Feasibility of Three-Dimensional MR Angiography Image Fusion Guidance for Endovascular Abdominal Aortic Aneurysm Repair

Advanced Imaging Techniques for Complex Endovascular Aortic Repair: Preoperative, Intraoperative and Postoperative Advancements

BACKGROUND

Endovascular aortic repair (EVAR) requires extensive preoperative, intraoperative, and postoperative imaging for planning, surveillance, and detection of endo-leaks. There have been manyadvancements in imaging modalities to achieve this purpose. This review discussed different imaging modalities used at different stages of treatment of complex EVAR.

METHODS

We conducted a literature review of all the imaging modalities utilized in EVAR by searching various databases.

RESULTS

Preoperative techniques include analysis of images obtained via modified central line using analysis software and intravascular ultrasound. Fusion imaging (FI), carbon dioxide (CO2) angiography, intravascular ultrasound, and Fiber Optic RealShape (FORS) technology have been crucial in obtaining real-time imaging for the detection of endo-leaks during operative procedures. Conventional imaging modalities like computed tomography (CT) angiography (CTA) and magnetic resonance (MR) angiography are still employed for postoperative surveillance along with computational fluid dynamics and contrast-enhanced ultrasound (CEUS). The advancements in artificial intelligence (AI) have been the breakthrough in developing robust imaging applications.

CONCLUSIONS

This review explains the advantages, disadvantages, and side-effect profile of the abovementioned imaging modalities.

Improved 3D Catheter Shape Estimation Using Ultrasound Imaging for Endovascular Navigation: A Further Study

OBJECTIVE

Two-dimensional fluoroscopy is the standard guidance imaging method for closed endovascular intervention. However, two-dimensional fluoroscopy lacks depth perception for the intervention catheter and causes radiation exposure for both surgeons and patients. In this paper, we extend our previous study and develop the improved three-dimensional (3D) catheter shape estimation using ultrasound imaging. In addition, we perform further quantitative evaluations of endovascular navigation.

METHOD

First, the catheter tracking accuracy in ultrasound images is improved by adjusting the state vector and adding direction information. Then, the 3D catheter points from the catheter tracking are further optimized based on the 3D catheter shape optimization with a high-quality sample set. Finally, the estimated 3D catheter shapes from ultrasound images are overlaid with preoperative 3D tissue structures for the intuitive endovascular navigation.

RESULTS

the tracking accuracy of the catheter increased by 24.39%, and the accuracy of the catheter shape optimization step also increased by approximately 17.34% compared with our previous study. Furthermore, the overall error of catheter shape estimation was further validated in the catheter intervention experiment of in vitro cardiovascular tissue and in a vivo swine, and the errors were 2.13 mm and 3.37 mm, respectively.

CONCLUSION

Experimental results demonstrate that the improved catheter shape estimation using ultrasound imaging is accurate and appropriate for endovascular navigation.

SIGNIFICANCE

Improved navigation reduces the radiation risk because it decreases use of X-ray imaging. In addition, this navigation method can also provide accurate 3D catheter shape information for endovascular surgery.

Immediate and 1-year success rate of type 2 endoleak treatment using three-dimensional image fusion guidance

PURPOSE

To retrospectively assess immediate and 1-year success rate of type 2 endoleak (T2E) treatment with ethylene-vinyl-alcohol-polymer using three-dimensional (3D) image fusion guidance with cone beam computed tomography via trans-arterial embolization (TAE) or direct percutaneous sac injection (DPSI).

MATERIALS AND METHODS

A total of 37 patients with T2E who were treated either using TAE (34/37; 92%) or DPSI (9/37; 8%) were included. There were 34 men and 3 women with a mean age of 86±9 (SD) years (range: 67-104years). Mean aneurysm diameter was 67±14 (SD) mm (range: 42-101mm) at pre-procedure evaluation. Immediate success was complete embolization of the sac and feeding artery. 1-year success was reduction or stability of the aneurysmal sac diameter based on pre-procedure and 12-month follow-up examinations. Safety (treatment-related complications), patient demographics, duration of procedure and contrast volume were reported.

