Defining a role for contrast-enhanced ultrasound in endovascular aneurysm repair surveillance

EVAR Follow-Up with Ultrasound Superb Microvascular Imaging (SMI) Compared to CEUS and CT Angiography for Detection of Type II Endoleak

The aim of this study was to evaluate the usefulness of superb microvascular imaging (SMI) versus contrast-enhanced ultrasound (CEUS) and compared to computed tomography angiography (CTA) as a reference standard, for detection of type II endoleak during follow-up of endovascular abdominal aortic aneurysm repair (EVAR). Between April 2017 and September 2020, 122 patients underwent post-EVAR follow-up with CTA at 3 months and with ultrasound SMI and CEUS at 4 months from the EVAR procedure. Aneurysmal sac diameter and graft patency were evaluated; endoleaks were assessed and classified. Sensitivity, specificity, positive and negative predictive values, and diagnostic accuracy were calculated both for SMI and CEUS and compared to CTA. Furthermore, the percentage of agreement and Cohen’s Kappa coefficient were calculated. CTA revealed 54 type II endoleaks. Ultrasound SMI and CEUS presented the same sensitivity (91.5%), specificity (100%), positive (100%), and negative (92.8%) predictive and accuracy (95.9%) value for detecting type II endoleak. The same percentage of agreement of 94.9% was found between SMI/CEUS, and CTA with a Cohen’s Kappa coefficient of 0.89. The diagnostic accuracy of SMI is comparable with CEUS in the identification of type II endoleaks after EVAR. Since SMI is less invasive, less expensive, and less time-consuming, this method may be considered to be a potential tool for monitoring patients after EVAR implantation.

Imaging modalities for endoleak surveillance

As the global population ages, the issue of abdominal aortic aneurysm continues to grow. With the evolution of new devices and refined operative technique, aneurysm treatment via endovascular aortic repair is becoming increasingly favourable. This, however, is not without drawbacks, where regular surveillance is paramount to long-term success and detection of post-procedure complications. Of these complications, endoleak is the most notable and poses the greatest risk of potential future aortic rupture. The purpose of this review paper is to discuss the armada of imaging modalities used in the detection and evaluation of endoleak and their varying usefulness. Plain abdominal X-ray is a cost-effective tool in detecting gross graft abnormalities such as stent migration or deformity (kinking or fracture). Though it may raise suspicion for endoleak, X-ray does not allow accurate classification of endoleak type when used alone. Duplex ultrasonography quantifies both aortic anatomy and real time flow dynamics. Most screening programmes are conducted using two-dimensional ultrasound. Unfortunately, observer and equipment variability may lead to surveillance discrepancies-but reduced when utilising a dedicated vascular sonography laboratory. Contrast enhanced ultrasonography is a promising alternative to computed tomography, though still is emerging. Computed tomography angiography certainly has disadvantages (ionising radiation, contrast-nephropathy, limited differentiation of endoleak type)-however, it provides near-real surgical dimensions and highlights graft complications and concomitant disease (such as neighbouring infection). With widespread availability and short scan time, it certainly remains valuable in surveillance. Magnetic resonance angiography has a similar sensitivity to computed tomography (minus the radiation), however is plagued by movement and metal artefact. Other novel modalities in endoleak surveillance include four-dimensional ultrasound, multiplanar intra-operative probes, nuclear medicine and wall stress analysis.

Use of contrast ultrasound in differentiating thrombosed pseudoaneurysm from sarcoma, prior to surgery

We describe a case of a 69-year-old male with a right-sided popliteal mass following a motor vehicle accident 15 years ago. The mass was indeterminate via multiple modalities (magnetic resonance imaging, digital subtraction angiography, and vascular ultrasound) with biopsy requested prior to surgical removal to determine the appropriate surgical team – vascular versus sarcoma oncologic surgery. Contrast ultrasound was utilized to determine if biopsy was indicated and if so, to determine the most appropriate target. Contrast ultrasound showed no areas of enhancement, therefore biopsy was not performed and the patient safely proceeded to vascular surgery. Pathology confirmed the mass to be a thrombosed pseudoaneurysm of the popliteal artery. We present the benefits of using contrast ultrasound in the work up and diagnosis of a popliteal neoplasm versus suspected vascular complication.

