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J Vasc Surg Cases Innov Tech
J Vasc Surg Cases Innov Tech
Journal of Vascular Surgery Cases, Innovations and Techniques
2468-4287
Elsevier

S2468-4287(24)00164-3
10.1016/j.jvscit.2024.101580
101580
Innovative technique
Carbon dioxide cone-beam computed tomography for the technical assessment of endovascular aortic intervention
Antonello Michele MD, PhD
Bilato Marco James MD
Menara Sabrina MD
Grego Franco MD
Piazza Michele MD
Squizzato Francesco MD francesco.squizzato@unipd.it
∗
Vascular and Endovascular Surgery Division, Department of Cardiac, Thoracic, Vascular Sciences and Public Health, Padova University, Padova, Italy
∗ Correspondence: Francesco Squizzato, MD, Vascular and Endovascular Surgery Division, Department of Cardiac, Thoracic, Vascular Sciences and Public Health, Padova University, School of Medicine, Via Giustiniani 2 35125, Padova, Italy francesco.squizzato@unipd.it
22 7 2024
10 2024
22 7 2024
10 5 10158013 3 2024
2 7 2024
© 2024 The Author(s)
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Cone-beam computed tomography (CBCT) is widely used for the technical assessment of standard and complex endovascular aortic interventions. Use of iodinated contrast in CBCT imaging might provide useful additional information; however, this also increases the procedural contrast dose, which may cause renal function deterioration, and the radiation exposure. We describe the technique and feasibility of carbon-dioxide (CO2)-enhanced CBCT for the technical assessment of standard and complex endovascular aortic repair. In our experience CO2-CBCT had no related adverse events and provided satisfactory imaging quality to assess endograft integrity, vessels patency, and was safely performed in case of severe chronic renal insufficiency.

Keywords

Abdominal
Aortic aneurysm
Carbon dioxide
Cone-beam computed tomography
Endovascular aneurysm repair
Renal insufficiency
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pmcEndovascular aortic repair has progressively evolved from standard endovascular aortic repair (EVAR) to fenestrated-branched repair (F-BEVAR) for the treatment of disease involving the renal-mesenteric arteries. Both standard and complex EVAR can be performed with high rates of technical success and durability; however, the risk for reinterventions still represents the major drawback of endovascular interventions.1, 2, 3 In particular, early reinterventions or complications may be caused by technical defects that are not immediately recognized during the index procedure,4, 5, 6 and their intraoperative identification and correction can prevent clinical complications and secondary interventions during follow-up.4,7, 8, 9, 10

Several imaging techniques are available for the technical assessment of EVAR and F-BEVAR, such as completion angiography, cone-beam computed tomography (CBCT), or intravascular ultrasound.7,9,11 CBCT can provide valuable information regarding the conformation of the endograft components and identify significant structural defects such as kink, compression, or disconnection.4,7,8 Contrast-enhanced CBCT can provide additional information on patency of the endograft components, target vessels, and the presence of endoleaks. However, the use of iodinated contrast agents during CBCT increases the overall procedural contrast dose and may cause adverse events, especially in patients with baseline impaired renal function or allergies. Moreover, compared with contrast-free CBCT, contrast-enhanced CBCT determines an additional radiation exposure.

Carbon dioxide (CO2) had emerged as a contrast dye alternative. Being physiologically present within the human body, it appears to be safer than iodinated dye, with no reported risk of allergic reaction and lack of nephrotoxicity.12,13 The use of CO2 for conventional angiography14 has been broadly investigated; however, its role in CBCT imaging is unknown. The aim of this report is to describe the feasibility, safety, and image quality of CO2-enhanced CBCT for the technical assessment of standard and complex endovascular aortic repair.

Technique

We started using CO2-CBCT in selected patients at risk for contrast-induced nephrotoxicity, but the technique can be applied to virtually all patients. Patients’ consent was obtained. Main contraindications to intravascular CO2 administration are severe chronic obstructive pulmonary disease, pulmonary hypertension, and right to left cardiopulmonary shunt. Also, CO2 should not be injected in the thoracic aorta, to avoid the risk of cerebral air embolism.

