Abstract
Background
Selecting intervention strategies for renal artery aneurysms (RAAs) is challenging especially for those located at the vessel bifurcation. The relationship between the aneurysm and renal branches could not always be accurately viewed from traditional computed tomography angiography (CTA) images.
Case presentation
This study proposed a new method to investigate the anatomy and affected vessel branches of RAAs using automated software. Two patients with RAAs located at the renal artery bifurcation underwent Cone beam CTA (CBCTA) analysis. We sequentially coupled the “two-click AVA” function of Vessel IQ Xpress (GE Healthcare) with the “vascular tree extraction” function from FlightPlan for Embolization (GE Healthcare) to evaluate the relationship among the main renal artery, vessel branches, and aneurysms. The results showed that one patient had 1 out of 3 branches affected by the aneurysm, whereas the other’s branches were all affected. Endovascular repair and open surgery were performed respectively based on the image analysis. Both patients recovered well at follow-up examination.
Conclusions
Based on CBCTA analysis, the combination use of the “two-click AVA” function of VesselIQ Xpress and FlightPlan for Embolization software could assist in aneurysm assessment and intervention choices for RAAs.
Background
Renal artery aneurysm (RAA) occurs in approximately 0.1% of the general population and its rupture could be life-threatening.1,2 Endovascular repair is increasingly performed for RAA due to its low-invasive nature. 3 However, for aneurysms located at the vessel bifurcation, coil embolization may increase the risk of nontarget vessel branch occlusion. 3 Intervention strategies were selected based on anatomy, as well as local expertise, patient input, comorbidities, and patient preference. Under some circumstances, the relationship between the aneurysm and renal branches could not be accurately viewed from routine computed tomography angiography (CTA). Methods for evaluating anatomic characteristics and guiding operative choices are still in great need.
Cone beam CTA (CBCTA) is a technique that incorporates the images of 3-dimensional (3D) rotational angiography with CT postprocessing methods to visualize the vessels and peripheral soft tissues with increased contrast resolution. 4 It has been reported previously for visualizing aneurysms located at various locations.5,6 The use of automated software could increase the efficiency of CBCTA analysis. In this study, we sequentially coupled the “two-click AVA” function from VesselIQ Xpress with the “vascular tree extraction” function from the software: FlightPlan for Embolization, to investigate the anatomy and affected vessel branches of RAA for 2 patients.
Case Presentation
Technique
For each patient receiving DSA, a mobile single flat panel detector angiographic system (GE Healthcare Discovery IGS 7OR, Buc, France) was used intraoperatively to acquire CBCTA images during the injection of contrast medium while asking the patients to hold their breath. A 3D CBCTA was performed in the renal artery with an injection of 30-36 mL of contrast medium (iodixanol Injection, 320 mg(l)/ml) at a rate of 3 mL/sec. CBCTA was acquired 1-2 seconds after the start of the contrast medium injection. One hundred and fifty frames were obtained during a 5-second rotation, over an angular range of 200° (40°/sec rotation speed). 3D images were reconstructed in both subtracted and native fill modes and visualized as multiplanar and volume-rendered reconstructions (Figure 1). The CBCT images were sequentially analyzed with 2 dedicated software. Firstly, the “two-click AVA” function of Vessel IQ Xpress (GE Healthcare) was utilized. By clicking on the origin and distal end of each branch from the images, all the branches were reconstructed through the centerline (in green) in a straightened mode. This method clearly illustrated the relationship between each branch and the aneurysm (Figure 2 B-D, F-I). Branches with a fusiform aneurysm were considered at high risk of occlusion after embolization. Secondly, a recent-developed post-processing software (FlightPlan for Embolization, GE Healthcare) was utilized. After depositing an interested point at the origin for each branch, the blood flow of all the branches were demonstrated automatically with different color (Figure 3). By evaluating the blood supply of high-risk branches and estimating the potential percentage of parenchymal renal losses, choices of endovascular repair (coil embolization) or open surgery were made. The study was approved by the Institutional Review Board of Peking Union Medical College Hospital. Written informed consent was obtained from the patient or their legally authorized guardian. Pre-operative CTA or DSA and CBCT reconstructing images for the 2 patients. (A) Pre-operative CTA for patient Num. 1. (B) CBCT reconstructing images for patient Num. 1. (C) Pre-operative DSA for patient Num. 2. (D) CBCT reconstructing images for patient Num. 2. “Two-click AVA” (VesselIQ Xpress) analysis of renal branches on the CBCT images. (A) Renal branches for patient Num. 1. (B-D) “Two-click AVA” analysis for patient Num. 1. Each branch demonstrated the relationship between aneurysm and the branch. (E) Renal branches for patient Num. 2. (F-I) “Two-click AVA” analysis for patient Num. 2. Blood supply for each renal branches illustrated by FlightPlan for Embolization and post-operative DSA or CTA. (A) FlightPlan for Embolization analysis for patient Num. 1. (B) Post-operatively DSA for patient Num. (C) FlightPlan for Embolization analysis for patient Num. 2. (D) Post-operatively CTA for patient Num.
