New tools to reduce radiation exposure during aortic endovascular procedures

ABSTRACT

Introduction

The evolution of endovascular surgery over the past 30 years has made it possible to treat increasingly complex vascular pathologies with an endovascular method. Although this generally speeds up the patient’s recovery, the risks of health problems caused by long-term exposure to radioactive radiation increase. This warrants the demand for radiation-reducing tools to reduce radiation exposure during these procedures.

Areas covered

For this systematic review Pubmed, Embase and Cochrane library databases were searched on 28 December 2021 to provide an overview of tools that are currently used or have the potential to contribute to reducing radiation exposure during endovascular aortic procedures. In addition, an overview is presented of radiation characteristics of clinical studies comparing a (potential) radiation-reducing device with conventional fluoroscopy use.

Expert opinion

Radiation-reducing instruments such as fiber optic shape sensing or electromagnetic tracking devices offer the possibility to further reduce or even eliminate the use of radiation during endovascular procedures. In an era of increasing endovascular interventional complexity and awareness of the health risks of long-term radiation exposure, the use of these technologies could have a major impact on an ongoing challenge to move toward radiation-free endovascular surgery.

KEYWORDS:

• Fiber optic shape sensing
• electromagnetic
• IVUS
• robotic navigation system
• image fusion
• radiation dose reduction

1. Introduction

Since the first endovascular aortic aneurysm repairs described by Volodos et al [1]. and Parodi et al [2]. in 1991, there has been a major shift from open to endovascular aortic treatment. These newly developed endovascular methods offer new treatment options for the management of vascular pathologies that are often less invasive than conventional open surgery and lead, among other things, to a reduced risk of complications and a shorter hospital stay [3–6]. On the other hand, there are also limitations associated with their application. When using fluoroscopy, three-dimensional (3D) structures are projected onto monitors only in two-dimensional (2D) grayscale images. Spatial perception of tortuosity and depth is thereby eliminated, making navigation more difficult and increasing the potential for procedural errors, prolonged procedural time, and increased radiation exposure. Exposure to fluoroscopy imposes potential long-term DNA damage and health effects, which limits the risks of perioperative radiation exposure, and therefore plays a major role during these procedures [7,8]. In order to achieve the lowest possible radiation exposure at which the endovascular procedure can be performed safely, current radiation guidelines are based on the ‘as low as reasonably achievable’ (ALARA) principle. However, the increasing complexity of endovascular treatments of vascular pathologies prolongs the procedure time, which despite ALARA guidelines still results in increased radiation exposure for both the patient and the treatment team [9–11].

Over the past decade, there have been many new developments that help mitigate the risks of perioperative radiation exposure during endovascular procedures. Studies show that the introduction of hybrid operating rooms with a fixed C-arm and advanced applications such as image fusion (IF) of preoperatively acquired Magnetic Resonance Angiography (MRA) or Computed Tomography Angiography (CTA) images contribute to the reduction of radiation exposure and contrast agent [12–14]. However, its application is limited to projecting a 3D outline of the anatomical structures onto real-time fluoroscopy images with only 2D information about the positioning and orientation of the endovascular devices used. As a result, with increasing complexity of the endovascular procedure, radiation exposure will also increase. Developed endovascular navigation systems using, for example, electromagnetic (EM) tracking or fiber optic shape sensing (FOSS) methods may provide the solution to overcome this problem [15–17]. These techniques improve the spatial perception of the devices within anatomical imaging and lead to a potential reduction of radiation exposure during the navigation phase of endovascular procedures. However, most of these techniques are still under development and the added value in reducing radiation exposure has not yet been proven. Therefore, the aim of this review is to provide an overview of current and potential radiation reducing techniques used during aortic endovascular procedures.

2. Method

2.1. Data search and collection

This literature review was performed according to the ‘Preferred Reporting Items for Systematic Reviews and Meta-Analysis’ (PRISMA) statement [18]. Pubmed, Embase, and Cochrane library databases were searched on 28 December 2021, using the following MeSH terms: ‘Aorta,’ ‘Endovascular procedures,’ ‘Radiation,’ ‘Radiation monitoring,’ ‘Radiation dosage,’ ‘Fluoroscopy.’ Only articles with publication date from 2011 until moment of search. The applied search strategy yielded 452 potentially interesting articles; 152 in Pubmed, 264 in Embase, and 36 in Cohrance library, of which 295 remained after duplicate removal. An overview of the complete electronic search strategy is presented in supplementary material A.

Two independent qualified observers (J.K. and L.J.V.) performed title and abstract screening of the remaining 295 potentially relevant articles. All studies describing interventional tools that can be used radiation-free, simplify navigation tasks or reduce navigation time and are used in aortic endovascular interventions were included in this review. No distinction was made between the aortic pathology for which the treatment was performed. Articles focusing on pre- or post-operative radiation exposure reduction protocols, as well as C-arm hardware or integrated dose reduction software, such as AlluraClarity, were excluded. In addition, articles were excluded that are not written in the English language or where the full text was not available. Applying these criteria in combination with cross-references ultimately leads to the discussion of 23 remaining articles that focus on the current or potential reduction of radiation exposure in endovascular aortic procedures. An overview of data collection process is presented in Figure 1.

Figure 1. Flowchart of the search strategy for this systematic review.

2.2. Data extraction

Selected studies were grouped based on the examined tool that contributes to reduction of radiation exposure. The following main outcome characteristics were extracted from the selected studies: first author, year of publication and type of study, type of intervention or used model, conclusion, and limitations. Subsequently, if reported, the following characteristics were extracted from all included clinical studies in which (potential) radiation reducing tool is compared with a conventional control group: used tool, number of patients included, type of intervention, procedure time (minutes), cumulative radiation dose expressed in air kerma (AK, mGy) or dose area product (DAP, Gycm2), fluoroscopy time (minutes), and contrast volume (mL). In addition, for studies describing tools used during endovascular cannulation of target vessels, the following characteristics were extracted: used tool, study type, model/intervention, cannulation tasks, cannulation attempts, vessel wall hits, cannulation time (minutes), and fluoroscopy time (minutes).

3. Results

In this review 23 articles were included describing the robotic navigation system (RNS), EM-tracking, Intravascular Ultrasound (IVUS), FOSS and IF. An overview of all included articles is presented in Table 1.

Table 1. Overview of articles included in the review.