Contrast-enhanced ultrasound and/or colour duplex ultrasound for surveillance after endovascular abdominal aortic aneurysm repair: a systematic review and economic evaluation

BACKGROUND

Endovascular abdominal aortic aneurysm repair (EVAR) of abdominal aortic aneurysm (AAA) is less invasive than open surgery, but may be associated with important complications. Patients receiving EVAR require long-term surveillance to detect abnormalities and direct treatments. Computed tomography angiography (CTA) has been the most common imaging modality adopted for EVAR surveillance, but it is associated with repeated radiation exposure and the risk of contrast-related nephropathy. Colour duplex ultrasound (CDU) and, more recently, contrast-enhanced ultrasound (CEU) have been suggested as possible, safer, alternatives to CTA.

OBJECTIVES

To assess the clinical effectiveness and cost-effectiveness of imaging strategies, using either CDU or CEU alone or in conjunction with plain radiography, compared with CTA for EVAR surveillance.

DATA SOURCES

Major electronic databases were searched, including MEDLINE, EMBASE, Science Citation Index, Scopus' Articles-in-Press, Cochrane Central Register of Controlled Trials (CENTRAL), Database of Abstracts of Reviews of Effects (DARE) and NHS Economic Evaluation Database from 1996 onwards. We also searched for relevant ongoing studies and conference proceedings. The final searches were undertaken in September 2016.

METHODS

We conducted a systematic review of randomised controlled trials and cohort studies of patients with AAAs who were receiving surveillance using CTA, CDU and CEU with or without plain radiography. Three reviewers were involved in the study selection, data extraction and risk-of-bias assessment. We developed a Markov model based on five surveillance strategies: (1) annual CTA; (2) annual CDU; (3) annual CEU; (4) CDU together with CTA at 1 year, followed by CDU on an annual basis; and (5) CEU together with CTA at 1 year, followed by CEU on an annual basis. All of these strategies also considered plain radiography on an annual basis.

RESULTS

We identified two non-randomised comparative studies and 25 cohort studies of interventions, and nine systematic reviews of diagnostic accuracy. Overall, the proportion of patients who required reintervention ranged from 1.1% (mean follow-up of 24 months) to 23.8% (mean follow-up of 32 months). Reintervention was mainly required for patients with thrombosis and types I-III endoleaks. All-cause mortality ranged from 2.7% (mean follow-up of 24 months) to 42% (mean follow-up of 54.8 months). Aneurysm-related mortality occurred in < 1% of the participants. Strategies based on early and mid-term CTA and/or CDU and long-term CDU surveillance were broadly comparable with those based on a combination of CTA and CDU throughout the follow-up period in terms of clinical complications, reinterventions and mortality. The economic evaluation showed that a CDU-based strategy generated lower expected costs and higher quality-adjusted life-year (QALYs) than a CTA-based strategy and has a 63% probability of being cost-effective at a £30,000 willingness-to-pay-per-QALY threshold. A CEU-based strategy generated more QALYs, but at higher costs, and became cost-effective only for high-risk patient groups.

LIMITATIONS

Most studies were rated as being at a high or moderate risk of bias. No studies compared CDU with CEU. Substantial clinical heterogeneity precluded a formal synthesis of results. The economic model was hindered by a lack of suitable data.

CONCLUSIONS

Current surveillance practice is very heterogeneous. CDU may be a safe and cost-effective alternative to CTA, with CTA being reserved for abnormal/inconclusive CDU cases.

FUTURE WORK

Research is needed to validate the safety of modified, more-targeted surveillance protocols based on the use of CDU and CEU. The role of radiography for surveillance after EVAR requires clarification.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42016036475.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Is contrast-enhanced ultrasound (CEUS) superior to computed tomography angiography (CTA) in detection of endoleaks in post-EVAR patients? A systematic review and meta-analysis

OBJECTIVE

The purpose of this systematic review and meta-analysis was to assess the sensitivity and specificity of contrast-enhanced ultrasound (CEUS) compared to computed tomography angiography (CTA) for the detection of endoleaks within endovascular aortic aneurysm repair (EVAR) surveillance at time of follow up.

METHODS

A comprehensive literature search was undertaken among the four major databases (PubMed, Embase, Scopus and Ovid) to identify all articles assessing diagnostic specificity and accuracy with comparative modality (CEUS vs CTA) for endoleaks in adult patients at time of follow-up following EVAR. Databases where evaluated and assessed to October 2018.

