Comparison of portable ultrasound system and high end ultrasound system in detection of endoleaks

Abstract

PURPOSE: To compare the value of a portable ultrasound system and a high end ultrasound system in detection of endoleaks after EVAR.

MATERIAL AND METHODS: In this retrospective study, a cohort of 25 patients underwent both standard examination using a portable ultrasound system (Philips VISIQ) and a second examination using a high end ultrasound system (Philips EPIQ 7). The examination included B-mode and color Doppler in detection of endoleaks. Additional the maximum diameter of the aneurysm was measured in two planes (right-left and ventral-dorsal). The gold standard was contrast-enhanced ultrasound (CEUS) in detection of endoleaks.

RESULTS: 25 patients were included in the study. Patients were predominantly male (n = 23) with an average age of 73,30±7.82 years (range 54–85). Diameters of the treated aneurysms were in the right-left plane 5,32±1.88 cm and ventral-dorsal 4,99±1.78 cm using the high end system. Diameters of the treated aneurysms were in the right-left plane 5,30±1.82 cm and ventral-dorsal 4,87±1.74 cm using portable ultrasound system. In 80% of the cases CEUS could detect an endoleak. Whereas the high end system could detect in B-mode 40% and color Doppler 45% of the cases an endoleak. The portable system could detect in B-mode 30% and in color Doppler 35% of the cases an endoleak. On both systems in B-mode a false positive endoleak was found on the same patient. All high flow endoleaks, which needed intervention, could be detected on all systems.

CONCLUSION: The high end ultrasound system does not seem to have an additional advantage in the measurement of the aneurysm diameter. Due to a higher resolution, more endoleaks could be detected in B-mode and color Doppler by using the high end system. The presence of small endoleaks could only be detected by using contrast enhanced ultrasound on an high end ultrasound system. High flow endoleaks could be reliable seen on both systems.

Keywords

Endoleak EVAR AAA CEUS portable ultrasound system

1 Introduction

Endovascular aneurysm repair was first used in 1991 as an alternative to open surgical repair and has gained increasing acceptance over the past years [7]. It is less invasive than open repair but has a higher complication rate, thus necessitating a lifelong surveillance [1, 3].

Endoleaks are the most common complication after EVAR and are defined as the persistence of blood flow outside the lumen of the endoluminal graft but within the aneurysmal sac [7, 19]. They occur in up to 45% of patients [27]. The existence of an endoleak is a cause for concern, as it perfuses and pressurizes the aneurysmal sac, which can lead to its enlargement with an associated risk of rupture [13].

White et al. categorized endoleaks into five groups [2]. Type I and type III endoleaks are characterized as high flow endoleaks, which are most likely prone to need an intervention after the detection of such an endoleak.

There are various available modalities for the follow-up after EVAR. Computed tomography (CT) is currently still considered the preferred examination, but CEUS is being increasingly used and was recommended in the EFSUMB guidelines for the first time in 2011 [22].

Despite the different excellent imaging techniques available, it is sometimes still difficult to tell whether there is an endoleak or not and which kind it is. Therefore the search for new methods to improve the detection and classification of endoleaks is ongoing.

Portable ultrasound devices have been subject of several studies investigating their impact on saving time [8], the possibility to assess specific clinical questions [23, 30], or to supplement computed tomography scans [20]. The clinical utility of portable ultrasound devices so far is limited [29], but the technology continues to evolve.

The aim of this study was to evaluate whether portable ultrasound examination including B-mode and color Doppler is a helpful new feature in confirming the presence and type of endoleak in comparison to high-resolution ultrasound examination.

2 Material and methods

2.1 Study design

2.1.1 Patient population

This retrospective study included, a cohort of 25 patients underwent both standard examination using a portable ultrasound system (Philips VISIQ) and a second examination using a high-end ultrasound system (Philips EPIQ 7) in the follow-up examination after EVAR during the time period between October 2014 until December 2014.

According to the study protocol, included patients received both B-mode and color Doppler in the standard examination. The gold standard of this study was contrast-enhanced ultrasound in detection of endoleaks after EVAR using the Philips EPIQ 7 scanner. CEUS was used as the preferred examination in determining the presence of an endoleak.

