Use of 3D Printing to Guide Creation of Fenestrations in Physician-Modified Stent-Grafts for Treatment of Thoracoabdominal Aortic Disease

Metamaterial design for aortic aneurysm simulation using 3D printing

INTRODUCTION

The use of three-dimensional (3D) printed anatomic models is steadily increasing in research and as a tool for clinical decision-making. The mechanical properties of polymers and metamaterials were investigated to evaluate their application in mimicking the biomechanics of the aortic vessel wall.

METHODOLOGY

Uniaxial tensile tests were performed to determine the elastic modulus, mechanical stress, and strain of 3D printed samples. We used a combination of materials, designed to mimic biological tissues' properties, the rigid VeroTM family, and the flexible Agilus30™. Metamaterials were designed by tessellating unit cells that were used as lattice-reinforcement to tune their mechanical properties. The lattice-reinforcements were based on two groups of patterns, mainly responding to the movement between links/threads (chain and knitted) or to deformation (origami and diamond crystal). The mechanical properties of the printed materials were compared with the characteristics of healthy and aneurysmal aortas.

RESULTS

Uniaxial tensile tests showed that the use of a lattice-reinforcement increased rigidity and may increase the maximum stress generated. The pattern and material of the lattice-reinforcement may increase or reduce the strain at maximum stress, which is also affected by the base material used. Printed samples showed max stress ranging from 0.39 ± 0.01 MPa to 0.88 ± 0.02 MPa, and strain at max stress ranging from 70.44 ± 0.86% to 158.21 ± 8.99%. An example of an application was created by inserting a metamaterial designed as a lattice-reinforcement on a model of the aorta to simulate an abdominal aortic aneurysm.

CONCLUSION

The maximum stresses obtained with the printed models were similar to those of aortic tissue reported in the literature, despite the fact that the models did not perfectly reproduce the biological tissue behavior.

Unsuspected Limitations of 3D Printed Model in Planning of Complex Aortic Aneurysm Endovascular Treatment

OBJECTIVE

Static 3-dimensional (3D) printing became attractive for operative planning in cases that involve difficult anatomy. An interactive (low cost, fast) 3D print allowing deliberate surgical practice can be used to improve interventional simulation and planning.

BACKGROUND

Endovascular treatment of complex aortic aneurysms is technically challenging, especially in case of narrow aortic lumen or significant aortic angulation (hostile anatomy). The risk of complications such as graft kinking and target vessel occlusion is difficult to assess based solely on traditional software measuring methods and remain highly dependent on surgeon skills and expertise.

METHODS

A patient with juxtarenal AAA with hostile anatomy had a 3-dimensional printed model constructed preoperatively according to computed tomography images. Endovascular graft implantation in the 3D printed aorta with a standard T-Branch Cook (Cook® Medical, Bloomington, IN, USA) was performed preoperatively in the simulation laboratory enabling optimized feasibility, surgical planning and intraoperative decision making.

RESULTS

The 3D printed aortic model proved to be radio-opaque and allowed simulation of branched endovascular aortic repair (BREVAR). The assessment of intervention feasibility, as well as optimal branch position and orientation was found to be useful for surgeon confidence and the actual intervention in the patient. There was a remarkable agreement between the 3D printed model and both CT and X-ray angiographic images. Although the technical success was achieved as planned, a previously deployed renal stent caused unexpected difficulty in advancing the renal stent, which was not observed in the 3D model simulation.

CONCLUSION

The 3D printed aortic models can be useful for determining feasibility, optimizing planning and intraoperative decision making in hostile anatomy improving the outcome. Despite already offering satisfying accuracy at present, further advancements could enhance the 3D model capability to replicate minor anatomical deformities and variations in tissue density.

Three-Dimensional Printing Application in a Challenging Case of Type II Endoleak

PURPOSE

To highlight the importance of 3-dimensional (3D) arterial printing in a case of type II endoleak (EL) embolization.

CASE REPORT

An 81-year-old patient, previously treated with endovascular aortic repair (EVAR), developed a type II EL requiring treatment. The EL's main origin was the median sacral artery (MSA). Initial attempts in embolization via a transsealing and transarterial approach were unsuccessful owing to extremely tortuous arterial communications between the left hypogastric artery and the MSA. The construction of a clear resin 3D model of the aorta and iliolumbar arteries improved anatomy understanding and moreover allowed a preoperative simulation. The subsequent transarterial attempt in embolization was resolutive, significantly reducing total procedural time and radiation dose.

CONCLUSION

Printing of clear resin 3D arterial models facilitates type II EL transarterial embolization, improving anatomy understanding and allowing simple fluoroscopy-free simulations.

CLINICAL IMPACT

The aim of our work is to highlight the additional value of three-dimensional (3D) printing during preoperative planning of challenging endovascular cases. To our best knowledge, this is the first report about 3D printing use in a case of type II endoleak (EL). We believe that realizing life-size aortic models in selected cases where a complex type II EL embolization procedure is indicated, could lead to a better understanding of arterial anatomy, thus allowing to increase procedural success and reduce operative and most importantly fluoroscopy time.

The Utility of Three-Dimensional Printing in Physician-Modified Stent Grafts for Aortic Lesions Repair

Background: Three-dimensional (3D) printing is becoming increasingly popular around the world not only in engineering but also in the medical industry. This trend is visible, especially in aortic modeling for both training and treatment purposes. As a result of advancements in 3D technology, patients can be offered personalized treatment of aortic lesions via physician-modified stent grafts (PMSG), which can be tailored to the specific vascular conditions of the patient. The objective of this systematic review was to investigate the utility of 3D printing in PMSG in aortic lesion repair by examining procedure time and complications. Methods: The systematic review has been performed using the PRISMA 2020 Checklist and PRISMA 2020 flow diagram and following the Cochrane Handbook. The systematic review has been registered in the International Prospective Register of Systematic Reviews: CRD42024526950. Results: Five studies with a total number of 172 patients were included in the final review. The mean operation time was 249.95± 70.03 min, and the mean modification time was 65.38 ± 10.59 min. The analysis of the results indicated I2 of 99% and 100% indicating high heterogeneity among studies. The bias assessment indicated the moderate quality of the included research. Conclusions: The noticeable variance in the reviewed studies' results marks the need for larger randomized trials as clinical results of 3D printing in PMSG have great potential for patients with aortic lesions in both elective and urgent procedures.

