Deterministic effects after fenestrated endovascular aortic aneurysm repair

National Diagnostic Reference Levels for Standard Descending Thoracic Endovascular Aortic Repair and Optimisation Strategies

OBJECTIVE

The International Commission on Radiological Protection has highlighted the large number of medical specialties that use fluoroscopy outside diagnostic imaging departments without radiation protection programmes for patients and staff. Vascular surgery is one of these specialties. Thoracic endovascular aortic repair (TEVAR) is a complicated procedure requiring radiation protection guidance and optimisation. The recent EU Basic Safety Standards Directive requires the use and periodic updating of diagnostic reference levels (DRLs) for interventional procedures. The aim of this study was to determine doses for patients undergoing TEVAR with mobile Xray systems and hybrid rooms (fixed Xray systems) to obtain national DRLs and to suggest optimisation actions.

METHODS

This was a retrospective cross sectional study. The Spanish Chapter of Endovascular Surgery conducted a national survey in 11 autonomous communities representing around 77.6% of the Spanish population (47.33 million inhabitants). A total of 266 TEVAR procedures from 17 Spanish centres were analysed, of which 53.0% were performed in hybrid operating rooms. National DRLs were obtained and defined as the third quartile of the median values from the different participating centres.

RESULTS

The proposed national DRLs are: for kerma area product (KAP), 113.81 Gy·cm2 for mobile Xray systems and 282.59 Gy·cm2 for hybrid rooms; and for cumulative air kerma (CAK) at the patient entry reference point, 228.38 mGy for mobile systems and 910.64 mGy for hybrid rooms.

CONCLUSION

Based on the requirement to know radiation doses for standard endovascular procedures, this study of TEVARs demonstrated that there is an increased factor of 2.48 in DRLs for KAP when the procedure is performed in a hybrid room compared with mobile C-arm systems, and an increased factor of 3.98 in DRLs for CAK when the procedure is performed with hybrid equipment. These results will help to optimise strategies to reduce radiation doses during TEVAR procedures.

Initial single-center experience using Fiber Optic RealShape guidance in complex endovascular aortic repair

OBJECTIVE

In the present study, we have described the technical success using Fiber Optic RealShape (FORS) endovascular guidance and its effects on the overall procedural time and radiation usage during complex endovascular aortic repair (EVAR).

METHODS

Fenestrated and branched EVARs performed at a single center from 2017 to 2022 were prospectively studied. FORS-guided procedures were matched retrospectively 1:3 to non-FORS-guided procedures by the incorporated target arteries and body mass index. Technical success was defined as successful target vessel cannulation using FORS for the entirety of navigation (wire insertion to exchange for a stiff wire). The predictors of technical success were evaluated via logistic regression. The procedural times and radiation doses were compared between the matched cohorts using the Wilcoxon rank sum test.

RESULTS

A total of 21 FORS-guided procedures were matched to 61 non-FORS-guided procedures. A total of 95 FORS cannulations were attempted (87 for the visceral target artery and 8 for the bifurcate gate). Technical success was achieved in 81 cannulations (85%); 15 (16%) were completed without the use of live fluoroscopy. The univariate predictors of FORS technical success included <50% target artery stenosis, <50% target artery calcification, and the target vessel attempted (P < .05 for each). FORS failures were attributed to device material properties in six cases, device failure in two cases, and the wire/catheter combination in six. The use of FORS guidance was associated with shorter median procedural and fluoroscopy times and a lower dose area product and air kerma (P ≤ .0001 for each).

CONCLUSIONS

The results from our initial experience with FORS during complex EVAR, including our learning curve, has shown promise, with acceptable technical success and reductions in procedural times and radiation usage.

Radiation exposure during angiographic interventions in interventional radiology - risk and fate of advanced procedures

PURPOSE

Advanced angiographic procedures in interventional radiology are becoming more important and are more frequently used, especially in the treatment of several acute life-threatening diseases like stroke or aortic injury. In recent years, technical advancement has led to a broader spectrum of interventions and complex procedures with longer fluoroscopy times. This involves the risk of higher dose exposures, which, in rare cases, may cause deterministic radiation effects, e.g. erythema in patients undergoing angiographic procedures. Against this background, these procedures recently also became subject to national and international regulations regarding radiation protection. At the same time, individual risk assessment of possible stochastic radiation effects for each patient must be weighed up against the anticipated benefits of the therapy itself. Harmful effects of the administered dose are not limited to the patient but can also affect the radiologist and the medical staff. In particular, the development of cataracts in interventionalists is a rising matter of concern. Furthermore, long-term effects of repeated and prolonged x-ray exposure have long been neglected by radiologists but have come into focus in the past years.