RESULTS

A total of 1773 patients were analysed from across 18 included studies in the quantitative analysis of the parameters of interest. There was no significant difference in detection rate of endoleak type I with detection rate 4.3% for both groups OR 1.09, 95% CI [0.78, 1.53], p = 0.62; type II endoleak detection rate was 22% in the CEUS group vs 23% in the CTA group OR 1.16, 95% CI [0.75-1.79], p = 0.50; while type III detection rate was 1.8% in CEUS group vs 2% in CTA group OR 0.85, 95% CI [0.43, 1.68], p = 0.64. However, the sensitivity rate for endoleak detection was higher in CEUS (p = 0.001) while no difference in specificity rate was noted (p = 0.28). There was higher rate of missed endoleaks in CTA groups (n = 12 vs n = 20).

CONCLUSION

Evidences from this study suggest that contrast-enhanced ultrasound scan post-EVAR can be utilised as safe and effective method in screening for endoleaks during post-EVAR surveillance without exposing the patient for additional risk of radiation and contrast. CEUS conveys no inferiority to CTA in detecting endoleaks.

A Narrative Review on Contrast-Enhanced Ultrasound in Aortic Endograft Endoleak Surveillance

Endovascular repair of abdominal aortic aneurysms have been performed successfully since 1991. However, 20% to 50% of these patients may develop an endoleak or continued aneurysmal sac expansion or perfusion despite stent graft coverage. Current recommendations suggest lifelong surveillance with computed tomographic angiography (CTA) at least 1 month after intervention and yearly after that. In select patients with a stable aneurysm sac on computed tomography performed 1 year after treatment, future screening could be performed with ultrasonography. However, color Doppler ultrasound can fail to detect as many as 31% of endoleaks. Contrast-enhanced ultrasound (CEUS) provides an alternative approach to excluded aneurysm sac follow-up imaging. The Society for Vascular Surgery notes a need for further research on the role of CEUS in endovascular aortic repair surveillance. The European Federation of Societies for Ultrasound in Medicine and Biology suggests that early results are promising. Meta-analyses report pooled sensitivities and specificities of CEUS compared with CTA for the detection of endoleak between 89% and 98% and 86% and 88%, respectively. Owing to the dynamic flow information it provides, CEUS may actually be more sensitive than CTA at detection and characterization in select circumstances. Challenges with adoption, patient selection, and operator dependency remain, but current and future research suggests a role for CEUS in endoleak surveillance.

Contrast-enhanced ultrasound of the abdominal aorta - current status and future perspectives

Ultrasound has been established as an important diagnostic tool in assessing vascular abnormalities. Standard B-mode and Doppler techniques have inherent limitations with regards to detection of slow flow and small vasculature. Contrast-enhanced ultrasound (CEUS) is a complementary tool and is useful in assessing both the macro- and microvascular anatomy of the aorta. CEUS can also provide valuable physiological information in real-time scanning sessions due to the physical and safety profiles of the administered microbubbles. From a macrovascular perspective, CEUS has been used to characterize aortic aneurysm rupture, dissection and endoleaks post-EVAR repair. With regard to microvasculature CEUS enables imaging of adventitial vasa vasorum thereby assessing aortic inflammation processes, such as monitoring treatment response in chronic periaortitis. CEUS may have additional clinical utility since adventitial vasa vasorum has important implications in the pathogenesis of aortic diseases. In recent years, there have been an increasing number of studies comparing CEUS to cross-sectional imaging for aortic applications. For endoleak surveillance CEUS has been shown to be equal or in certain cases superior in comparison to CT angiography. The recent advancement of CEUS software along with the ongoing development of drug-eluting contrast microbubbles has allowed improved targeted detection and real-time ultrasound guided therapy for aortic vasa vasorum inflammation and neovascularization in animal models. Therefore, CEUS is uniquely suited to comprehensively assess and potentially treat aortic vascular diseases in the future.

