Multidetector CT in Abdominal Aortic Aneurysm Treated with Endovascular Repair: Are Unenhanced and Delayed Phase Enhanced Images Effective for Endoleak Detection?

Retrospective Cohort Study on EVAR Open Surgical Conversion: Focus on Endoleaks With Wrong Preoperative Categorization

BACKGROUND

Late open conversion (LOC) following endovascular aneurysm repair (EVAR) is a rare complication with a high morbidity and mortality and is often proposed as the last line of treatment after failure of endovascular reintervention of any type. This study aimed to highlights the limitations of EVAR follow-up imaging in characterizing endoleaks, which may contribute to the failure of endovascular reinterventions and lead to LOC.

METHODS

This retrospective cohort study recruited all EVAR implanted in Amiens University Hospital (France) between January 2008 and December 2022. Elective LOC was defined as surgical conversion >1 month after EVAR. The primary endpoint was the rate of wrong categorization of endoleaks by follow-up exams before LOC. Secondary endpoints were the morbidity and the mortality associated with LOC.

RESULTS

Seven hundred eight EVARs were performed in our institution, 30 required elective LOC. Twenty-five of them were treated for sac enlargement due to an endoleak (83.3%) (all types). Wrong categorization of the endoleak was noted in 13 patients (52.2%). Twelve of these recategorizations involved the preoperative diagnosis of a type II endoleaks (92.3%). The change in categorization in 7 out of 12 cases (58%) was in favor of a type I endoleak, other recategorization included 1 type III (8%) and 4 type IV (33%). One patient died during the 30-day postoperative period and 7 patients (28%) presented a major complication; the median length of stay was 13 days (interquartile range 9-21).

CONCLUSIONS

Routine follow-up examinations such as angioscanner and contrast Doppler ultrasound appear to be limited in their ability to categorize the type of persistent endoleak, which may increase the number of patients requiring LOC. New precision diagnostic imaging techniques, such as dynamic examinations, need to be developed to limit the need for LOC.

Unenhanced computed tomography radiomics help detect endoleaks after endovascular repair of abdominal aortic aneurysm

OBJECTIVES

To explore the feasibility of unenhanced CT images for endoleak detection of abdominal aortic aneurysm (AAA) after endovascular repair (EVAR).

METHODS

Patients who visited our hospital after EVAR from July 2014 to September 2021 were retrospectively collected. Two radiologists evaluated the presence or absence of endoleaks using the combination of contrast-enhanced and unenhanced CT as the referenced standard. After segmenting the aneurysm sac of the unenhanced CT, the radiomic features were automatically extracted from the region of interest. Histogram features of patients with and without endoleak were statistically analyzed to explore the differences between the two groups. Twelve common machine learning (ML) models based on radiomic features were constructed to evaluate the performance of endoleak detection with unenhanced CT images.

RESULTS

The study included 216 patients (69 ± 8 years; 191 men) with AAA, including 64 patients with endoleaks. A total of 1955 radiomic features of unenhanced CT were extracted. Compared with patients without endoleak, the aneurysm sac outside the stent of patients with endoleak had higher CT attenuation (41.7 vs. 33.6, p < 0.001) with smaller dispersion (51.5 vs. 58.8, p < 0.001). The average area under the curve (AUC) of the ML models constructed with unenhanced CT radiomics was 0.86 ± 0.05, the accuracy was 81% ± 4, the sensitivity was 88% ± 10, and the specificity was 78% ± 5. When fixing the sensitivity to > 90% (92% ± 2), the models retained specificity at 72% ± 10.

CONCLUSIONS

Unenhanced CT features exhibit significant differences between patients with and without endoleak and can help detect endoleaks in AAA after EVAR with high sensitivity.

CLINICAL RELEVANCE STATEMENT

Unenhanced CT radiomics can help provide an alternative method of endoleak detection in patients who have adverse reactions to contrast media. This study further exploits the value of unenhanced CT examinations in the clinical management and surveillance of postoperative abdominal aortic aneurysm.

KEY POINTS

• Unenhanced CT features of the aneurysm sac outside the stent exhibit significant differences between patients with and without endoleak. The endoleak group showed higher unenhanced CT attenuation (41.7 vs 33.6, p < .001) with smaller dispersion (51.5 vs 58.8, p < .001) than the nonendoleak group. • Unenhanced CT radiomics can help detect endoleaks after intervention. The average area under the curve (AUC) of twelve common machine learning models constructed with unenhanced CT radiomics was 0.86 ± 0.05, the average accuracy was 81% ± 4. • When fixing the sensitivity to > 90% (92% ± 2), the machine learning models retained average specificity at 72% ± 10.

Review of Clinical Applications of Dual-Energy CT in Patients after Endovascular Aortic Repair

Abdominal aortic aneurysms (AAAs) are a significant cause of mortality in developed countries. Endovascular aneurysm repair (EVAR) is currently the leading treatment method for AAAs. Due to the high sensitivity and specificity of post-EVAR complication detection, CT angiography (CTA) is the reference method for imaging surveillance in patients after EVAR. Many studies have shown the advantages of dual-energy CT (DECT) over standard polyenergetic CTA in vascular applications. In this article, the authors briefly discuss the technical principles and summarize the current body of literature regarding dual-energy computed tomography angiography (DECTA) in patients after EVAR. The authors point out the most useful applications of DECTA in this group of patients and its advantages over conventional CTA. To conduct this review, a search was performed using the PubMed, Google Scholar, and Web of Science databases.