Additional the maximum diameter of the aneurysm was measured in two planes (right-left and ventral-dorsal).

2.1.2 Inclusion criteria

Only patients undergoing follow-up after EVAR who had received at least one CEUS examination after stent implantation (biiliacal or monoiliacal stent) were included in this study.

2.1.3 Exclusion criteria

Patients with an abdominal tube stent were excluded. Additional exclusion criteria were: patients with acute heart failure, acute myocardial infarction, known allergy to SonoVue^® ultrasound contrast agent and patient non-compliance.

2.1.4 Ethical aspects

The local ethics committee approved this retrospective study. The study data were collected within the framework of an external quality control in compliance with the principles of the Helsinki/Edinburgh Declaration of 2002 and performed in accordance with the guidelines of Clinical Haemorheology and Microcirculation (Clin Hemorheol Microcirc 44, 1-2 (2010)). Oral and written informed consent of all patients was obtained prior to each examination.

2.1.5 Examination protocol

The ultrasound examinations in the follow-up after EVAR of abdominal aortic aneurysms were performed by an experienced sonographer (15 years of experience) using a Philips Visiq-system (Philips Medical Systems, Bothell, WA) with curved array 5 - 2 MHz multi-frequency transducer. An internally standardized scanning protocol was used for assessing the abdominal aneurysm. The protocol includes transverse and sagittal imaging. The field of view was minimized to the area of interest and automatic grayscale optimization was used. A conventional grayscale ultrasound was initially performed, followed by color-coded duplex sonography. During the ultrasound examination cine loops were acquired and stored in the picture archiving and communication system. Mean examination time was 5 minutes for the complete examination. Additionally the examination was repeated using a Philips EPIQ 7 system (Philips Medical Systems, Bothell, WA) with curved array 9 - 2 MHz broadband transducer. The protocol includes the same presets as the previous used portable system. Mean examination time was 8 minutes for the complete examination.

For contrast-enhanced ultrasound examination the Philips EPIQ 7 system was used. An intravenous bolus injection of 1.0 ml of a second-generation blood pool contrast agent (SonoVue, Bracco, Milan, Italy), consisting of stabilized microbubbles of sulfur hexafluoride, was administered into an antecubital vein through an 18 G needle and was followed by a flush of 10 mL saline solution (0,9% NaCl) on all patients [10]. The ultrasound device features a high performance processor and allows the documentation of dynamic image sequences in cine mode by digital frame buffer. 1.0 ml contrast agent allows diagnostic views for about 3 minutes.

Additional the maximum diameter of the aneurysm was measured in two planes (right-left and ventral-dorsal) using both systems.

2.2 Data and statistical analysis

Data evaluation was performed using the digitally stored video sequences and image data sets of the ultrasound examination.

All ultrasound cineloops were assessed via consens reading by two experienced radiologists.

CEUS was used as the reference standard in determining the presence of an endoleak. B-mode and color Doppler findings were considered true positive if CEUS revealed evidence of an endoleak; if the findings were not confirmed in CEUS they were considered false-positive. Conventional measures of diagnostic performance, such as sensitivity and specificity for the detection of an endoleak were calculated.

CEUS was considered to be the reference standard.

3 Results

Between 15th October until 20th December 2014 we obtained a cohort of 25 patients in the follow-up after EVAR who received both standard examination using a portable ultrasound system (Philips VISIQ) and in a second examination using a high end ultrasound system (Philips EPIQ 7). The examination included B-mode, color Doppler and contrast enhanced ultrasound after EVAR (Figs. 1–10). Additional the maximum diameter of the aneurysm was measured in two planes (right-left and ventral-dorsal) using both systems.

None of our patients had to be excluded due to medical conditions like allergies or major pulmonary or heart diseases. No patient withdrew consent for the examination.

Patients were predominantly male (n = 23) with an average age of 73.3±7.82 years (range 54–85).