Author, Year	Study type, design	N	Intervention/ model	Conclusion	Limitations
Electromagnetic tracking:
Cochennec [19], 2013	Phantom study	9 operators	Transparent anthromorphic aortic arch phantom	EM navigation might be beneficial as complementary image modality in terms of radiation exposure and cannulation performance	Small sample size, lack off aortic pulsatility movements and spatial variability in this in vitro set-up.
Condino [20], 2014	Phantom study	15 operators	Abdominal aortic aneurysm model	Proof of concept for simultaneous use of EM navigation of guidewires and catheters is feasible without fluoroscopy use	Used navigating system can’t compensate for breathing and cardiac cycle movements.
Manstad-Hulaas [21], 2012	Clinical study, Prospective	17 patients	EVAR	3D EM navigation is a feasible technology for guidance during EVAR procedures	Only used tracked catheters because guidewires were too fragile to use.
Tystad-Lund [22], 2017	Phantom study	5 operators	Elastic phantom of abdominal aorta and iliac arteries	3D EM navigation is not inferior to fluoroscopy in its ability to guide endovascular interventions	Simple phantom was used without complex tortuous anatomy. EM relies on static image volumes and can’t compensate for dynamic in vivo factors. Commercially available equipment rarely features EM tracking support. Therefore setup is complicated as often custom-made devices must be used.
Image Fusion:
Ahmad [13], 2019	Clinical study, Retrospective	146 patients	TEVAR	Use of IF results in lower contrast usage and tends toward a reduction in procedure time during complex TEVAR	Retrospective design with somewhat inhomogeneous cohort. Moreover, high-rate of poor quality of used preoperative CTA and outcomes might be affected by learning curve of surgeons.
Ahmad [23], 2018	Clinical study, Retrospective	152 patients	EVAR	IF registration using two bi-planar fluoroscopy images is sufficiently accurate and reduces radiation exposure and procedure time when surgeons are more experienced	Retrospective design and outcomes can be influenced by learning curve of operators
De Beaufort [29], 2021	Clinical study, Randomized controlled pilot	37 patients	Aortoilliac occlusive disease	Use of IF results in reduction of radiation related measured parameters with similar procedure time and higher contrast agent doses	Small number of cases with a wide range of complexity and not stratified on TASC lesion scores. In addition, outcomes can be influenced by learning curve as surgeons did not perform same number of cases.
Dias [24], 2015	Clinical study, Retrospective	226 patients	EVAR, FEVAR, BrEVAR, TEVAR	Protocol that combines use of reduced fluoroscopy frame rate, low concentration iodine contrast medium and IF seems to provide more complete approach toward reduction of radiation exposure and contrast volume	Retrospective design and matching of control group was limited due to progressive introduction of different measures
Dijkstra [25], 2011	Clinical study, Retrospective	89 patients	FEVAR	Use of IF with CBCT is a valuable addition in endovascular procedures as its use results in lower contrast agent doses and ultimately reduce operative and fluoroscopy times	Retrospective design
Hertault [30], 2014	Clinical study, Prospective	497 patients	EVAR, FEVAR, BrEVAR, TEVAR	Compared to previous studies significant reduction in radiation exposure for both patient and operators	Comparison between Mobile C-arm without IF and Hybrid OR with IF. Moreover surgeon experience is not taken into account
Hiraoka [26], 2018	Clinical study, Retrospective	263 patients	EVAR, TEVAR	Use of intraoperative 3D IF decreases radiation exposure and contrast use	Retrospective study in a single center with relatively small sample number. In addition, no adjustment for surgeon experience and possible learning curve
McNally [14], 2015	Clinical study, Retrospective	72 patients	FEVAR	Use of intraoperative 3D IF during FEVAR decreases radiation exposure, procedure time and contrast agent usage	Procedures are performed by a single surgeon in a single center which probably introduces bias. Moreover, study can’t account for influence of procedure difficulty radiation exposure
Rolls [31], 2016	Clinical study, Prospective	42 patients	FEVAR	IF may contribute to overall improved awareness of radiation safety practices that lead to significant overall reduction in radiation	Comparison between modern practice and historic group. Lack of consistency in frame rate in control group could contribute to large radiation doses
Sailer [32], 2014	Clinical study, Prospective	62 patients	FEVAR, BrEVAR	IF guidance provided added value for FEVAR/BrEVAR procedures in terms of procedure time and contrast volume reduction	Procedure complexity influences procedure time, contrast volume and radiation dose and controls were retrieved from primarily historical procedures. Moreover, possible introduction of bias in operator experience
Stangenberg [27], 2015	Clinical study, Retrospective	32 patients	EVAR	IF allowed significant reduction in radiation dose, fluoroscopy time contrast agent and procedure length	Retrospective design with matched case-control groups.
Tacher [28], 2013	Clinical study, Retrospective	37 patients	FEVAR, BrEVAR, ChEVAR	IF reduces injected contrast volume and maintains radiation exposure and procedure time	Retrospective analysis on a small number of patients. Chronological enrollment of patients could be considered as bias based on operators learning curve. In addition, in the conventional 2D fluoroscopy group were less FEVAR procedures included.
Intravascular Ultrasound:
Pecoraro [33], 2019	Clinical study, Retrospective	52 patients	EVAR	Use of IVUS during EVAR is feasible and determined significant reduction in contrast volume and radiation exposure	Retrospective study with a small sample size. In addition there are slight differences between propensity matched groups.
Intravascular Ultrasound in combination with electromagnetic tracking:
Shi [34], 2016	Phantom study	-	Rigid transparent descending aortic model	Practical solution for real-time intravascular reconstruction based on sensor fusion between IVUS and position information of EM-tracking	Only tested in single phantom set-up. No participants performing procedure.
Robotic navigation system:
Riga [35], 2011	Phantom study	17 operators	Type 1 and type 3 Aortic arch phantom	Robotic technology has the potential to reduce time, risk of embolization, radiation exposure and manual skill required for carotid arch vessel cannulation	Phantom does not reflect all challenges of navigation within clinical setting.
Robotic navigation system in combination with electromagnetic tracking:
Schwein [36], 2018	Phantom study	6 operators	Rigid aortic aneurysmal phantom	Value of combination of 3D control and 3D navigation is confirmed and shows promising results in further reduction of procedure time and improved catheter motion	In vitro nature of study
Schwein [16], 2017	Phantom study	18 operators	Rigid aortic aneurysmal phantom	Use of flexible robotic catheters combined with EM tracking of catheter tip allows better real-time 3D orientation and significantly reduces fluoroscopy and cannulation time	EM-sensor in the catheter lumen prevented the use of a guidewire and therefore comparison with 2D fluoroscopy is difficult. Moreover study is limited by small number of participants and in vitro nature.
Fiber Optic Shape Sensing:
Jäckle [37], 2019	Phantom study	-	3D Printed aortic model	Test within endovascular scenario shows promising results for use of multicore fibers for shape sensing in catheters	Tests were performed under ideal circumstances. No navigational or cannulation tasks were performed
Van Herwaarden [17], 2021	Clinical study, Prospective	22 patients	EVAR, FEVAR, BrEVAR, IBD, Peripheral	Real-time 3D navigation using FORS technology is safe and feasible in endovascular procedures	Learning curve during clinical practice. Moreover there are only two available catheters and limited working length