Type 2 endoleaks in endovascular aortic repair: cone beam CT and automatic vessel detection to guide the embolization

Background Dual-phase cone beam computed tomography (DP-CBCT) and automatic vessel detection (AVD) software are helpful tools for detecting arteries before planned endovascular interventions. Purpose To evaluate the usefulness of DP-CBCT and AVD software in guiding the trans-arterial embolization (TAE) of challenging T2 lumbar endoleaks (T2-L-EL). Material and Methods Ten patients with T2-L-EL were included in this study. The accuracy of DP-CBCT and the AVD software was defined by the ability to detect the endoleak and arterial feeding vessel, respectively. Technical success was defined as the correct positioning of the microcatheter using AVD software and the successful embolization of the endoleak. Clinical success was defined as the absence of recurrent endoleaks during follow-up and the stability of the sac diameter for persistent endoleaks. The total volume of iodinated contrast medium, overall procedure time, mean procedural radiation dose, and mean fluoroscopy time were recorded. Results The EL was detected by DP-CBCT in all patients. The AVD software identified the feeding arterial branch in all cases. In one patient, the nidus of the endoleak was not reached due to the small caliber of the feeding artery, even though the software had clearly identified the vessel route. The mean contrast volume was 109 mL, the mean overall procedural time was 74.3 min. The mean procedural radiation dose was 140.97 Gy cm², and the mean fluoroscopy time was 29.8 min. Conclusion The use of DP-CBCT and the AVD software is feasible and may facilitate successful embolization in challenging occult T2-L-EL with complex vasculature.

Multimodality imaging assessment of endoleaks post-endovascular aortic repair

Endoleaks are a common complication of endovascular aortic repair (EVAR). As a result, patients require lifelong imaging surveillance following EVAR. In current clinical practice, evaluation for endoleaks is predominantly performed with CT angiography (CTA). Due to the significant cumulative radiation burden associated with repetitive CTA imaging, as well as the repeated administration of nephrotoxic contrast agent, contrast-enhanced ultrasound (CEUS) and magnetic resonance angiography (MRA) have evolved as potential modalities for lifelong surveillance post-EVAR. In this paper, multimodality imaging, including CTA, CEUS and MRA, for the surveillance of endoleaks is discussed. Further, new CTA techniques for radiation reduction are elaborated. Additionally, imagery for three cases of aortic endoleak detection using CTA and five cases using MRA are presented. Imaging for different types of endoleaks with CTA, MRA and CEUS are presented. For lifelong endoleak surveillance post-EVAR, CTA is still regarded as the imaging modality of choice. However, advancements in CEUS and MRA technique enable partial replacement of CTA in certain patients.

Complications of endovascular aneurysm repair of the thoracic and abdominal aorta: evaluation and management

In recent decades, endovascular aneurysm repair or endovascular aortic repair (EVAR) has become an acceptable alternative to open surgery for the treatment of thoracic and abdominal aortic aneurysms and other aortic pathologies such as the acute aortic syndromes (e.g., penetrating aortic ulcer, intramural hematoma, dissection). Available data suggest that endovascular repair is associated with lower perioperative 30-day all-cause mortality as well as a significant reduction in perioperative morbidity when compared to open surgery. Additionally, EVAR leads to decreased blood loss, eliminates the need for cross-clamping the aorta and has shorter recovery periods than traditional surgery. It is currently the preferred mode of treatment of thoracic and abdominal aortic aneurysms in a subset of patients who meet certain anatomic criteria conducive to endovascular repair. The main disadvantage of EVAR procedures is the high rate of post-procedural complications that often require secondary re-intervention. As a result, most authorities recommend lifelong imaging surveillance following repair. Available surveillance modalities include conventional radiography, computed tomography, magnetic resonance angiography, ultrasonography, nuclear imaging and conventional angiography, with computed tomography currently considered to be the gold standard for surveillance by most experts. Following endovascular abdominal aortic aneurysm (AAA) repair, the rate of complications is estimated to range between 16% and 30%. The complication rate is higher following thoracic EVAR (TEVAR) and is estimated to be as high as 38%. Common complications include both those related to the endograft device and systemic complications. Device-related complications include endoleaks, endograft migration or collapse, kinking and/or stenosis of an endograft limb and graft infection. Post-procedural systemic complications include end-organ ischemia, cerebrovascular and cardiovascular events and post-implantation syndrome. Secondary re-interventions are required in approximately 19% to 24% of cases following endovascular abdominal and thoracic aortic aneurysm repair respectively. Typically, most secondary reinterventions involve the use of percutaneous techniques such as placement of cuff extension devices, additional endograft components or stents, enhancement of endograft fixation, treatment of certain endoleaks using various embolization techniques and embolic agents and thrombolysis of occluded endograft components. Less commonly, surgical conversion and/or open surgical modification are required. In this article, we provide an overview of the most common complications that may occur following endovascular repair of thoracic and AAAs. We also summarize the current surveillance recommendations for detecting and evaluating these complications and discuss various current secondary re-intervention approaches that may typically be employed for treatment.