Improved Detection of Endoleaks in Virtual Monoenergetic Images in Dual-Energy CT Angiography Following EVAR

OBJECTIVES

The objective of this prospective study was to evaluate the virtual monoenergetic images (VMI) and virtual noncontrast (VNC) phase in the detection of endoleaks after endovascular abdominal aortic repair (EVAR). The potential dose reduction of abbreviated examination protocols was calculated.

MATERIALS AND METHODS

Ninety-seven patients after the EVAR procedure were enrolled in this study. An initial single-source noncontrast acquisition was followed by two dual-energy acquisitions (arterial and 60 s delayed). Fast-kVp switching scanner was used. VNC images were reconstructed from the delayed phase. First examination session (reference) included a full triphasic study protocol consisting of true noncontrast (TNC) images and two postcontrast phases, the latter ones presented as classical polyenergetic reconstructions. Reading sessions II and III were performed by two independent and blinded readers evaluating VMIs in abbreviated protocols-biphasic (VNC + arterial, delayed phase), monophasic (VNC + delayed phase). The diagnostic accuracy of sessions II and III was calculated.

RESULTS

The calculated sensitivity of the biphasic protocol with the use of VMIs in endoleak detection was 100%, with a statistically significant increase in the number of endoleaks detected in comparison with the reference study. The monophasic protocol showed 83.33% sensitivity. The use of abbreviated examination protocols led to a decrease in the mean effective dose (ED) of 23.28% (biphasic protocol) and 61.37% (monophasic protocol).

CONCLUSION

The use of VMIs increases the number of endoleaks diagnosed with a possible radiation reduction by up to ¼ (biphasic protocol). Further reduction to a monophasic protocol leads to over 60% dose reduction but with a decrease in diagnostic accuracy.

Photon-Counting Detector CT Angiography for Endoleak Detection After Endovascular Aortic Repair: Triphasic CT With True Noncontrast Versus Biphasic CT With Virtual Noniodine Imaging

OBJECTIVES

The aim of this study was to compare image quality and endoleak detection after endovascular abdominal aortic aneurysm repair between a triphasic computed tomography (CT) with true noncontrast (TNC) and a biphasic CT with virtual noniodine (VNI) images on photon-counting detector CT (PCD-CT).

MATERIALS AND METHODS

Adult patients after endovascular abdominal aortic aneurysm repair who received a triphasic examination (TNC, arterial, venous phase) on a PCD-CT between August 2021 and July 2022 were retrospectively included. Endoleak detection was evaluated by 2 blinded radiologists on 2 different readout sets (triphasic CT with TNC-arterial-venous vs biphasic CT with VNI-arterial-venous). Virtual noniodine images were reconstructed from the venous phase. The radiologic report with additional confirmation by an expert reader served as reference standard for endoleak presence. Sensitivity, specificity, and interreader agreement (Krippendorf α) were calculated. Image noise was assessed subjectively in patients using a 5-point scale and objectively calculating the noise power spectrum in a phantom.

RESULTS

One hundred ten patients (7 women; age, 76 ± 8 years) with 41 endoleaks were included. Endoleak detection was comparable between both readout sets with a sensitivity and specificity of 0.95/0.84 (TNC) versus 0.95/0.86 (VNI) for reader 1 and 0.88/0.98 (TNC) versus 0.88/0.94 (VNI) for reader 2. Interreader agreement for endoleak detection was substantial (TNC: 0.716, VNI: 0.756). Subjective image noise was comparable between TNC and VNI (4; IQR [4, 5] vs 4; IQR [4, 5], P = 0.44). In the phantom, noise power spectrum peak spatial frequency was similar between TNC and VNI (both f peak = 0.16 mm -1 ). Objective image noise was higher in TNC (12.7 HU) as compared with VNI (11.5 HU).

CONCLUSIONS

Endoleak detection and image quality were comparable using VNI images in biphasic CT as compared with TNC images in triphasic CT offering the possibility to reduce scan phases and radiation exposure.

Utility of Dual-Energy CT in Abdominal Interventions

Dual-energy computed tomography (DECT) is an emerging CT technique based on data acquisition at two different settings. Various postprocessing techniques generate different sets of images, each with unique advantages. With DECT, it is possible to obtain virtual unenhanced images from monochromatic reconstructions and attenuation maps of different elements, thereby improving the detection and characterization of a variety of lesions. Presently, DECT is widely used to evaluate pulmonary embolism, characterize abdominal masses, determine the composition of urinary calculi, and detect tophi in gout. CT angiography is an essential prerequisite for endovascular intervention. DECT allows a better quality of angiographic images with a lesser dose of contrast. Various postprocessing techniques in DECT also help in a better evaluation of response to locoregional therapy. Virtual noncontrast images and iodine map differentiate residual or recurrent tumors from intrinsically hyperdense materials. Superior metallic artifact reduction allows better evaluation of vascular injuries adjacent to bony fractured fragments or previously deployed embolization coils. In addition to metal artifacts reduction, virtual monochromatic spectral imaging could further mitigate metal artifacts during CT-guided biopsy, providing an improved depiction of lesions and safe and versatile access for long puncture pathways. This article reviews and illustrates the different applications of DECT in various abdominal interventions. Familiarity with the capabilities of DECT may help interventional radiologists to improve their practice and ameliorate patient care.

