Combined visualization in endovascular treatment lower limb arteries pathology

• Агарков М.В.
• Козлов К.Л.
• Герцог О.Б.
• Любивый Е.Д.
• Попов В.В.
• Шнейдер Ю.А.
• Лебеденко Е.О.

Резюме

Objective. The purpose of the study was to investigate the effect of intraoperative 3D fusion imaging on the time of surgery, radiation dose and volume of contrast medium during endovascular treatment of peripheral artery disease.

Patients and methods. This prospective, single-center, randomized comparative 30-month trial included a total of 395 patients with lesions of aortofemoral, femoropopliteal segments and tibial arteries. They were all candidates for endovascular revascularization and divided into two groups. The Study Group patients (n=197) underwent operations with combined 3D fusion navigation, whereas the Control Group patients (n=198) were operated on without 3D-imaging. We compared the operation time, radiation dose, and contrast medium volume, followed by analyzing the learning curve.

Results. The operation time in the Study Group amounted to 62.53 (10÷195) min versus 87.82 (6÷340) min in the Control Group (p<0.05), with a time reduction of 29%. The volume of contrast medium in the Study Group amounted to 91.19 (10÷850) vs 168.05 (20÷440) ml in the Control Group (p<0.05), with a decrease of the contrast medium used amounting to 46.6%. The radiation dose in the Study Group was 245.25 (9÷2756) vs 472.92 (5÷3987) mGy in the Control Group (p<0.05), thus showing a reduction by 63.38%. Stratification of the group of combined navigation into 4 subgroups according to the dates of the procedure demonstrated no influence of the potential learning curve on the parameters examined.

Conclusion. The obtained findings demonstrated a significant reduction in the contrast volume (p<0.05), time of surgery (p<0.05) and radiation dose (p<0.05) during endovascular treatment of obliterating sclerosis of lower limb vessels using the technology of combined navigation. These results highlight the potential benefits of routine use of 3D-fusion hybrid imaging when performing endovascular revascularization in patients with PAD.

Ключевые слова:hybrid (combined) visualization; 3D image fusion; peripheral artery disease; contrast volume; operation time; radiation safety; endovascular revascularization

Introduction

Atherosclerosis is one of the most important problems of modern medicine [1]. Obliterating sclerosis of lower limb vessels has a significant negative impact on quality of life, disability and overall mortality of the population [2]. Recent years have witnessed a growing number of endovascular operations as a minimally invasive and nigh-technological variant of treatment [3]. Thus, according to the Transatlantic Inter-Society Consensus Document on Management of Peripheral Arterial Disease (TASC II), type A arterial lesions are considered to be most suitable for treatment using endovascular strategy, whereas type D lesions are most complicated for endovascular revascularization and by the remote results are inferior to open reconstructive surgery. Such lesions are represented by extended occlusions, occlusive lesions of the popliteal artery, involving several segments. In patients with such lesions, it is recommended to perform “open” operations [4]. The development of technologies resulted in the fact that type C and D lesions became more promising for treatment with endovascular methods [5]. However, treatment of patients with complicated lesions is a serious problem and requires high-quality imaging of vessels, which may result in higher irradiation of patients and the operator. It was proved that C/D type lesions require a larger volume of contrast medium and longer time for operation.

It was shown that combined navigation with dynamic fusion of data of preoperative computed tomography (MSCT) in a real time mode resulted in decreased time of operation, duration of the procedure and volume of contrast medium used during endovascular operations in patients with aneurysms of the aorta and iliac arteries [6-8]. Nevertheless, despite the fact that endovascular revascularization of lower limbs is performed significantly more often than implantation of aortic stent grafts, the data on operations with the use of combined visualization in endovascular treatment of obliterating atherosclerosis of lower limb vessels (OALLV) are scarce [9]. A series of literature-reported clinical cases of treatment of OALLV demonstrated that the use of this method of visualization could decrease the volume of contrast medium. It was shown that intraoperative navigation according to the previously performed MSCT may bring benefit in supporting the concept of ALARA (as low as reasonably achievable), diminish the dose of radiation, volume of contrast medium and total time of intervention in endovascular treatment of OALLV [10-12],with more precise positioning of the tool contributing to increased probability of success.

Patients and methods

The presented consecutive, prospective, single-center, randomized study was performed at the “Gusev Central District Hospital” of the Kaliningrad Region and approved by the Local Ethics Committee.

The study included patients with atherosclerotic lesions of aorto-iliac, femoroiliac and femoropopliteal regions, as well as tibial artery lesions with chronic ischemia stage IIb-IV according to A.V. Pokrovsky-Fontaine classification. All patients were eligible for endovascular revascularization. Patients requiring hybrid operations, open surgical procedure, as well as those with acute ischemia of extremities were excluded form the study. All procedures were performed under local anesthesia. All operations were carried out on one angiographic unit General Electric IGS 530 (USA). The contrast medium during surgery was administered by hand with a 5-ml syringe. The contrast media used contained iodine at a dose of 300 mg/ml and were diluted 2-fold with normal saline prior to administration.