CONCLUSIONS

With all this in mind, this review discusses different efforts to reduce radiation exposition levels for patients and medical staff by means of technical, personal as well as organizational measures.

Use of a 2 Dimensional Vessel Navigator Roadmap Decreases Patient Radiation Dose Compared to Standard 3D Mapping for Fenestrated Endovascular Aneurysm Repair

OBJECTIVE

For fenestrated endovascular aneurysm repair (FEVAR), the implementation of the VesselNavigator (Philips Healthcare, Best, The Netherlands) to provide a 3-dimensional vessel roadmap has been shown to reduce patient radiation exposure. Unfortunately, FEVAR radiation doses remain substantial despite utilization of this technology. Traditionally, registration of the live fluoroscopy with the pre-operative CTA is performed via the acquisition of a low-dose cone-beam CT scan. However, this registration can also be accomplished with the acquisition of 2D X-rays using the c-arm in 2 different projection angles. We hypothesized that the 2D image acquisition for vessel roadmap development would result in a significant reduction in patient radiation dose in comparison to the 3D CT registration without compromising image quality or increasing procedural length.

METHODS

This single-center, retrospective study included FEVARs performed from January 2015 to May 2019. For patient data, the cumulative reference air kerma (RAK) was presented as geometric mean and standard deviation. A general linear model with log-normal distribution was used to test the difference in patient RAK between 2D X-ray and 3D CT VesselNavigator registration after adjusting for BMI and the number of vessel fenestrations (1 to 2 vs. 3 to 4). Fluoroscopy time was recorded and used as a surrogate for case complexity. All analyses were done in SAS 9.4 (SAS Institute, Inc., Cary, North Carolina).

RESULTS

One hundred and sixty four FEVARs were performed on a Philips Allura Xper FD 20 fluoroscopy system equipped with clarity technology. The VesselNavigator registration was completed using 3D CT mapping in 99 cases and 2D X-rays in 65 procedures. On average, utilization of 2D mapping versus 3D mapping for the VesselNavigator resulted in a 20.4% reduction in patient RAK after controlling for BMI and number of vessel fenestrations, P = 0.0135. There was no significant difference in fluoroscopy time between the 2 study groups (P= 0.81) suggesting that image quality was not compromised by the use of 2D mapping leading to the need for additional fluoroscopy.

CONCLUSION

Acquisition of 2D films rather than a 3D CT scan for VesselNavigator registration allows for a significant reduction in patient radiation dose during FEVAR without increasing the case complexity or compromising image quality.

The Effects of Gender on Radiation Dose during Fenestrated Endovascular Aneurysm Repair

BACKGROUND

Female gender is considered a risk factor for worse perioperative outcomes after fenestrated endovascular aneurysm repair (FEVAR). We hypothesized that women would have more unfavorable anatomy, increasing case complexity and leading to higher radiation doses. Our aim was to evaluate the effect of gender on radiation dose during FEVARs.

METHODS

This single-center retrospective study was performed from 1/2015 to 2/2018. For patient data, linear model and stepwise variable selection algorithm were used. All dose measurements were log transformed before analysis. Significance level for parameter estimates and corresponding 95% confidence intervals were all transformed back using an exponential function. P-value of <0.05 was considered statistically significant. All analyses were performed in SAS 9.4 (SAS Institute Inc., Cary, NC).

RESULTS

A total of 169 FEVARs (45 women) were performed on a Philips Allura Xper FD 20 fluoroscopy system equipped with clarity technology. There was no difference in body mass index (BMI) or operative time between genders, P = 0.9. The median reference air kerma for women was significantly lower than that for men (1,672 mGy vs. 2,496 mGy), P < 0.001. Women had on average a 28% total dose reduction after controlling for BMI, number of vessels fenestrated, operative time, and type of device, P < 0.001. The median fluorography and fluoroscopy doses for women were significantly lower than those for men (973 mGy vs. 1,401 mGy and 659 mGy vs. 1,008 mGy), resulting in a 24% fluorography dose reduction and a 38% fluoroscopy dose reduction for women, P < 0.001.

CONCLUSIONS

FEVARs can be performed successfully in women with comparatively lower radiation doses.

SURVEY OF KEY RADIATION SAFETY PRACTICES IN INTERVENTIONAL RADIOLOGY: AN IRISH AND ENGLISH STUDY

Interventional radiology is a rapidly evolving speciality with potential to deliver high patient radiation doses, as a result high standards of radiation safety practice are imperative. IR radiation safety practice must be considered before during and after procedures through appropriate patient consent, dose monitoring and patient follow-up. This questionnaire-based study surveyed fixed IR departments across Ireland and England to establish clinical practice in relation to radiation safety. Pre-procedure IR patient consent includes all radiation effects in 11% of cases. The patient skin dose surrogate parameter of Kerma to air at a reference point (Kar) is under-reported. Only 39% of respondents use a substantial radiation dose level and inform patients after these have been reached. Poor compliance with unambiguous, readily available best practice guidance was observed throughout highlighting patient communication, patient dose quantification and subsequent patient dose management concerns.