Abbreviations: EM, electromagnetic; IF, image fusion; IVUS, intravascular ultrasound; FORS, FiberOptic Real shape; CTA, computed tomography angiography; CBCT, cone-beam computed tomography; OR, operating room; 2D, two-dimensional; 3D, three-dimensional; EVAR, endovascular aortic aneurysm repair; TEVAR, thoracic endovascular aortic aneurysm repair; FEVAR, fenestrated endovascular aortic aneurysm repair; BrEVAR, branched endovascular aortic aneurysm repair; ChEVAR, chimney endovascular aortic aneurysm repair; TASC, Trans-Atlantic Inter-Society Consensus Document

3.1. Overview of included techniques

3.1.1. Electromagnetic tracking

Four articles [19–22] described the standalone use of EM tracking and reported the ability of EM-tracked devices to support guidance during endovascular interventions. Three of the articles describing EM-tracking reported results of phantom studies [19,20,22] and one a prospective clinical study [21]. Three of these studies use the Aurora tracking system [20–22] and one the StealthStation Treon plus system [19].

EM-tracking systems consist of a low magnetic field generator and EM position coils integrated within the tip of the used catheter or guidewire. Information about the EM field within the EM coils at the tip of the devices is analyzed in a control box that converts this information into a 3D position of the coil. In combination with navigation software, the system can visualize the 3D position and orientation of the devices relative to the anatomy, segmented from a preoperative CTA. This allows this technology to be used in addition to or even without the use of fluoroscopy when performing navigation or cannulation tasks. However, visual cues that indicate the full configuration and tension of the instrument body are limited by the number of sensor coils placed in the EM tracking devices, as the system can only track the points where the sensor coils are located. Three studies reported the specifications of the five degrees of freedom EM sensor coils (0.5x8mm [20,22] and 0.5x11mm [21]) placed into catheters and two studies of the five degrees of freedom EM sensor coils (0.3x12mm [20] and 0.5x8mm [22]) placed into guidewires. In addition, commercially available interventional devices hardly support the use of EM tracking, often requiring additional and custom-built devices during these procedures. For example, in the registered studies, the control cables of steerable catheters [20] or the balloon of percutaneous transluminal angioplasty (PTA) balloon catheters [21,22] have been removed to use the extra lumen in these catheters to insert the EM sensor coils, making these devices suitable for EM tracking. Another limitation is that nearby electronic devices such as the C-arm, for example, can cause interference in the EM field, reducing the tracking quality of the system. To minimize the impact of this, it is recommended to position the C-arm away from the navigation field when using EM tracking. Moreover, the system setup time and learning curve during use also cause the procedure time to be extended at the moment.

3.1.2. Image fusion

IF as radiation exposure reducing technology is discussed in 12 of the articles in this review. Eight of the included articles on IF were retrospective clinical studies [13,14,23–28], while four studies described prospective clinical studies [29–32]. Of these studies, three described the VesselNavigator application [13,23,27], one the CYDAR application [29], three the Syngo application [24,25,31], one the Advantage Workstation application [30], two the Ziostation 2 Plus ZWS-2000 application [26,28], one the Leonardo application [14] and one the Xtra vision 8.3 application [32]. The IF studies included in this review reported three different methods by which preoperatively acquired CTA images can be registered to the live situation and then projected onto fluoroscopy images by IF. Four studies described a two-dimensional (2D) registration method (2D/3D) in which two bi-planar fluoroscopy images are acquired to register the preoperative CTA images [13,23,26,30]. This registration method requires the user to manually position the segmentation of the preoperatively acquired CTA in the correct position on these two fluoroscopy images. Six studies reported the use of a 3D registration method (3D/3D) in which a preoperatively acquired CBCT is used to register the segmentation of the preoperatively acquired CTA [14,24,25,28,31,32]. This method allows the user to select corresponding locations in the preoperative and perioperative scan based on anatomical landmarks such as atherosclerotic plaques. The software then automatically positions the preoperative CTA over the live fluoroscopy images. One selected study reported the use of both 2D/3D and 3D/3D IF registration methods [27]. Finally, one study reported the use of an automatic registration method for IF [29]. This technique compares the anatomy, mainly vertebrae, visible on live fluoroscopy images with the anatomy of the preoperative CTA and then automatically produces a 3D overlay. In contrast to the 2D/3D and 3D/3D registration methods, this technique is able to automatically update the roadmap during the endovascular procedure by adapting the roadmap to the new position visible anatomy and mostly the position of the visible vertebrae.

IF is a technology that improves anatomical understanding during endovascular procedures without the need to perform digital subtraction angiography (DSA). It is a relatively easy-to-use method that significantly reduces radiation exposure and contrast volume, but does not eliminate the need to use fluoroscopy or reduce overall procedure time. Moreover, only the CYDAR image fusion technology is able to automatically adapt the anatomical roadmap according to the real-time situation. All other described image fusion methods are based on a rigid registration method of the preoperatively acquired CTA with real-time fluoroscopy images. As a result, the roadmap created with these methods must therefore be adjusted manually, whether or not on the basis of a DSA, to changes in the real-time situation that arise due to, for example, the introduction of a rigid guidewire.

3.1.3. Intravascular ultrasound

One of the included articles [33] for this review reported the use of IVUS during endovascular aortic repair (EVAR) procedures in a retrospective clinical study. The study [34] discussing a combination of IVUS with EM tracking is presented in the section ‘combined tools.’ IVUS creates intraluminal images of the blood vessel using high-frequency sound waves. This technique allows users to determine, among other things, characteristics of the aneurysm neck, such as diameter, and compare them with the values found in CTA obtained preoperatively. In addition, IVUS can also determine the location of branches without using radiation and thus has the potential to reduce radiation exposure.

Pecoraro et al [33]. reported results of a retrospective study on the feasibility of using IVUS and its ability to significantly reduce the amount of radiation exposure and contrast volume during EVAR procedures. In addition, IVUS reduced the rate of endoleaks, did not lead to an increase in operative time, and no adverse events associated with IVUS use were reported.

3.1.4. Robotic navigation system

The use of a RNS was reported by one included study [35] and two studies [16,36] discussing a combination of RNS with EM tracking are presented in the section ‘combined tools.’ This study describes the Sensei Robotic Catheter System that consists of a hand operated joystick and an instinctive motion controller with a steerable catheter. Since this joystick for operating this device can be placed at a distance from the radiation source, the use of this technology reduces radiation exposure for the operator.

