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DOI:10.2214/AJR.05.0532
AJR 2007; 188:W262-W268
© American Roentgen Ray Society

Clinical Observations

Detecting Endoleaks in Aortic Endografts Using Contrast-Enhanced Sonography

Marcus J. Dill-Macky1, Stephanie R. Wilson, Yarron Sternbach, John Kachura and Thomas Lindsay

1 All authors: University Health Network, Mount Sinai Hospital, University of Toronto; and Division of Abdominal Imaging, Princess Margaret Hospital 3-923, 610 University Ave., Toronto, ON M5G 2M9, Canada.

Received April 15, 2005; accepted after revision September 18, 2005.

 
Address correspondence to M. J. Dill-Macky.

WEB This is a Web exclusive article.

This study was partially supported by Bristol-Myers Squibb Medical Imaging.

FOR YOUR INFORMATION

A data supplement for this article features AVI files of a contrast-enhanced sonography sweep and CTA, available in the information box in the upper right corner of the Web page.


Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
OBJECTIVE. We performed this pilot study to investigate the utility of contrast-enhanced sonography for the detection of endoleaks in patients with abdominal aortic endografts.

CONCLUSION. Contrast-enhanced sonography evaluation of abdominal aortic endografts is a technically feasible alternative to our current practice standard.

Keywords: aorta • cardiac imaging • cardiovascular imaging • contrast media • CT • endograft • endoleak • sonography • stents


Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
The significant morbidity and mortality associated with surgical repair of an abdominal aortic aneurysm motivated researchers to develop an endoluminal approach to treatment using grafts designed to exclude the aneurysm by placing a stent across it. These grafts are increasingly used worldwide; their use involves implantation of a metallic self-expanding framework covered with variable nonporous material. The grafts are inserted using a femoral artery cutdown procedure in an interventional suite or operative theater. Aortic endografts are designed to exclude an aneurysm from the systemic circulation and thereby prevent further enlargement and possible rupture.

Incomplete exclusion of an aneurysm results in the leakage of blood into the aneurysmal sac and is termed an "endoleak." Endoleaks are classified according to the origin of the leak: Type I leaks originate from the attachment sites; type II, from retrograde flow in the aortic branches; type III, from between joints in the modular components; and type IV, from graft porosity [1, 2].

The reported incidence of endoleaks varies widely. Endoleaks may develop at any time, although they are most prevalent during the first 30 days after surgery. In recent large series, researchers have reported the incidence of endoleaks at 5.9-22.7% [3-6]. The detection of endoleaks is critical because if untreated, endoleaks may lead to the progressive enlargement of the aneurysm, which then increases the risk of aneurysm rupture [7-9].

The potential benefits of aortic endografts in terms of reducing morbidity and mortality must be balanced against the requirement for life-long surveillance to detect endoleaks and other forms of device failure. The accepted gold standard for monitoring patients with endografts has been life-long annual contrast-enhanced CT and radiography of the abdomen [10]. Unfortunately, however, many treated patients may already have impaired renal function that precludes the use of IV iodinated contrast material and necessitates the use of other methods of evaluation that may be more expensive and less readily available, such as MRI. Annual CT surveillance also carries the risks associated with radiation exposure, although this may be a somewhat less important consideration in the elderly population who are most often treated with this procedure.

Contrast-enhanced sonography could be a practical alternative to CT for annual surveillance because it is readily available, is inexpensive, and can be used safely in patients with impaired renal function. Sonography contrast agents consist of microbubbles that resonate when interrogated with sound of low intensity, as measured by the mechanical index, enhancing backscatter and thereby increasing the detected signal and thus the blood pool contrast. Pulse-inversion imaging is a contrast-specific imaging technique in which two pulses are transmitted for each scanning line. The second pulse is inverted, 180° out of phase, with respect to the first pulse. Echoes from both pulses are collected by the transducer and summed. Linear reflectors, such as normal tissue, produce no net signal. However, nonlinear reflectors, such as microbubbles, produce echoes that are asymmetric and do not sum to zero. The resulting image, obtained using a low-mechanical-index technique, has little signal originating from background tissue and high-intensity depiction of echoes from microbubbles. This produces high image contrast between tissue and microbubble contrast agents within the blood pool. In addition, movement and blooming artifacts are eliminated, thereby allowing real-time depiction of vessels at resolutions afforded by gray-scale imaging [11-13].