The endovascular aortic procedure is performed in a hybrid operating room equipped with a ArtisPheno angiographer (Siemens) under general anesthesia. Intraoperative angiographies are usually performed using an Angiodroid CO2 injector (Angiodroid Spa). After completion of the endovascular procedure in a standard way, a 6 Fr 55-cm long sheath is advanced from a femoral access and positioned at the desired level. The tip of the sheath should be placed slightly (2-3 cm) above the major region of interest: above the celiac trunk for the visualization of the visceral-renal arteries (Fig 1), above the renal arteries for the visualization of renal arteries and infrarenal aorta (Fig 2), or in the infrarenal abdominal aorta for the visualization of the distal aorta and iliac axis (Fig 3). The angiographer is then set up for the acquisition of a contrast-free CBCT (using Siemens Pheno “4sDR Surgery P” protocol). The CO2 injector is flushed and armed for an injection of 100 ml of CO2 at 700 ± 50 mmHg using the preset aortic protocol (Fig 4). There is virtually no limit to the total CO2 dose during a single procedure, but a minimum of 2 minutes time is required between consecutive injections, in order to avoid excessive CO2 accumulation. CBCT acquisition and CO2 injection are started simultaneously; this allows for the synchronization of the rotation of the angiographer with the CO2 injection and diffusion, because both acquisition and CO2 diffusion are characterized by a similar time delay from the input signal (approximately 2 seconds). The dose area product for each CO2-enhanced CBCT is typically around 2000 uGy∗m.2Fig 1 A, Three-dimensional reconstruction of the preoperative computed tomography angiography (CTA) of a juxtarenal aortic aneurysm. Note the presence of a celiac-mesenteric trunk. B, Completion angiogram with carbon dioxide (CO2), after fenestrated endovascular repair (FEVAR). C, Multiplanar reconstruction (MPR) reconstruction of the CO2-cone-beam computed tomography (CBCT), showing integrity and patency of all the endograft components. The 6Fr sheath was positioned with the tip at the level of the pararenal aorta (arrow). D, Axial view of the CO2-CBCT, detailing the celiac-mesenteric trunk. E, Axial view of the CO2-CBCT, detailing the right renal artery (white arrow). Note the contrast layering on the anterior aspect of the aorta (red arrow). F, Axial view of the CO2-CBCT, detailing the left renal artery. Note the contrast layering on the anterior aspect of the aorta. G, Axial view of the CO2-CBCT, detailing the complete sac exclusion without evidence of endoleaks.

Fig 2 A, Three-dimensional reconstruction of the preoperative computed tomography angiography (CTA) of an infrarenal aortic aneurysm. B, Completion angiogram with carbon dioxide (CO2), after endovascular aortic repair (EVAR) with endoanchors and aneurysm sac embolization. C, Multiplanar reconstruction (MPR) of the CO2-cone-beam computed tomography (CBCT), showing integrity and patency of all the endograft components. The 6Fr sheath was positioned with the tip at the level of the pararenal aorta. D, Axial view of the CO2-CBCT, detailing the superior mesenteric artery (arrow). E, Axial view of the CO2-CBCT, detailing the origin of the right renal artery (arrow). F, Axial view of the CO2-CBCT, detailing the proximal landing zone at the level of the endoanchors. The arrow indicates the left renal artery.

Fig 3 A, Three-dimensional reconstruction of the preoperative computed tomography angiography (CTA) of a bilateral common iliac aneurysm. B, Completion angiogram with carbon dioxide (CO2), after endovascular aortic repair (EVAR) with bilateral iliac branch device. C. Multiplanar reconstruction (MPR) of the CO2-cone-beam computed tomography (CBCT), showing integrity and patency of all the endograft components. The 6Fr sheath was positioned with the tip at the level of the infrarenal aorta. D, Axial view of the CO2-CBCT at the level of the aortic main body. E, Axial view of the CO2-CBCT at the level of the aortic bifurcation. F, Axial view of the CO2-CBCT, detailing the bilateral iliac bifurcation, with adequate CO2 filling of the external and hypogastric branch components.