RESULTS

Immediate and 1-year successful outcomes were reported in 94% (n=32) and 88% (n=28) of patients after TAE and 100% (n=9) and 89% (n=8) after DPSI. T2E treatments were immediately successful for 95% of the procedures (41/43) and for 88% (36/41) at 1year. Overall, T2E treatment was effective in 33 patients (89%). No major complications occurred. Mean procedure time and contrast volume were significantly different between the 2 techniques with respectively 87±16 (SD) min (range: 65-120min) and 75±26 (SD) mL (range: 40-130mL) for TAE and 32±10 (SD) min (range: 20-50min) (P<0.01) and 6±6 (SD) mL (range: 2-22mL) (P<0.01) for DPSI. Mean aneurysm diameter at 1-year was 68±17 (SD) mm (range: 43-101mm). No significant differences in the pre-procedure sac diameter were found at long-term follow-up between patients without T2E and those with persistent T2E (P=0.1) in the successful embolization group (n=33).

CONCLUSION

TAE or DPSI treatments of T2E with ethylene-vinyl-alcohol-polymer using 3D-image fusion guidance were immediately successful for 95% of the procedures and remained effective for 88%. Longer follow-up is necessary to assess sac stability in the case of persistent endoleak.

CBCT-Based Image Guidance for Percutaneous Access: Electromagnetic Navigation Versus 3D Image Fusion with Fluoroscopy Versus Combination of Both Technologies-A Phantom Study

PURPOSE

We set out to compare three types of three-dimensional CBCT-based imaging guidance modalities in a phantom study: image fusion with fluoroscopy (IF), electromagnetic navigation (EMN) and the association of both technologies (CEMNIF).

MATERIALS AND METHODS

Four targets with a median diameter of 11 mm [first quartile (Q1): 10; third quartile (Q3): 12] with acute angle access (z-axis < 45°) and four targets of 10 mm [8-15] with large angle access (z-axis > 45°) were defined on an abdominal phantom (CIRS, Meditest, Tabuteau, France). Acute angle access targets were punctured using IF, EMN or CEMNIF and large angle access targets with EMN by four operators with various experiences. Efficacy (target reached), accuracy (distance between needle tip and target center), procedure time, radiation exposure and reproducibility were explored and compared.

RESULTS

All targets were reached (100% efficacy) by all operators. For targets with acute angle access, procedure times (EMN: 265 s [236-360], IF: 292 s [260-345], CEMNIF: 320 s [240-333]) and accuracy (EMN: 3 mm [2-5], IF: 2 mm [1-3], CEMNIF: 3 mm [2-4]) were similar. Radiation exposure (EMN: 0; IF: 708 mGy.cm² [599-1128]; CEMNIF: 51 mGy.cm² [15-150]; p < 0.001) was significantly higher with IF than with CEMNIF and EMN. For targets with large angle access, procedure times (EMN: 345 s [259-457], CEMNIF: 425 s [340-473]; p = 0.01) and radiation exposure (EMN: 0, CEMIF: 159 mGy.cm² [39-316]; p < 0.001) were significantly lower with EMN but with lower accuracy (EMN: 4 mm [4-6] and CEMNIF: 4 mm [3, 4]; p = 0.01). The operator's experience did not impact the tested parameters regardless of the technique.

CONCLUSION

In this phantom study, EMN was not limited to acute angle targets. Efficacy and accuracy of puncture for acute angle access targets with EMN, IF or CEMNIF were similar. CEMNIF is more accurate for large angle access targets at the cost of a slightly higher procedure time and radiation exposure.