Figure 1
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  		Fig. 1A —75-year-old man with type III endoleak. Figures S1G and S1H are available in supplemental data. Images from arterial phase contrast-enhanced sonography cine loop sweep show endoleak (arrows) between enhancing iliac limbs of endograft.

 


Figure 2
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  		Fig. 1B —75-year-old man with type III endoleak. Figures S1G and S1H are available in supplemental data. Images from arterial phase contrast-enhanced sonography cine loop sweep show endoleak (arrows) between enhancing iliac limbs of endograft.

 


Figure 3
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  		Fig. 1C —75-year-old man with type III endoleak. Figures S1G and S1H are available in supplemental data. Images from arterial phase contrast-enhanced sonography cine loop sweep show endoleak (arrows) between enhancing iliac limbs of endograft.

 


Figure 4
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  		Fig. 1D —75-year-old man with type III endoleak. Figures S1G and S1H are available in supplemental data. Axial arterial phase CT angiography (CTA) images, which correspond to A-C, show exact concordance in depiction of endoleak (arrows) between two imaging techniques.

 


Figure 5
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  		Fig. 1E —75-year-old man with type III endoleak. Figures S1G and S1H are available in supplemental data. Axial arterial phase CT angiography (CTA) images, which correspond to A-C, show exact concordance in depiction of endoleak (arrows) between two imaging techniques.

 


Figure 6
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  		Fig. 1F —75-year-old man with type III endoleak. Figures S1G and S1H are available in supplemental data. Axial arterial phase CT angiography (CTA) images, which correspond to A-C, show exact concordance in depiction of endoleak (arrows) between two imaging techniques.

 
In this article, we describe our initial experience in evaluating the feasibility of accurate detection of endoleaks in aortic endografts using a second-generation sonography contrast agent and state-of-the-art imaging techniques.


Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
This study was approved by our research ethics board. All subjects gave informed consent.

Subjects
Between April 2003 and June 2004, 20 nonconsecutive patients, 17 men and three women ranging in age from 67 to 92 years (mean age, 80 years), underwent contrast-enhanced sonography evaluation between 2 days and 32 weeks after endograft implantation. The patients were recruited at our preadmission and follow-up vascular surgery outpatient clinics. Nine patients were evaluated within 2 weeks of endograft implantation (before discharge), and 15 were evaluated at the time of routine surveillance imaging. Four patients were evaluated on two separate occasions: two as part of routine follow-up, one before and after endoleak repair, and one twice in the initial postoperative period. Patients with inadequate renal function (calculated creatinine clearance of < 30 mL/min in nondiabetic patients and < 50 mL/min in diabetic patients), precluding them from receiving iodinated contrast material, were excluded because the practice standard, CT angiography (CTA), could not be performed. Contrast-enhanced sonography and CTA were performed on the same day in 18 cases and within 1 month of each other in the remaining five cases. In one patient, CTA was performed immediately after contrast-enhanced sonography verifying the sonography result.

Imaging Techniques
Contrast-enhanced sonography—All sonography scans were obtained by a single investigator on HDI 5000 machines (Philips Medical Systems) using contrast-specific software including pulse-inversion imaging. The results of previous investigations were unknown at the time of the contrast-enhanced sonography evaluations. No special patient preparation was required. We used nonlinear imaging techniques with a low mechanical index of between 0.1 and 0.2. All images and cine loops were stored on our PACS. Cine loops were acquired with a smooth sweep, drawing the transducer along the length of the graft (Fig. 1A, 1B, 1C, 1D, 1E, 1F). Figures S1G and S1H, audio-video interleave (AVI) files of a contrast-enhanced sonography sweep and CTA, respectively, can be seen in the supplemental data.

The contrast-enhanced sonography imaging protocol included the following six steps. First, the optimal sweep for visualization of the aortic stent-graft in the axial and sagittal planes was established. Second, a baseline cine loop sweep was taken in the axial plane before the injection of contrast material. Third, SH U 508A (Definity, Bristol-Myers Squibb) (0.5 mL) was then injected IV via a catheter in a large arm vein over 10 seconds, and the contrast injection was followed by a flush of 10 mL of normal saline. Fourth, an axial arterial phase sweep along the length of the graft was acquired as soon as bubbles filled the endograft lumen (15-30 seconds after injection). Fifth, real-time interrogation of the aortic aneurysmal sac was then performed looking for the presence of contrast material to indicate an endoleak. A destruction-reperfusion technique was used in areas of uncertain enhancement. For this technique, a brief pulse of high-intensity (high-mechanical-index) sound was used to confirm the presence of contrast material in an endoleak by its complete destruction. Immediately after this, reperfusion of the endoleak could also be documented in real time (Fig. 2A, 2B, 2C, 2D). Figure S2E, an AVI file, depicts destruction-reperfusion imaging and can be seen in the data supplement to this article. Sixth, characterization of the endoleak, if present, was performed.