The Control Group included patients undergoing revascularization without image fusion. The Study Group patients were operated on with the use of the software package for image fusion VISION 2. The clinical and anatomical characteristics of patients are shown in Table 1.

The study was carried out from January 2020 to June 2022, including a total of 395 patients (293 males, 74.2%), mean age 67.8±9.5 years. Randomization into groups was performed with the help of the electron resource: http://www.jerrydallal.com/random/permute.htm, 10.01.2020. Later on the patients were distributed according to the randomization protocol. All patients underwent endovascular revascularization of the aortoiliac segment and arteries of lower limbs with (n=197) or without (n=198) combined navigation.

The working process of preparing a 3D-model obtained by the findings of MSCT AG

The procedure of preparing a three-dimensional model began from analyzing the data of MSCT. Based on these findings, we created two volumetric models: a) arterial model; b) model of bones of the target extremity. Transparency of the bone model was maintained at 80% (Fig. 1).

The volumetric model was subjected to the following analysis: assessing the length of the lesion, diameter of the vessel in the healthy zones and sites of stenosis and occlusions. On the three-dimension model, we marked the boundaries of zones of balloon angioplasty, sites of stent implantation (Fig. 2).

We also analyzed calcium distribution in the occlusion in order to determine the type of revascularization. In case of calcified occlusion, the primary subintimal approach was considered to be more justified (Fig. 3).

On the arterial model, we assessed the site of puncture, choosing the place with minimal calcification and the possibility of reliable hemostasis on completion of the intervention (Fig. 4).

Image fusion

In order to fuse the 3D-model with roentgenoscopy of the angiograph, we performed real-time synchronization guided by the screen of roentgenoscopy. For synchronization of data, there are several methods: synchronization by bone landmarks (Fig. 5, 6).

Another method of synchronization is superimposition by calcium in arteries (Fig. 7).

The third method is synchronization of models in administration of contrast medium into the artery (Fig. 8).

An obligatory condition of accurate fusion of data was superposition of models in the direct and oblique projections. After superposition of data in 2 plains, the physician confirmed synchronization.

Synchronization allows the three-dimensional model superimposed on fluoroscopy to change the viewing angle synchronously with rotation of the C- and L-arms of the angiograph and movements of the operating table. There is certain inaccuracy between the prepared three-dimensional model obtained by the MSCT AG findings and dynamic image of arteries in direct roentgenoscopy. Areas that are prone to these phenomena are the distal segments below the knee vessels that move because of the discrepancy between the relative positions of the leg intraoperatively and preoperatively [10]. Fusion imaging errors were mitigated using a leg holder to maintain the leg position corresponding to MSCT AG.

Operation

Synchronization of data was followed by operative intervention during which we restored the lumen of arteries with the help of balloon angioplasty or stenting of arteries. With each movement of the table, C-arm or L-arm, the software synchronized the current image in real time mode (fluorographic image) over which displayed was previously prepared three-dimensional model. The model’s position made it possible to uninterruptedly correlate surgical landmarks with the tool inside the vessel during the whole operation without additional control angiographies (Fig. 9).

The process of fusion was displayed in real time on the screen of the workstation next to the screens of roentgenoscopy (Fig. 10, 11) [9].

The summarized operational data of patients are presented in Table 2.

Methods of statistical processing

The statistical analysis of the obtained clinical findings was performed using the STATISTICA for Windows (version 10).

The quantitative parameters (age, creatinine, operation time, contrast agent volume and others) in the analyzed groups of patients were compared using the Mann-Whitney U test, Kolmogorov-Smirnov criteria, median c-square and ANOVA module, since the distribution of all parameters did not correspond to normal. The frequency of qualitative parameters (type of lesion, localization of lesion, vascular accesses and others) was assessed using nonparametric methods of chi-squared test, Pearson criterion and Fisher criterion.

Results

Creation of the three-dimensional model and data fusion were technically possible and used in all patients (100%) of the Study Group. Comparison of the groups by the examined parameters is shown in Table 3.

Comparing the contrast agent volume (ml), radiation dose (mGy), time of intervention (min) and number of performed angiographic scans is shown in Fig. 12.

Contrast agent. The volume of the contrast medium turned out to be less in the Study Group (91.20±79.34 ml versus 168.05±80.50 ml in the Control Group (p<0.0000), thus showing a reduction in contrast volume averagely by 46.6%.