Fig 4 A, The automated carbon dioxide (CO2) injector (Angiodroid) is a portable device incorporated with a touch screen for injection setting. B, The CO2 circuit of the injector is connected to the injections sheath through a dedicated tube (black arrow). C, Image of the operating table setting for the cone-beam computed tomography (CBCT) acquisition. The CO2 connection tube (black arrow) is directly connected with the 6Fr 55-cm long sheath used for the injection (red arrow).

This technique was adopted in nine patients undergoing standard EVAR (n = 5), EVAR with iliac branch device (n = 1), and FEVAR (n = 3) (Video 1, online only). On CBCT images, CO2 appears as a dark (black) area filling the arterial lumen (Fig 5). Summary of CO2-CBCT findings are reported in Table I. There were no related adverse events, and image quality was satisfactory in all cases. No patient received an intraoperative revision based on CO2-CBCT. No technical defects or endoleaks occurred after a median 6 months of imaging follow-up by CT angiography or contrast-enhanced ultrasound.Fig 5 Carbon dioxide (CO2)-cone-beam computed tomography (CBCT) three-dimensional multiplanar reconstruction (MPR) of the superior mesenteric artery after fenestrated endovascular repair (FEVAR). A, Axial view, showing the filling of the superior mesenteric artery (SMA) (white arrow) and the contrast layering in the anterior part of the aortic lumen (red arrow). B, Sagittal view, showing the patency of the SMA. C, Coronal view, showing adequate bridging stent conformation at the level of the fenestration (arrow).

Table Summary of the seven patients undergoing carbon dioxide (CO2) cone-beam computed tomography (CBCT) for the technical assessment of endovascular aortic repair (EVAR)

Patient ID	Sex	Age	Type of endovascular repair	Procedural iodinated contrast volume, ml	Procedural CO2 volume, ml	CBCT technical success	CBCT site of CO2 injection	CBCT DAP/total procedural DAP, uGym2	Notes	
1	M	77	EVAR + left iliac branch device	10	400	Yes	Infrarenal	2048/7051	Good visualization of infrarenal aorta and hypogastric arteries. No visualization of renal arteries because of infrarenal CO2 injection.	
2	M	84	EVAR + endoanchors	0	300	Yes	Suprarenal	2209/8902	Adequate visualization of SMA and renal arteries. Type II endoleak fed by lumbar arteries.	
3	M	80	EVAR	0	300	Yes	Suprarenal	2041/7990	Adequate visualization of renal arteries and SMA. CO2 layering at the level of the pararenal aorta.	
4	M	81	EVAR	0	300	Yes	Infrarenal	2101/7539	Adequate visualization of infrarenal aorta and iliac arteries. No visualization of renal arteries because of infrarenal CO2 injection	
5	M	79	FEVAR	20	400	Yes	Pararenal	2148/20434	Good visualization of renal arteries. Adequate enhancement of infrarenal aorta and iliac arteries.	
6	F	71	EVAR	0	200	Yes	Infrarenal	2039/6853	Adequate enhancement of infrarenal aorta and iliac arteries. No visualization of renal arteries because of infrarenal CO2 injection.	
7	M	74	EVAR	0	300	Yes	Infrarenal	2056/6961	Good visualization of infrarenal aorta and iliac arteries. Type II endoleak fed by lumbar arteries. No visualization of renal arteries because of infrarenal CO2 injection.	
8	M	72	EVAR	0	300	Yes	Suprarenal	2056/7002	Adequate visualization of renal arteries.	
9	M	75	FEVAR	40	400	Yes	Pararenal	2094/14083	Adequate visualization of renal arteries and SMA. CO2 layering at the level of the pararenal aorta.	
DAP, Dose-area product; FEVAR, fenestrated endovascular aneurysm repair; SMA, superior mesenteric artery.

