Image Fusion During Endovascular Aneurysm Repair, how to Fuse? An Overview of Registration and Implementation Strategies Plus Tips and Tricks

Introduction: The use of image fusion in the hybrid operating room is increasingly used. Image fusion enables physicians to deploy endovascular devices with a 3D roadmap of the vascular anatomy based on preoperative CTA or MRA. Previous studies described a decrease in nephrotoxic contrast volume, fluoroscopy time, radiation dose and procedure time in complex endovascular aortic repair (EVAR).1-4 However, there is no general consensus or guideline on the optimal technique and timing of image fusion. There are several options; 2D-3D bony landmark registration, 3D-3D aortic calcification registration, contrast enhanced cone beam CT (ceCBCT) registration. Moreover, registration can be done before or after the insertion of sheaths and (stiff) guidewires. The goal of this study was to determine image fusion accuracy. Methods: Several fusion strategies were analyzed. Strategy 1: 2D-3D registration before insertion of sheaths and guidewires. Strategy 2: 3D-3D registration before insertion of sheaths and guidewires. Strategy 3: 2D-3D registration after insertion of sheaths and guidewires. Strategy 4: 3D-3D registration after insertion of sheaths and guidewires. An overview is displayed in Figure 1A-1D. Strategy 1 was evaluated with clinical patient data. Strategies 2, 3 and 4 were evaluated with an infrarenal AAA phantom model with pelvis, vertebral column and renal calcifications as displayed in Figure 1E. For strategy 1, in total 11 EVAR patients (median age 75.5, all male) were included of which 4 were complex EVAR (fenestrated) and 7 standard EVAR. In all patients, digital subtraction angiography (DSA) was used as roadmap to deploy the devices. After DSA, manual correction was performed to correct fusion overlay to match the lowest renal artery between image fusion and DSA. Registration accuracy was determined by ostium displacement (in millimeters) of the lowest renal artery (proximal accuracy) and ostium displacement of the right and left internal iliac arteries (distal accuracy), when compared to the intra-operative DSA images (see Figure 1A & 1F). Proximal accuracy was measured before and after DSA correction. Displacement accuracy was defined as follows; accurate (0-1 mm), medium (1-4 mm) and poor (>4 mm). Tips are to register with vertebral L1/L2 centered and to correct navigation markers in axial CT-view to prevent misplacement due to ostia calcification, as displayed in Figure 1 G-H. Results: For the 11 patients the mean proximal accuracy was 0.7 (0.4-0.9) mm and distal accuracy was 5.8 (1.3-12.3) mm compared to the DSA. Before DSA correction proximal accuracy was 7.4 (1.4-11) mm. With phantom data, proximal accuracy was 0.8 (0.5-1.1) mm and distal accuracy was 2.3 (0.6-1.2) mm for strategy 2. Strategy 3 resulted in a proximal accuracy of 2.6 (1.9-3.4) mm and distal accuracy of 14.0 (13.0-15.0) mm. Strategy 4 resulted in a proximal accuracy of 1.6 (1.5-1.8) mm and distal accuracy of 4.0 (2.0- 5.9) mm. See Table 1 for an overview. Conclusion: Based on this data, image fusion proximal accuracy is equal with 2D-3D and 3D-3D registration before sheath and guidewire insertion. Manual DSA correction for 2D-3D registration is required to improve accuracy. After the insertion of guidewires, the accuracy of 3D-3D registration is superior to 2D-3D registration

Deep Learning–Based Intraoperative Stent Graft Segmentation on Completion Digital Subtraction Angiography During Endovascular Aneurysm Repair

Purpose: Modern endovascular hybrid operating rooms generate large amounts of medical images during a procedure, which are currently mostly assessed by eye. In this paper, we present fully automatic segmentation of the stent graft on the completion digital subtraction angiography during endovascular aneurysm repair, utilizing a deep learning network. Technique: Completion digital subtraction angiographies (cDSAs) of 47 patients treated for an infrarenal aortic aneurysm using EVAR were collected retrospectively. A two-dimensional convolutional neural network (CNN) with a U-Net architecture was trained for segmentation of the stent graft from the completion angiographies. The cross-validation resulted in an average Dice similarity score of 0.957 ± 0.041 and median of 0.968 (IQR: 0.950 – 0.976). The mean and median of the average surface distance are 1.266 ± 1.506 mm and 0.870 mm (IQR: 0.490 – 1.430), respectively. Conclusion: We developed a fully automatic stent graft segmentation method based on the completion digital subtraction angiography during EVAR, utilizing a deep learning network. This can provide the platform for the development of intraoperative analytical applications in the endovascular hybrid operating room such as stent graft deployment accuracy, endoleak visualization, and image fusion correction

Repeat Rupture of a Giant Abdominal Aortic Aneurysm after EVAR

Introduction: Ruptured abdominal aortic aneurysms (AAAs) are known to be associated with high fatal outcomes. Giant AAAs are often defined as having a maximum diameter over 13 cm. Large AAAs over 8 cm have demonstrated a yearly rupture rate of 30–50%, which explains the rarity of giant AAAs. Endovascular repair of ruptured AAAs (rAAAs) is increasingly advocated because of the shorter hospital stay and fewer post-operative complications. Nonetheless, outcomes regarding mortality and cost-effectiveness show a large variability and long-term outcomes are lacking. Few data have been published on treatment of giant AAAs and rAAAs; however, open surgery is generally the preferred option. Report: An 83 year old presented to the Emergency Department with a history of ruptured abdominal aortic aneurysm treated with an aorto-uni-iliac endograft and a femorofemoral crossover bypass. During follow up, this was complicated by a symptomatic type III endoleak, which was treated by endovascular repair. During the current admission, he presented with a re-rupture of his former aneurysm, which now was 18 cm diameter because of a type IA endoleak. Open surgical repair was performed and the post-operative course was without complications. Discussion: The current case underlines the value of vascular surgeons being able to perform both open and endovascular surgery in rAAA. Keywords: Giant abdominal aorta aneurysm, Re-rupture, Endoleak, EVAR, Open repai