Quest for cardiovascular interventions: precise modeling and 3D printing of heart valves

Digitalization of health care practices is substantially manifesting itself as an effective tool to diagnose and rectify complex cardiovascular abnormalities. For cardiovascular abnormalities, precise non-invasive imaging interventions are being used to develop patient specific diagnosis and surgical planning. Concurrently, pre surgical 3D simulation and computational modeling are aiding in the effective surgery and understanding of valve biomechanics, respectively. Consequently, 3D printing of patient specific valves that can mimic the original one will become an effective outbreak for valvular problems. Printing of these patient-specific tissues or organ components is becoming a viable option owing to the advances in biomaterials and additive manufacturing techniques. These additive manufacturing techniques are receiving a full-fledged support from burgeoning field of computational fluid dynamics, digital image processing, artificial intelligence, and continuum mechanics during their optimization and implementation. Further, studies at cellular and molecular biomechanics have enriched our understanding of biomechanical factors resulting in valvular heart diseases. Hence, the knowledge generated can guide us during the design and synthesis of biomaterials to develop superior extra cellular matrix, mimicking materials that can be used as a bioink for 3D printing of organs and tissues. With this notion, we have reviewed current opportunities and challenges in the diagnosis and treatment of heart valve abnormalities through patient-specific valve design via tissue engineering and 3D bioprinting. These valves can replace diseased valves by preserving homogeneity and individuality of the patients.

Intraoperative Imaging and Image Fusion for Venous Interventions

Advanced imaging for intraoperative evaluation of venous pathologies has played an increasingly significant role in this era of evolving minimally invasive surgical and interventional therapies. The evolution of dedicated venous stents and other novel interventional devices has mandated the need for advanced imaging tools to optimize safe and accurate device deployment. Most venous interventions are typically performed using a combination of standard 2-dimensional (2D) fluoroscopy, digital-subtraction angiography, and intravascular ultrasound imaging techniques. Latest generation computer tomography (CT) and magnetic resonance imaging (MRI) scanners have been shown to provide high-resolution 3D and 4D information about venous vasculature. In addition to morphological imaging, novel MRI techniques such as 3D time-resolved MR venography and 4D flow sequences can provide quantitative information and help visualize intricate flow patterns to better understand complex venous pathologies. Moreover, the high-fidelity information from multiple imaging techniques can be integrated using image fusion to overcome the limitations of current intraoperative imaging techniques. For example, the limitations of standard 2D fluoroscopy and luminal angiography can be compensated for by perivascular and soft-tissue information from MRI during complex venous interventions using image fusion techniques. Intraoperative dynamic evaluation of devices such as venous stents and real-time understanding of changes in flow patterns during venous interventions may be routinely available in future interventional suites with integrated multimodality CT or MR imaging capabilities. The purpose of this review is to discuss the outlook for intraoperative imaging and multimodality image fusion techniques and highlight their value during complex venous interventions.

The 2D-3D Registration Method in Image Fusion Is Accurate and Helps to Reduce the Used Contrast Medium, Radiation, and Procedural Time in Standard EVAR Procedures

OBJECTIVE

This study aimed to evaluate the accuracy and the effectiveness of 2D-3D registration method of image fusion (IF) technology in endovascular aneurysm repair (EVAR).

METHODS

We performed a review of our institutional endovascular aortic database of patients who had undergone EVAR between 2011 and 2015 before and after the installation of a 3D IF computed tomography system in our hybrid operating room.

RESULTS

The accuracy was assessed in 14 endovascular procedures and showed a median registration error of 1.8 mm at the origin of the right renal artery and 1.0 mm at the origin of the left renal artery and a complete visual accuracy in 42% of the cases. EVAR was performed using the intraoperative IF technique with a 2D-3D registration method in 105 patients (group IF), whereas 47 patients done without served as controls. The IF group had a significantly reduced amount of used contrast compared with controls with a median of 58 mL and P < 0.0001. The intraoperative exposition to radiation was similar between the 2 groups with a median dose area product of 2,343.7 cGy cm² in the IF group and 3,219 cGy cm² among the controls (P = 0.457). The radiation dose in the sub group IF (including patients operated by the 2 most experienced surgeons) was lower than that in sub controls (median, 1,087 cG cm² vs. 2,705.3 cG cm², P = 0.012). The procedure time and the time of intraoperative radiation did not differ between the study groups (P = 0.117 and 0.106, respectively), as did not fluoroscopy time in the sub group IF (median, 6.3 min, vs. 9.5 min, P = 0.067), but for the 2 most experienced surgeons, the procedural time was shortened when using IF (P = 0.002).