Discussion

CBCT is commonly used for the technical assessment of standard and complex EVAR and has been demonstrated to reduce early complications and secondary interventions4,7,8,15 after aortic endovascular interventions. Compared with contrast-free CBCT, contrast-enhanced CBCT provides additional information on patency of the endograft components and target arteries and presence of endoleaks. Although CO2 use as angiographic contrast media is well-established, its use during CBCT has not been previously described.

In our experience, CO2-CBCT is feasible and safe, with no reported related adverse events and satisfactory imaging quality from the clinical standpoint. CO2 carries the advantage of completely avoiding the use of nephrotoxic agents and can be safely performed also in cases with severe chronic renal insufficiency at risk for dialysis. Also, adequate images can be obtained using contrast-free CBCT software protocol acquisition, with a significant reduction of radiation exposure, that in our setting is approximately 2000 uGym2 for CO2-CBCT and 4000 uGym2 for iodinated contrast-CBCT.

To obtain useful images, it is important to standardize the modality and site of CO2 injection. The main issue is related to the extremely high solubility and diffusivity of CO2 gas, that acts as a contrast agent by displacing intra-arterial blood. The gas injection through a diagnostic catheter or a small-size sheath (6 Fr), increases the flow resistance within the CO2 circuit, which permits a sufficient delay for tomography acquisition. Compared with iodinated contrast CBCT, the CO2-enhanced region is more restricted and usually does not cover the entire abdominal aorta from the visceral to the hypogastric arteries. For this reason, the injection sheath should be carefully positioned according to the aortic region to be investigated: above the celiac trunk for F-BEVAR, above the renal arteries for standard EVAR, and at the level of the renals for iliac branch devices.

The quality of the images was generally good, with adequate visualization of large, medium, and small arteries. In large arteries (aorta), CO2 may not completely displace blood, creating a CO2 “layering” with a posterior lack of filling on axial images, especially in the cranial region. Aortic side branches with a posterior orientation (ie, hypogastric arteries) may not always be adequately assessed, owing to the CO2 antigravitational migration. Also, it is not unusual to observe gas bubbles within the aneurysm, which may derive either from endoleaks or air “trapping” in case CO2 is used for angiographies during the intervention. However, it may difficult to establish the exact cause of gas visualization within the aneurysm sac and to clearly determine the type of endoleak, which might remain indeterminate, as it has been described also with standard contrast-CBCT or CT angiography.10,16 Therefore, this information should be completed by the evaluation for any structural defect on CBCT, and comparison with the final completion angiogram.10 Further studies are necessary to establish the sensitivity of CO2-CBCT in the assessment of endoleaks and vessels’ patency, compared with other imaging modalities.

Conclusion

This initial experience on CO2-CBCT demonstrates its feasibility, safety, and satisfactory quality of the images, offering a viable alternative to traditional contrast CBCT based on iodinated contrast, with reduction of the overall radiation dose. CO2-CBCT can be safely performed in patients with renal impairment at risk for dialysis or allergies and may be considered also in other patients to reduce the overall contrast dose. Further studies are needed to optimize the technique and investigate its clinical significance.

Author Contributions

Conception and design: MA, FG, MP, FS

Analysis and interpretation: MA, FS

Data collection: MB, SM

Writing the article: MA, FS

Critical revision of the article: MA, MB, SM, FG, MP, FS

Final approval of the article: MA, MB, SM, FG, MP, FS

Statistical analysis: Not applicable

Obtained funding: Not applicable

Overall responsibility: MA

Disclosures

None.

Supplementary data

Supplementary Video

Carbon dioxide (CO2)-cone-beam computed tomography (CBCT) after endovascular aneurysm repair (EVAR) + inferior mesenteric artery embolization. The CO2 injection was performed from the infrarenal aorta; note the presence of a type II endoleak fed by a large lumbar artery (arrow).

Additional material for this article may be found online at www.jvscit.org.