Case 1
A 65-year-old female came to the hospital with refractory high blood pressure (max: 180-100mmHg) for 40 years. CTA revealed a right RAA located at the first vessel bifurcation (Figure 1). Renal 99mTc‐DTPA imaging indicated that the glomerular filtration rate (GFR) was 41.72 mL/min·1.73 m2 for the right and 30.78 mL/min·1.73 m2 for the left kidney. Considering her unsatisfactory renal function, renal blood flow preservation became crucial for intervention choices. The patient underwent DSA and received CBCT analysis for further evaluation (Figure 1). The “two-click AVA” function illustrated that for vessel 1 and vessel 2 (Figure 2) reconstruction, the aneurysm was in side-wall saccular form, whereas a fusiform form was found in vessel 3 (Figure 2). FlightPlan for Embolization demonstrated that vessel 3 supplied a limited part of renal blood flow and could be sacrificed if embolization failed (Figure 3(A)). After evaluating high-risk branches and estimating the potential percentage of parenchymal renal losses, coil embolization was chosen for the patient. Angiography at the end of the operation showed patency of all 3 vessel branches (Figure 3). Blood pressure returned to normal after the operation. Follow-up Doppler ultrasound at 6 months revealed patency of all 3 branches and blood creatinine level was 58 μmol/L.
Case 2
A 16-year-old male had high blood pressure (max: 180-105mmHg). CTA suggested right RAA and proximal renal artery stenosis. GFR was 40.9 mL/min·1.73 m2 for the right and 50.6 mL/min·1.73 m2 for the left kidney. The patient underwent 3D DSA (Figure 1) and received CBCT analysis (Figure 1). As shown in Figure 2, the “two-click AVA” function illustrated that the aneurysm was fusiform on all 4 vessel branches. FlightPlan for Embolization illustrated that the blood flow of the whole kidney was affected (Figure 3). The patient was recommended to receive open surgery, and ex vivo aneurysm reconstruction and auto-transplantation was performed. Detail operative procedures were reported previously. 7 The patients underwent the operation successfully. Systole blood pressure fluctuated from 120 to 140 mmHg without anti-hypertensive medicine. Follow-up CTA at 6 months showed patency of the right renal artery. GFR level was 56.79 mL/min·1.73 m2 for the right kidney and 72.98 mL/min·1.73 m2 for the left kidney.
Discussion and Conclusions
The most prevalent classification system for guiding RAA intervention choice was proposed by Rundback et al 8 , in 2000. However, this classification did not emphasize the location of the aneurysms, especially those on the first bifurcation of the renal arteries that were most encountered. 9 These aneurysms influence the blood supply of more than one segmental branch, and treatment selection remains controversial.10,11 At our center, an endovascular-first approach using simple or stent-assist coil embolization was adopted, and the sequential use of “two-click AVA” technique and FlightPlan for Embolization could identify RAAs unsuitable for endovascular repair.
Previous reports of utilizing CBCTA for aneurysm imaging mainly focused on intracranial lesions. For visceral artery aneurysm, Mohammad et al conducted 3D rotational angiography in 8 aneurysms to provide anatomical and technical assessments for endovascular treatment. 12 Marton and colleagues used intraoperative CBCT for better delineation of aneurysm morphology in a series of 10 visceral aneurysms, including 4 RAAs.5,13 Our cases indicated that combined with automated software, the advantage of CBCTA could not only be used for anatomic analysis but also in direct visualization of regional blood supply for solid organs.
Based on CBCTA 3D angiography images, the “two-click AVA” technique could calculate the path of each renal branch separately and provide 2D reconstruction images for accurate aneurysm measurements such as size or neck diameter. Thus, the relationships among the main renal artery, vessel branches, and aneurysms could be easily visualized. The FlightPlan software was first applied to detect the feeding vessels for trans-arterial chemoembolization (TACE) of liver tumors. 14 Similarly, the recently-developed FlightPlan for Embolization separates the vascular tree from other structures and directly highlights the area for blood supply for different branches. The software was designed to assist in embolization planning for arteriovenous fistulas. To the best of our knowledge, using FlightPlan for Embolization for aneurysm repair has not been reported. Furthermore, the radiation dose of CBCTA for the 2 patients was less than 100 mGy, which is notably lower than the dose typically administered for traditional CTA at our center (generally exceeding 300 mGy), and the contrast media used (30-36 mL) was approximately 30% of that used for traditional aortic CTA. The CBCTA offers the advantage of reduced radiation exposure and contrast utilization compared to CTA. 15 Regarding procedural efficiency, endovascular repair could be applied directly applied to suitable patients (eg, in Case 1) after the software assessment, which could reduce the risk of renal damage from repetitive CTA examinations.
This study has its limitations. Compared to DSA, CBCTA scanning is time-consuming and may result in a higher dose area product and stochastic risks. 16 More cases are required in the future to validate our preliminary method.
In conclusion, based on intraoperative CBCTA analysis, the combination use of “two-click AVA” function of VesselIQ Xpress and FlightPlan for Embolization software could assist in aneurysm assessment and intervention choices for RAAs.
Footnotes
Author Contributions
SL, FL, and YZ designed the study. SL and FL analyzed and interpreted the patient data. SL wrote the manuscript. RZ, XL, ZL, and YZ performed the operation. All authors read and approved the final manuscript.
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the grants from the Natural Science Foundation of China (grant number 82070492, 82100519, and 51890894), the CAMS Innovation Fund for Medical Sciences (grant number CIFMS 2021-I2M-C&T-A-006, CIFMS2021-I2M-1-016), and the National High Level Hospital Clinical Research Funding (Grant No.2022-PUMCH-B-100 and 2022-PUMCH-C-062).
Data Availability Statement
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.