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.

Abdominal vessel depiction on virtual triphasic spectral detector CT: initial clinical experience

Purpose

To evaluate vessel assessment in virtual monoenergetic images (VMI_40keV) and virtual-non-contrast images (VNC) derived from venous phase spectral detector computed tomography (SDCT) acquisitions in comparison to arterial phase and true non-contrast (TNC) images.

Methods

Triphasic abdominal SDCT was performed in 25 patients including TNC, arterial and venous phase. VMI_40keV and VNC were reconstructed from the venous phase and compared to conventional arterial-phase images (CI_art), TNC and conventional venous-phase images (CI_ven). Vessel contrast and virtual contrast removal were analyzed with region-of-interest-based measurements and in a qualitative assessment.

Results

Quantitative analysis revealed no significant attenuation differences between TNC and VNC in arterial vessels (p-range 0.07–0.47) except for the renal artery (p = 0.011). For venous vessels, significant differences between TNC and VNC were found for all veins (p < 0.001) except the inferior vena cava (p = 0.26), yet these differences remained within a 10 HU range in most patients. No significant attenuation differences were found between CI_art/VMI_40keV in arterial vessels (p-range 0.06–0.86). Contrast-to-noise ratio provided by VMI_40keV and CI_art was equivalent for all arterial vessels assessed (p-range 0.14–0.91).

Qualitatively, VMI_40keV showed similar enhancement of abdominal and pelvic arteries as CI_art and VNC were rated comparable to TNC.

Conclusion

Our study suggests that VNC and VMI_40keV derived from single venous-phase SDCT offer comparable assessment of major abdominal vessels as provided by routine triphasic examinations, if no dynamic contrast information is required.

Endotension: twenty years of a controversial term

Use of the term endotension in the treatment of aortic aneurysm is currently controversial. Initially it was proposed to define the circumstance in which there is an enlargement of the aneurysm sac after endovascular repair without a demonstrable endoleak. The term was established with the aim of transmitting the possibility of causes other than pressure applying stress to the aneurysm wall. Twenty years have passed since the proposal of this terminology was published. The literature is reviewed with the purpose of providing an update on advances in the knowledge of the possible etiological mechanisms. The experimental studies call into question that causes other than pressure determine the increase of the aneurysm. On the basis of this review, the term `Sac Expansion Without Evident Leak´ (SEWEL) is proposed as a more accurate and precise denomination for what is aimed to be defined. Evidence suggests that the more likely mechanisms of persistent pressurization of the aneurysm sac are an unidentified endoleak (likely type I or low-flow Type II) or thrombus occluding wide and short channels that connects with the excluded aneurysm sac (at the attachment sites of the stent-graft or at the branch vessels orifices).

Surveillance Imaging following Endovascular Aneurysm Repair: State of the Art

Endovascular aneurysmal repair (EVAR) has become a prominent modality for the treatment of abdominal aortic aneurysm. Surveillance imaging is important for the detection of device-related complications, which include endoleak, structural abnormalities, and infection. Currently used modalities include ultrasound, X-ray, computed tomography, magnetic resonance imaging, and angiography. Understanding the advantages and drawbacks of each modality, as well available guidelines, can guide selection of the appropriate technique for individual patients. We review complications following EVAR and advances in surveillance imaging modalities.

Contrast Enhancement Boost Technique at Aortic Computed Tomography Angiography: Added Value for the Evaluation of Type II Endoleaks After Endovascular Aortic Aneurysm Repair

RATIONALE AND OBJECTIVES

Delayed-phase acquisition of the computed tomography (CT) angiography is important for the evaluation of type II endoleaks after endovascular aortic aneurysm repair because the endoleak cavity area is associated with aneurysm sac expansion. Contrast enhancement boost (CE-boost) is a postprocessing technique for increasing the degree of contrast enhancement on contrast-enhanced CT. We aimed to investigate the usefulness of the CE-boost technique for the visualization of type II endoleaks.

MATERIALS AND METHODS

This retrospective study included 28 patients with type II endoleaks after endovascular aortic aneurysm repair who underwent triphasic contrast-enhanced CT. Objective (CT number, signal-to-noise ratio, and contrast-to-noise ratio) and subjective quality analyses using a four-point scale (1, poor; 4, excellent) were performed for the conventional early- and delayed-phase images as well as CE-boost delayed-phase images.