The editors and reviewers of this article have no relevant financial relationships to disclose per the Journal policy that requires reviewers to decline review of any manuscript for which they may have a conflict of interest.
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References

1 Oderich G.S. Forbes T.L. Chaer R. Reporting standards for endovascular aortic repair of aneurysms involving the renal-mesenteric arteries J Vasc Surg 73 2021 4S 52S 32615285
2 Chaikof E.L. Dalman R.L. Eskandari M.K. The Society for Vascular Surgery practice guidelines on the care of patients with an abdominal aortic aneurysm J Vasc Surg 67 2018 2 77.e2 29268916
3 Patel R. Sweeting M.J. Powell J.T. Greenhalgh R.M. Endovascular versus open repair of abdominal aortic aneurysm in 15-years’ follow-up of the UK endovascular aneurysm repair trial 1 (EVAR trial 1): a randomised controlled trial Lancet 388 2016 2366 2374 27743617
4 Tenorio E.R. Oderich G.S. Sandri G.A. Prospective nonrandomized study to evaluate cone beam computed tomography for technical assessment of standard and complex endovascular aortic repair J Vasc Surg 71 2020 1982 1993.e5 31611108
5 Squizzato F. Piazza M. Forcella E. Coppadoro S. Grego F. Antonello M. Clinical impact and determinants of fenestration to target vessel misalignment in fenestrated endovascular aortic repair Eur J Vasc Endovasc Surg 67 2024 765 774 37858703
6 Squizzato F. Antonello M. Forcella E. Geometrical determinants of target vessel instability in fenestrated endovascular aortic repair J Vasc Surg 76 2022 335 343.e2 35276259
7 Dijkstra M.L. Eagleton M.J. Greenberg R.K. Mastracci T. Hernandez A. Intraoperative C-arm cone-beam computed tomography in fenestrated/branched aortic endografting J Vasc Surg 53 2011 583 590 21129898
8 Tenorio E.R. Oderich G.S. Sandri G.A. Impact of onlay fusion and cone beam computed tomography on radiation exposure and technical assessment of fenestrated-branched endovascular aortic repair J Vasc Surg 69 2019 1045 1058.e3 30527938
9 Squizzato F. Piazza M. Vio E. Dall’Antonia A. Grego F. Antonello M. Possible added value of intravascular ultrasound in the evaluation of the bridging grafts in branched aortic stent-grafting Cardiovasc Intervent Radiol 44 2021 1469 1472 34021377
10 Törnqvist P. Dias N. Sonesson B. Kristmundsson T. Resch T. Intra-operative cone beam computed tomography can help avoid reinterventions and reduce CT follow up after infrarenal EVAR Eur J Vasc Endovasc Surg 49 2015 390 395 25736514
11 Asciutto G. Ibrahim A. Leone N. Intravascular ultrasound in the detection of bridging stent graft instability during fenestrated and branched endovascular aneurysm repair procedures: a multicentre study on 274 target vessels Eur J Vasc Endovasc Surg 67 2024 99 104 37704100
12 Hawkins I.F. Cho K.J. Caridi J.G. Carbon dioxide in angiography to reduce the risk of contrast-induced nephropathy Radiol Clin 47 2009 813 825
13 Hawkins I.F. Carbon dioxide digital subtraction arteriography AJR Am J Roentgenol 139 1982 19 24 6807073
14 Hawkins I.F. Caridi J.G. Carbon dioxide (CO2) digital subtraction angiography: 26-year experience at the University of Florida Eur Radiol 8 1998 391 402 9510571
15 Colacchio E.C. Berton M. Squizzato F. The role of multimodal imaging in emergency vascular conditions: the journey from diagnosis to hybrid operating rooms Semin Vasc Surg 36 2023 355 362 37330247
16 Squizzato F. Antonello M. Modena M. Fate of primary determinate and indeterminate target vessel endoleaks after fenestrated-branched endovascular aortic repair J Vasc Surg 79 2024 207 216.e4 37804955