The results presented by Riga et al [35] of an in vitro study of cannulation tasks in a type I and a type III aortic arch phantom show that a robotic navigation system can contribute to reducing radiation exposure and operation duration. The increased accuracy of catheter positioning makes this technique a suitable adjunct for navigation during complex endovascular procedures. However, a limitation to the use of this technology is that larger sheaths must be used for vascular access and that careless advancing of the devices increases the risk of dissections.

3.1.5. Fiber optic shape sensing

Two included studies describe the use of multicore fiber integrated shape sensing devices for navigation during endovascular procedures [17,37]. These devices are connected to the system that sends laser light through the optical fibers. Shape changes in the integrated optical fiber caused by the twisting and bending of the devices influences the returning light. By analyzing these changes in the returning light spectrum, the system is able to create three-dimensional reconstructions along the full length of the integrated optical fiber, making it possible to visualize the devices in real time without the need for radiation.

One study reported promising results of a shape detection multicore fiber used in a 3D printed aortic model [37]. Tests in the endovascular model show high accuracy. However, these experiments only describe the use of optical fibers that have not yet been integrated into endovascular devices. In addition, the measurements were performed under ideal conditions, which may reduce the accuracy under more complex conditions. Van Herwaarden et al [17], on the other hand, described the first in human use of optical shape-sensitive devices with a prospective study design. In this study, they describe the use of Fiber Optic RealShape (FORS) technology to perform navigation tasks during endovascular procedures and demonstrate the safety and feasibility of its use. Improving the understanding of the spatial course of the devices and the unrestricted viewing angles in particular is considered to be of added value. In addition, it is shown that cannulation tasks can be performed with minimal radiation exposure. However, although it has been reported that cannulation tasks can be performed with minimal use of radiation, this study does not demonstrate the reduction in radiation exposure.

3.1.6. Combined tools

Two studies [16,36] reported the combination of a Magellan robotic navigation system with Aurora EM-tracking technology. Schwein et al [16,36]. reported the value of remotical 3D catheter control in combination with improved 3D device orientation using EM-tracking technology in two subsequent studies. Outcomes show a reduction in fluoroscopy and cannulation time.

One study reported the combination of IVUS and Aurora EM-tracking technology. Shi et al [34]. proposed a new real-time intravascular reconstruction and navigation for endovascular aortic stent grafting. In this method, anatomical information is obtained with IVUS and linked to the catheter position obtained via EM tracking. Results show significant potential for clinical applications, efficiency improvement of precision alignment and placement of grafts by real-time reconstruction and navigation.

3.2. Radiation reduction in clinical studies

In this review, 14 articles were selected in which outcomes of radiation-related measured parameters of a (potentially) radiation-reducing tool were compared with outcomes in a control group. Twelve articles examined the influence of IF [13,14,23–32], one the influence of EM tracking [21] and one the influence of IVUS [33] on radiation exposure reduction. Table 2 presents an overview of extracted radiation-related measured parameters, if available, of all included clinical studies.

Table 2. Overview of clinical studies in which a (potential) radiation reducing tool is compared with a conventional control group.