Diameters of the treated measured with the portable system from the left to the right side of the aneurysm were 5,11±1.58 cm and from ventral to the dorsal side were 4,69±1.55 cm (Fig. 11).

Diameters of the treated measured with the high end system from the left to the right side of the aneurysm were 5,11±1.66 cm and from ventral to the dorsal side were 4,77±1.51 cm (Fig. 12).

The included females (n = 2) in this study had an average age of 62±8,49 years (range 56–68).

Diameters of the treated aneurysms measured with the high end system from the left to the right side were 7,45±3,61 cm and from ventral to the dorsal side were 7,45±3,61 cm.

Diameters of the treated aneurysms measured with the portable system from the left to the right side were 7,43±3,78 cm and from ventral to the dorsal side were 4,76±3,19 cm.

The diameters could be reliable measured on both systems with a pearson’s correlation coefficient of 0,99 (p = >0.0001) for the diameter from the left to the right side and 0,99 (p = >0.0001) for the diameter from the ventral to the dorsal side.

Patient and endoleaks characteristics are detailed in Tables 1 and 2.

All examinations were performed successfully and without complications and side effects.

Out of 25 patients in the study cohort, CEUS as the gold standard detected endoleaks in 20/25 cases (80%). No endoleaks were found in 5/25 (20%) patients. Table 3 shows a breakdown of the results for each system in the various modes. Sensitivity and specificity for each system are shown in Table 4. The endoleaks could be divided in three groups according to their feeding vessels. Type IIa endoleaks with contrast uptake over the left or right lumbar artery 11/20 (55%), Type IIa endoleaks with contrast uptake over the mesenteric artery 8/20 (40%) and Type III endoleak 1/20 (5%). Whereas the high-end system could detect in B-mode 32% (8/20) and color Doppler 36% (9/20) of the cases an endoleak. The portable system could detect in B-mode 24% (6/20) and in color Doppler 28% (7/20) of the cases an endoleak. On both systems in B-mode a false positive endoleak was found on the exactly same patient. All high flow type endoleaks could be detected on all system.

As detailed in Table 4, the sensitivity for the detection of endoleaks was generally lower in B-mode and in Color Doppler compared to CEUS as the reference standard. Though, color Doppler was slightly better than B-mode sonography and the high-end Epiq system was slightly better than the portable Visiq system.

Comparing B-mode and color Doppler of the high-end Epiq system and the portable Visiq system in the detection of endoleaks, both systems showed comparable results. With a kappa coefficient of 0.6 (p = 0,002) for the B-mode and 0,82 (p = <0,001) for the color Doppler both systems showed a good comparability in detecting endoleaks.

4 Discussion

Endoleaks are the most common complication after EVAR and may potentially result in rupture of the aneurysmal sac [17]. Endoleaks can occur any time after stent graft placement, thus a lifelong surveillance is necessary [6, 17]. Because of the radiation dose, the use of nephrotoxic contrast agent and the relatively high costs associated with CT, attempts to find alternative new methods in detecting endoleaks are being undertaken [1 , 14].

In 2010 Mirza performed a systematic review and meta-analysis of seven studies which compared CEUS with MS-CT, which is currently seen as gold standard, and found a pooled sensitivity of 98% and a specificity of 88% for the detection of endoleaks with CEUS [18]. In a previous study of our group, we were able to show with a sensitivity of 96.6% and a specifity of 92.9% that CEUS is appropriate as an accurate follow-up method after EVAR [12].

In another study of our group, we compared compression elastography to CEUS in detection of endoleaks. The hypothesis behind our study was that flowing blood is less elastic than the softer tissue and this new technique could detect endoleaks. With a low sensitivity of 58.3% and a specificity of 55.6% the results of our study could not support our hypothesis [11].

The study by Mirza et al. also evaluated 21 studies with 2601 patients comparing color Doppler US with CTA. The pooled sensitivity of color Doppler US for endoleak detection was 77% and the pooled specificity 94% [18].

