly different than that of the aorta and that endoleaks may not be adequately evaluated with conventional biphasic CT protocols. The use of dynamic CT angiography is associated with a significantly increased detection rate of endoleaks compared with the detection rates at the time points of conventional biphasic CT.© RSNA, 2013.Radiology 04/2013; 268(3). DOI:10.1148/radiol.13120197 · 6.21 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: Purpose: To assess the feasibility and diagnostic performance of dynamic volumetric computed tomography (CT) angiography with large-area detectors in the detection and classification of endoleaks after endovascular aneurysm repair (EVAR). Materials and Methods: Low-dose dynamic volumetric CT angiography performed with the patient in Fowler position was used to scan the entire stent graft with a 16-cm-area detector during the first follow-up examination after EVAR. There were 39 consecutive patients (36 men and 3 women; mean age, 74 y +/- 8.7) examined with approximately 14-20 intermittent scans (temporal resolution, 2 s; scan range, 160 mm). The effective radiation dose, image quality, interobserver and intraobserver agreement for endoleak detection, and time delay between peak enhancement of the aorta and endoleaks were evaluated. Results: All examinations with the patient in Fowler position enabled the entire stent graft to be scanned and were rated as diagnostic. The mean effective radiation dose was 13.1 mSv. Endoleaks were detected in eight patients (type Ia, n = 1; type II, n = 6; type III, n = 1). Interobserver agreement (kappa = 0.794) and intraobserver agreement (kappa = 1.00) for detection of endoleaks were excellent. The mean time delay between peak enhancement of the aorta and the endoleaks was significantly less for type I/III endoleaks (2.0 s +/- 0) compared with type II endoleaks (5.3 s +/- 1.0; P < .001). Conclusions: Low-dose dynamic volumetric CT angiography performed with the patient in Fowler position is feasible after EVAR. Dynamic information, including cine imaging, the timing of peak enhancement, and the Hounsfield units index, is useful in detecting and classifying endoleaks.Journal of vascular and interventional radiology: JVIR 05/2014; 25(8). DOI:10.1016/j.jvir.2014.03.019 · 2.15 Impact Factor