CONCLUSIONS

The 2D-3D registration method of IF guidance is accurate to delineate the vessels of interest and could help the execution of the EVAR procedures with a significantly reduced amount of contrast medium and also with reduced radiation and shorter procedural duration when surgeons are more familiar with EVAR and IF.

Computed tomography angiography-fluoroscopy image fusion allows visceral vessel cannulation without angiography during fenestrated endovascular aneurysm repair

BACKGROUND

Fenestrated endovascular aneurysm repair (FEVAR) is an evolving technique to treat juxtarenal abdominal aortic aneurysms (AAAs). Catheterization of visceral and renal vessels after the deployment of the fenestrated main body device is often challenging, usually requiring additional fluoroscopy and multiple digital subtraction angiograms. The aim of this study was to assess the clinical utility and accuracy of a computed tomography angiography (CTA)-fluoroscopy image fusion technique in guiding visceral vessel cannulation during FEVAR.

METHODS

Between August 2014 and September 2016, all consecutive patients who underwent FEVAR at our institution using image fusion guidance were included. Preoperative CTA images were fused with intraoperative fluoroscopy after coregistering with non-contrast-enhanced cone beam computed tomography (syngo 3D3D image fusion; Siemens Healthcare, Forchheim, Germany). The ostia of the visceral vessels were electronically marked on CTA images (syngo iGuide Toolbox) and overlaid on live fluoroscopy to guide vessel cannulation after fenestrated device deployment. Clinical utility of image fusion was evaluated by assessing the number of dedicated angiograms required for each visceral or renal vessel cannulation and the use of optimized C-arm angulation. Accuracy of image fusion was evaluated from video recordings by three raters using a binary qualitative assessment scale.

RESULTS

A total of 26 patients (17 men; mean age, 73.8 years) underwent FEVAR during the study period for juxtarenal AAA (17), pararenal AAA (6), and thoracoabdominal aortic aneurysm (3). Video recordings of fluoroscopy from 19 cases were available for review and assessment. A total of 46 vessels were cannulated; 38 of 46 (83%) of these vessels were cannulated without angiography but based only on image fusion guidance: 9 of 11 superior mesenteric artery cannulations and 29 of 35 renal artery cannulations. Binary qualitative assessment showed that 90% (36/40) of the virtual ostia overlaid on live fluoroscopy were accurate. Optimized C-arm angulations were achieved in 35% of vessel cannulations (0/9 for superior mesenteric artery cannulation, 12/25 for renal arteries).

CONCLUSIONS

Preoperative CTA-fluoroscopy image fusion guidance during FEVAR is a valuable and accurate tool that allows visceral and renal vessel cannulation without the need of dedicated angiograms, thus avoiding additional injection of contrast material and radiation exposure. Further refinements, such as accounting for device-induced aortic deformation and automating the image fusion workflow, will bolster this technology toward optimal routine clinical use.

Feasibility of three-dimensional magnetic resonance angiography-fluoroscopy image fusion technique in guiding complex endovascular aortic procedures in patients with renal insufficiency

OBJECTIVE

Three-dimensional image fusion of preoperative computed tomography (CT) angiography with fluoroscopy using intraoperative noncontrast cone-beam CT (CBCT) has been shown to improve endovascular procedures by reducing procedure length, radiation dose, and contrast media volume. However, patients with a contraindication to CT angiography (renal insufficiency, iodinated contrast allergy) may not benefit from this image fusion technique. The primary objective of this study was to evaluate the feasibility of magnetic resonance angiography (MRA) and fluoroscopy image fusion using noncontrast CBCT as a guidance tool during complex endovascular aortic procedures, especially in patients with renal insufficiency.

METHODS

All endovascular aortic procedures done under MRA image fusion guidance at a single-center were retrospectively reviewed. The patients had moderate to severe renal insufficiency and underwent diagnostic contrast-enhanced magnetic resonance imaging after gadolinium or ferumoxytol injection. Relevant vascular landmarks electronically marked in MRA images were overlaid on real-time two-dimensional fluoroscopy for image guidance, after image fusion with noncontrast intraoperative CBCT. Technical success, time for image registration, procedure time, fluoroscopy time, number of digital subtraction angiography (DSA) acquisitions before stent deployment or vessel catheterization, and renal function before and after the procedure were recorded. The image fusion accuracy was qualitatively evaluated on a binary scale by three physicians after review of image data showing virtual landmarks from MRA on fluoroscopy.