Comparison of Patient Skin Dose Evaluated Using Radiochromic Film and Dose Calculation Software

PURPOSE

To compare, in an interventional radiology setting, peak skin doses (PSDs) delivered as calculated using a dedicated software tool and as measured using radiochromic film. To assess the utility of this dose calculation software tool in routine clinical practice.

MATERIALS AND METHODS

First, radiochromic films were positioned on the examination table in the back of an adult anthropomorphic phantom to measure PSD, and X-ray examinations were simulated. Then, films were again positioned in the patient's back for 59 thoracic or abdominopelvic endovascular interventions. The results obtained with the radiochromic films were taken as a reference and were statistically compared with those of the software.

RESULTS

With measured PSDs ranging from 100 to 7000 mGy, the median software-film difference was 8.5%. Lin's concordance coefficient was 0.98 [0.97; 0.99] (p < 0.001), meaning that concordance was excellent between the two methods. For the films where PSD exceeded 1000 mGy, the median difference in the measured value was 8.7% [- 1.3; 21.1], with a maximum discrepancy of 34%. Lin's concordance coefficient was 0.98 [0.96; 1] (p < 0.001), meaning that concordance was excellent between the two methods.

CONCLUSION

Comparison between radiochromic films and the software tool showed that the software is a suitable tool for a simple and reliable estimation of PSD. The software seems to be a good alternative to films, whose use remains complex.

Defining the Key Competencies in Radiation Protection for Endovascular Procedures: A Multispecialty Delphi Consensus Study

OBJECTIVES

Radiation protection training courses currently focus on broad knowledge topics which may not always be relevant in daily practice. The goal of this study was to determine the key competencies in radiation protection that every endovascular team member should possess and apply routinely, through multispecialty clinical content expert consensus.

METHODS

Consensus was obtained through a two round modified Delphi methodology. The expert panel consisted of European vascular surgeons, interventional radiologists, and interventional cardiologists/angiologists experienced in endovascular procedures. An initial list of statements, covering knowledge skills, technical skills and attitudes was created, based on a literature search. Additional statements could be suggested by the experts in the first Delphi round. Each of the statements had to be rated on a 5- point Likert scale. A statement was considered to be a key competency when the internal consistency was greater than alpha = 0.80 and at least 80% of the experts agreed (rating 4/5) or strongly agreed (rating 5/5) with the statement. Questionnaires were emailed to panel members using the Surveymonkey service.

RESULTS

Forty-one of 65 (63.1%) invited experts agreed to participate in the study. The response rates were 36 out of 41 (87.8%): overall 38 out of 41(92.6%) in the first round and 36 out of 38 (94.7%) in the second round. The 71 primary statements were supplemented with nine items suggested by the panel. The results showed excellent consensus among responders (Cronbach's alpha = 0.937 first round; 0.958 s round). Experts achieved a consensus that 30 of 33 knowledge skills (90.9%), 23 of 27 technical skills (82.1%), and 15 of 20 attitudes (75.0%) should be considered as key competencies.

CONCLUSIONS

A multispecialty European endovascular expert panel reached consensus about the key competencies in radiation protection. These results may serve to create practical and relevant radiation protection training courses in the future, enhancing radiation safety for both patients and the entire endovascular team.

Edge-preserving denoising for intra-operative cone beam CT in endovascular aneurysm repair

C-arm cone-beam computed tomography (CBCT) acquisition during endovascular aneurysm repair (EVAR) is an emergent technology with more and more applications. It offers real time imaging with a stationary patient and provides 3-D information to achieve guidance of intervention. However, there is growing concern on the overall radiation doses delivered to patients all along the endovascular management due to pre-, intra-, and post-operative X-ray imaging. Manufactures may have their low dose protocols to realize reduction of radiation dose, but CBCT with a low dose protocol has too many artifacts, particularly streak artifacts, and decreased contrast-to-noise ratio (CNR). To reduce noise and artifacts, a penalized weighted least-squares (PWLS) algorithm with an edge-preserving penalty is proposed. The proposed method is evaluated by quantitative parameters including a defined signal-to-noise ratio (SNR), CNR, and modulation transfer function (MTF) on clinical CBCT. Comparisons with PWLS algorithms with isotropic, TV, Huber, anisotropic penalties demonstrate that the proposed edge-preserving penalty performs well not only on edge preservation, but also on streak artifacts suppression, which may be crucial for observing guidewire and stentgraft in EVAR.