Author, year	N	Type of intervention	Procedure time, minutes	Cumulative radiation dose, AK (mGy) or DAP (Gycm^2)	Fluoroscopy time, minutes	Contrast volume, mL
Electromagnetic tracking:
Manstad-Hulaas [21], 2012	17	EVAR (EM 7 & Control 10)	EM; 141 ± 24; Control 118 ± 24; P = 0.108	DAP: EM 273.76 ± 92.39; Control 169.59 ± 60.57; P = 0.043	-	EM 232 ± 66; Control 243 ± 69; P = 0.950
Image Fusion:
Ahmad [13], 2019	146	TEVAR (IF 98 & Control 48)	-	-	-	IF 70 (IQR 50–101); Control 104 (IQR 69–168); P < 0.001
		TEVAR without carotid subclavian bypass (IF 44 & control 30)	IF 74 (IQR 54–116); Control 85 (IQR 64–111); P = 0.545	DAP: IF 19.92 (IQR 10.89–39.48); Control 30.97 (IQR 16.11–48.83); P = 0.281	IF 9; Control 9; P < 0.848	IF 83 (IQR 54–120); Control 120 (IQR 75–160); P = 0.058
		TEVAR with carotid subclavian bypass (IF 26 & control 11)	IF 162 (IQR 139–199); Control 213 (IQR 189–298) P = 0.015	DAP: IF 36.657 (IQR 12.371–51.831); Control 24.83 (IQR 11.885–35.201); P = 0.370	IF 9 (IQR 6–13); Control 23 (IQR 12–45); P < 0.005	IF 64 (IQR 43–81); Control 98 (IQR 60–180); P = 0.003
Ahmad [23], 2018	152	EVAR (IF 105 & Control 47)	-	DAP: IF 23.437 (15.77–51.44); Control 32.19 (14.31–49.42); P = 0.457	-	IF 58 (IQR 38–88); Control 98 (IQR 66–113); P < 0.001
De Beaufort [29], 2021	37	Aortoiliac occlusive disease (IF 18 & Control 19)	IF 60 (IQR 42–90); Control 60 (IQR 30–90)	AK: IF 100 (IQR 40–300); Control 120 (IQR 60–200) DAP: IF 18.5 (IQR 6.9–45.5); Control 21.8 (IQR 9.9–36.8)	IF 5.1 (IQR 3.7–15.4); Control 5.7 (IQR 1.8–10.8)	IF 41 (IQR 30–60); Control 30 (IQR 22–55)
Dias [24], 2015	226	All EVAR (IF 103 & Control 123)	IF 230 (IQR 134–331); Control 235 (IQR 158–364); P = 0.942	DAP: IF 199.34 (IQR 113.34–306.15); Control 328.56 (IQR 195.62–556.78); P < 0.0001	IF 66 (IQR 33–102); Control 72 (IQR 42–102); P = 0.837	IF 103 (IQR 63–145); Control 215 (IQR 166–280); P < 0.0001
		Thoracoabdominal aneurysm repair (IF 33 & Control 23)	IF 349 (IQR 261–438); Control 459 (IQR 391–607); P = 0.007	DAP: IF 262.87 (IQR 202.98–367.67); Control 638.91 (IQR 436.96–1002.66); P < 0.0001	IF 103 (IQR 84–139); Control 127 (IQR 104–157); P = 0.103	IF 143 (IQR 196–197); Control 298 (IQR 234–363); P < 0.0001
		Juxtarenal aneurysm repair (IF 21 & Control 36)	IF 231 (IQR 163–332); Control 277 (IQR 193–374); P = 0.319	DAP: IF 241.72 (IQR 140.44–432.04); Control 283.24 (IQR 192.08–499.57); P = 0.581	IF 72 (IQR 48–131); Control 87 (IQR 58–99); P = 0.581	IF 96 (IQR 69–144); Control 208 (IQR 162–238); P < 0.0001
		Aortoiliac aneurysm repair with IBD (IF 17 & Control 24)	IF 191 (IQR 130–258); Control 249 (IQR 191–281); P = 0.131	DAP: IF 188.76 (IQR 121.94–234.93); Control 468.67 (IQR 328.87–617.08); P < 0.0001	IF 57 (IQR 35–76); Control 80 (IQR 60–101); P = 0.077	IF 132 (IQR 85–185); Control 255 (IQR 224–312); P < 0.0001
		Infrarenal aneurysm repair (IF 22 & Control 25)	IF 128 (IQR 102–151); Control 149 (IQR 119–193); P = 0.459	DAP: IF 98.85 (IQR 83.63–164.70); Control 213.83 (IQR 123.99–290.14); P = 0.013	IF 25 (IQR 18–40); Control 38 (IQR 30–45.3); P = 0.185	IF 84 (IQR 49–136); Control 160 (IQR 146–204); P < 0.0001
		Thoracic aneurysm repair (IF 10 & Control 15)	IF 83 (IQR 56–183); Control 144 (IQR 95–144); P = 0.459	DAP: IF 90.40 (IQR 61.95–158.49); Control 172.98 (IQR 143.76–386.32); P = 0.41	IF 14 (IQR 9–31); Control 28 (IQR 19–39); P = 0.688	IF 53 (IQR 40–175); Control 178 (IQR 128–282); P = 0.400
Dijkstra [25], 2011	89	FEVAR (IF 40 & Control 49)	IF 330 (IQR 273–522); Control 387 (IQR 290–477); P = 0.651	AK: IF 7 (IQR 4–12); Control 7 (IQR 5–10); P = 0.782	IF 81 (IQR 54–118); Control 90 (IQR 46–128); P = 0.932	IF 94 (IQR 72–131); Control 136 (IQR 96–199); P = 0.001
Hertault [30], 2014	397	EVAR (IF 44 & Control 199)	IF 92.5 (IQR 75–120); Control 93 (IQR 75.120); P = 0.97	DAP: IF 12.2 (IQR 8.7–19.9); Control 30.0 (IQR 20.0–43.5); P < 0.01	-	IF 59 (IQR 50–75); Control 80 (IQR 65–106); P = 0.34
		FEVAR (IF 18 & Control 54)	IF 150 (IQR 150–160); Control 150 (IQR 105–180); P = 0.39	DAP: IF 43.7 (IQR 24.7–57.5); Control 72.9 (IQR 52–109.2); P < 0.01	-	IF 105 (IQR 70–136); Control 138 (IQR 100–160); P = 0.03
		BrEVAR (IF 20 & Control 20)	IF 205 (IQR 169–240); Control 210 (IQR 150–260); P = 0.87	DAP: IF 47.4 (IQR 37.2–108.2); Control 159.0 (IQR 101.8–222.4); P < 0.01	-	IF 120 (IQR 100–170); Control 226 (IQR 150–278); P < 0.01
		TEVAR (IF14 & Control 28)	IF 80 (IQR 60–105); Control 117 (IQR 60–138); P = 0.22	DAP: IF 24.7 (IQR 22.0–28.7); Control 20.0 (IQR 11.4–30.0); P = 0.63	-	IF 80 (IQR 50–100); Control 100 (IQR 78–140); P = 0.07
Hiraoka [26], 2018	263	EVAR (IF 81& Control 62)	IF 116 ± 27; Control 113 ± 37; P = 0.487	AK: IF 768 ± 529; Control 880 ± 833; P = 0.333	-	IF 76.2 ± 27.6; Control 89 ± 28.5; P = 0.009
		TEVAR (IF 83 & Control 37)	IF 86.2 ± 23.9; Control 96.4 ± 27.0; P = 0.023	AK: IF 638 ± 463; Control 872 ± 623; P = 0.033	-	IF 72.6 ± 21.1; Control 85.6 ± 31.1; P = 0.009
McNally [14], 2015	72	All FEVAR (IF 31 & Control 41)	-	AK: IF 2200 ± 1300; Control 5000 ± 280; P < 0.0001	IF 55 ± 21; Control 84 ± 36; P = 0.0004	IF 34 ± 15; Control 86 ± 25; P < 0.0001
		2 FEVAR (IF 12 & Control 8)	-	AK: IF 1380 ± 520; Control 3400 ± 1900; P = 0.001	IF 41 ± 11; Control 63 ± 29; P = 0.02	IF 26 ± 8; Control 69 ± 16; P < 0.0001
		3 or 4 FEVAR (IF 19 & Control 33)	IF 230 ± 50; Control 330 ± 100; P = 0.002	AK: IF 2700 ± 1400; Control 5400 ± 2225; P < 0.0001	IF 64 ± 21; Control 89 ± 36; P = 0.02	IF 39 ± 17; Control 90 ± 25; P < 0.0001
Rolls [31], 2016	42	FEVAR (IF 19 (2 lost due to learning curve) & Control 21)	IF 282 (IQR 268–322); Control 450 (IQR 360–450); P < 0.001	AK: IF 1590 (IQR 1090–2110); Control 4400 (IQR 3200–7000); P < 0.001 DAP: IF 158 (IQR 123–226); Control 264 (IQR 173.3–366.8); P = 0.006	-	-
Sailer [32], 2014	62	FEVAR and BrEVAR (IF 23 & Control 23)	IF 312 ± 108; Control 378 ± 144; P = 0.022	-	IF 50.43 ± 29.58; Control 59.48 ± 28.02; P = 0.38	IF 159 ± 27; Control 199 ± 29; P = 0.037
Stangenberg [27], 2015	32	EVAR (IF 16 & Control 16)	IF 80.4 ± 21.1; Control 110 ± 29.1; P = 0.005	AK: IF 1067 ± 470.4; Control 1768 ± 696.2; P = 0.004	IF 18.4 ± 6.8; Control 26.8 ± 10.0; P = 0.01	IF37.4 ± 21.3; Control 77.3 ± 23.0; P < 0.001
Tacher [28], 2013	37	FEVAR, BrEVAR and ChEVAR (IF 14 & 3D 14 & 2D 9)	IF 189 ± 60; 3D 181 ± 53; 2D 233 ± 123; P = 0.59 (IF vs 3D vs 2D)	DAP: IF 656 ± 457; 3D 984 ± 581; 2D 1188 ± 1067; P = 0.18 (2D vs 3D vs IF)	IF 80 ± 36; 3D 42 ± 22; 2D 82 ± 46; P = 0.04 (2D vs 3D vs IF) & P = 0.18 (3D vs 2D) & P = 0.02 (3D vs IF)	IF 65 ± 28; 3D 225 ± 119; 2D 235 ± 145; P = 0.0002 (IF vs 2D) & P = <0.0001 (IF vs 3D)
Intravascular Ultrasound:
Pecoraro [33], 2019	52	EVAR (IVUS 26 & Control 26)	IVUS 179 (IQR 120–210); Control 176 (IQR 124–210); P = 0.48	DAP: IVUS 15 (IQR 9–21); Control 32 (IQR 16–44); P = 0.002	IVUS 12 (IQR 9–16); Control 20 (IQR 12–25); P = 0.001	IVUS 50 (IQR 20–68); Control 92 (IQR 50–125); P = 0.003