Operation time. The operation time was less in the group of hybrid visualization amounting to 62.53±37.9 versus 87.82±49.13 min (p<0.0000), with a reduction by 29.03% (Fig. 12).

Radiation dose. An average radiation dose during operative intervention in the hybrid visualization group was 245.25±340.2 mGy versus 472.92±536.83 mGy in the Control Group, with a dose reduction by 63.38% (see Figure 12).

Learning curve

We performed stratification of the Study Group into 4 subgroups of the same number of patients: from January 2020 to August 2020, from September 2020 to March 2021, and from October 2021 to June 2022 (Fig. 13), with no data obtained on the effect of the potential learning curve on such operative parameters as contrast agent volume, radiation dose and operation time.

Discussion

As far as we know, this is the first comparative prospective study of using combined navigation in treatment for PAD in routine hospital practice. Thus, “hybrid” visualization being an important component of technical success has increasingly been used in order to decrease the radiation exposure and the volume of contrast agent during implantation of stent grafts into the aorta and iliac arteries [6, 8]. In its turn, it was confirmed that only routine use of protective shields, collimation, remoteness from the radiation source (X-ray tube) and technical progress in medical visualization decrease overexposure to radiation of both medical personnel and patients [13]. Despite the fact that the level of radiation of the patient and operating team is significantly lower during operations on peripheral arteries than that in percutaneous coronary interventions, any technology decreasing intraoperative risks complies with the international principle of radiation safety ALARA (as low as reasonably achievable) [14, 15]. Professional training of endovascular surgeons is associated with increased risk of genetic anomalies, the development of occupational radiation cataract and potentially malignant neoplasms [16]. In modern medicine, the ALARA radiation safety principle is applicable not only for effective radiation dose decrease but also for decreasing the volume of contrast agents used. Contrast-induced acute kidney injury (CI-AKI) is a dreaded complication of peripheral vascular interventions that depends on the volume of contrast administered, as well as a patient’s baseline kidney function and is strongly associated with both short- and long-term postoperative mortality [17]. In any case, the risk of PC-AKI should be minimized by using safe thresholds of contrast volume.

The findings of our study demonstrated that the use of combined visualization resulted in significant reduction of the radiation dose and volume of the contrast agent used. A considerable decrease in the amount of the contrast medium in the Study Group patients was due to the fact that the endovascular surgeon decreased the number of contrast agent injections during the intervention and the first administration was often performed as control of the already performed balloon angioplasty of the artery. Thus, the number of performed angiographies amounted to 22.8±12.9 versus 31.5±15.78 in the Study Group and Control Group, respectively (p<0.0001). We should not forget possible orthopedic problems in members of a surgical team due to prolonged time of wearing heavy protective aprons [18]. In our study, the use of hybrid visualization resulted in decreasing the operation time, thus also contributing to prevention of musculoskeletal problems associated with prolonged wearing of X-ray protective clothing.

Nevertheless, there remain unsolved problems during operations using hybrid visualization. Thus, M. Haga in 2019 presented a series of clinical cases demonstrating that fusion imaging facilitated identification of lesions and bifurcations of peripheral artery branches, but with some limitations reported [10]. There is a need to control the patient’s movements, since movement disturbs synchronization between the 3D-model and dynamic roentgenoscopy of the angiograph. If the procedure is carried out under local anesthesia, it is rather difficult for the patient to maintain the leg motionless for a long time, and virtually all patients are prone to involuntary movements and limb displacement. Inconsiderable (1-2 mm) displacements did not influence the operation quality while working on the aortoiliac and femoropopliteal segments. The exception was the ostium of the superficial femoral artery where positioning of the stent without closure of the deep femoral artery ostium is important in the context of possible stent thrombosis, thus requiring precise positioning of the stent. A change in the leg position should be followed by control of synchronization by bone landmarks and if necessary by repeat synchronization using one of the appropriate methods (more often by the osseous model). In the performed study, various radiotransparent leg holders were used. It resulted in decreased movement of the leg, facilitated the work of the operating team and improved patient comfort [19].

Conclusion

The use of technology of combined (hybrid) navigation during endovascular operations in patients with PAD demonstrated the possibility to significantly decrease the volume of contrast medium used, reduce operation time and radiation dose. A 30% and more decrease for all studied parameters was obtained without long-term requirements for learning. These results suggest potential advantages of routine use of combined intraoperative visualization during endovascular operations in patients with PAD.

Limitations. The results of this prospective, randomized, single-center study should be interpreted in the context of its design, making it possible to perform reliable comparison of the groups. However, such nonparametric data as the learning curve could have influenced the obtained findings. Hence, to test this hypothesis, both groups were operated on during the same time period, with no alterations in either operators or endovascular technique; the procedures were performed in the same operating room, using the same angiograph.

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