Ultrasonography for endoleak detection after endoluminal abdominal aortic aneurysm repair

BACKGROUND

People with abdominal aortic aneurysm who receive endovascular aneurysm repair (EVAR) need lifetime surveillance to detect potential endoleaks. Endoleak is defined as persistent blood flow within the aneurysm sac following EVAR. Computed tomography (CT) angiography is considered the reference standard for endoleak surveillance. Colour duplex ultrasound (CDUS) and contrast-enhanced CDUS (CE-CDUS) are less invasive but considered less accurate than CT.

OBJECTIVES

To determine the diagnostic accuracy of colour duplex ultrasound (CDUS) and contrast-enhanced-colour duplex ultrasound (CE-CDUS) in terms of sensitivity and specificity for endoleak detection after endoluminal abdominal aortic aneurysm repair (EVAR).

SEARCH METHODS

We searched MEDLINE, Embase, LILACS, ISI Conference Proceedings, Zetoc, and trial registries in June 2016 without language restrictions and without use of filters to maximize sensitivity.

SELECTION CRITERIA

Any cross-sectional diagnostic study evaluating participants who received EVAR by both ultrasound (with or without contrast) and CT scan assessed at regular intervals.

DATA COLLECTION AND ANALYSIS

Two pairs of review authors independently extracted data and assessed quality of included studies using the QUADAS 1 tool. A third review author resolved discrepancies. The unit of analysis was number of participants for the primary analysis and number of scans performed for the secondary analysis. We carried out a meta-analysis to estimate sensitivity and specificity of CDUS or CE-CDUS using a bivariate model. We analysed each index test separately. As potential sources of heterogeneity, we explored year of publication, characteristics of included participants (age and gender), direction of the study (retrospective, prospective), country of origin, number of CDUS operators, and ultrasound manufacturer.

MAIN RESULTS

We identified 42 primary studies with 4220 participants. Twenty studies provided accuracy data based on the number of individual participants (seven of which provided data with and without the use of contrast). Sixteen of these studies evaluated the accuracy of CDUS. These studies were generally of moderate to low quality: only three studies fulfilled all the QUADAS items; in six (40%) of the studies, the delay between the tests was unclear or longer than four weeks; in eight (50%), the blinding of either the index test or the reference standard was not clearly reported or was not performed; and in two studies (12%), the interpretation of the reference standard was not clearly reported. Eleven studies evaluated the accuracy of CE-CDUS. These studies were of better quality than the CDUS studies: five (45%) studies fulfilled all the QUADAS items; four (36%) did not report clearly the blinding interpretation of the reference standard; and two (18%) did not clearly report the delay between the two tests.Based on the bivariate model, the summary estimates for CDUS were 0.82 (95% confidence interval (CI) 0.66 to 0.91) for sensitivity and 0.93 (95% CI 0.87 to 0.96) for specificity whereas for CE-CDUS the estimates were 0.94 (95% CI 0.85 to 0.98) for sensitivity and 0.95 (95% CI 0.90 to 0.98) for specificity. Regression analysis showed that CE-CDUS was superior to CDUS in terms of sensitivity (LR Chi² = 5.08, 1 degree of freedom (df); P = 0.0242 for model improvement).Seven studies provided estimates before and after administration of contrast. Sensitivity before contrast was 0.67 (95% CI 0.47 to 0.83) and after contrast was 0.97 (95% CI 0.92 to 0.99). The improvement in sensitivity with of contrast use was statistically significant (LR Chi² = 13.47, 1 df; P = 0.0002 for model improvement).Regression testing showed evidence of statistically significant effect bias related to year of publication and study quality within individual participants based CDUS studies. Sensitivity estimates were higher in the studies published before 2006 than the estimates obtained from studies published in 2006 or later (P < 0.001); and studies judged as low/unclear quality provided higher estimates in sensitivity. When regression testing was applied to the individual based CE-CDUS studies, none of the items, namely direction of the study design, quality, and age, were identified as a source of heterogeneity.Twenty-two studies provided accuracy data based on number of scans performed (of which four provided data with and without the use of contrast). Analysis of the studies that provided scan based data showed similar results. Summary estimates for CDUS (18 studies) showed 0.72 (95% CI 0.55 to 0.85) for sensitivity and 0.95 (95% CI 0.90 to 0.96) for specificity whereas summary estimates for CE-CDUS (eight studies) were 0.91 (95% CI 0.68 to 0.98) for sensitivity and 0.89 (95% CI 0.71 to 0.96) for specificity.