Outcomes of fenestrated endovascular abdominal aortic repair in distal entry tears of chronic debakey IIIb aortic dissection

Currently, there have been very few reports within the literature which specifically address using fenestrated and branched stent grafts to completely isolate and repair distal entry tears of chronic DeBakey IIIb aortic dissection. This study aimed to evaluate the clinical outcomes of a 3-dimensional (3D) printed aortic model-guided fenestrated stent in the treatment of distal tears of chronic DeBakey IIIb aortic dissection after thoracic endovascular aortic repair (TEVAR). The study was a one-center retrospective study comprising 36 patients who underwent TEVAR and fenestrated endovascular abdominal aortic repair (F-EVAR) between April 2014 and December 2022. Patient data was compiled and analysed for preoperative, intraoperative, and perioperative characteristics. In total, 36 patients (12 females and 24 males) were incorporated into this study. All of the patients included in this study had hypertension, and among them, the leading cause for undergoing II-stage F-EVAR was the progression of a false lumen, accounting for 24 cases (66.7% of the total). The technical success rate was 97.2% and there were no cases of 30-day mortality, myocardial infarction, permanent paraparesis, or organ failure. One year post-F-EVAR treatment, surviving patients showed significant false and true lumen remodelling with 100% complete false-lumen thrombosis. A total of five patients died during the follow-up, two patients died related to aorta complications and three patients died of heart failure, multiple organ failure, or septic shock. II-stage F-EVAR was safe and feasible operation to repair all distal tears of chronic DeBakey IIIb aortic dissection.

Accuracy and Sterilizability of In-House Printed Patient-Specific Aortic Model for Surgeon-Modified Stent Grafts-A Workflow Description for Emergency Aortic Endovascular Procedures

Introduction: The use of 3D-printed aortic models for the creation of surgeon-modified endoprostheses represents a promising avenue in aortic surgery. By focusing on the potential impact of sterilization on model integrity and geometry, this report sheds light on the suitability of these models for creating customized endoprostheses. The study presented here aimed to investigate the safety and viability of 3D-printed aortic models in the context of sterilization processes and subsequent remodeling. Methods: The study involved the fabrication of 3D-printed aortic models using patient-specific imaging data and established additive manufacturing techniques. Five identical aortic models of the same patient were printed. Two models were subjected to sterilization and two to disinfection using commonly employed methods, and one model remained untreated. The models were checked by in-house quality control for deformation (heat map analyses) after the sterilization and disinfection processes. Three models (sterilized, disinfected, and untreated) were sent for ex-house (Lufthansa Technik, AG, Materials Technologies and Central Laboratory Services, Hamburg, Germany) evaluation and subsequent quantification of possible structural changes using advanced imaging and measurement technologies (macroscopic and SEM/EDX examinations). After sterilization and disinfection, each aortic model underwent sterility checks. Results: Based on macroscopic and SEM/EDX examinations, distinct evidence of material alterations attributed to a treatment process, such as a cleaning procedure, was not identified on the three implants. Comparative material analyses conducted via the EDX technique yield consistent results for all three implants. Disinfected and sterilized models tested negative for common pathogens. Conclusions: The evaluation of 3D-printed aortic models' safety after sterilization as well as their suitability for surgeon-modified endoprostheses is a critical step toward their clinical integration. By comprehensively assessing changes in model integrity and geometry after sterilization, this research has contributed to the broader understanding of the use of 3D-printed models for tailor-made endovascular solutions. As medical technologies continue to evolve, research endeavors such as this one can serve as a foundation for harnessing the full potential of 3D printing to advance patient-centered care in aortic surgery.

Clinical comparative analysis of 3D printing-assisted extracorporeal pre-fenestration and Castor integrated branch stent techniques in treating type B aortic dissections with inadequate proximal landing zones

BACKGROUND

This study aims to compare the clinical effects of two distinct surgical approaches, namely 3D printing-assisted extracorporeal pre-fenestration and Castor integrated branch stent techniques, in treating patients with Stanford type B aortic dissections (TBAD) characterized by inadequate proximal landing zones.

METHODS

A retrospective analysis was conducted on 84 patients with type B aortic dissection (TBAD) who underwent thoracic endovascular aortic repair (TEVAR) with left subclavian artery (LSA) reconstruction at our center from January 2022 to July 2023. Based on the different surgical approaches, the patients were divided into two groups: the group assisted by 3D printing for extracorporeal pre-fenestration (n = 44) and the group using the castor integrated branch stent (n = 40). Clinical indicators: including general patient information, operative time, surgical success rate, intraoperative and postoperative complication rates, re-intervention rate, and mortality, as well as postoperative aortic remodeling, were compared between the two groups. The endpoint of this study is the post-TEVAR mortality rate in patients.