A review by Karthikesalingamet al. compared duplex sonography and CEUS with CTA for detection of type I and type III endoleaks. 25 studies with 3975 paired scans compared duplex ultrasonography with CTA for all endoleaks. The pooled sensitivity was 74% (CI 0.62 to 0.83) and the pooled specificity was 94% (CI 0.90 to 0.97). 13 studies with 2650 paired scans recorded detection of types 1 and 3 endoleak by duplex ultrasonography. The pooled sensitivity of duplex sonography was 83% (CI 0.40 to 0.97) and the pooled specificity was 100% (CI 0.97 to 1.00). 11 studies (961 paired scans) compared CEUS with CTA for all endoleaks. The pooled sensitivity of CEUS was 96% (CI 0.85 to 0.99) and the pooled specificity was 85% (CI 0.76 to 0.92). 8 studies (887 paired scans) reported detection of types 1 and 3 endoleak by CEUS. The pooled sensitivity of CEUS was 99% (0.25 to 1.00) and the pooled specificity was 100% (0.98 to 1.00). The authors concluded that duplex sonography detects types 1 and 3 endoleak with sufficient accuracy for surveillance after EVAR [15].

The detection and treatment of endoleaks can be very challenging, even digital subtraction angiography (DSA) has had problems in the past to detect small endoleaks. In such cases contrast enhanced ultrasound could be used to improved detection rate [28]. Additionally CTA may miss low-flow endoleaks as usually only two contrast enhanced scans are available. CEUS on the other hand enables a better classification of endoleaks as it provides haemodynamic information [4]. Therefore some authors recommend CEUS as the image modality of choice for endoleak detection [3, 21].

Furthermore detection of blood flow direction in type 2 endoleak, offered by CEUS is important information for guiding the technique of the eventual endovascular re-intervention [16].

In another previous study, we compared CEUS and CTA in detection of endoleaks after EVAR. The results of this study show that even low blood flow can be depicted due to real time imaging of endoleaks using CEUS. In unclear cases additional ultrasound image fusion with CEUS and CT angiography improves the visualization of small endoleaks and this may cause a change in the follow-up interval [5].

Portable, handheld ultrasound devices have been successfully used in the intensive care setting [24] and for echocardiography [25, 26]. So far there is limited data according duplex sonography using hand-held ultrasound devices suggesting a potential use for hand-held ultrasound devices for performing duplex sonography [9].

5 Conclusion

The high-end ultrasound system does not seem to have an additional advantage in the measurement of the aneurysm diameter. Due to a higher resolution, more endoleaks could be detected in B-mode and color Doppler by using the high-end system. The presence of small endoleaks could only be detected by using contrast-enhanced ultrasound on an high-end ultrasound system. High flow endoleaks could be reliable seen on both systems. Comparing CEUS, native B-mode sonography and color Doppler in the detection of endoleaks, CEUS seems to be the reference standard. Comparing B-mode sonography and color Doppler of the high-end and portable ultrasound system in the detection of endoleaks, both systems show comparable results.

References

Bakken

A.M.

and Illig

K.A.

, Long-term follow-up after endovascular aneurysm repair: Is ultrasound alone enough? Perspectives in Vascular Surgery and Endovascular Therapy 22 (2010), 145–151.

Barbiero

, Baratto

, Ferro

, Dall’Acqua

, Fitta

and Miotto

, Strategies of endoleak management following endoluminal treatment of abdominal aortic aneurysms in 95 patients: How, when and why, Radiol Med 113 (2008), 1029–1042.

Cantisani

, Ricci

, Grazhdani

, Napoli

, Fanelli

, Catalano

, et al., Prospective comparative analysis of colour-Doppler ultrasound, contrast-enhanced ultrasound, computed tomography and magnetic resonance in detecting endoleak after endovascular abdominal aortic aneurysm repair, European Journal of Vascular and Endovascular Surgery: The Official Journal of the European Society for Vascular Surgery 41 (2011), 186–192.

Clevert

D.A.

, Gürtler

V.M.

, Meimarakis

, D’Anastasi

, Weidenhagen

, Reiser

M.F.

and Becker

C.R.

, Classification of endoleaks in the follow-up after EVAR using the time-to-peak of the contrast agent in CEUS examinations, Clin Hemorheol Microcirc 55 (2013), 183–191.