RESULTS

The CE-boost delayed-phase images yielded a significantly higher CT number (134.5 ± 41.7 HU), signal-to-noise ratio (23.4 ± 10.5), and contrast-to-noise ratio (15.3 ± 8.4) and showed a significantly larger endoleak area (145.0 ± 134.8 mm²) than did the conventional early-phase (95.6 ± 53.2 HU, 7.3 ± 4.7, 4.0 ± 4.2, and 56.2 ± 99.3 mm², respectively) and delayed-phase (110.5 ± 33.3 HU, 8.2 ± 2.7, 4.9 ± 2.0, and 124.8 ± 131.9 mm², respectively) images (p < 0.01). The endoleak visibility score was highest for the CE-boost delayed-phase images (2.0 ± 1.0, 3.0 ± 0.6, and 3.4 ± 0.7 for conventional early-phase, delayed-phase, and delayed-phase CE-boost images, respectively; p < 0.001).

CONCLUSION

The CE-boost technique facilitates clear visualization of type II endoleak cavities.

New predictors of aneurysm sac behavior after endovascular aortic aneurysm repair

OBJECTIVES

This study aimed to identify new predictors of sac behavior after endovascular aortic aneurysm repair (EVAR) and to investigate whether sac behavior is associated with long-term clinical outcomes.

METHODS

A total of 168 patients undergoing successful EVAR for abdominal aortic aneurysms with CTA follow-up of at least 1 year were included. Predictors of aneurysm sac behavior and its impact on long-term clinical outcomes were retrospectively analyzed.

RESULTS

According to sac behavior, eligible patients were stratified into the sac regression group (n = 79, 47.0%) and the sac non-regression group (n = 89, 53.0%). Patients in the regression group were younger (p = 0.036) and more likely to take sarpogrelate hydrochloride postoperatively (p = 0.011) than those in the non-regression group. The incidence of postimplantation syndrome (PIS) was significantly higher in the regression group (p = 0.005). On multivariate analysis, sac regression was more likely to occur in those with PIS (hazard ratio [HR], 1.68; 95% confidence interval [CI], 1.07-2.64; p = 0.023) and less likely to occur in those with transient type II endoleaks (HR, 0.43; 95% CI, 0.20-0.95; p = 0.037) and higher thrombus density within the sac on follow-up CTA (HR, 0.97; 95% CI, 0.95-0.99; p = 0.013). Non-regression of the sac was associated with significantly higher rates of re-intervention during the follow-up period (p = 0.001).

CONCLUSIONS

In addition to type II endoleaks, PIS and thrombus density are new predictors of aneurysm sac behavior, and sac regression is significantly associated with lower rates of re-intervention.

KEY POINTS

• After endovascular aortic aneurysm repair (EVAR), patients with sac regression were younger and more likely to take sarpogrelate hydrochloride postoperatively than those with sac non-regression. • The incidence of postimplantation syndrome (PIS) was significantly higher in patients with sac regression. • In our analysis, PIS and thrombus density within the sac were newly identified predictors of aneurysm sac behavior after EVAR.

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.

Contemporary imaging methods for the follow-up after endovascular abdominal aneurysm repair: a review

Abdominal aortic aneurysm (AAA) is defined as a localized enlargement of the aortic cross-section where the diameter is greater than 3 cm or more than 50% larger than the diameter in a normal segment. The most important complication of AAA is rupture, which, if untreated, results in mortality rates of up to 90%. Conventional open surgical repair is associated with significant 30-day mortality. Endovascular aneurysm repair (EVAR) is a significantly less invasive procedure; it is related to a lower early mortality rate and a lower number of perioperative complications. Although EVAR is a minimally invasive technique, lifelong follow-up imaging is necessary due to possible late complications including endoleak, recurrent aneurysm formation, graft infection, migration, kinking and thrombosis. The total rate of complications after EVAR is estimated at approximately 30%, and the rate of complications that require intervention is 2–3%. Early detection and progression analysis of such situations is crucial for proper intervention.

Incidental extravascular findings in CT angiograms in patients post endovascular abdominal aortic aneurysm repair: clinical relevance and frequency

Background

To evaluate the incidence and clinical relevance of extravascular incidental findings (EVIF), particularly malignancies, in planning and follow-up CT angiograms (CTA) of the abdominal aorta in patients who underwent endovascular aneurysm repair (EVAR) of abdominal aortic aneurysm. Retrospective study of 2203 planning and follow-up CTAs of 418 patients who underwent EVAR in a single tertiary centre between 2006 and 2015. CTA reports were scrutinized for EVIFs, which were classified according to clinical relevance, into (I) immediate, (II) potential and (III) no clinical relevance. Clinical follow-up and management were reviewed for significant findings. Follow-up CTAs of patients with incidental malignancies were re-reviewed by two consultant radiologists to evaluate if early missed malignant findings on previous CTAs were present.

Results

In total, 950 EVIFs were noted in 418 patients [31 females (7.4%), 387 males (92.6%); age range 63–93, mean age 79.0 years]. The number of patients with findings in each category were; Category I (115), Category II (165), Category III (304). Incidental malignant findings were reported in 51 patients (12.2%), of which 27 were noted on the initial CTA (6.5%) and 24 on follow-up CTAs (5.7%). Of the 24 patients with malignancies on follow-up CTAs, 13 had early malignant findings missed or misinterpreted on previous CTAs, while 11 had no significant abnormality even on retrospective review.

Conclusion

A high number of significant EVIFs, particularly incidental malignancies, can be identified in follow-up CTAs of patients who undergo EVAR. Specific ‘review areas’ when reporting surveillance CTAs can be recommended based on the findings of our study.