RESULTS

Between November 2012 and March 2016, 10 patients underwent endovascular procedures for aortoiliac aneurysmal disease or aortic dissection using MRA image fusion guidance. All procedures were technically successful. A paired t-test analysis showed no difference between preimaging and postoperative renal function (P = .6). The mean time required for MRA-CBCT image fusion was 4:09 ± 01:31 min:sec. Total fluoroscopy time was 20.1 ± 6.9 minutes. Five of 10 patients (50%) underwent stent graft deployment without any predeployment DSA acquisition. Three of six vessels (50%) were cannulated under image fusion guidance without any precannulation DSA runs, and the remaining vessels were cannulated after one planning DSA acquisition. Qualitative evaluation showed 14 of 22 virtual landmarks (63.6%) from MRA overlaid on fluoroscopy were completely accurate, without the need for adjustment. Five of eight incorrect virtual landmarks (iliac and visceral arteries) resulted from vessel deformation caused by endovascular devices.

CONCLUSIONS

Ferumoxytol or gadolinium-enhanced MRA imaging and image fusion with fluoroscopy using noncontrast CBCT is feasible and allows patients with renal insufficiency to benefit from optimal guidance during complex endovascular aortic procedures, while preserving their residual renal function.

Magnetic resonance venography and three-dimensional image fusion guidance provide a novel paradigm for endovascular recanalization of chronic central venous occlusion

OBJECTIVE

Endovascular recanalization is considered first-line therapy for chronic central venous occlusion (CVO). Unlike arteries, in which landmarks such as wall calcifications provide indirect guidance for endovascular navigation, sclerotic veins without known vascular branching patterns impose significant challenges. Therefore, safe wire access through such chronic lesions mostly relies on intuition and experience. Studies have shown that magnetic resonance venography (MRV) can be performed safely in these patients, and the boundaries of occluded veins may be visualized on specific MRV sequences. Intraoperative image fusion techniques have become more common to guide complex arterial endovascular procedures. The aim of this study was to assess the feasibility and utility of MRV and intraoperative cone-beam computed tomography (CBCT) image fusion technique during endovascular CVO recanalization.

METHODS

During the study period, patients with symptomatic CVO and failed standard endovascular recanalization underwent further recanalization attempts with use of intraoperative MRV image fusion guidance. After preoperative MRV and intraoperative CBCT image coregistration, a virtual centerline path of the occluded segment was electronically marked in MRV and overlaid on real-time two-dimensional fluoroscopy images. Technical success, fluoroscopy times, radiation doses, number of venograms before recanalization, and accuracy of the virtual centerline overlay were evaluated.

RESULTS

Four patients underwent endovascular CVO recanalization with use of intraoperative MRV image fusion guidance. Mean (± standard deviation) time for image fusion was 6:36 ± 00:51 mm:ss. The lesion was successfully crossed in all patients without complications. Mean fluoroscopy time for lesion crossing was 12.5 ± 3.4 minutes. Mean total fluoroscopy time was 28.8 ± 6.5 minutes. Mean total radiation dose was 15,185 ± 7747 μGy/m², and mean radiation dose from CBCT acquisition was 2788 ± 458 μGy/m² (18% of mean total radiation dose). Mean number of venograms before recanalization was 1.6 ± 0.9, whereas two lesions were crossed without any prior venography. On qualitative analysis, virtual centerlines from MRV were aligned with actual guidewire trajectory on fluoroscopy in all four cases.

CONCLUSIONS

MRV image fusion is feasible and may improve success, safety, and the surgeon's confidence during CVO recanalization. Similar to arterial interventions, three-dimensional MRV imaging and image fusion techniques could foster innovative solutions for such complex venous interventions and have the potential to affect a great number of patients.