Abbreviations: EVAR, endovascular aortic aneurysm repair; TEVAR, thoracic endovascular aortic aneurysm repair; FEVAR, fenestrated endovascular aortic aneurysm repair; BrEVAR, branched endovascular aortic aneurysm repair; ChEVAR, chimney endovascular aortic aneurysm repair; IBD, iliac branched device; EM, electromagnetic; IF, image fusion; IVUS, intravascular ultrasound; AK, air kerma; DAP, dose area product; IQR, interquartile range; 2D, two-dimensional; 3D, three-dimensional.

One study [21] presented results of a prospective clinical study on the influence of the use of EM tracking on the reduction of radiation exposure in EVAR procedures. This study showed that compared to the use of conventional fluoroscopy, the use of EM tracking significantly increased radiation dose, prolonged procedure time and comparable contrast volume utilization. No results were presented in this study for fluoroscopy time. While the results actually show increased radiation exposure, it should be noted that the intraoperative CBCT performed and the setup and testing of the EM tracking equipment also influence these parameters and thus may not affect the true contribution of EM tracking to the reduction of the radiation dose. Due to the available 3D information about the position of the EM-tracked device, the authors certainly see this technology of added value in cannulation tasks during complex procedures. It is therefore expected that with increasing experience with this navigation technology, radiation exposure, and procedure time will eventually decrease.

In two of the twelve clinical studies examining the influence of IF on radiation reduction, the use of IF resulted in a significant reduction in procedure time, radiation dose, fluoroscopy time and contrast volume. Stangenberg et al [27]. reported a significant reduction in the above mentioned parameters during EVAR procedures and McNally et al [14]. during fenestrated endovascular aortic repair (FEVAR) procedures when using IF. In addition, eight studies [23–25,28–32] showed a trend toward a reduction in radiation exposure with IF. In fact, one of these studies [31] showed a significant reduction in radiation exposure during FEVAR procedures, while in two studies [24,30], this reduction was significant only in the subgroups of EVAR, FEVAR, and branched endovascular aortic repair (BrEVAR) procedures. One study [28] showed a significant reduction in fluoroscopy time during complex EVAR procedures and another study [13] only in a subset of TEVAR procedures Furthermore, two studies [24,32] reported a trend toward reduction in fluoroscopy time when using IF during standard or complex EVAR procedures and one study [29] during treatment of aortoiliac occlusive disease. The procedure time was significantly shorter in two studies [31,32] reporting the use of IF during FEVAR procedures, while in one two studies [13,26] subgroup results with TEVAR and one study [24] with subgroup results with complex EVAR procedures yielded the same result. In addition, three other studies [25,28,30] and the remaining subgroups of two studies [13,24] show a trend toward shortening of procedure time when using IF, while only one study [23] reported no results. Eight studies [13,23–26,28,30,32] showed a significant decrease in contrast volume. In contrast, one study [29] reported a non-significant increase in contrast volume and one study [31] reported no outcomes for contrast volume.

Finally, one study [33] presented the results of a prospective clinical study comparing the influence of IVUS on total radiation exposure during EVAR procedures with conventional fluoroscopy. In this study, radiation dose, fluoroscopy time, and contrast volume are significantly decreased, while procedure time remains almost the same.

3.3. Cannulation task characteristics

Cannulation task characteristics were reported in seven studies included in this review, of which five studies [16,19,20,35,36] reported an in vitro design and two studies [17,21] a prospective in vivo design. An overview of all articles with, if available, cannulation task characteristics can be found in Table 3. Three studies reported characteristics of cannulation tasks while using an EM tracking device; two studies [19,20] presented the results of phantom studies, while one study [21] presented the outcome of a prospective clinical trial. Two studies [19,20] reported results of fluoroscopy time and showed a reduction in the use of EM-tracking devices. Two studies also presented cannulation time results, with one study [19] showing a reduction in cannulation time while using EM tracking equipment and the other study [21] reporting an increase. Furthermore, one study [19] reported only on vessel wall hits, one study [21] only the number of cannulation attempts and one study [20] reported both. In all these cases, the use of EM tracking equipment resulted in a reduction compared to the use of conventional fluoroscopy.

Table 3. Overview of studies reporting cannulation task characteristics.