Experimental feasibility of spectral photon-counting computed tomography with two contrast agents for the detection of endoleaks following endovascular aortic repair

Objectives

After endovascular aortic repair (EVAR), discrimination of endoleaks and intra-aneurysmatic calcifications within the aneurysm often requires multiphase computed tomography (CT). Spectral photon-counting CT (SPCCT) in combination with a two-contrast agent injection protocol may provide reliable detection of endoleaks with a single CT acquisition.

Methods

To evaluate the feasibility of SPCCT, the stent-lined compartment of an abdominal aortic aneurysm phantom was filled with a mixture of iodine and gadolinium mimicking enhanced blood. To represent endoleaks of different flow rates, the adjacent compartments contained either one of the contrast agents or calcium chloride to mimic intra-aneurysmatic calcifications. After data acquisition with a SPCCT prototype scanner with multi-energy bins, material decomposition was performed to generate iodine, gadolinium and calcium maps.

Results

In a conventional CT slice, Hounsfield units (HU) of the compartments were similar ranging from 147 to 168 HU. Material-specific maps differentiate the distributions within the compartments filled with iodine, gadolinium or calcium.

Conclusion

SPCCT may replace multiphase CT to detect endoleaks without sacrificing diagnostic accuracy. It is a unique feature of our method to capture endoleak dynamics and allow reliable distinction from intra-aneurysmatic calcifications in a single scan, thereby enabling a significant reduction of radiation exposure.

Key Points

• SPCCT might enable advanced endoleak detection.

• Material maps derived from SPCCT can differentiate iodine, gadolinium and calcium.

• SPCCT may potentially reduce radiation burden for EVAR patients under post-interventional surveillance.

Identification of Factors Influencing Cumulative Long-Term Radiation Exposure in Patients Undergoing EVAR

Patients who undergo endovascular repair of aortic aneurysms (EVAR) require life-long surveillance because complications including, in particular, endoleaks, aneurysm rupture, and graft dislocation are diagnosed in a certain share of the patient population and may occur at any time after the original procedure. Radiation exposure in patients undergoing EVAR and post-EVAR surveillance has been investigated by previous authors. Arriving at realistic exposure data is essential because radiation doses resulting from CT were shown to be not irrelevant. Efforts directed at identification of factors impacting the level of radiation exposure in both the course of the EVAR procedure and post-EVAR endovascular interventions and CTAs are warranted as potentially modifiable factors may offer opportunities to reduce the radiation. In the light of the risks found to be associated with radiation exposure and considering the findings above, those involved in EVAR and post-EVAR surveillance should aim at optimal dose management.

Split-bolus intravenous contrast material injection vs. single-bolus injection in patients following endovascular abdominal aortic repair (EVAR)

PURPOSE

To investigate the feasibility and accuracy of a split-bolus contrast injection CTA (SB-CTA) compared to a single-bolus injection CTA (SI-CTA) protocol of post-EVAR patients.

MATERIALS AND METHODS

In this IRB-approved study, patients who underwent SB-CTA and SI-CTA after EVAR were evaluated. Attenuation and contrast-to-noise ratio (CNR) of vessels and parenchymal organs were assessed. Subjective enhancement of vessels, quality of 3D reconstructions, and enhancement phase of parenchymal organs were assessed by two independent readers. Endoleak visibility and incidental findings were evaluated.

RESULTS

Fifty-six patients with SB-CTA and SI-CTA at two different time points after EVAR were included in the study (112 imaging studies, mean age 75 ± 9 years). There was no difference in attenuation and CNR for aorta between SB-CTA and SI-CTA (310 ± 87 vs. 311 ± 80 HU, p = 0.88; 31.1 ± 12.6 vs. 29.0 ± 12.2, p = 0.20), although both were improved in the venous structures and parenchymal organs with SB-CTA (portal vein: 149 ± 33 vs. 88 ± 32 HU, 11.6 ± 5.6 vs. 4.3 ± 3.4; liver: 91 ± 19 vs. 68 ± 20 HU, 4.4 ± 2.8 vs. 2.1 ± 2.0; pancreas: 108 ± 27 vs. 82 ± 23 HU, 6.4 ± 3.1 vs. 3.6 ± 2.4; p < 0.0001). Subjectively, enhancement of veins, liver, spleen, bowel, and kidneys was improved (p < 0.001), while there was no difference for the aorta (p = 0.46) and 3D reconstructions (p = 0.58). None of the 18/56 (32.1%) endoleaks was missed with the SB-CTA. More incidental findings were detected with SB-CTA (158/56) compared to SI-CTA (135/56), p < 0.001. SB-CTA was able to adequately characterize 7/15 (47%) of the findings that needed further evaluation in SI-CTA. 4/15 (26%) incidental findings that were missed with SI-CTA but seen with SB-CTA required further evaluation.

CONCLUSION

Split-bolus injection CTA in the follow-up of EVAR patients allows reliable visualization of endoleaks with improved subjective and objective image quality.

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.

Endoleak detection using single-acquisition split-bolus dual-energy computer tomography (DECT)

OBJECTIVES

To assess a single-phase, dual-energy computed tomography (DECT) with a split-bolus technique and reconstruction of virtual non-enhanced images for the detection of endoleaks after endovascular aneurysm repair (EVAR).