Figure 7
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  		Fig. 2A —87-year-old man with subtle type II endoleak from left lumbar artery. Figure S2E can be viewed in supplemental data. Axial contrast-enhanced sonography image at level of iliac components of endograft depicts suspicious bright area (arrow) at periphery of aneurysmal sac.

 

Figure 8
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  		Fig. 2B —87-year-old man with subtle type II endoleak from left lumbar artery. Figure S2E can be viewed in supplemental data. By applying brief high-mechanical-index pulse, all contrast agent bubbles in field of view are disrupted, thereby producing bright flash (arrow) (destruction-reperfusion technique).

 

Figure 9
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  		Fig. 2C —87-year-old man with subtle type II endoleak from left lumbar artery. Figure S2E can be viewed in supplemental data. Axial contrast-enhanced sonography image at same level as A and B obtained immediately after high-mechanical index pulse reveals absence of previously described suspected enhancement, indicating presence of endoleak.

 

Figure 10
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  		Fig. 2D —87-year-old man with subtle type II endoleak from left lumbar artery. Figure S2E can be viewed in supplemental data. Axial contrast-enhanced sonography image obtained at same level as A-C shows return of microbubbles (arrow) to that region after short delay.

 

Steps 3-6 were repeated as described except the cine loop acquisitions were in the sagittal plane along the graft. At completion of each contrast-enhanced sonography examination, a final opinion regarding the presence or absence of an endoleak and, if present, its classification was recorded.

CTA: practice standard—All CTA scans were obtained using MDCT scanners, and 100 mL of IV contrast material (iodixanol [Visipaque 270, Nycomed]) was administered at a rate of 4 mL/s by a power injector. Our routine stent-graft follow-up CTA protocol includes arterial phase (slice thickness/reconstruction interval, 2.5 mm/1.5 mm) and 2-minute delayed phase (5 mm/2.5 mm) data sets along the length of the aorta.

Image Analysis
Cine loop sweeps from the contrast-enhanced sonography examinations were reviewed independently by three radiologists experienced in the use of sonography contrast material. The reviewers were blinded to the follow-up CTA results, which were considered the practice standard. The presence or absence of an endoleak was recorded by each reviewer. Results were analyzed by consensus and compared with reported results from the practice standard. As the best representation of the clinical truth, a reference standard was also devised after reviewing all available clinical and imaging data with respect to the presence or absence of an endoleak at the time of imaging evaluation. The reference standard was then compared with both the contrast-enhanced sonography and practice standard data independently.


Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
All patients completed the protocol. Both contrast-enhanced sonography and our practice standard depicted eight endoleaks with 83% (20/24) agreement (Table 1). When compared with the practice standard, contrast-enhanced sonography had a sensitivity of 75%, a specificity of 88%, a positive predictive value of 75%, and a negative predictive value of 88%. Our reference standard showed 10 endoleaks in total, consisting of three type I, five type II, and two type III endoleaks.


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  		TABLE 1: Positive Studies for Endoleak Detection

 


Figure 15
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  		Fig. 4A —81-year-old man with large transient type I endoleak. Figure S4E is available in supplemental data. Axial contrast-enhanced sonography image at level of iliac components shows endoleak (arrow).

 

Figure 16
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  		Fig. 4B —81-year-old man with large transient type I endoleak. Figure S4E is available in supplemental data. Sagittal contrast-enhanced sonography images along graft with duplex Doppler imaging depict large high-flow endoleak anterior to aortic component of graft with relatively damped pulse Doppler waveform (arrow, C).

 

Figure 17
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  		Fig. 4C —81-year-old man with large transient type I endoleak. Figure S4E is available in supplemental data. Sagittal contrast-enhanced sonography images along graft with duplex Doppler imaging depict large high-flow endoleak anterior to aortic component of graft with relatively damped pulse Doppler waveform (arrow, C).