AUTHORS' CONCLUSIONS

This review demonstrates that both ultrasound modalities (with or without contrast) showed high specificity. For ruling in endoleaks, CE-CDUS appears superior to CDUS. In an endoleak surveillance programme CE-CDUS can be introduced as a routine diagnostic modality followed by CT scan only when the ultrasound is positive to establish the type of endoleak and the subsequent therapeutic management.

Characteristics and Echogenicity of Clinical Ultrasound Contrast Agents: An In Vitro and In Vivo Comparison Study

OBJECTIVES

To compare physicochemical characteristics and in vitro and in vivo contrast-enhanced ultrasound imaging performance of 3 commercially available ultrasound contrast agents: SonoVue (Bracco Imaging SpA, Colleretto Giacosa, Italy; also marketed as Lumason in the USA), Definity (Lantheus Medical Imaging, North Billerica, MA) and Optison (GE Healthcare AS, Oslo, Norway).

METHODS

Physicochemical characteristics were measured with a Multisizer Coulter Counter (Beckman Coulter, Fullerton, CA). Two ultrasound systems (Aplio 500; Toshiba Medical Systems Corp, Tochigi-ken, Japan; and Logiq E9; GE Healthcare, Little Chalfont, England) were used with different transducers. Contrast enhancement was measured in vitro by dose-ranging measurements using a custom-built beaker setup; in vivo imaging performances were compared in pigs (heart and liver) and rabbits (liver). Quantitative analyses were performed with VueBox quantification software (Bracco Suisse SA, Plan-les-Ouates, Switzerland).

RESULTS

Measured physicochemical characteristics were in agreement with those provided by the manufacturers. In vitro data demonstrated that the performance of SonoVue was similar to or better than that of Definity but superior to Optison (normalized scattered power 2- to 10-fold higher with SonoVue). Similar results were obtained in vivo, although the duration of enhancement in the pig heart was longer for SonoVue compared to Definity, and quantitative analysis revealed higher enhancement for SonoVue (1.5-fold increase). For liver imaging, SonoVue and Definity showed similar contrast enhancement and duration of enhancement, but compared to Optison, both peak enhancement and duration of enhancement were superior for SonoVue (up to 2-fold increase).

CONCLUSIONS

Imaging performance of SonoVue was similar to or slightly better than that of Definity, but it was superior to Optison for the conditions used in this study.

[Quality standards for duplex ultrasonographic assessment (duplex us) of abdominal aortic stent grafts]

The quality standards of the French Society of Vascular Medicine for the ultrasound assessment of lower limb arteries in vascular medicine practice are based on the principle that these examinations have to meet two requirements: technical know-how (knowledge of devices and methodologies); medical know-how (level of examination matching the indication and purpose of the examination, interpretation and critical analysis of results).

OBJECTIVES OF THE QUALITY STANDARDS

To describe an optimal level of examination adjusted to the indication or clinical hypothesis; to establish harmonious practices, methodologies, terminologies, results description and report; to provide good practice reference points and to promote a high quality process.

THEMES OF THE QUALITY STANDARDS

The three levels of examination, indications and objectives for each level; the reference standard examination (level 2) and its variants according to indications; the minimal content of the exam report, the medical conclusion letter to the corresponding physician (synthesis, conclusion and management suggestions); commented glossary (anatomy, hemodynamics, signs and symptoms); technical basis; device settings. Here, we discuss duplex ultrasound for the supervision of the aortic stent grafts.