RESULTS

The surgical success rate and device deployment success rate were 100% in both groups, with no statistically significant difference (P > 0.05). However, the group assisted by 3D printing for extracorporeal pre-fenestration had a significantly longer operative time (184.20 ± 54.857 min) compared to the group using the castor integrated branch stent (152.75 ± 33.068 min), with a statistically significant difference (t = 3.215, p = 0.002, P < 0.05). Moreover, the incidence of postoperative cerebral infarction and beak sign was significantly lower in the group assisted by 3D printing for extracorporeal pre-fenestration compared to the castor-integrated branch stent group, demonstrating statistical significance. There were no significant differences between the two groups in terms of other postoperative complication rates and aortic remodeling (P > 0.05). Notably, computed tomography angiography images revealed the expansion of the vascular true lumen and the reduction of the false lumen at three specified levels of the thoracic aorta. The follow-up duration did not show any statistically significant difference between the two groups (10.59 ± 4.52 vs. 9.08 ± 4.35 months, t = 1.561, p = 0.122 > 0.05). Throughout the follow-up period, neither group experienced new endoleaks, spinal cord injuries, nor limb ischemia. In the castor-integrated branch stent group, one patient developed a new distal dissection, prompting further follow-up. Additionally, there was one case of mortality due to COVID-19 in each group. There were no statistically significant differences between the two groups in terms of re-intervention rate and survival rate (P > 0.05).

CONCLUSION

Both 3D printing-assisted extracorporeal pre-fenestration TEVAR and castor-integrated branch stent techniques demonstrate good safety and efficacy in treating Stanford type B aortic dissection with inadequate proximal anchoring. The 3D printing-assisted extracorporeal pre-fenestration TEVAR technique has a lower incidence of postoperative cerebral infarction and beak sign, while the castor-integrated branch stent technique has advantages in operative time.

Accurate Embolization for Endoleak after F-TEVAR of Thoracic Aortic Dissection by Detachable Coils

OBJECTIVES

To evaluate the efficacy and clinical outcomes of accurate embolization of endoleaks after fenestrated thoracic endovascular aortic repair (F-TEVAR) for thoracic aortic dissections.

METHODS

Twenty patients with endoleaks (17 type I and 3 type II) after fenestrated thoracic endovascular aortic repair (F-TEVAR) were embolized using detachable and ordinary coils. We assessed the success rate and complications of the operation, and its effects, through clinical and CT follow-up.

RESULTS

The mean clinical follow-up duration was 25.68 ± 11.07 months (3-44 months). During follow-up, all endoleaks were completely embolized and aortic remodeling was improved. Secondary endoleaks occurred in four patients who were embolized twice. No other complications or death were reported.

CONCLUSION

Embolization using detachable and ordinary coils is effective and safe for the treatment of endoleaks after fenestrated thoracic endovascular aortic repair.

Fenestrated Physician-Modified Endografts for Preservation of Main and Accessory Renal Arteries in Juxtarenal Aortic Aneurysms

BACKGROUND

There is a paucity of reporting outcomes of complex aortic aneurysm treatment such as juxtarenal abdominal aortic aneurysms, where additional techniques to preserve renal artery perfusion are required.

METHODS

Retrospective analysis of consecutive patients who underwent emergent and elective aortic repair with fenestrated PMEGs between March 2019 and January 2023. Endpoints were technical success, reinterventions, secondary reinterventions and target vessel patency.

RESULTS

Forty-seven target vessels in 37 patients (23 male, median age 75 years) were targeted, of which 44 were renal arteries (RAs) with a mean diameter of 5.4 ± 1.0 mm. Thirteen were accessory RAs and six had a diameter ≤ 4 mm. Technical success rate was 87% overall; 97% for main and 62% for accessory RAs respectively. Target vessel patency and freedom from secondary reintervention was 100% and 97% at 30 days and 96% and 91% at one year, respectively. There was no 30-day mortality.

CONCLUSION

Fenestrated physician-modified endografts are safe and effective for the treatment of patients with juxtarenal abdominal aortic aneurysms when incorporating main renal arteries. Limited technical success may be expected when targeting accessory renal arteries, especially when small in diameter. Long-term follow-up is needed to confirm durability of PMEGs for renal artery preservation.

An efficient 3D reconstruction method based on WT-TV denoising for low-dose CT images

BACKGROUND

In order to reduce the impact of CT radiation, low-dose CT is often used, but low-dose CT will bring more noise, affecting image quality and subsequent 3D reconstruction results.

OBJECTIVE

The study presents a reconstruction method based on wavelet transform-total variation (WT-TV) for low-dose CT.

METHODS

First, the low-dose CT images were denoised using WT and TV denoising methods. The WT method could preserve the features, and the TV method could preserve the edges and structures. Second, the two sets of denoised images were fused so that the features, edges, and structures could be preserved at the same time. Finally, FBP reconstruction was performed to obtain the final 3D reconstruction result.

RESULTS

The results show that The WT-TV method can effectively denoise low-dose CT and improve the clarity and accuracy of 3D reconstruction models.

CONCLUSION

Compared with other reconstruction methods, the proposed reconstruction method successfully addressed the issue of low-dose CT noising by further denoising the CT images before reconstruction. The denoising effect of low-dose CT images and the 3D reconstruction model were compared via experiments.

3D Printing-guided endovascular repair of enormous twisted thoracoabdominal aortic aneurysm with branch stenosis and occlusion

A 67-year-old male patient was admitted with an enormous twisted thoracoabdominal aortic aneurysm (TAAA) with multiple branch arteries stenosis and occlusion. Three-dimensional (3D) printing technology combined with mechanics was used for developing a transparent model of lesion to simulate the segment of diseased aorta. A stent graft was deployed in the 3D model to make a physician-modified stent graft (PMSGs) on table. The locations of the opening of branches were marked twice during operation. The PMSG was successfully deployed during the surgery and repaired the TAAA, with no endoleak and all the branched arteries patency in follow-up. This technique could offer precision individualized therapy and could simplify the procedure process greatly.

