Hong-Sik Na

Technical concepts for vascular electromagnetic navigated interventions: Aortic in situ fenestration and transjugular intrahepatic porto-systemic shunts

Abstract This work presents concepts for complex endovascular procedures using electromagnetic navigation technology (EMT). Navigation software interfacing a standard commercially available navigation system was developed, featuring registration, electromagnetic field distortion correction, breathing motion detection and gating, and state-of-the-art 3D imaging post processing. Protocols for endovascularly placed, in-situ fenestrated abdominal aortic stent grafts and an EMT guided transjugular intrahepatic portosystemic shunt (TIPSS) creation have been designed. A dedicated set of interventional devices was developed for each of the procedures: For aortic in-situ fenestration a combination of high-porosity stentgrafts, steerable catheters and electromagnetically navigated guidewires was used, for TIPSS a dual-navigated (sheath and stylet) TIPSS-device was designed and manufactured. The developed devices underwent phantom testing, in preparation for animal experiments to prove the feasibility of the approach. Once established, these systems could aid in performing these challenging interventional radiology procedures, exploiting the unique characteristics of electromagnetic navigation and solving multiple of the problems associated with these interventions being performed under X-ray fluoroscopy, such as lacking real-time 3D information or extensive exposure to ionizing radiation.

Surgical Treatment of Neonatal Mastitis by Periareolar Drainage

PURPOSE Neonatal mastitis is a rare but challenging problem that commonly appears within the first 8 weeks after birth. Abscess formation in an infants breast can lead to acute complications and longterm dysfunction. To our knowledge, no publication focuses on surgical techniques and postoperative care to avoid breast scarring in neonates. We herein present our surgical approach by periareolar drainage to avoid this long term complications. METHODS After reviewing the medical database of our hospital from 2002 to 2012, 11 cases (6 females and 5 males; 10 unilateral and 1 bilateral) of neonatal mastitis were found. Four cases required surgery, performed by periareolar drainage (n = 4, 4:11). Our data were compared with data obtained from a literature review using Medline and Cochrane databases. RESULTS In all our patients that underwent surgery, clinical symptoms were reduced directly after surgery. Our results were comparable with those reported in the literature, which included 163 patients (105 [64.42%] required surgery) from seven publications. Regarding our surgical technique, we have not observed any long-term complications during follow up examinations (range 12-116 months postoperative; mean, 77.36 months), which have been reported in the literature. CONCLUSIONS Even if the acute infection can be cured by parenteral antibiotics and surgical incision if necessary, the longterm problems of scarring after mastitis, especially from surgical incisions at the site of maximum swelling, can lead to severe functional and aesthetic problems. To avoid such scarring, we herein present our surgical approach to mastitis by periareolar drainage.

Software-assisted post-interventional assessment of radiofrequency ablation

Radiofrequency ablation (RFA) is becoming a standard procedure for minimally invasive tumor treatment in clinical practice. Due to its common technical procedure, low complication rate, and low cost, RFA has become an alternative to surgical resection in the liver. To evaluate the therapy success of RFA, thorough follow-up imaging is essential. Conventionally, shape, size, and position of tumor and coagulation are visually compared in a side-by-side manner using pre- and post-interventional images. To objectify the verification of the treatment success, a novel software assistant allowing for fast and accurate comparison of tumor and coagulation is proposed. In this work, the clinical value of the proposed assessment software is evaluated. In a retrospective clinical study, 39 cases of hepatic tumor ablation are evaluated using the prototype software and conventional image comparison by four radiologists with different levels of experience. The cases are randomized and evaluated in two sessions to avoid any recall-bias. Self-confidence of correct diagnosis (local recurrence vs. no local recurrence) on a six-point scale is given for each case by the radiologists. Sensitivity, specificity, positive and negative predictive values as well as receiver operating curves are calculated for both methods. It is shown that the software-assisted method allows physicians to correctly identify local tumor recurrence with a higher percentage than the conventional method (sensitivity: 0.6 vs. 0.35), whereas the percentage of correctly identified successful ablations is slightly reduced (specificity: 0.83 vs. 0.89).

In.nrw Hyther: Electromagnetically navigated in situ fenestration of aortic stent grafts

The endovascular repair of aortic aneurysms overlapping regions with side branches (e.g. renal arteries) is a remaining challenge, as sufficient fixation of the stent graft with preservation of the blood flow to abdominal organs is hindered considerably, frequently necessitating open surgery or complex debranching operations followed by graft implantation. In this abstract we present a concept and phantom study for in-situ fenestration of aortic stent grafts using an electromagnetically guided catheter/guidewire system to allow for endovascular repair of large AAA.