Clevert

D.A.

, Helck

, D’Anastasi

, Gürtler

, Sommer

W.H.

, Meimarakis

, Weidenhagen

and Reiser

, Improving the follow up after EVAR by using ultrasound image fusion of CEUS and MS-CT, Clin Hemorheol Microcirc 49 (2011), 91–104.

Clevert

D.A.

, Minaifar

, Kopp

, Stickel

, Meimarakis

, Sommer

, et al., Imaging of endoleaks after endovascular aneurysm repair (EVAR) with contrast-enhanced ultrasound (CEUS). A pictorial comparison with CTA, Clin Hemorheol Microcirc 41 (2009), 151–168.

Clevert

D.A.

, Minaifar

, Weckbach

, Kopp

, Meimarakis

and Reiser

, Color duplex ultrasound and contrast-enhanced ultrasound in comparison to MS-CT in the detection of endoleak following endovascular aneurysm repair, Clin Hemorheol Microcirc 39 (2008), 121–132.

Fischer

, Filimonow

, Petersein

, et al., Ultrasound at the bedside: Does a portable ultrasound device save time? Ultraschall Med 23 (2002), 311–314.

Gravvanis

, Tsoutsos

, Delikonstantinou

, Dimitriou

, Katsikeris

and Karakitsos

, Impact of portable duplex ultrasonography in head and neck reconstruction, J Craniofac Surg 23 (2012), 140–144.

10.

Greis

, Technical aspects of contrast-enhanced ultrasound (CEUS) examinations: Tips and tricks, Clin Hemorheol Microcirc 58 (2014), 89–95.

11.

Gürtler

.VM.

, Rjosk-Dendorfer

, Reiser

and Clevert

D.A.

, Comparison of contrast-enhanced ultrasound and compression elastography in the follow-up after endovascular aortic aneurysm repair, Clin Hemorheol Microcirc 57 (2014), 175–183.

12.

Gurtler

V.M.

, Sommer

W.H.

, Meimarakis

, Kopp

, Weidenhagen

, Reiser

M.F.

, et al., A comparison between contrast-enhanced ultrasound imaging and multislice computed tomography in detecting and classifying endoleaks in the follow-up after endovascular aneurysm repair, Journal of vascular surgery: Official Publication, the Society for Vascular Surgery [and] International Society for Cardiovascular Surgery, North American Chapter 58 (2013), 340–345.

13.

Hiatt

M.D.

and Rubin

G.D.

(2004), Surveillance for endoleaks: How to detect all of them, Semin Vasc Surg 17, 268–278.

14.

Iezzi

, Basilico

, Giancristofaro

, Pascali

, Cotroneo

A.R.

and Storto

M.L.

, Contrast-enhanced ultrasound versus color duplex ultrasound imaging in the follow-up of patients after endovascular abdominal aortic aneurysm repair, Journal of vascular surgery: Official Publication, the Society for Vascular Surgery [and] International Society for Cardiovascular Surgery, North American Chapter 49 (2009), 552–560.

15.

Karthikesalingam

, Al-Jundi

, Jackson

, Boyle

J.R.

, Beard

J.D.

, Holt

P.J.

and Thompson

M.M.

, Systematic review and meta-analysis of duplex ultrasonography, contrast-enhanced ultrasonography or computed tomography for surveillance after endovascular aneurysm repair, Br J Surg 99 (2012), 1514–1523.

16.

Lawrence-Brown

, Sun

, Semmens

J.B.

, Liffman

, Sutalo

and Hartley

D.B.

, Type II endoleaks: When is intervention indicated and what is the index of suspicion for types I or III? J Endovasc Ther 16(Suppl. I) (2009), I106–I-118.

17.

Matsumura

J.S.

and Moore

W.S.

, Clinical consequences of periprosthetic leak after endovascular repair of abdominal aortic aneurysm. Endovascular Technologies Investigators, Journal of Vascular Surgery: Official Publication, the Society for Vascular Surgery [and] International Society for Cardiovascular Surgery, North American Chapter 27 (1998), 606–613.