 

Figure 18
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  		Fig. 4D —81-year-old man with large transient type I endoleak. Figure S4E is available in supplemental data. Arterial phase CT angiography image obtained at same level as B and C 1 day after B and C reveals no evidence of leak, which is confirmed at repeat contrast-enhanced sonography (not shown).

 

Figure 19
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  		Fig. 5A —88-year-old woman with subtle type II endoleak. Axial contrast-enhanced sonography image obtained at level of iliac endograft components reveals subtle endoleak (arrow) not identified prospectively in blinded interpretation (false-negative).

 

Figure 20
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  		Fig. 5B —88-year-old woman with subtle type II endoleak. Arterial phase CT angiogram obtained at same level as A shows endoleak (arrow), which was detected prospectively.

 

Figure 11
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  		Fig. 3A —86-year-old man with type I endoleak detected at contrast-enhanced sonography but occult at CT angiography (CTA). Axial arterial phase contrast-enhanced sonography image reveals subtle endoleak (arrow) adjacent to left iliac limb of endograft.

 

Figure 12
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  		Fig. 3B —86-year-old man with type I endoleak detected at contrast-enhanced sonography but occult at CT angiography (CTA). Axial contrast-enhanced sonography image obtained at same level as A acquired 2 minutes after contrast injection depicts larger endoleak (arrows) than that shown in arterial phase (A).

 

Figure 13
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  		Fig. 3C —86-year-old man with type I endoleak detected at contrast-enhanced sonography but occult at CT angiography (CTA). Axial arterial phase (C) and 2-minute delayed phase (D) CTA images at same level as two previous images in retrospect reveals subtle evidence of endoleak (arrow, D) depicted at contrast-enhanced sonography.

 

Figure 14
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  		Fig. 3D —86-year-old man with type I endoleak detected at contrast-enhanced sonography but occult at CT angiography (CTA). Axial arterial phase (C) and 2-minute delayed phase (D) CTA images at same level as two previous images in retrospect reveals subtle evidence of endoleak (arrow, D) depicted at contrast-enhanced sonography.

 
Compared with the reference standard, contrast-enhanced sonography had 92% (22/24) agreement (sensitivity of 80%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 88%), and our practice standard had 96% (23/24) agreement (sensitivity of 89%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 94%). Our scanning radiologist's blinded assessment agreed with the subsequently devised reference standard regarding the presence of endoleaks in 96% (23/24) of the cases and for the type of endoleak in 100% of the cases.


Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
We are the first group, to our knowledge, to report results from the interrogation of aortic endografts for endoleaks using a second-generation microbubble agent and pulse-inversion techniques. Most earlier studies used the first-generation agent SH U 508A (Levovist, Schering) in combination with color Doppler, power Doppler, or tissue harmonic imaging [14-17]. SH U 508A is composed of relatively fragile bubbles and is best imaged with a high-mechanical-index technique whereby the agent is destroyed as it is imaged. The strength of SH U 508A is its unique enhancement of the liver during the postvascular phase, which has been shown to improve the detection of liver metastases and to help characterize liver masses [11, 12, 18, 19]. Vascular phase interrogation, however, is weakly performed with SH U 508A because the agent is destroyed as it is imaged, reducing its sensitivity for the detection of slow-flowing blood. In addition, color and power Doppler imaging are affected by blooming and movement-related artifacts that make accurate interpretation of the examinations difficult. Despite these limitations, authors report sensitivities for the detection of endoleaks ranging from 50% to 100%, although there were many false-positives. More recently, Napoli et al. [20] performed contrast-enhanced sonography with a second-generation agent (SonoVue [an aqueous suspension of stabilized sulfur fluoride microbubbles], Bracco) using Contrast Tuned Imaging (Esaote Biomedica) and were able to detect 10 endoleaks that had been occult on routine CTA imaging [20] (Table 2).


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  		TABLE 2: Published Series Evaluating Aortic Endografts with Contrast-Enhanced Sonography

 

Definity is a second-generation microbubble contrast agent consisting of a perfluoropropane gas surrounded by a phospholipid shell. It is relatively robust, allowing real-time detection without significant agent destruction, when low-mechanical-index techniques are used. This contrast agent gives us the ability to meticulously interrogate an endograft in real time from many different angles over several minutes, enabling more practical and reproducible evaluations of these patients in a routine clinical setting. In addition, we can use a brief pulse of high-intensity (high-mechanical-index) sound to instantly destroy all bubbles in the field of view (destruction-reperfusion technique) and thereby confirm the presence of subtle endoleaks by imaging before and immediately after the bubble destruction [11, 12] (Fig. 2A, 2B, 2C, 2D).