The quantity of bone cement influences the anchorage of augmented pedicle screws in the osteoporotic spine: A biomechanical human cadaveric study

Background:: The aim of this comparative biomechanical human cadaveric study was to investigate the anchorage of augmented screws with two different volumes of bone cement. For this purpose the effect of cranio‐caudal loadings on pedicle screws was evaluated and axial pullout tests were performed. Methods:: A total of 50 pedicle screws (25 augmented/25 non‐augmented) were instrumented into osteoporotic vertebra of fresh human cadavers. The augmented screws were grounded by two different volumes of bone cement (1.5cm3 vs 4cm3). Biomechanical performance was assessed by performing a cyclic loading protocol (frequency: 3 Hz, load range: 20–200 N, number of cycles: 100,000), followed by axial pullout (13 augmented/11 non‐augmented) or by either directly measuring axial pullout strength (12 augmented/12 non‐augmented). Findings:: The median T‐score of the specimens was − 4.25 (range: − 6.38 to − 2.4). Pullout tests with and without cyclic preloading showed significantly increased pullout strength in augmented screws (Fmax: augmented: 1159 N (SD 395 N); non‐augmented: 532 N (SD 297 N); p < 0.05). No significant difference in the pullout strength was found concerning the quantity of cement (Fmax (direct pullout): 4.0 cm3: 1463 N (SD 307 N); 1.5 cm3: 1214 N (SD 236 N); p > 0.05). The pullout strength significantly decreased in high‐volume augmented screws after cyclic loading (Fmax (4.0 cm3): direct pullout 1463 N (SD 307 N); cyclic preload: 902 N (SD 435 N); p < 0.05). Interpretation:: Biomechanical advantages of augmented pedicle screws can also be found after cyclic preload. However, our results indicate that the anchoring stability of high‐volume augmented pedicle screws after cyclic loading is disadvantageous compared to moderate augmented screws; thus high‐volume augmentation should be avoided.

Electromagnetic Real Time Navigation in the Region of the Posterior Pelvic Ring: An Experimental In-Vitro Feasibility Study and Comparison of Image Guided Techniques.

Background Electromagnetic tracking is a relatively new technique that allows real time navigation in the absence of radiation. The aim of this study was to prove the feasibility of this technique for the treatment of posterior pelvic ring fractures and to compare the results with established image guided procedures. Methods Tests were performed in pelvic specimens (Sawbones®) with standardized sacral fractures (Type Denis I or II). A gel matrix simulated the operative approach and a cover was used to disable visual control. The electromagnetic setup was performed by using a custom made carbon reference plate and a prototype stainless steel K-wire with an integrated sensor coil. Four different test series were performed: Group OCT: Optical navigation using preoperative CT-scans; group O3D: Optical navigation using intraoperative 3-D-fluoroscopy; group Fluoro: Conventional 2-D-fluoroscopy; group EMT: Electromagnetic navigation combined with a preoperative Dyna-CT. Accuracy of screw placement was analyzed by standardized postoperative CT-scan for each specimen. Operation time and intraoperative radiation exposure for the surgeon was documented. All data was analyzed using SPSS (Version 20, 76 Chicago, IL, USA). Statistical significance was defined as p< 0.05. Results 160 iliosacral screws were placed (40 per group). EMT resulted in a significantly higher incidence of optimal screw placement (EMT: 36/40) compared to the groups Fluoro (30/40; p< 0.05) and OCT (31/40; p< 0.05). Results between EMT and O3D were comparable (O3D: 37/40; n.s.). Also, the operation time was comparable between groups EMT and O3D (EMT 7.62 min vs. O3D 7.98 min; n.s.), while the surgical time was significantly shorter compared to the Fluoro group (10.69 min; p< 0.001) and the OCT group (13.3 min; p< 0.001). Conclusion Electromagnetic guided iliosacral screw placement is a feasible procedure. In our experimental setup, this method was associated with improved accuracy of screw placement and shorter operation time when compared with the conventional fluoroscopy guided technique and compared to the optical navigation using preoperative CT-scans. Further studies are necessary to rule out drawbacks of this technique regarding ferromagnetic objects.

Endovascular placement of an extraluminal arterial bypass graft - in vitro feasibility study

Abstract Purpose: A novel approach for arterial bypass grafting using exclusively endovascular techniques was established in-vitro in a phantom model. Material and methods: The experimental setting consisted of a gel-wax phantom with two embedded parallel fluid-filled silicon tubes simulating the superficial femoral vessels. Through an 8-French sheath, a re-entry catheter (OUTBACK®, Cordis) was placed in the simulated artery and used to puncture the vascular wall. Then a 0.014-inch guide wire was advanced into the extravascular space. With the curved needle of the re-entry catheter, the guide wire was steered on a course parallel to the vessel wall in the extravascular space for 5-10 cm. At the desired reentry site, the re-entry catheter was used to puncture the vascular wall again in order to regain access to the endovascular space. Once the tip of the guide wire had safely been placed in the vascular lumen, a self-expandable stent graft (VIABAHN® GORE®) was deployed to complete the extraluminal bypass. Results: Endovascular placement of an extraluminal bypass was successfully achieved in 20 attempts. The mean duration of the procedure amounted to 14:58 (minutes: seconds) (SD ± 3:56). Conclusions: This in-vitro study suggests that endovascular placement of an extraluminal arterial bypass graft is technically feasible.