18.

Mirza

T.A.

, Karthikesalingam

, Jackson

, Walsh

S.R.

, Holt

P.J.

, Hayes

P.D.

, et al., Duplex ultrasound and contrast-enhanced ultrasound versus computed tomography for the detection of endoleak after EVAR: Systematic review and bivariate meta-analysis, European Journal of Vascular and Endovascular Surgery: The Official Journal of the European Society for Vascular Surgery 39 (2010), 418–428.

19.

Moll

F.L.

, Powell

J.T.

, Fraedrich

, et al., Management of abdominal aortic aneurysms clinical practice guidelines of the European society for vascular surgery, Eur J Vasc Endovasc Surg 41(Suppl 1) (2011), 1–58.

20.

Oschatz

, Prosch

, Schober

and Mostbeck

, Evaluation of a portable ultrasound device immediately after spiral computed tomography, Ultraschall Med 25 (2004), 433–437.

21.

Perini

, Sediri

, Midulla

, Delsart

, Mouton

, Gautier

, et al., Singlecentre prospective comparison between contrast-enhanced ultrasound and computed tomography angiography after EVAR, Eur J Vasc Endovasc Surg 42 (2011), 797–802.

22.

Piscaglia

, Nolsoe

, Dietrich

C.F.

, Cosgrove

D.O.

, Gilja

O.H.

, Bachmann Nielsen

, et al., The EFSUMB Guidelines and Recommendations on the Clinical Practice of Contrast Enhanced Ultrasound (CEUS): Update on non-hepatic applications, Ultraschall Med 33 (2012), 33–59.

23.

Ryan

S.M.

, Smith

and Sidhu

P.S.

, Comparison of the SonoSite and Acuson 128/XP10 ultrasound machines in the ‘bed-side’ assessment of the post liver transplant patient, Eur J Ultrasound 15 (2002), 37–43.

24.

Schleder

, Dornia

, Poschenrieder

, Dendl

, Cojocaru

, Bein

, Schmid

, Stroszczynski

, Jung

E.M.

and Heiss

, Bedside diagnosis of pleural effusion with a latest generation hand-carried ultrasound device in intensive care patients, Acta Radiol 53 (2012), 556–560.

25.

Shmueli

, Burstein

, Sagy

, Perry

Z.H.

, Ilia

, Henkin

, Shafat

, Liel-Cohen

and Kobal

S.L.

, Briefly trained medical students can effectively identify rheumatic mitral valve injury using a hand-carried ultrasound, Echocardiography 30 (2013), 621–626.

26.

Siqueira

V.N.

, Mancuso

F.J.

, Campos

, De Paola

A.A.

, Carvalho

A.C.

and Moises

V.A.

, Training program for cardiology residents to perform focused cardiac ultrasound examination with portable device, Echocardiography (2015). [Epub ahead of print].

27.

Sommer

W.H.

, Becker

C.R.

, Haack

, et al., Time-resolved CT angiography for the detection and classification of endoleaks, Radiology 263 (2012), 917–926.

28.

Sommer

W.H.

, Hoffmann

R.T.

, Becker

C.R.

, Reiser

M.F.

and Clevert

D.A.

, Comparison of time-resolved CT-angiography, contrast-enhanced ultrasound and digital subtraction angiography in a patient with a small type II endoleak after endovascular aneurysm repair, Clin Hemorheol Microcirc 45 (2010), 19–25.

29.

Stock

K.F.

, Klein

, Steubl

, Lersch

, Heemann

, Wagenpfeil

, Eyer

and Clevert

D.A.

, Comparison of a pocket-size ultrasound device with a premium ultrasound machine: Diagnostic value and time required in bedside ultrasound examination, Abdom Imaging (2015). [Epub ahead of print].

30.

Vourvouri

E.C.

, Poldermans

, Schinkel

A.F.L.

, et al., Abdominal aortic aneurysm screening using a hand-held ultrasound device. “A pilot study”, Eur J Vasc Endovasc Surg 22 (2001), 352–354.