Contrast-enhanced US-guided Interventions: Improving Success Rate and Avoiding Complications Using US Contrast Agents

Ultrasonography (US) is an established modality for intervention. The introduction of microbubble US contrast agents (UCAs) has the potential to further improve US imaging for intervention. According to licensing, UCAs are currently approved for clinical use in restricted situations, but many additional indications have become accepted as having clinical value. The use of UCAs has been shown to be safe, and there is no risk of renal toxic effects, unlike with iodinated or gadolinium contrast medium. Broadly speaking, UCAs can be injected into the bloodstream (intravascular use) or instilled into almost any accessible body cavity (endocavitary use), either in isolation or synchronously. In microvascular applications, contrast-enhanced US (CEUS) enhances delineation of necrotic areas and the vascularized target to improve real-time targeting. The ability of CEUS to allow true assessment of vascularity has also been used in follow-up of devascularizing intervention. In macrovascular applications, real-time angiographic images can be obtained with CEUS without nephrotoxic effects or radiation. In endocavitary applications, CEUS can achieve imaging similar to that of iodinated contrast medium-based fluoroscopy; follow-up to intervention (eg, tubography and nephrostography) can be performed at the bedside, which may be advantageous. The use of UCAs is a natural progression in US-guided intervention. The aim of this article is to describe the indications, contraindications, and techniques of using UCAs as an adjunctive tool for US-guided interventional procedures to facilitate effective treatment, improve complication management, and increase the overall success of interventional procedures. Online supplemental material is available for this article. ^©RSNA, 2016.

Contemporary Applications of Ultrasound in Abdominal Aortic Aneurysm Management

Ultrasound (US) is a well-established screening tool for detection of abdominal aortic aneurysms (AAAs) and is currently recommended not only for those with a relevant family history but also for all men and high-risk women older than 65 years of age. The advent of minimally invasive endovascular techniques in the treatment of AAAs [endovascular aneurysm repair (EVAR)] has increased the need for repeat imaging, especially in the postoperative period. Nevertheless, preoperative planning, intraoperative execution, and postoperative surveillance all mandate accurate imaging. While computed tomographic angiography and angiography have dominated the field, repeatedly exposing patients to the deleterious effects of cumulative radiation and intravenous nephrotoxic contrast, US technology has significantly evolved over the past decade. In addition to standard color duplex US, 2D, 3D, or 4D contrast-enhanced US modalities are revolutionizing AAA management and postoperative surveillance. This technology can accurately measure AAA diameter and volume, and most importantly, it can detect endoleaks post-EVAR with high sensitivity and specificity. 4D contrast-enhanced US can even provide hemodynamic information about the branch vessels following fenestrated EVARs. The need for experienced US operators and accredited vascular labs is mandatory to guarantee the reliability of the results. This review article presents a comprehensive overview of the literature on the state-of-art US imaging in AAA management, including post-EVAR follow-up, techniques, and diagnostic accuracy.

Contrast-enhanced Ultrasound in Detecting Endoleaks with Failed Computed Tomography Angiography Diagnosis after Endovascular Abdominal Aortic Aneurysm Repair

Background:

Endovascular aneurysm repair (EVAR) is one of the first-line therapies of abdominal aortic aneurysms. Postoperative endoleak is the most common complication of EVAR. Computed tomography angiography (CTA), which is routine for follow-up, has side effects (e.g., radiation) and also has a certain percentage of missed diagnosis. Preliminary studies on contrast-enhanced ultrasound (CEUS) have shown that the sensitivity of CEUS for detecting endoleak is no lower than that of CTA. To investigate the advantages of CEUS, we conducted CEUS examinations of post-EVAR cases in which CTA failed to detect endoleak or could not verify the type of endoleak.

Methods:

Post-EVAR patients, who were clinically considered to have endoleak and met the inclusion criteria were enrolled between March 2013 and November 2014. All of the patients underwent color Doppler flow imaging (CDFI) and a CEUS examination. Size, location, microbubble dispersion, and hemodynamic characteristics of leaks were recorded. Comparison between the diagnosis of CEUS and CDFI was conducted using Fisher's exact test and clinical outcomes of all patients were followed up.

Results:

Sixteen patients were enrolled, and 12 (75%) had endoleaks with verified types by CEUS. Among 12 cases of endoleaks were positive by CEUS, 10 were CDFI-positive, and the four CEUS-negative cases were all negative by CDFI. The diagnostic values of CEUS and CDFI were statistically different (P = 0.008). Six patients with high-pressure endoleaks received endovascular re-intervention guided by CEUS results. One patient with type III endoleak had open surgery when endovascular repair failed.

