Editor's Choice - Radiation Dose Reduction During Contralateral Limb Cannulation Using Fiber Optic RealShape Technology in Endovascular Aneurysm Repair

OBJECTIVE

The increasing number of endovascular procedures has resulted in an increasing radiation burden, particularly for the treatment team. Fiber Optic RealShape (FORS) technology uses laser light instead of fluoroscopy to visualise the endovascular guidewire and catheters. These devices can be used during the navigational part of procedures, such as cannulation of the contralateral limb (CL) in endovascular aneurysm repair (EVAR). The aim of this study was to describe the effect of using FORS on radiation dose during CL cannulation in standard EVAR.

METHODS

This was a non-randomised, retrospective comparison study of prospectively collected, single centre data from FORS guided EVAR compared with a conventional fluoroscopy only guided EVAR cohort. A total of 27 FORS guided cases were matched 1:1 based on sex, age, and body mass index (BMI) with 27 regular (fluoroscopy only) EVARs. This study primarily focused on (1) technical success of FORS and (2) navigation time and radiation dose (cumulative air kerma [CAK], air kerma area product [KAP], and fluoroscopy time [FT]) during cannulation of the CL. In addition, overall procedure time and radiation dose of the complete EVAR procedure were studied.

RESULTS

In 22 (81%) of the 27 FORS guided cases the CL was successfully cannulated using FORS. All radiation dose parameters were significantly lower in the FORS group (CAK, p < .001; KAP, p = .009; and FT, p < .001) for an equal navigation time (p = .95). No significant differences were found when comparing outcomes of the complete procedure.

CONCLUSION

Use of FORS technology significantly reduces radiation doses during cannulation of the CL in standard EVAR.

Fiber Optic RealShape imaging using upper extremity and transfemoral access for fenestrated-branched endovascular aortic aneurysm repair

We report our initial experience using Fiber Optic RealShape (FORS), an innovative real-time three-dimensional visualization technology that uses light instead of radiation, to achieve upper extremity (UE) access during fenestrated/branched endovascular aortic aneurysm repair (FBEVAR). An 89-year-old male patient with a type III thoracoabdominal aortic aneurysm, unfit for open aortic repair, underwent FBEVAR. Dual fluoroscopy, intravascular ultrasound, and three-dimensional fusion overlay were used, in addition to FORS. All target artery catheterizations were successfully accomplished using FORS, from UE access, without radiation. Our experience demonstrates that FBEVAR with FORS using UE access can be used for target artery catheterization without radiation.

3D Visualisation of Navigation Catheters for Endovascular Procedures Using a 3D Hub and Fiber Optic RealShape Technology: Phantom Study Results

Objective

Fiber Optic RealShape (FORS) is a new technology that visualises the full three dimensional (3D) shape of guidewires using an optical fibre embedded in the device. Co-registering FORS guidewires with anatomical images, such as a digital subtraction angiography (DSA), provides anatomical context for navigating these devices during endovascular procedures. The objective of this study was to demonstrate the feasibility and usability of visualising compatible conventional navigation catheters, together with the FORS guidewire, in phantom with a new 3D Hub technology and to understand potential clinical benefits.

Methods

The accuracy of localising the 3D Hub and catheter in relation to the FORS guidewire, was evaluated using a translation stage test setup and a retrospective analysis of prior clinical data. Catheter visualisation accuracy and navigation success was assessed in a phantom study where 15 interventionists navigated devices to three pre-defined targets in an abdominal aortic phantom using an Xray or computed tomography angiography (CTA) roadmap. Additionally, the interventionists were surveyed about the usability and potential benefits of the 3D Hub.

Results

The location of the 3D Hub and catheter along the FORS guidewire was detected correctly 96.59% of the time. During the phantom study, all 15 interventionists successfully reached the target locations 100% of the time and the error in catheter visualisation was 0.69 mm. The interventionists agreed or strongly agreed that the 3D Hub was easy to use and the greatest potential clinical benefit over FORS is in offering interventionists choice over which catheter they used.

Conclusion

This set of studies has shown that FORS guided catheter visualisation, enabled by a 3D Hub, is accurate and easy to use in a phantom setting. Further evaluation is needed to understand the benefits and limitations of the 3D Hub technology during endovascular procedures.