Risk factors for target vessel endoleaks after physician-modified fenestrated or branched endovascular aortic repair for postdissection thoracoabdominal aortic aneurysms

OBJECTIVE

Patients with postdissection thoracoabdominal aortic aneurysms (TAAAs) have been more likely to develop endoleaks than those with degenerative TAAAs after fenestrated or branched endovascular aortic repair (F/BEVAR). In the present study, we aimed to determine the risk factors for target vessel (TV)-related endoleaks after visceral segment F/BEVAR for postdissection TAAAs.

METHODS

We performed a retrospective analysis of all patients with degenerative and postdissection TAAAs treated with F/BEVAR between 2017 and 2021. All the patients had undergone computed tomography angiography before and 3 months, 6 months, and annually after discharge. Two experienced vascular surgeons had used data from computed tomography angiography and vascular angiography to judge the presence of endoleaks. The study end points were mortality, aneurysm rupture, and the emergence of and reintervention for TV-related endoleaks.

RESULTS

A total of 195 patients (mean age, 66 ± 10 years; 69% men) had undergone F/BEVAR for 99 postdissection TAAAs and 96 degenerative TAAAs. During a mean follow-up of 16 ± 12 months, we found that the patients with postdissection TAAAs were younger (age, 64 ± 10 years vs 69 ± 9 years; P = .001), had required more prior aortic repairs (58% vs 40%; P = .012), and had had a higher body mass index (26.1 ± 3.4 kg/m² vs 24.8 ± 3 kg/m²; P = .008), a larger visceral segment aortic diameter (47.1 ± 7.5 mm vs 44.5 ± 7.5 mm; P = .016), and more TV-related endoleaks (18% vs 7%; P = .023) compared with those with degenerative TAAAs. Of the 99 patients with postdissection TAAAs, 327 renal-mesenteric arteries were revascularized using 12 scallops, 141 fenestrations, and 174 inner or outer branch stents. A total of 25 TV-related endoleaks were identified among 18 patients during follow-up, including 6 type Ic (retrograde from the distal end of the branch), 3 type IIIb (bridging stent fabric tear), and 16 type IIIc endoleaks (detachment or loose connection of the bridging stent). The patients with an endoleak had had a larger visceral aortic diameter (52.7 ± 6.4 mm vs 45.8 ± 7.2 mm; P < .001) and had undergone revascularization of more TVs (3.7 ± 0.7 vs 3.2 ± 0.9; P = .032). In contrast, true lumen compression did not seem to affect the occurrence of TV endoleaks (39% vs 27%; P = .323). The use of presewn branch stents in the fenestration position was associated with a lower risk of TV-related endoleaks (5% vs 11%; P = .025). In addition, TVs derived entirely or partially from the false lumen were more prone to the development of endoleaks after reconstruction (19% vs 4% [P < .001]; and 15% vs 4% [P = .047], respectively).

CONCLUSIONS

We found that patients with postdissection TAAAs were more likely to have TV-related endoleaks after F/BEVAR in the visceral region than those with degenerative TAAAs. Additionally, patients with a larger aortic diameter and a greater number of fenestrations in the visceral region were more likely to have experienced TV-related endoleaks. Branch vessels deriving from the false lumen were also more likely to develop endoleaks after reconstruction, and prefabricated branch stents were related to a lower possibility of TV-related endoleaks.

Applications of Three-Dimensional Printing in the Management of Complex Aortic Diseases

The use of three-dimensional (3D) printing is gaining considerable success in many medical fields, including surgery; however, the spread of this innovation in cardiac and vascular surgery is still limited. This article reports our pilot experience with this technology, applied as an additional tool for 20 patients treated for complex vascular or cardiac surgical diseases. We have analyzed the feasibility of a "3D printing and aortic diseases project," which helps to obtain a more complete approach to these conditions. 3D models have been used as a resource to improve preoperative planning and simulation, both for open and endovascular procedures; furthermore, real 3D aortic models were used to develop doctor-patients communication, allowing better knowledge and awareness of their disease and of the planned surgical procedure. A 3D printing project seems feasible and applicable as an adjunctive tool in the diagnostic-therapeutic path of complex aortic diseases, with the need for future studies to verify the results.

3D printing in the planning and teaching of endovascular procedures

BACKGROUND

The introduction of 3D printing in the medical field led to new possibilities in the planning of complex procedures, as well as new ways of training junior physicians. Especially in the field of vascular interventions, 3D printing has a wide range of applications.

METHODOLOGICAL INNOVATIONS

3D-printed models of aortic aneurysms can be used for procedural training of endovascular aortic repair (EVAR), which can help boost the physician's confidence in the procedure, leading to a better outcome for the patient. Furthermore, it allows for a better understanding of complex anatomies and pathologies. In addition to teaching applications, the field of pre-interventional planning benefits greatly from the addition of 3D printing. Especially in the preparation for a complex endovascular aortic repair, prior orientation and test implantation of the stent grafts can further improve outcomes and reduce complications. For both teaching and planning applications, high-quality imaging datasets are required that can be transferred into a digital 3D model and subsequently printed in 3D. Thick slice thickness or suboptimal contrast agent phase can reduce the overall detail of the digital model, possibly concealing crucial anatomical details.

CONCLUSION

Based on the digital 3D model created for 3D printing, another new visualization technique might see future applications in the field of vascular interventions: virtual reality (VR). It enables the physician to quickly visualize a digital 3D model of the patient's anatomy in order to assess possible complications during endovascular repair. Due to the short transfer time from the radiological dataset into the VR, this technique might see use in emergency situations, where there is no time to wait for a printed model.

Imaging-Based, Patient-Specific Three-Dimensional Printing to Plan, Train, and Guide Cardiovascular Interventions: A Systematic Review and Meta-Analysis

BACKGROUND

To tailor cardiovascular interventions, the use of three-dimensional (3D), patient-specific phantoms (3DPSP) encompasses patient education, training, simulation, procedure planning, and outcome-prediction.