In our experience, contrast-enhanced sonography was quick and easy to perform, with an average examination time of 20 minutes. In addition, we found contrast-enhanced sonography to be a robust procedure that allowed adequate examination of the aortic endografts in all patients.

Although the number of patients in our pilot project is small, our results showed excellent agreement between contrast-enhanced sonography and our practice standard. Our reference standard yielded two incongruent results: Two true endoleaks detected at contrast-enhanced sonography were not reported prospectively at CTA. In one case, retrospective review of the CTA scan revealed subtle evidence of the leak that had been detected at contrast-enhanced sonography (Fig. 3A, 3B, 3C, 3D). This endoleak was a large type I leak at contrast-enhanced sonography; however, it was not fully depicted until 1-2 minutes after contrast injection. This delayed enhancement is the reason the 2-minute delayed study is performed on CTA [21]. The discordance between the two techniques might be explained by differences in contrast resolution and the time course of its appearance in the aneurysmal sac. Two minutes after injection, the detected iodinated contrast density on CT within the aorta and an endoleak is relatively low compared with the arterial phase. With contrast-enhanced sonography, however, because contrast-specific imaging techniques allow detection of single bubbles, the contrast resolution remains high even as the agent becomes diluted over time. Thus, enhancement of blood can be easily depicted for at least 3 minutes after a bolus injection. This allows sensitive and reproducible visualization of even slow-flowing endoleaks because microbubbles do not have to be moving to be detected. In the second discordant case, we detected an obvious high-flow (type I) leak on contrast-enhanced sonography that was not depicted on CTA, which was performed the morning after sonography (within 18 hours) (Figs. 4A, 4B, 4C, 4D and S4E). Immediate reevaluation with contrast-enhanced sonography confirmed the CTA findings, indicating that the large endoleak had resolved between the time of the initial contrast-enhanced sonography examination and the subsequent CTA examination. This patient was imaged during the first week after insertion of the endograft when endoleaks—even if large—may be transient. These are, however, not without risk to the patient. Figure 5A, 5B shows a type II endoleak.

With the aid of real-time interrogation of the endograft and using destruction-reperfusion techniques, our scanning radiologist was able to achieve the same agreement statistics with our reference standard as with our current practice standard.

False-negative CTA examinations have been documented in two of the five previous studies [16, 20]. We suggest, as did those authors, that this is due to an insensitive practice standard, particularly insensitive to endoleaks with delayed enhancement rather than true false-positive contrast-enhanced sonography studies.

Patients were recruited for the study by our vascular surgeons in outpatient and preadmission clinics, which may have resulted in some selection bias and may explain the relatively high incidence of endoleaks in our small population. However, the purpose of the study was not to investigate the incidence of endoleaks but rather to investigate the sensitivity of their detection with contrast-enhanced sonography.

We believe our use of the reference standard in our results analysis has enabled us to document a more accurate comparison between the performance of contrast-enhanced sonography and our practice standard.

Although large prospective studies are needed to further evaluate the utility of contrast-enhanced sonography in detecting endoleaks in aortic endografts, our results concur with those of others supporting the clinical application of this technique. Intraoperative applications of this technique should also be investigated because contrast-enhanced sonography may allow otherwise occult endoleaks to be identified and repaired while endograft replacement is under way.

In conclusion, contrast-enhanced sonography evaluation of aortic endografts appears to be an accurate alternative to the current practice standard of CTA. In addition, we believe contrast-enhanced sonography is more sensitive to the detection of slow-flowing endoleaks due to its superior contrast resolution on delayed imaging.