Conclusions:

CEUS is a new, safe, and effective means for detection of endoleaks post-EVAR. This technique can be used as a supplement for routine CTA follow-up to provide more detailed information on endoleak and its category.

The role of contrast-enhanced ultrasound imaging in the follow-up of patients post-endovascular aneurysm repair

Endovascular aneurysm repair is a minimally invasive technique for the treatment of abdominal aortic aneurysms. Patients who undergo endovascular aneurysm repair are potentially at risk of developing problems related to the graft such as the development of endoleaks. Endoleaks can cause expansion of the aneurysmal sac, which can potentially lead to rupture. It is for this reason that lifelong surveillance of patients is required to assess the graft and the aneurysmal sac. This article discusses the role of contrast-enhanced ultrasound in the follow-up of patients post-endovascular aneurysm repair. Contrast-enhanced ultrasound is rapidly becoming a powerful, accurate and cost-effective tool to complement computed tomography in the follow-up of endovascular aneurysm repair patients. Real-time imaging of contrast filling into the arterial system means that contrast-enhanced ultrasound is an excellent problem-solving tool, particularly when assessing for the type and anatomy of endoleaks. In some instances, contrast-enhanced ultrasound can detect endoleaks when other modalities are equivocal.

Contrast-enhanced ultrasound after endovascular aortic repair-current status and future perspectives

An increasing number of patients with abdominal aortic aneurysms (AAAs) are undergoing endovascular aortic repair (EVAR) instead of open surgery. These patients require lifelong surveillance, and the follow-up imaging modality of choice has been traditionally computed tomography angiography (CTA). Repetitive CTA imaging is associated with cumulative radiation exposure and requires the administration of multiple doses of nephrotoxic contrast agents. Contrast-enhanced ultrasound (CEUS) has emerged as an alternative strategy in the follow-up of patients with EVAR and demonstrates high sensitivity and specificity for detection of endoleaks. In fact, a series of studies have shown that CEUS is at least performing equal to computed tomography for the detection and classification of endoleaks. This article summarizes current evidence of CEUS after EVAR and demonstrates its usefulness via various patient cases.

Surveillance Imaging Following Endovascular Aneurysm Repair

There is a significant risk of complication following endovascular abdominal repair (EVAR), including endoleak, graft translocation, thrombosis, and infection. Surveillance imaging is important for detecting EVAR complication. Surveillance modalities include conventional X-ray, computed tomography, magnetic resonance imaging, ultrasound, and conventional angiography, with inherent advantages and drawbacks to each modality. The authors present common complications following EVAR, and recent advances in the key modalities for surveillance.

Essentials of endovascular abdominal aortic aneurysm repair imaging: postprocedure surveillance and complications

OBJECTIVE

Lifelong postprocedural imaging surveillance is necessary after endovascular abdominal aortic aneurysm repair (EVAR) to assess for complications of endograft placement, as well as device failure and continued aneurysm growth. Refinement of the surveillance CT technique and development of ultrasound and MRI protocols are important to limit radiation exposure.

CONCLUSION

A comprehensive understanding of EVAR surveillance is necessary to identify life-threatening complications and to aid in secondary treatment planning.

Duplex Ultrasound versus Computed Tomography for the Postoperative Follow-Up of Endovascular Abdominal Aortic Aneurysm Repair. Where Do We Stand Now?

In the last decade, endovascular aneurysm repair (EVAR) has rapidly developed to be the preferred method for infrarenal abdominal aortic aneurysm repair in patients with suitable anatomy. EVAR offers the advantage of lower perioperative mortality and morbidity but carries the cost of device-related complications such as endoleak, graft migration, graft thrombosis, and structural graft failure. These complications mandate a lifelong surveillance of EVAR patients and their endografts. The purpose of this study is to review and evaluate the safety of color-duplex ultrasound (CDU) as compared with computed tomography (CT), based on the current literature, for post-EVAR surveillance. The post-EVAR follow-up modalities, CDU versus CT, are evaluated questioning three parameters: (1) accuracy of aneurysm size, (2) detection and classification of endoleaks, and (3) detection of stent-graft deformation. Studies comparing CDU with CT scan for investigation of post-EVAR complications have produced mixed results. Further and long-term research is needed to evaluate the efficacy of CDU versus CT, before CDU can be recommended as the primary imaging modality for EVAR surveillance, in place of CT for stable aneurysms.