AIM

This systematic review and meta-analysis aims to investigate the current and future perspective of 3D printing for cardiovascular interventions.

METHODS

We systematically screened articles on Medline and EMBASE reporting the prospective use of 3DPSP in cardiovascular interventions by using combined search terms. Studies that compared intervention time depending on 3DPSP utilisation were included into a meta-analysis.

RESULTS

We identified 107 studies that prospectively investigated a total of 814 3DPSP in cardiovascular interventions. Most common settings were congenital heart disease (CHD) (38 articles, 6 comparative studies), left atrial appendage (LAA) occlusion (11 articles, 5 comparative, 1 randomised controlled trial [RCT]), and aortic disease (10 articles). All authors described 3DPSP as helpful in assessing complex anatomic conditions, whereas poor tissue mimicry and the non-consideration of physiological properties were cited as limitations. Compared to controls, meta-analysis of six studies showed a significant reduction of intervention time in LAA occlusion (n=3 studies), and surgery due to CHD (n=3) if 3DPSPs were used (Cohen's d=0.54; 95% confidence interval, 0.13 to 0.95; p=0.001), however heterogeneity across studies should be taken into account.

CONCLUSIONS

3DPSP are helpful to plan, train, and guide interventions in patients with complex cardiovascular anatomy. Benefits for patients include reduced intervention time with the potential for lower radiation exposure and shorter mechanical ventilation times. More evidence and RCTs including clinical endpoints are needed to warrant adoption of 3DPSP into routine clinical practice.

Personalized Health Care Technology in Managing Postoperative Gastrointestinal Surgery Complications: Proof of Concept Study

Background: Advances in three-dimensional (3D) printing technology have allowed the development of customized medical devices. Endoscopic internal drainage (EID) is a novel method to facilitate drainage of an abscess cavity into the lumen of the gastrointestinal tract by placing a double pigtail biliary stent through the fistula opening, originally designed for biliary drainage. They are available in manufacture-determined sizes and shapes. The aim of this study is to explore the feasibility of 3D printing personalized internal drainage stents for the treatment of leaks following gastrointestinal surgery over a sequential period. Methods: We retrospectively identified patients who underwent gastrointestinal anastomotic surgery complicated by postoperative leaks and underwent serial EID for treatment. Computerized Tomography scans were reviewed over a period of time, abscess cavity dimensions and characterizations were evaluated, and 3D reconstructions were obtained. The stents were designed, their shape and size were customized to the unique dimensions of the abscess and lumen of the patient. Stereolithography (SLA) 3D printing technique was used to produce the stents. Results: A total of 8 stents were produced, representing 3 patients. These stents corresponded to 2 or 3 stents per patients. Each patient underwent several endoscopic treatments, before resolution of leak. Conclusions: Customized stents may improve drainage of intra-abdominal abscesses after gastrointestinal surgery, if based on unique anatomy. This proof-of-concept study is a real-world application of personalized health care, which introduces the novel description of customizable 3D printed stents to manage complications following gastrointestinal surgery and may advance therapy for this complex clinical condition. Research Ethics Committees (REC) number is A-2021-012.

Systematic Review and Meta-analysis of Physician Modified Endografts for Treatment of Thoraco-Abdominal and Complex Abdominal Aortic Aneurysms

OBJECTIVE

Perform a systematic review and meta-analysis of the outcomes of physician modified endografts (PMEG) for treatment of thoraco-abdominal (TAAA) and complex abdominal aortic aneurysm (C-AAA) repair.

METHODS

We searched MEDLINE, CENTRAL, Web of Science Core Collection, Scielo and Open Grey databases from inception to July 2021 for studies reporting on outcomes of PMEGs for TAAA or C-AAA repair. A systematic review was conducted (protocol CRD42021267856) and data were pooled using a random-effects model of proportions. The outcomes analyzed were major adverse events at 30-days [30-day mortality, myocardial infarction, respiratory failure requiring prolonged ventilation (>24h or re-intubation), renal failure requiring dialysis, bowel ischemia requiring surgery, major stroke or definitive paraplegia]; technical success; 30-day mortality; ruptures; spinal cord ischemia; endoleaks; re-interventions and target vessel patency.

RESULTS

Twenty studies were included. Overall study quality assessment was found to be low. Overall, 909 PMEGs were reported and analyzed. Regarding aneurysm location (n=867), 222 patients had extent I-III TAAAs and 645 had C-AAA or extent IV TAAA. Regarding presentation, 14 studies reported if the patients were treated in an elective or urgent setting (n=782 patients). Overall, 500 (63.9%) patients were treated in an elective setting and 282(36.1%) in an urgent setting. Major adverse events (at thirty-days) occurred in 15.5% of patients (95%CI:10.8;20.8;I²=63%,135/832cases), being 11.6%(95%CI:8.1;15.7;I²=0%,23/280 cases) for elective patients and 24.6% for urgent (95%CI:14.1;36.6;I²=65%,50/192cases). Overall technical success was 97.2%(95%CI:95.4;98.7;I²=0%,587/611cases), being 98.0%(95%CI:92.1;100;I²=0%,106/113cases) for extent I-III TAAAs and 99.4%(95%CI:97.5;100;I²=0%,317/324cases) for C-AAA and extent IV TAAAs. Regarding technique, technical success was 96.1% for FEVAR (95%CI:93.2;98.4;I²=0%,313/329cases) and 99.8% for F/B-EVAR (95%CI:99.8;100;I²=0%,17/18 cases).

CONCLUSION

Physician modified fenestrated or branched grafts for endovascular aortic repair seems feasible and safe in the short-term follow-up. However, the quality of the available data is low which highlights the need for better and more accurate data regarding this technique.