Intravenous Targeted Microbubbles Carrying Urokinase versus Urokinase Alone in Acute Peripheral Arterial Thrombosis in a Porcine Model

Background Standard therapy in acute peripheral arterial occlusion consists of intra-arterial catheter-guided thrombolysis. As microbubbles may be used as a carrier for fibrinolytic agents and targeted to adhere to the thrombus, we can theoretically deliver the thrombolytic medication locally following simple intravenous injection. In this intervention-controlled feasibility study, we compared intravenously administered targeted microbubbles incorporating urokinase and locally applied ultrasound, with intravenous urokinase and ultrasound alone. Methods In 9 pigs, a thrombus was created in the left external iliac artery, after which animals were assigned to either receive targeted microbubbles and urokinase (UK + tMB group) or urokinase alone (UK group). In both groups, ultrasound was applied at the site of the occlusion. Blood flow through the iliac artery and microcirculation of the affected limb were monitored and the animals were euthanized 1 hr after treatment. Autopsy was performed to determine the weight of the thrombus and to check for adverse effects. Results In the UK + tMB group (n = 5), median improvement in arterial blood flow was 5 mL/min (range 0–216). Improvement was seen in 3 of these 5 pigs at conclusion of the experiment. In the UK group (n = 4), median improvement in arterial blood flow was 0 mL/min (−10 to 18), with slight improvement in 1 of 4 pigs. Thrombus weight was significantly lower in the UK + tMB group (median 0.9383 g, range 0.885–1.2809) versus 1.5399 g (1.337–1.7628; P = 0.017). No adverse effects were seen. Conclusions Based on this experiment, minimally invasive thrombolysis using intravenously administered targeted microbubbles carrying urokinase combined with local application of ultrasound is feasible and might accelerate thrombolysis compared with treatment with urokinase and ultrasound alone

An in vitro method to keep human aortic tissue sections functionally and structurally intact

The pathophysiology of aortic aneurysms (AA) is far from being understood. One reason for this lack of understanding is basic research being constrained to fixated cells or isolated cell cultures, by which cell-to-cell and cell-to-matrix communications are missed. We present a new, in vitro method for extended preservation of aortic wall sections to study pathophysiological processes. Intraoperatively harvested, live aortic specimens were cut into 150 μm sections and cultured. Viability was quantified up to 92 days using immunofluorescence. Cell types were characterized using immunostaining. After 14 days, individual cells of enzymatically digested tissues were examined for cell type and viability. Analysis of AA sections (N = 8) showed a viability of 40% at 7 days and smooth muscle cells, leukocytes, and macrophages were observed. Protocol optimization (N = 4) showed higher stable viability at day 62 and proliferation of new cells at day 92. Digested tissues showed different cell types and a viability up to 75% at day 14. Aortic tissue viability can be preserved until at least 62 days after harvesting. Cultured tissues can be digested into viable single cells for additional techniques. Present protocol provides an appropriate ex vivo setting to discover and study pathways and mechanisms in cultured human aneurysmal aortic tissue

Open surgical repair of ruptured juxtarenal aortic aneurysms with and without renal cooling: Observations regarding morbidity and mortality

ObjectivesLittle is known about the outcome of ruptured juxtarenal aortic aneurysm (RJAA) repair. Surgical treatment of RJAAs requires suprarenal aortic cross-clamping, which causes additional renal ischemia-reperfusion injury on top of the pre-existing hypovolemic shock syndrome. As endovascular alternatives rarely exist in this situation, open repair continues to be the gold standard. We analyzed our results of open RJAA repair during an 11-year period.DesignRetrospective observational study.Materials and methodsBetween July 1997 and December 2008, all consecutive patients with RJAAs were included in the study. Part of these patients received cold perfusion of the kidneys during suprarenal aortic cross-clamping. Perioperative variables, morbidity, and 30-day or in-hospital mortality were assessed. Renal insufficiency was defined as an acute rise of ≥0.5 mg/dL in serum creatinine level. Multiple organ failure (MOF) was scored using the sequential organ failure assessment score (SOFA score).ResultsA total of 29 consecutive patients with an RJAA, confirmed by computed tomography-scanning, presented to our hospital. In eight patients, the operation was aborted before the start of aortic repair, because no blood pressure could be regained in spite of maximal resuscitation measures. They were excluded from further analysis. Of the remaining 21 patients, 10 died during hospital stay. Renal insufficiency occurred in 11 out of 21 of the patients. Eleven out of 21 patients developed MOF postoperatively. In a subgroup of patients who received renal cooling during suprarenal aortic clamping, the 30-day or in-hospital mortality was two of 10 vs eight of 11 in patients who did not receive renal cooling (P = .03); renal insufficiency occurred in one out of 10 patients in the subgroup with renal cooling vs 10 out of 11 without renal cooling (P < .001) and MOF in two of 10 vs nine of 11, respectively (P = .009).ConclusionsOpen surgical repair of RJAAs is still associated with high mortality and morbidity. To our knowledge, this is the first report of cold perfusion of the kidneys during RJAA repair. Although numbers are small, a beneficial effect of renal cooling on the outcome of RJAA repair is suggested, warranting further research with this technique