References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

  1. White GH, Yu W, May J, et al. Endoleak as a complication of endoluminal grafting of abdominal aortic aneurysms: classification, incidence, diagnosis, and management. J Endovasc Surg1997; 4:152 -168[CrossRef][Medline]
  2. White GH, May J, Waugh RC, et al. Type III and type IV endoleak: toward a complete definition of blood flow in the sac after endoluminal AAA repair. J Endovasc Surg 1998;5 : 305-309[CrossRef][Medline]
  3. Carpenter JP; Endologix Investigators. Midterm results of a multicenter trial of the powerlink bifurcated system for endovascular aortic aneurysm repair. J Vasc Surg 2004;40 : 849-859[CrossRef][Medline]
  4. Carpenter JP, Anderson WN, Brewster DC, et al. Multicenter pivotal trial results of the Lifepath System for endovascular aortic aneurysm repair. J Vasc Surg 2004;39 : 34-43[CrossRef][Medline]
  5. Matsumura JS, Brewster DC, Makaroun MS. A multicenter controlled clinical trial of open versus endovascular treatment of abdominal aortic aneurysm. J Vasc Surg 2003;37 : 262-271[CrossRef][Medline]
  6. Alric P, Hinchliffe RJ, MacSweeney ST, Wenham PW, Whitaker SC, Hopkinson BR. The Zenith aortic stent-graft: a 5-year single-center experience. J Endovasc Ther 2002;9 : 719-728[CrossRef][Medline]
  7. Hinchliffe RJ, Sing-Ranger R, Davidson IR, et al. Rupture of abdominal aortic aneurysm secondary to type II endoleak. Eur J Vasc Endovasc Surg 2001; 22:563 -565[CrossRef][Medline]
  8. Meier GH, Parker FM, Godziachvili V, Demasi RJ, Parent FN, Gayle RG. Endotension after endovascular repair: the Ancure experience. J Vasc Surg 2001; 34:421 -427[CrossRef][Medline]
  9. Harris PL, Vallabhaneni SR, Desgranges P, Becquemin JP, van Marrewijk C, Laheij RJ. Incidence and risk factors of late rupture, conversion, and death after endovascular repair of infrarenal aortic aneurysms: the EUROSTAR experience. European Collaborators on Stent/graft techniques for aortic aneurysm repair. J Vasc Surg2000; 32:739 -749[CrossRef][Medline]
  10. Thurnher S, Cejna M. Imaging of aortic stentgrafts and endoleaks. Radiol Clin North Am 2002;40 : 799-833[CrossRef][Medline]
  11. Brannigan M, Burns PN, Wilson SR. Blood flow patterns in focal liver lesions at microbubble-enhanced US. RadioGraphics 2004;24 : 921-935[Abstract/Free Full Text]
  12. Dill-Macky MJ, Burns PN, Khalili K, Wilson SR. Focal hepatic masses: enhancement patterns with SH U 508A and pulse-inversion US. Radiology 2002;222 : 95-102[Abstract/Free Full Text]
  13. Wilson SR, Burns PN. Liver mass evaluation with ultrasound: the impact of microbubble contrast agents and pulse inversion imaging. Semin Liver Dis 2001;21 : 147-159[CrossRef][Medline]
  14. McWilliams RG, Martin JM, White D, et al. Use of contrast-enhanced ultrasound in follow-up after endovascular aortic aneurysm repair. J Vasc Interv Radiol 1999;10 : 1107-1114[Medline]
  15. McWilliams RG, Martin JM, White D, et al. Detection of endoleak with enhanced ultrasound imaging: comparison with biphasic computed tomography. J Endovasc Ther 2002;9 : 170-179[CrossRef][Medline]
  16. Bendick PJ, Bove PG, Long GW, et al. Efficacy of ultrasound scan contrast agents in the noninvasive follow-up of aortic stent grafts. J Vasc Surg 2003;37 : 381-385[CrossRef][Medline]
  17. Giannoni MF, Palombo G, Sbarigia E, Speziale F, Zaccaria A, Fiorani P. Contrast-enhanced ultrasound imaging for aortic stent-graft surveillance. J Endovasc Ther 2003;10 : 208-217[CrossRef][Medline]
  18. Hohmann J, Albrecht T, Hoffmann CW, et al. Ultrasonographic detection of focal liver lesions: increased sensitivity and specificity with microbubble contrast agents. Eur J Radiol2003; 46:147 -156[CrossRef][Medline]
  19. Albrecht T, Blomley MJ, Burns PN, et al. Improved detection of hepatic metastases with pulse-inversion US during the liver-specific phase of SHU 508A: multicenter study. Radiology2003; 227:361 -370[Abstract/Free Full Text]
  20. Napoli V, Bargellini I, Sardella SG, et al. Abdominal aortic aneurysm: contrast-enhanced US for missed endoleaks after endoluminal repair. Radiology 2004;233 : 217-225[Abstract/Free Full Text]
  21. Rozenblit AM, Patlas M, Rosenbaum AT, et al. Detection of endoleaks after endovascular repair of abdominal aortic aneurysm: value of unenhanced and delayed helical CT acquisitions. Radiology2003; 227:426 -433[Abstract/Free Full Text]

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