Initial Experience with Fenestrated Physician-Modified Stent Grafts Using 3D Aortic Templates

The goal of this study was to describe the surgical results of physician-modified endografts (PMEG) utilizing a 3D aortic template in a center with no prior experience in complex endovascular aortic repairs. Forty-three patients underwent physician-modified graft stent implantation using a 3D aortic model. The inclusion criteria were juxtarenal and suprarenal aortic aneurysms, type IV thoracoabdominal aneurysms, and type IA endoleak after endovascular aortic repair. In asymptomatic patients, the diameter threshold for aneurysm repair was 5.5 cm in males and 5.0 cm in females. 3D aortic templates were prepared from the patient’s computed tomography angiography scans and sterilized before use in the operating suite. Forty-three stent grafts were modified with the use of a 3D printing template. A total of 162 reinforced fenestrations (37 celiac, 43 right renal, 39 left renal, 43 superior mesenteric) with a mean of 3.8 per patient were performed. All PMEGs had a posterior reducing-diameter tie and a preloaded guidewire. The mean modification time was 86 ± 12 min. The mean follow-up was 14 ± 12 months. The 30-day mortality was 12%. During the follow-up period, the patency rate was 95% per the superior mesenteric artery, 93% per right renal artery, 95% per left renal artery, and 89% per celiac trunk. Twelve (28%) patients had endoleak, of which type I or III was present in 5 (12%) patients, and type II in 7 (16%). 3D printing can be successfully integrated into the physician’s everyday practice of stent graft modification. However, the use of this approach in centers without experience performing complex aortic procedures results in worse surgical metrics than those previously reported.

Translating Imaging Into 3D Printed Cardiovascular Phantoms

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3D printed patient specific phantoms can visualize complex cardiovascular anatomy

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Common imaging modalities for 3D printing are CCT and CMR

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Material jetting/PolyJet and stereolithography are widely used printing techniques

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Standardized validation is warranted to compare different 3D printing technologies

Translation of imaging into 3-dimensional (3D) printed patient-specific phantoms (3DPSPs) can help visualize complex cardiovascular anatomy and enable tailoring of therapy. The aim of this paper is to review the entire process of phantom production, including imaging, materials, 3D printing technologies, and the validation of 3DPSPs. A systematic review of published research was conducted using Embase and MEDLINE, including studies that investigated 3DPSPs in cardiovascular medicine. Among 2,534 screened papers, 212 fulfilled inclusion criteria and described 3DPSPs as a valuable adjunct for planning and guiding interventions (n = 108 [51%]), simulation of physiological or pathological conditions (n = 19 [9%]), teaching of health care professionals (n = 23 [11%]), patient education (n = 3 [1.4%]), outcome prediction (n = 6 [2.8%]), or other purposes (n = 53 [25%]). The most common imaging modalities to enable 3D printing were cardiac computed tomography (n = 131 [61.8%]) and cardiac magnetic resonance (n = 26 [12.3%]). The printing process was conducted mostly by material jetting (n = 54 [25.5%]) or stereolithography (n = 43 [20.3%]). The 10 largest studies that evaluated the geometric accuracy of 3DPSPs described a mean bias <±1 mm; however, the validation process was very heterogeneous among the studies. Three-dimensional printed patient-specific phantoms are highly accurate, used for teaching, and applied to guide cardiovascular therapy. Systematic comparison of imaging and printing modalities following a standardized validation process is warranted to allow conclusions on the optimal production process of 3DPSPs in the field of cardiovascular medicine.

Effects of Sterilization Methods on Different 3D Printable Materials for Templates of Physician-Modified Aortic Stent Grafts Used in Vascular Surgery-A Preliminary Study

Three-dimensionally-printed aortic templates are increasingly being used to aid in the modification of stent grafts in the treatment of urgent, complex aortic disorders, often of an emergency nature. The direct contact between the aortic template and the stent graft implies the necessity of complete sterility. Currently, the efficacy of sterilizing aortic templates and the effect of sterilization on the geometry of tubular aortic models are unknown. A complex case of aortic arch dissection was selected to prepare a 3D-printed aortic arch template, which was then manufactured in six popular printing materials: polylactic acid (PLA), nylon, polypropylene (PP), polyethylene terephthalate glycol (PETG), and a rigid and flexible photopolymer resin using fused deposition modeling (FDM) and stereolithography (SLA). The 3D models were contaminated with Geobacillus stearothermophilus broth and Bacillus atrophaeus. The sterilization was performed using three different methods: heat (105 °C and 121 °C), hydrogen peroxide plasma, and ethylene oxide gas. Before and after sterilization, the aortic templates were scanned using computed tomography to detect any changes in their morphology by comparing the dimensions. All sterilization methods were effective in the elimination of microorganisms. Steam sterilization in an autoclave at 121 °C caused significant deformation of the aortic templates made of PLA, PETG, and PP. The other materials had stable geometries, and changes during mesh comparisons were found to be submillimeter. Similarly, plasma, gas, and heat at 105 °C did not change the shapes of aortic templates observed macroscopically and using mesh analysis. All mean geometry differences were smaller than 0.5 mm. All sterilization protocols tested in our study were equally effective in destroying microorganisms; however, differences occurred in the ability to induce 3D object deformation. Sterilization at high temperatures deformed aortic templates composed of PLA, PETG, and PP. This method was suitable for nylon, flexible, and rigid resin-based models. Importantly, plasma and gas sterilization were appropriate for all tested printing materials, including PLA, PETG, PP, nylon, flexible and rigid resins. Moreover, sterilization of all the printed models using our novel protocol for steam autoclaving at 105 °C was also 100% effective, which could represent a significant advantage for health centers, which can therefore use one of the most popular and cheap methods of medical equipment disinfection for the sterilization of 3D models as well.