Endovascular navigation with Fiber Optic RealShape technology

OBJECTIVE

Fiber Optic RealShape (FORS) technology has recently been introduced as an adjunctive guidance technology that allows real-time three-dimensional visualization of dedicated endovascular devices while avoiding radiation exposure. It consists of equipment which sends pulses of light through hair-thin optical fibers that run within a dedicated hydrophilic wire and selective catheters. The purpose of the study was to report the observed benefits and limitations related to the first edition of FORS technology.

METHODS

Data were collected prospectively from the first 50 patients undergoing FORS-guided endovascular repair at a single center between February 2020 and February 2021 as part of the global multicenter FORS Learn registry. All consecutive, elective procedures with one or more navigation tasks attempted with FORS were included. Factors related to FORS navigation task success were assessed. The time required for the catheterization of each task as well as the amount of radiation exposure (fluoroscopy time, dose area product, and estimated skin dose) were collected. A per-task analysis was conducted. End points included the success rate in achieving a stable FORS-guided catheterization, catheterization time, and radiation dose during catheterization.

RESULTS

During the study period from February 2020 to February 2021, 50 patients were treated using FORS technology. Forty-five patients were treated for aortic aneurysm, 4 for iliac artery aneurysm, and 1 for splenic artery aneurysm. Overall, 201 navigation tasks were completed for these procedures and FORS was used in 186 tasks (92.5%). No FORS-related complication was recorded and a success rate of 60.2% (n = 116) was observed. Target vessel (TV) angle of 45° or greater, TV stenosis, and the renal arteries as navigation tasks (compared with celiac artery or superior mesenteric artery) were associated with a lower success rate. Catheterization of a TV through a branch more frequently required a standard catheter in combination with the FORS-enabled guidewire. Successful task catheterization using FORS guidance was associated with a shorter catheterization time 6 minutes (interquartile range, 3-11 minutes) versus 16 minutes (interquartile range, 10-24 minutes) (P < .001) and lower radiation exposure compared with unsuccessful catheterization (dose area product, 4.4 cGy/cm² vs 12.5 cGy/cm²; P < .001).

CONCLUSIONS

FORS technology was implemented successfully as a new guidance technology in a complex endovascular aortic repair program and was associated with an encouraging success rate and a high potential for radiation reduction.

Characterization of Surgical Tools for Specific Endovascular Navigation

PURPOSE

The aim of this work was to mechanically characterize a specific active guidewire and catheters that are commercially available, for further implementation into numerical simulation of endovascular navigation towards complex targets.

METHODS

For the guidewire, 3-point bending tests and bending with added masses were used to obtain the Young moduli of its various components. To study its behavior, the guidewire was activated under "ideal" conditions and its performance was investigated. As for the various catheters, they were measured and 3-point bending tests were conducted to determine their mechanical properties.

RESULTS & CONCLUSION

The Young moduli of the shaft and the distal tip of the guidewire were determined. We defined a suitable current intensity to activate the guidewire related to an optimal curvature. Then, the time of activation/deactivation was measured at 1.7 s. On the flip side, parts of the catheters were considered either elastic or viscoelastic. In all cases, the rigidity gradients along the various catheters were highlighted. The characterization of the aforementioned surgical tools provides the opportunity to simulate the endovascular nagivation process.

Radiation-free Thoracic Endovascular Aneurysm Repair with Fiberoptic and Electromagnetic Guidance:A Phantom Study

PURPOSE

The purpose of this study was to evaluate the feasibility and accuracy of a radiation-free implantation of a thoracic aortic stent-graft employing fiberoptic and electromagnetic tracking in an anthropomorphic phantom.

MATERIALS AND METHODS

An anthropomorphic phantom was manufactured based on computed tomography angiography (CTA) data from a patient. An aortic stent-graft application system was equipped with a fiber Bragg gratings fiber and three electromagnetic sensors. The stent-graft was navigated in the phantom by three interventionalists using the tracking data generated by both technologies. One implantation procedure was performed. The technical success of the procedure was evaluated using digital subtraction angiography and pre- and post-interventional CTA. Tracking accuracy was determined at various anatomical landmarks based on separately acquired fluoroscopic images. The mean/maximum errors were measured for the stent-graft application system and the tip/end of the stent-graft.

RESULTS

The procedure resulted in technical success with a mean error below 3 mm for the entire application system and <2 mm for the position of the tip of the stent-graft. Navigation/implantation and handling of the device were rated sufficiently accurate and on a par with comparable, routinely used stent-graft application systems.

CONCLUSION

Our study demonstrates successful stent-graft implantation during a thoracic endovascular aortic repair procedure employing advanced guidance techniques and avoiding fluoroscopic imaging. This is an essential step in facilitating the implantation of stent-grafts and reducing the health risks associated with ionizing radiation during endovascular procedures.