METHODS

Fifty patients referred for routine follow-up post-EVAR CT and a history of at least one post-EVAR follow-up CT examination using our standard biphasic (arterial and venous phase) routine protocol (which was used as the reference standard) were included in this prospective trial. An in-patient comparison and an analysis of the split-bolus protocol and the previously used double-phase protocol were performed with regard to differences in diagnostic accuracy, radiation dose, and image quality.

RESULTS

The analysis showed a significant reduction of radiation dose of up to 42 %, using the single-acquisition split-bolus protocol, while maintaining a comparable diagnostic accuracy (primary endoleak detection rate of 96 %). Image quality between the two protocols was comparable and only slightly inferior for the split-bolus scan (2.5 vs. 2.4).

CONCLUSIONS

Using the single-acquisition, split-bolus approach allows for a significant dose reduction while maintaining high image quality, resulting in effective endoleak identification.

KEY POINTS

• A single-acquisition, split-bolus approach allows for a significant dose reduction. • Endoleak development is the most common complication after endovascular aortic repair (EVAR). • CT angiography is the imaging modality of choice for aortic aneurysm evaluation.

Type 2 Endoleaks: The Diagnostic Performance of Non-Specialized Readers on Arterial and Venous Phase Multi-Slice CT Angiography

Purpose

To define the diagnostic precision of non-specialized readers in the detection of type 2 endoleaks (T2EL) in arterial versus venous phase acquisitions, and to evaluate an approach for radiation dose reduction.

Methods

The pre-discharge and final follow-up multi-slice CT angiographies of 167 patients were retrospectively analyzed. Image data were separated into an arterial and a venous phase reading set. Two radiology residents assessed the reading sets for the presence of a T2EL, feeding vessels, and aneurysm sac size. Findings were compared with a standard of reference established by two experts in interventional radiology. The effective dose was calculated.

Results

Overall, experts detected 131 T2ELs, and 331 feeding vessels in 334 examinations. Persistent T2ELs causing aneurysm sac growth > 5 mm were detected in 20 patients. Radiation in arterial and venous phases contributed to a mean of 58.6% and 39.0% of the total effective dose. Findings of reader 1 and 2 showed comparable sensitivities in arterial sets of 80.9 versus 85.5 (p = 0.09), and in venous sets of 73.3 versus 79.4 (p = 0.15), respectively. Reader 1 and 2 achieved a significant higher detection rate of feeding vessels with arterial compared to venous set (p = 0.04, p < 0.01). Both readers correctly identified T2ELs with growing aneurysm sac in all cases, independent of the acquisition phase.

Conclusion

Arterial acquisitions enable non-specialized readers an accurate detection of T2ELs, and a significant better identification of feeding vessels. Based on our results, it seems reasonable to eliminate venous phase acquisitions.

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.

Detecting Aortic Graft Complications: A Spectrum of Computed Tomography Findings

Endovascular aneurysm repair (EVAR) is a successful technique as well as an excellent alternative to the surgical management of abdominal aortic aneurysms. EVAR has improved the mortality and morbidity of many patients who would have otherwise suffered greatly from the consequences of abdominal aortic aneurysms. However, EVAR is not without complications. Some complications require lifelong surveillance, whereas others may necessitate immediate surgical intervention. We discuss the various modalities available for the surveillance as well as the common complications that can be seen on computed tomography.

Radiological Evaluation of Abdominal Endovascular Aortic Aneurysm Repair

Endovascular aortic aneurysm repair (EVAR) is an alternative to open surgical repair of aortic aneurysms offering lower perioperative mortality and morbidity. As experience increases, clinicians are undertaking complex repairs with hostile aortic anatomy using branched or fenestrated devices or extra components such as chimneys to ensure perfusion to visceral branch vessels whilst excluding the aneurysm. Defining the success of EVAR depends on both clinical and radiographic criteria, but ultimately depends on complete exclusion of the aneurysm from the circulation. Aortic stent grafts are monitored using a combination of imaging modalities including computed tomography angiography (CTA), ultrasonography, magnetic resonance imaging, plain films, and nuclear medicine studies. This article describes when and how to evaluate aortic stent grafts using each of these modalities along with the characteristic features of several of the main stent grafts currently used in clinical practice. The commonly encountered complications from EVAR are also discussed and how they can be detected using each imaging modality. As the radiation burden from serial follow up CTA imaging is now becoming a concern, different follow-up imaging strategies are proposed depending on the complexity of the repair and based on the relative merits and disadvantages of each imaging modality.

Contrast-enhanced ultrasound (CEUS) versus computed tomography angiography (CTA) in detection of endoleaks in post-EVAR patients. Are delayed type II endoleaks being missed? A systematic review and meta-analysis

PURPOSE

The purpose of this systematic review is to assess the accuracy of contrast-enhanced ultrasound (CEUS) to computed tomography angiography (CTA) for the detection of endoleaks within EVAR surveillance program.