Development of an automatic modeling method for patient-specific aortic graft reconstruction guide in thoracoabdominal aortic repair

BACKGROUND AND OBJECTIVES

Because repairing visceral and segmental arteries in open surgical repair for thoracoabdominal aortic aneurysms is essential, two types of patient-specific graft reconstruction guides for reconstruction in the operating room have been developed that are applied clinically. However, designing the patient-specific guides is a time-consuming, laborious task. The aim of this study was to develop an automatic modeling method and to evaluate its accuracy.

METHODS

In 10 patients with thoracoabdominal aortic aneurysms, computer-aided designing was performed with conventional and automatic modeling methods for aortic reconstruction guides as follows: 1) a visualizing guide that presented the accurate shape of the aortic graft, visualizing the main aortic body and major blood vessels; and 2) a marking guide wherein the vessels in the visualizing guide were replaced by the protruding marking regions detectable by tactile sense. The script-based automatic guide modeling program was developed using an application programming interface presented in the 3-matic software with Python. For accuracy, the absolute mean differences of both modeling methods were assessed using Hausdorff distance. The modeling between conventional and automatic modeling methods was compared and evaluated using the Wilcoxon signed-rank test.

RESULTS

The absolute mean difference between the conventional and automatic modeling methods were 6.05 ± 4.86 µm for the visualizing guide and 5.51 ± 4.85 µm for the marking guide. For the visualizing guide, the modeling time of the automatic modeling method was reduced by approximately more than thirtyfold than the conventional modeling method (p<0.001). The marking guide was reduced about fortyfold (p<0.001).

CONCLUSIONS

Compared to the conventional method, the automatic modeling method was demonstrated to reduce the modeling time with reasonable accuracy, which could lead to a more efficient modeling and clinical application.

The accuracy and reliability of 3D printed aortic templates: a comprehensive three-dimensional analysis

Background

Advances in 3D printing technology allow us to continually find new medical applications. One of them is 3D printing of aortic templates to guide vascular surgeons or interventional radiologists to create fenestrations in the stent-graft surface for the implantation procedure called fenestrated endovascular aortic aneurysm repair. It is believed that the use of 3D printing significantly improves the quality of modified fenestrated stent-grafts. However, the accuracy and reliability of personalized 3D printed models of aortic templates are not well established.

Methods

Thirteen 3D printed templates of the visceral aorta and sixteen of the aortic arch and their corresponding computer tomography of angiography images were included in this accuracy study. The 3D models were scanned in the same conditions on computed tomography (CT) and evaluated by three physicians experienced in vascular CT assessment. Model and patient CT measurements were performed at key landmarks to maintain quality for stent-graft modification, including side branches and aortic diameters. CT-scanned aortic templates were segmented, aligned with sourced patient data, and evaluated for the Hausdorff matrix. Next, Bland-Altman plots determined the degree of agreement.

Results

The Intraclass Correlation Coefficients values were more than 0.9 for all measurements of aortic diameters and aortic branches diameter in all landmark locations. Therefore, the reliability of the aortic templates was considered excellent. The Bland-Altman plots analysis indicated measurement biases of 0.05 to 0.47 for aortic arch templates and 0.06 to 0.38 for reno-visceral aortic templates. The arithmetic mean of Hausdorff's mean distances of the aortic arch templates was 0.47 mm (SD =0.06) and ranged from 0.34 to 0.58. The mean metrics for abdominal models was 0.24 mm (SD =0.03) and ranged from 0.21 to 0.31.

Conclusions

The printed models of 3D aortic templates are accurate and reliable, thus can be widely used in endovascular surgery and interventional radiology departments as aortic templates to guide the physician-modified fenestrated stent-graft fabrication.

Three-dimensional printed personalized drug devices with anatomical fit: a review

OBJECTIVES

Three-dimensional printing (3DP) has opened the era of drug personalization, promising to revolutionize the pharmaceutical field with improvements in efficacy, safety and compliance of the treatments. As a result of these investigations, a vast therapeutic field has opened for 3DP-loaded drug devices with an anatomical fit. Along these lines, innovative dosage forms, unimaginable until recently, can be obtained. This review explores 3DP-engineered drug devices described in recent research articles, as well as in patented inventions, and even devices already produced by 3DP with drug-loading potential.

KEY FINDINGS

3D drug-loaded stents, implants and prostheses are reviewed, along with devices produced to fit hard-to-attach body parts such as nasal masks, vaginal rings or mouthguards. The most promising 3DP techniques for such devices and the complementary technologies surrounding these inventions are also discussed, particularly the scanners useful for mapping body parts. Health regulatory concerns regarding the new use of such technology are also analysed.

SUMMARY

The scenario discussed in this review shows that for wearable 3DP drug devices to become a tangible reality to users, it will be necessary to overcome the existing regulatory barriers, create new interfaces with electronic systems and improve the mapping mechanisms of body surfaces.

Investigation of Three-dimensional Printing Materials for Printing Aorta Model Replicating Type B Aortic Dissection

AIM

This study aims to determine a printing material that has both elastic property and radiology equivalence close to the real aorta for simulation of endovascular stent-graft repair of aortic dissection.

BACKGROUND

With the rapid development of Three-Dimensional (3D) printing technology, a patient- specific 3D printed model is able to help surgeons to make a better treatment plan for Type B aortic dissection patients. However, the radiological properties of most 3D printing materials have not been well characterized. This study aims to investigate the appropriate materials for printing human aorta with mechanical and radiological properties similar to the real aortic Computed Tomography (CT) attenuation.

OBJECTIVE

Quantitative assessment of CT attenuation of different materials used in 3D printed models of aortic dissection for developing patient-specific 3D printed aorta models to simulate type B aortic dissection.