Author, Year	Study type	Model/Intervention	Task	Cannulation attempts	Vessel wall hits	Cannulation time, minutes	Fluoroscopy time, minutes
Electromagnetic tracking:
Cochennec [19], 2013	In vitro	Transparant anthropomorphic aortic arch phantom	LSA, LCCA, RCCA	-	EM 8.5 (IQR 16–38); Control 14 (IQR 11–16)	EM 1.27 (IQR 1.13–1.68); Control 1.45 (IQR 1.07–2.13)	EM 26.5 (IQR 19.7–30.7); Control 87 (IQR 64–128)
Condino [20], 2014	In vitro	Abdominal Aortic aneurysm model	LRA, RRA	EM 4.0 (IQR 2.00–5.00); Control 4.0 (IQR 2.00–5.00); P = 0.72	EM 3.50 (IQR 2.50–7.00); Control 5.50 (IQR 2.00–10.00); P = 0.65	-	EM 0; Control 2.10 (IQR 1.30–3.90)
Manstad-Hulaas [21], 2012	Prospective	EVAR	CL gate	EM 4.2 ± 2.8; Control 14.4 ± 12.4; P = 0.059	-	EM 7.0 ± 2.8; Control 5.3 ± 4.0; P = 0.282	-
Robotic navigation system:
Riga [35], 2011	In vitro	Type 1 Aortic Arch	LCCA	RNS 9 (IQR 7–25); Control 61 (IQR 51–165); P = 0.001	RNS 0 (IQR 0–1); Control 2 (IQR 1.5–13); P = 0.001	RNS 0.80 (IQR 0.30–1.57); Control 2.70 (IQR 1.92–3.98); P = 0.001	-
			RCCA	RNS 9 (IQR 6–10); Control 48 (IQR 21–81); P = 0.001	RNS 2 (IQR 1.5–3.5); Control 4.5 (IQR 3.5–11.3); P = 0.001	RNS 0.69 (IQR 0.44–0.99); Control 1.70 (IQR 1.20–3.35)	-
Riga [35], 2011 (continued)			LSA	RNS 7 (IQR 6–10); Control 18 (IQR 14–31); P = 0.001	-	RNS 0.25 (IQR 0.18–0.31); Control 0.76 (IQR 0.34–0.88); P = 0.002	-
			RSA	RNS 11 (IQR 81–15); Control 22 (IQR 15–48); P = 0.005	-	-	-
		Type 3 Aortic Arch	LCCA	RNS 14 (IQR 12–21); Control 89 (IQR 45–284); P = 0.001	RNS 0.5 (IQR 0.3–1.5); Control 13.8 (IQR 9.5–19); P = 0.001	RNS 1.02 (IQR 0.61–2.10); Control 3.78 (IQR 0.92–11.28); P = 0.01	-
			RCCA	RNS 30 (IQR 9–38); Control 209 (IQR 124–335); P = 0.001	CCA Origin Hits: RNS 5 (IQR 4–9); Control 9 (IQR 5–21.5); P = 0.04	RNS 1.81 (IQR 0.67–3.02); Control 6.2 (IQR 3.02–8.97); P = 0.001	-
			LSA	RNS 7 (IQR 6–11); Control 24 (IQR 17–38); P = 0.001	-	-	-
			RSA	RNS 31 (IQR 16–42); Control 69 (IQR 48–81); P = 0.003	-	-	-
Robotic navigation system in combination with electromagnetic tracking:
Schwein [36], 2018	In vitro	rigid aortic aneurysmal phantom	LRA	-	-	EM+RNS 2.07; Control 2.68	EM+RNS 0.08; Control 2.22
			CL gate	-	-	EM+RNS 2.15; Control 4.37	EM+RNS 0.03; Control 3.41
Schwein [16], 2017	In vitro	rigid aortic aneurysmal phantom	LRA	-	-	EM+RNS 0.08; Control 2.22	EM+RNS 2.07; Control 2.68
			CL gate	-	-	EM+RNS 0.03; Control 3.41	EM+RNS 2.15; Control 4.37
Fiber Optic Shape Sensing:
Van Herwaarden [17], 2021	Prospective	TEVAR, BrEVAR, FEVAR, peripheral	Combined	-	-	FOSS 13.3 ± 18.1	FOSS 3.15 ± 8.26
			CT	-	-	FOSS 15.3 ± 1.5	FOSS 2.99 ± 2.32
			SMA	-	-	FOSS 13.0 ± 6.2	FOSS 4.89 ± 4.49
			LRA	-	-	FOSS 33.6 ± 44.7	FOSS 10.29 ± 16.94
			RRA	-	-	FOSS 32.8 ± 33.1	FOSS 13.48 ± 21.93
			IIA	-	-	FOSS 24.5 ± 24.8	FOSS 5.10 ± 2.55

Abbreviations: EM, electromagnetic; RNS, robotic navigation system; FOSS, fiber optic shape sensing; LSA, left subclavian artery; RSA, right subclavian artery; LCCA, left common carotid artery; RCCA, right common carotid artery; CT, celiac trunk; SMA, superior mesenteric artery; LRA, left renal artery; RRA, right renal artery; IIA, internal iliac artery; EVAR, endovascular aortic aneurysm repair; TEVAR, thoracic endovascular aortic aneurysm repair; FEVAR, fenestrated endovascular aortic aneurysm repair; BrEVAR, branched endovascular aortic aneurysm repair.

One study [35] reported the use of RNS while performing four cannulation tasks in a type 1 and four in a type 3 aortic arch phantom. This study reported a reduction in cannulation time in five of the eight cannulation tasks, a reduction in the number of vessel wall hits in four of the eight tasks, and a reduction in the number of cannulation attempts in all cases. However, no elapsed fluoroscopy time information is presented.

Finally, there are three studies that only described the cannulation and fluoroscopy time; two studies [16,36] described the influence of the use of combination of EM and RNS in an aortic aneurysm phantom and one study [17] the use of FOSS in a prospective clinical trial. Both studies describing a combination of EM and RNS showed a reduction in both cannulation time and fluoroscopy time. In contrast, the study describing the use of FOSS only reported results while using this technology. As a result, there are no results of comparable tasks performed with conventional fluoroscopy to compare with FOSS results.

4. Discussion

A systematic review of studies describing a current or potential radiation-reducing technique used during aortic endovascular procedures resulted in 23 studies identifying 5 different instruments that alone or in combination may contribute to the reduction of radiation dose during endovascular procedures. Image fusion is the most widely described radiation exposure limiting tool in the included articles. Particularly in complex endovascular aortic procedures such as fenestrated or bifurcated endovascular aneurysm repair (FEVAR/BrEVAR), this instrument showed a trend toward reductions in cumulative radiation dose and contrast volume. In contrast, fluoroscopy time remained generally similar in both groups. This is most likely because the use of image fusion during navigation reduces the need to create DSA with contrast medium for navigational purposes, as the use of image fusion allows navigation based on projection of a preoperatively acquired CTA onto real-time 2D fluoroscopy display. In addition, the chosen registration method plays an important role in achieving radiation reduction. While the use of a 3D registration method often produces a more accurate image fusion result compared to the 2D method, CBCT necessary for the 3D registration method accounts for a significant portion of the radiation exposure [38,39]. Therefore, it is quite possible that this explains why in case of image fusion is used for example more simple EVAR procedures, the results show a trend rather than a significant reduction in radiation exposure.

Although in many cases, image fusion leads to a decrease in radiation exposure, this tool in itself is still completely dependent on the use of radiation during the visualization of endovascular procedures. The four other (potential) radiation-limiting instruments described, on the other hand, can be used almost completely radiation-free, whether or not in combination with image fusion. This is especially true for IVUS, as it is an intraluminal imaging technique that can visualize the vessel and surrounding structures. In addition, IVUS can also be used to compare neck aneurysm characteristics, such as diameter, with preoperative values obtained during the procedure and to accurately assess the position of the stent. In contrast, the other three techniques find their application in the reduction of radiation during the navigation phase of endovascular procedures. However, the use of these technologies also has limitations. The use of RNS, for example, has the great advantage that the devices have greater maneuverability and stability, but on the other hand the disadvantage that virtually no information is available about the course of the device without using fluoroscopy. Using EM tracking and FOSS technologies, the positioning and movement of the devices can be more accurately visualized, but the systems are prone to inaccuracy caused by disturbances in the magnetic field or optical signal. Moreover, there are currently only limited devices available for these three techniques and setting up the technology during procedures and the associated learning curve currently often extends the procedure time. While these techniques have the potential to reduce radiation exposure, they generally still increase radiation exposure at this stage.