MATERIAL AND METHODS

A systematic review in Pubmed, Embase and Cochrane database was performed. Articles assessing diagnostic accuracy and comparative modality (CTA vs. CEUS) for endoleaks in adult patients within surveillance programs were retrieved. Methodological assessment was performed, using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) tools. The sensitivity and specificity of data were extracted and statistical analysis was performed using MetaDiSc version 1.4.

RESULTS

Eight articles were found eligible (n = 454 patients). The pooled sensitivity of CEUS at detecting endoleak is 0.914 (CI 0.866-0.949) and pooled specificity is 0.782 (CI 0.741-0.820).

CONCLUSION

The CEUS with its dynamic nature and longer scanning window demonstrated to be a highly sensitive modality for endoleak detection in comparison to CTA in delayed endoleaks type II.

Cumulative radiation dose and radiation risk from medical imaging in patients subjected to endovascular aortic aneurysm repair

PURPOSE

This study was undertaken to quantify the cumulative effective dose (CED) of radiation and the dose to relevant organs in endovascular aortic repair (EVAR) patients, to assess radiation risks and to evaluate the clinical usefulness of multi-detector computed tomography (MDCT) follow-up.

MATERIALS AND METHODS

The radiation exposures were obtained from 71 consecutive EVAR patients with a follow-up duration ≥1 year. Dose calculations were performed on an individual basis and expressed as effective doses and organ doses. Radiation risk was expressed as risk of exposure-induced death (%), using the biological effects of ionising radiation model. Two radiologists independently assessed the images for abdominal aortic aneurysm expansion without endoleaks, thrombotic occlusion, endoleaks and device migration. They first reviewed arterial imaging alone and subsequently added non-contrast and delayed phases to determine the overall performance.

RESULTS

The median total CED and annual CED were 224 and 104 mSv per patient-year. The median cumulative organ doses were 191, 205, 230, 269 and 271 mSv for lung, bone marrow, liver, colon and stomach, respectively. The average risk of exposure-induced death was 0.8 % (i.e., odds 1 in 130). All the findings related to EVAR outcome and leading to a change in patient management were visible during the arterial phase of the MDCT angiography. Omission of the unenhanced scan and the venous phase of the MDCT angiography would have led to a significant reduction of about 60 % of the associated MDCT radiation exposure in a single patient.

CONCLUSIONS

EVAR patients received high radiation doses and the excess cancer risk attributable to radiation exposure is not negligible. The unenhanced scan and the venous phase of the MDCT angiography could have been omitted without compromising the utility of the examination and with a significant reduction of doses and associated risks.

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.

Carbon dioxide digital subtraction angiography as an option for detection of endoleaks in endovascular abdominal aortic aneurysm repair procedure

OBJECTIVE

The purpose of this study was to evaluate carbon dioxide digital subtraction angiography (CO2-DSA) as an option for the detection of endoleaks (ELs) in the endovascular abdominal aortic aneurysm repair (EVAR) procedure.

METHODS

Forty patients with abdominal aortic aneurysm who were scheduled to undergo EVAR were enrolled in the study. There were 35 men and five women (mean age, 77.9 years). All patients had both iodinated contrast conventional DSA (C-DSA) and CO2-DSA immediately after EVAR. The sensitivity and specificity were calculated for the ability of CO2-DSA to detect ELs. We also correlated with computed tomography findings 6 months after EVAR.

RESULTS

C-DSA showed that 27 of the 40 patients (68%) had 28 ELs (type I, four; type II, 20; type III, three; type IV, one). CO2-DSA showed that 16 of the 40 patients (40%) had 17 ELs (type I, four; type II, 10; type III, three; type IV, none). For the prediction of direct ELs (type I and type III) with use of C-DSA as the criterion standard, CO2-DSA has a sensitivity of 1.0 and a specificity of 1.0. For the detection of persistent type II ELs (n = 11) with use of computed tomography findings 6 months from EVAR as the criterion standard, CO2-DSA has a sensitivity of 0.87 and a specificity of 0.97. C-DSA has a sensitivity of 0.82 and a specificity of 0.64.

CONCLUSIONS

CO2-DSA is reliable for the detection of direct ELs and persistent type II ELs in EVAR. CO2-DSA can be an option to detect ELs in the EVAR procedure.

Dual-source dual-energy CT: dose reduction after endovascular abdominal aortic aneurysm repair

PURPOSE

This study was done to evaluate the possibility of reducing the dose of ionising radiation by using dual-source dual-energy computed tomography (CT) in patients undergoing CT angiography of the aorta to search for endoleaks after endovascular aneurysm repair (EVAR).

MATERIALS AND METHODS

One hundred and forty-eight patients (117 M, 31 F; mean age 75 ± 6.5) underwent 171 CT angiography scans for follow-up after EVAR. For each patient we performed a triple-phase acquisition protocol consisting of a nonenhanced phase, an arterial phase and a delayed phase; the latter acquired in dual energy. Two radiologists jointly evaluated the nonenhanced, arterial and delayed phase, and a third radiologist evaluated only the delayed phase and its virtual noncontrast (VNC) reconstruction. Moreover, we compared the cumulative effective doses of the triple-phase acquisition with the dual-energy acquisition.

RESULTS

We detected 34 endoleaks (19.8 %), with 100 % agreement between the triple-phase and dual-energy acquisitions. The effective dose of dual-energy acquisition performed during the delayed phase was 61.7 % lower than that of the triple-phase acquisition.