First in Human Clinical Feasibility Study of Endovascular Navigation with Fiber Optic RealShape (FORS) Technology

OBJECTIVE

Endovascular procedures are conventionally conducted using two dimensional fluoroscopy. A new technology platform, Fiber Optic RealShape (FORS), has recently been introduced allowing real time, three dimensional visualisation of endovascular devices using fiberoptic technology. It functions as an add on to conventional fluoroscopy and may facilitate endovascular procedures. This first in human study assessed the feasibility of FORS in clinical practice.

METHODS

A prospective cohort feasibility study was performed between July and December 2018. Patients undergoing (regular or complex) endovascular aortic repair (EVAR) or endovascular peripheral lesion repair (EVPLR) were recruited. FORS guidance was used exclusively during navigational tasks such as target vessel catheterisation or crossing of stenotic lesions. Three types of FORS enabled devices were available: a flexible guidewire, a Cobra-2 catheter, and a Berenstein catheter. Devices were chosen at the physician's discretion and could comprise any combination of FORS and non-FORS devices. The primary study endpoint was technical success of the navigational tasks using FORS enabled devices. Secondary study endpoints were user experience and fluoroscopy time.

RESULTS

The study enrolled 22 patients: 14 EVAR and eight EVPLR patients. Owing to a technical issue during start up, the FORS system could not be used in one EVAR. The remaining 21 procedures proceeded without device or technology related complications and involved 66 navigational tasks. In 60 tasks (90.9%), technical success was achieved using at least one FORS enabled device. Users rated FORS based image guidance "better than standard guidance" in 16 of 21 and "equal to standard guidance" in five of 21 procedures. Fluoroscopy time ranged from 0.0 to 52.2 min. Several tasks were completed without or with only minimal X-ray use.

CONCLUSION

Real time navigation using FORS technology is safe and feasible in abdominal and peripheral endovascular procedures. FORS has the potential to improve intra-operative image guidance. Comparative studies are needed to assess these benefits and potential radiation reduction.

Three-dimensional guidance including shape sensing of a stentgraft system for endovascular aneurysm repair

PURPOSE

During endovascular aneurysm repair (EVAR) procedures, medical instruments are guided with two-dimensional (2D) fluoroscopy and conventional digital subtraction angiography. However, this requires X-ray exposure and contrast agent is used, and the depth information is missing. To overcome these drawbacks, a three-dimensional (3D) guidance approach based on tracking systems is introduced and evaluated.

METHODS

A multicore fiber with fiber Bragg gratings for shape sensing and three electromagnetic (EM) sensors for locating the shape were integrated into a stentgraft system. A model for obtaining the located shape of the first 38 cm of the stentgraft system with two EM sensors is introduced and compared with a method based on three EM sensors. Both methods were evaluated with a vessel phantom containing a 3D-printed vessel made of silicone and agar-agar simulating the surrounding tissue.

RESULTS

The evaluation of the guidance methods resulted in average errors from 1.35 to 2.43 mm and maximum errors from 3.04 to 6.30 mm using three EM sensors, and average errors from 1.57 to 2.64 mm and maximum errors from 2.79 to 6.27 mm using two EM sensors. Moreover, the videos made from the continuous measurements showed that a real-time guidance is possible with both approaches.

CONCLUSION

The results showed that an accurate real-time guidance with two and three EM sensors is possible and that two EM sensors are already sufficient. Thus, the introduced 3D guidance method is promising to use it as navigation tool in EVAR procedures. Future work will focus on developing a method with less EM sensors and a detailed latency evaluation of the guidance method.

Three Dimensional Visualisation of Endovascular Guidewires and Catheters Based on Laser Light instead of Fluoroscopy with Fiber Optic RealShape Technology: Preclinical Results

OBJECTIVE

Fiber Optic RealShape (FORS) is a new technology platform that enables real time three dimensional (3D) visualisation of endovascular guidewires and catheters, based on the concepts of fibre optic technology instead of fluoroscopy. Anatomical context is provided by means of co-registered prior anatomical imaging, such as digital subtraction angiography or computed tomography. This preclinical study assesses the safety and feasibility of FORS technology.