4.1. Limitation of outcome parameters

In order to make an optimal comparison between all characteristics of radiation exposure and cannulation task, the conditions under which the data were obtained should be as similar as possible. However, the data compared in this review are highly heterogeneous, significantly increasing the potential for bias. For example, the amount of radiation exposure depends on multiple factors and achieving radiation reduction often involves addressing more than one of these factors. The X-ray settings selected during the procedure, such as the fluoroscopy protocol and the number of frames per second, the desired position and orientation of the C-arm and the application of the ALARA principle, influence the radiation exposure results [40,41]. In addition, the complexity of the procedure performed and the operator’s experience also affect radiation exposure results, such as cannulation task characteristics, procedure, and fluoroscopy time. For a fair comparison with the smallest possible chance of bias, the characteristics in both groups should be matched to create homogeneous groups. However, most factors, such as X-ray and contrast protocol, operator experience, and complexity of the procedure, are only mentioned to a limited extent in the included studies. This makes it difficult to determine the exact degree of difference between the included studies and the impact on the outcomes.

4.2. Study limitations

Nine of the fourteen included clinical studies have a retrospective design of which eight studies [13,14,23–28] reported outcomes of the use of IF and one study [33] of IVUS. Most of these studies describe the comparison made with a cohort composed of procedures performed with older technology. For a fair and unbiased comparison between the parameter outcomes of both groups, the properties such as co-morbidities, complexity, and conditions of the procedure in these groups should be matched as closely as possible. However, due to the current design of the included studies, it is quite possible that outcomes based on tasks performed will lead to different outcomes compared to the presented outcomes per procedure.

In addition to all 12 included IF studies [13,14,23–32], only three other clinical studies describing EM [21], IVUS [33] and FOSS [17] were included. This distribution of radiation-reducing devices in clinical studies makes it difficult to make a good comparison between the technologies, as it is based on one study for three technologies. Moreover, the comparison between outcomes found in clinical trials and in vivo studies should be done with extreme care, as in vivo studies can never mimic all factors of a clinical setting and will therefore always provide a simplified representation of reality. Thus, the in vivo results only show the potential for exposure reduction, while the clinical results confirm or refute this.

The purpose of this review is to provide an overview of new radiation-reducing instruments. It was therefore decided to emphasize radiation reduction in the design of the search strategy. By emphasizing radiation exposure reduction, articles describing potential radiation exposure-reducing tools, but not focusing on this goal, may have fallen outside the scope of this review. Many studies describing navigation methods are more focused on demonstrating the accuracy and safety of the devices used. The potential for radiation reduction is briefly mentioned in the discussion section, but no further data is given to support this. In these cases, the search strategy we choose usually excludes the article, so that it was ultimately not included in the analysis.

5. Conclusion

In this systematic review, five different tools are presented to reduce potential radiation exposure. At present, these studies provide evidence that image fusion leads to a greater degree of reduction in radiation exposure with increasing complexity of the procedure. The remaining instruments have the potential to make a specific contribution to reducing radiation exposure during endovascular procedures. However, due to factors such as limited availability of devices or long preparation time, these tools are currently not yet of added value in limiting radiation exposure.

6. Expert opinion

Vascular surgery has undergone enormous development over the past 30 years from open to endovascular surgery. These developments offer the possibility to perform increasingly complex procedures as minimally invasive as possible. Besides the fact that more and more patients can be treated adequately, it also reduces the risks of unwanted complications, such as infection, during or after these procedures. However, the disadvantage of the increasing number of endovascular procedures of increasing complexity is that the radiation exposure of performing physicians especially also increases. Because of the increased health risk associated with long-term radiation exposure, it is therefore important to keep radiation use as low as possible during these procedures. There is therefore a great need to develop techniques that can achieve the same results with less or no radiation exposure than used in conventional endovascular procedures.

As discussed in this review, the use of image fusion in particular is currently of added value in reducing radiation exposure in more complex procedures. This technology is widely available and provides the user with insight during procedures by projecting the anatomy onto real-time 2D fluoroscopy images, eliminating the need for DSA with contrast agent to facilitate navigation and reduce radiation exposure. Moreover, the implementation of this technique in current practice does not require much deviance from the current procedure, so that the first step toward radiation reduction can be taken in an easy and fast way. However, the limitation of this technology at present is that the anatomical roadmap created does not adapt to live changes during the procedure. As a result, it is sometimes necessary to adapt the registration made to the live situation, which in turn requires the use of radiation. In addition, with the standalone use of this technology, the need to visualize devices by means of fluoroscopy remains necessary. As a result, the technology contributes to a reduction in radiation, but will never lead to radiation-free procedures.

Technologies such as IVUS or FOSS and EM tracking, possibly in combination with robot navigation systems, offer great potential for realizing the next step toward radiation-free endovascular interventions. These techniques can be applied autonomously and virtually radiation-free. In addition, using these technologies it is possible to visualize the position and orientation of the devices relative to, for example, a cannulation target. The colorized display of these devices makes it easier to distinguish position from the background, which is often gray. This provides the user with more information and better discrimination while navigating compared to navigation with conventional 2D fluoroscopy. An additional advantage of IVUS is that this technology can provide direct information about the neck of the aneurysm, the exact origin of target vessels or the position of the expanded stent graft. This allows IVUS to be deployed during both the navigational and monitoring phases of the procedure, further reducing the need to use radiation.

Although these navigation techniques potentially have a lot to offer in reducing radiation exposure, they are still minimally applied in practice. The main problem is that the advantages of these techniques do not yet outweigh the limitations. For example, relatively few commercial devices are available and many of the setups are still experimental. In addition, the preparation of the set-up of the technology currently still takes a lot of time and in many cases, this even extends the procedure time. Add to this the often high purchase value of the technology with the necessary equipment and you quickly fall back on the current conventional fluoroscopy method. Nevertheless, increasing awareness of the risks of long-term radiation exposure can to lead to more widespread adoption of these technologies in the coming years. The increasing demand for radiation reduction methods during endovascular procedures will lead to a greater focus of the medical industry on developing existing options and expanding the number of available devices. As a result, it is not a question of whether, but when all operating rooms will be equipped with these radiation-reducing technologies. Ultimately, performing endovascular interventions without requiring any form of radiation is certainly the future.

Article highlights

• This review presents overview of possible radiation dose reducing tools used during endovascular aortic procedures

• Image fusion is currently the most widely adopted technology for reducing radiation dose during endovascular aortic procedures.

• Fiber Optic shape-sensing Technology, Intravascular Ultrasound and Electromagnetic Tracking have high potential to contribute to further reduction of radiation exposure during endovascular aortic procedures

Declaration of interest

JA van Herwaarden has served as a consultant for Philips Medical Systems B.V. Netherlands. CEVB. Hazenberg has served as a consultant for Philips Medical Systems B.V. Netherlands. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

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Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

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