CONCLUSIONS

A dual-energy CT scan acquired during the delayed phase and its VNC reconstruction allow detection of endoleaks with a substantial reduction of effective dose and a complete diagnostic agreement with a triple-phase acquisition protocol.

Dynamic volumetric CT angiography for the detection and classification of endoleaks: application of cine imaging using a 320-row CT scanner with 16-cm detectors

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 (κ = 0.794) and intraobserver agreement (κ = 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.

Computed tomography angiography of hybrid thoracic endovascular aortic repair of the aortic arch

Endovascular repair of the aorta has traditionally been limited to the abdominal aorta and, more recently, the descending thoracic aorta. However, recently hybrid repairs (a combination of open surgical and endovascular repair) have made endovascular repair of the aortic arch possible. Hybrid repair of the aortic arch typically involves an open surgical debranching procedure that allows for revascularization of the aortic arch vessels and subsequent endovascular stent placement. These approaches avoid the deep hypothermic circulatory arrest required for full, open surgical repair of the aortic arch. In hybrid repairs, the stent landing zone determines which branch vessels will be covered and therefore need revascularization. This article will review the preprocedure assessment with computed tomography angiography, techniques for revascularization and postprocedure complications.

Quando a fase de equilíbrio pode ser suprimida nos exames de tomografia computadorizada de abdome?

OBJETIVO: Avaliar a necessidade de realização da fase de equilíbrio nos exames de tomografia computadorizada de abdome. MATERIAIS E MÉTODOS: Realizou-se estudo retrospectivo, transversal e observacional, avaliando 219 exames consecutivos de tomografia computadorizada de abdome com contraste intravenoso, realizados num período de três meses, com diversas indicações clínicas. Para cada exame foram emitidos dois pareceres, um avaliando o exame sem a fase de equilíbrio (primeira análise) e o outro avaliando todas as fases em conjunto (segunda análise). Ao final de cada avaliação, foi estabelecido se houve mudança nos diagnósticos principais e secundários, entre a primeira e a segunda análise. Foi utilizada a extensão do teste exato de Fisher para avaliar a modificação dos diagnósticos principais (p < 0,05 como significante). RESULTADOS: Entre os 219 casos avaliados, a supressão da fase de equilíbrio provocou alteração no diagnóstico principal em apenas um exame (0,46%; p > 0,999). Com relação aos diagnósticos secundários, cinco exames (2,3%) foram modificados. CONCLUSÃO: Para indicações clínicas como estadiamento tumoral, abdome agudo e pesquisa de coleção abdominal, a fase de equilíbrio não acrescenta contribuição diagnóstica expressiva, podendo ser suprimida dos protocolos de exame.

Dual-energy CT: vascular applications

OBJECTIVE

Dual-energy CT permits a variety of image reconstructions for the depiction and characterization of vascular disease. Techniques include visualization of low- and high-peak-kilovoltage spectra image datasets and also material-specific reconstructions combining both low- and high-peak-kilovoltage data.

CONCLUSION

This article focuses on four main vascular areas: the aorta, the major visceral, lower limb, and cervical arteries. For each territory, the current status, potential advantages, and limitations of these techniques are described.

Systematic review and meta-analysis of duplex ultrasonography, contrast-enhanced ultrasonography or computed tomography for surveillance after endovascular aneurysm repair

BACKGROUND

Previous analyses suggested that duplex ultrasonography (DUS) detected endoleaks after endovascular aneurysm repair (EVAR) with insufficient sensitivity; they did not specifically examine types 1 and 3 endoleak, which, if untreated, may lead to aneurysm-related death. In light of changes to clinical practice, the diagnostic accuracy of DUS and contrast-enhanced ultrasonography (CEUS) for types 1 and 3 endoleak required focused reappraisal.

METHODS

Studies comparing DUS or CEUS with computed tomography (CT) for endoleak detection were identified. CT was taken as the standard in bivariable meta-analysis.

RESULTS

Twenty-five studies (3975 paired scans) compared DUS with CT for all endoleaks. The pooled sensitivity was 0·74 (95 per cent confidence interval 0·62 to 0·83) and the pooled specificity was 0·94 (0·90 to 0·97). Thirteen studies (2650 paired scans) reported detection of types 1 and 3 endoleak by DUS; the pooled sensitivity of DUS was 0·83 (0·40 to 0·97) and the pooled specificity was 1·00 (0·97 to 1·00). Eleven studies (961 paired scans) compared CEUS with CT for all endoleaks. The pooled sensitivity of CEUS was 0·96 (0·85 to 0·99) and the pooled specificity was 0·85 (0·76 to 0·92). Eight studies (887 paired scans) reported detection of types 1 and 3 endoleak by CEUS. The pooled sensitivity of CEUS was 0·99 (0·25 to 1·00) and the pooled specificity was 1·00 (0·98 to 1·00).

CONCLUSION

Both CEUS and DUS were specific for detection of types 1 and 3 endoleak. Estimates of their sensitivity were uncertain but there was no evidence of a clinically important difference. DUS detects types 1 and 3 endoleak with sufficient accuracy for surveillance after EVAR.