METHODS

Six physicians performed endovascular tasks in a phantom model and a porcine model using FORS enabled floppy guidewires, Cobra-2 catheters and Berenstein catheters. Each physician performed a set of predefined tasks in both models, including setup of the FORS system, device registration, and 12 aortic and peripheral target vessel cannulation tasks. The evaluation of the FORS system was based on (i) target vessel cannulation success; (ii) safety assessment; (iii) the accuracy of the FORS based device visualisation; and (iv) user experience.

RESULTS

Successful cannulation was achieved in 72 of the 72 tasks (100%) in the phantom model and in 70 of the 72 tasks (97%) in the porcine model. No safety issues were reported. The FORS based device visualisation had a median offset at the tip of 2.2 mm (interquartile range 1.2-3.8 mm). The users judged the FORS based device visualisation to be superior to conventional fluoroscopic imaging, while not affecting the mechanical properties (torquability, pushability) of the FORS enabled guidewire and catheters.

CONCLUSION

The combined outcomes of high cannulation success, positive user experience, adequate accuracy, and absence of safety issues demonstrate the safety and feasibility of the FORS system in a preclinical environment. FORS technology has great potential to improve device visualisation in endovascular interventions.

Fiber optical shape sensing of flexible instruments for endovascular navigation

Purpose

Endovascular aortic repair procedures are currently conducted with 2D fluoroscopy imaging. Tracking systems based on fiber Bragg gratings are an emerging technology for the navigation of minimally invasive instruments which can reduce the X-ray exposure and the used contrast agent. Shape sensing of flexible structures is challenging and includes many calculations steps which are prone to different errors. To reduce this errors, we present an optimized shape sensing model.

Methods

We analyzed for every step of the shape sensing process, which errors can occur, how the error affects the shape and how it can be compensated or minimized. Experiments were done with one multicore fiber system with 38 cm sensing length, and the effects of different methods and parameters were analyzed. Furthermore, we compared 3D shape reconstructions with the segmented shape of the corresponding CT scans of the fiber to evaluate the accuracy of our optimized shape sensing model. Finally, we tested our model in a realistic endovascular scenario by using a 3D printed vessel system created from patient data.

Results

Depending on the complexity of the shape, we reached an average error of 0.35–1.15 mm and maximal error of 0.75–7.53 mm over the whole 38 cm sensing length. In the endovascular scenario, we obtained an average and maximal error of 1.13 mm and 2.11 mm, respectively.

Conclusion

The accuracies of the 3D shape sensing model are promising, and we plan to combine the shape sensing based on fiber Bragg gratings with the position and orientation of an electromagnetic tracking to obtain the located catheter shape.

Electronic supplementary material

The online version of this article (10.1007/s11548-019-02059-0) contains supplementary material, which is available to authorized users.

Computer-assisted study of the axial orientation and distances between renovisceral arteries ostia

PURPOSE

Endovascular navigation in aortic, renal and visceral procedures are based on precise knowledge of arterial anatomy. Our aim was to define the anatomical localization of the ostia of renovisceral arteries and their distribution to establish anatomical landmarks for endovascular catheterization.

METHODS

Computer-assisted measurements performed on 55 CT scans and patients features (age, sex, aortic diameter) were analyzed. p values <0.05 were considered statistically significant.

RESULTS

The mean axial angulation of CeT and the SMA origin was 21.8° ± 10.1° and 9.9° ± 10.5°, respectively. The ostia were located on the left anterior edge of the aorta in 96 % of cases for the CeT and 73 % for the SMA. CeT and SMA angles followed Gaussian distribution. Left renal artery (LRA) rose at 96° ± 15° and in 67 % of cases on the left posterior edge. The right renal artery (RRA) rose at -62° ± 16.5° and in 98 % of cases on the right anterior edge of the aorta. RRA angle measurements and cranio-caudal RRA-LRA distance measurements did not follow Gaussian distribution. The mean distances between the CeT and the SMA, LRA, and RRA were 16.7 ± 5.0, 30.7 ± 7.9 and 30.5 ± 7.7 mm, respectively. CeT-SMA distance showed correlation with age and aortic diameter (p = 0.03). CeT-LRA distance showed correlation with age (p = 0.04). The mean distance between the renal ostia was 3.75 ± 0.21 mm. The RRA ostium was higher than the LRA ostium in 52 % of cases. RRA and LRA origins were located at the same level in 7 % of cases.

CONCLUSION

Our results illustrate aortic elongation with ageing and high anatomical variability of renal arteries. Our findings are complementary to anatomical features previously published and might contribute to enhance endovascular procedures safety and efficacy for vascular surgeons and interventional radiologists.