METHODS

A 25-mm length of aorta model was segmented from a patient's image dataset with a diagnosis of type B aortic dissection. Four different elastic commercial 3D printing materials, namely Agilus A40 and A50, Visijet CE-NT A30 and A70 were selected and printed with different hardness. Totally four models were printed out and CT scanned twice on a 192-slice CT scanner using the standard aortic CT angiography protocol, with and without contrast inside the lumen. Five reference points with the Region Of Interest (ROI) of 1.77 mm2 were selected at the aortic wall, and intimal flap and their Hounsfield units (HU) were measured and compared with the CT attenuation of original CT images. The comparison between the patient's aorta and models was performed through a paired-sample t-test to determine if there is any significant difference.

RESULTS

The mean CT attenuation of the aortic wall of the original CT images was 80.7 HU. Analysis of images without using contrast medium showed that the material of Agilus A50 produced the mean CT attenuation of 82.6 HU, which is similar to that of original CT images. The CT attenuation measured at images acquired with the other three materials was significantly lower than that of the original images (p<0.05). After adding contrast medium, Visijet CE-NT A30 had an average CT attenuation of 90.6 HU, which is close to that of the original images without a statistically significant difference (p>0.05). In contrast, the CT attenuation measured at images acquired with other three materials (Agilus A40, A50 and Visiject CE-NT A70) was 129 HU, 135 HU and 129.6 HU, respectively, which is significantly higher than that of original CT images (p<0.05).

CONCLUSION

Both Visijet CE-NT and Agilus have tensile strength and elongation close to actual patient's tissue properties producing similar CT attenuation. Visijet CE-NT A30 is considered the appropriate material for printing aorta to simulate contrast-enhanced CT imaging of type B aortic dissection. Due to the lack of body phantoms in the experiments, further research with the simulation of realistic anatomical body environment should be conducted.

Three-dimensional virtual and printed models for planning adult cardiovascular surgery

BACKGROUND

The objective of this study was to explore the usefulness of virtual models and three-dimensional (3D) printing technologies for planning complex non-congenital cardiovascular surgery.

METHODS

Between July 2018 and December 2019, adult patients with different cardiovascular structural diseases were included in a clinical protocol to explore the usefulness of Standard Tessellation Language (STL)-based virtual models and 3D printing for prospectively planning surgery. A qualitative descriptive analysis from the surgeon's viewpoint was done based on the characteristics, advantages and usefulness of 3D models for guiding, planning and simulating the surgical procedures.

RESULTS

A total of 14 custom 3D-printed heart and great vessel replicas with their corresponding 3D virtual models were created for preoperative surgical planning. Six of 14 models helped to redefine the surgical approach, 3 were useful to verify device delivery, while the rest did not change the surgical decision. In all open surgery cases, cardiac and vascular anatomy accuracy of virtual and physical 3D replicas was validated by direct visualisation of the organs during surgery. Printing was achieved through an external provider associated with the Hospital, who printed the final prototype in 5-7 days. Printed production cost was between 100 and 500 USD per model.

CONCLUSIONS

In the current study, the selected 3D printed models presented different advantages (visual, tactile, and instrumental) over the traditional flat anatomical images when simulating and planning some complex types of surgery. Notwithstanding 3D printing advantages, STL-based virtual models were pre-printing useful tools when instrumentation on a physical replica was not required.

Utility of 3D printed abdominal aortic aneurysm phantoms: a systematic review

BACKGROUND

3D printed (3DP) abdominal aortic aneurysm (AAA) phantoms are emerging in the literature as an adjunct for the visualization of complex anatomy, particularly for presurgical device selection and simulation. This is the first systematic review to provide a comprehensive overview of 3DP for endovascular aneurysm repair (EVAR) planning and intervention, evaluating the readiness of current levels of technology for mainstream implementation.

METHODS

A systematic literature search of PubMed and MEDLINE was performed as per PRISMA guidelines using the terms '3D Printing', 'AAA' OR 'EVAR' and related index terms, and further relevant articles were appraised via a snowballing approach. Our last search was conducted on 14 November 2020.

RESULTS

Twenty-five articles were identified for critical analysis, with 14 cases or technical reports. Nineteen publications utilized 3DP AAA phantoms to aid presurgical decision making, device selection and design. Four publications explored the utility of 3DP phantoms as EVAR trainers, and one publication examined the technology as a tool for patient education. Flexible, transparent phantoms were deemed most useful; however, the cost and availability of higher end machines limited accessibility.

CONCLUSION

3DP phantoms have been used in EVAR to facilitate visualization of complex patient anatomy, appropriate device selection, in predicting navigational difficulties and the shape and position of endograft after deployment. These phantoms show promise in reducing known complications such as endoleak, stent graft occlusion and migration; however, larger scale prospective studies are required to validate its impacts on patient outcomes and cost savings to the healthcare system.

Clinical Applications of Patient-Specific 3D Printed Models in Cardiovascular Disease: Current Status and Future Directions

Three-dimensional (3D) printing has been increasingly used in medicine with applications in many different fields ranging from orthopaedics and tumours to cardiovascular disease. Realistic 3D models can be printed with different materials to replicate anatomical structures and pathologies with high accuracy. 3D printed models generated from medical imaging data acquired with computed tomography, magnetic resonance imaging or ultrasound augment the understanding of complex anatomy and pathology, assist preoperative planning and simulate surgical or interventional procedures to achieve precision medicine for improvement of treatment outcomes, train young or junior doctors to gain their confidence in patient management and provide medical education to medical students or healthcare professionals as an effective training tool. This article provides an overview of patient-specific 3D printed models with a focus on the applications in cardiovascular disease including: 3D printed models in congenital heart disease, coronary artery disease, pulmonary embolism, aortic aneurysm and aortic dissection, and aortic valvular disease. Clinical value of the patient-specific 3D printed models in these areas is presented based on the current literature, while limitations and future research in 3D printing including bioprinting of cardiovascular disease are highlighted.