Development and Evaluation of a Novel Curved Biopsy Device for CT-Guided Biopsy of Lesions Unreachable Using Standard Straight Needle Trajectories.

PURPOSE: To evaluate the feasibility of a novel curved CT-guided biopsy needle prototype with shape memory to access otherwise not accessible biopsy targets. METHODS AND MATERIALS: A biopsy needle curved by 90° with specific radius was designed. It was manufactured using nitinol to acquire shape memory, encased in a straight guiding trocar to be driven out for access of otherwise inaccessible targets. Fifty CT-guided punctures were conducted in a biopsy phantom and 10 CT-guided punctures in a swine corpse. Biposies from porcine liver and muscle tissue were separately gained using the biopsy device, and histological examination was performed subsequently. RESULTS: Mean time for placement of the trocar and deployment of the inner biopsy needle was ~205 ± 69 and ~93 ± 58 s, respectively, with a mean of ~4.5 ± 1.3 steps to reach adequate biopsy position. Mean distance from the tip of the needle to the target was ~0.7 ± 0.8 mm. CT-guided punctures in the swine corpse took relatively longer and required more biopsy steps (~574 ± 107 and ~380 ± 148 s, 8 ± 2.6 steps). Histology demonstrated appropriate tissue samples in nine out of ten cases (90%). CONCLUSIONS: Targets that were otherwise inaccessible via standard straight needle trajectories could be successfully reached with the curved biopsy needle prototype. Shape memory and preformed size with specific radius of the curved needle simplify the target accessibility with a low risk of injuring adjacent structures.

Preoperative Embolization of the Celiac Axis or Common Hepatic Artery before Distal Pancreatectomy with Resection of the Celiac Axis.

Patients with locally advanced pancreatic cancer who undergo distal pancreatectomy with resection of the celiac axis (CA) are at risk for postoperative hepatic or gastric ischemia if collateral blood flow from the superior mesenteric artery (SMA) via the gastroduodenal artery is insufficient. This study presents a technique for preoperative angiographic evaluation of these collateral vessels by using an AMPLATZER Vascular Plug to temporarily occlude the CA or common hepatic artery while simultaneously performing digital subtraction angiography of the SMA. If collateral vessels are deemed sufficient, the plug can subsequently be released for permanent occlusion with the intent to enhance the blood flow in these collateral vessels.

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

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.

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.

Bipolar radiofrequency ablation: development of a new expandable device.

PURPOSE: To test the performance of an expandable bipolar probe as a simple technical solution for extending the coagulation volume. METHODS: On the basis of a commercially available monopolar radiofrequency (RF) probe (LeVeen), an expandable bipolar RF probe was developed by integrating a second electrode into the probe shaft. The influence of length on the second electrode, and the distance between both electrodes and generator output was investigated by performing ten ablations for each condition on a freshly excised bovine liver. Macroscopically quantified coagulation volumes, lesion shape characteristics, and procedure durations were recorded. Results of the prototype featuring the optimal configuration were compared to the original LeVeen probe and commonly used bipolar RF probe (CelonLabPower). RESULTS: Extension of the shaft electrode length, increasing distance between the shaft electrode and the tip electrode, and reduction of generator output resulted in increasing coagulation volumes. The coagulation volumes the prototype generated were significantly smaller and more elliptically shaped than the monopolar probe (9.4 ± 1.5 cm(3) vs. 12.1 ± 1.6 cm(3)), but were larger than the commercially available bipolar RF probe (vs. 7.3 ± 0.5). The procedure duration of the prototype was comparable to the monopolar probe (467 ± 31 s vs. 464 ± 17 s) and shorter than the bipolar probe (vs. 2009 ± 444 s). In comparison to the commercially available bipolar system, the developed prototype exhibited favorable results. CONCLUSION: The first benchmark testing of the developed bipolar prototype had promising results. However, further optimization of the applicator design and ablation protocol is needed to enlarge the achievable coagulation volume.

A trucut biopsy needle for bipolar radiofrequency ablation of needle tract: a proof-of-concept experiment.

OBJECTIVE: To develop a trucut biopsy needle featuring two electrodes that allow for bipolar radiofrequency (RF) coagulation of the puncture tract. METHODS: We modified a 14-G trucut biopsy needle to contain two insulated electrodes and connected the device to an RF generator. Biopsies in ex vivo porcine liver and kidney were performed. The puncture tract was coagulated by using different RF energy settings (5 W, 10 W, 20 W). Tissue specimens were dissected along the puncture tract and the coagulation area was macroscopically evaluated. CT-guided in vivo liver and kidney biopsies were performed in two domestic pigs. Lengths of specimens were measured. Post-biopsy contrast-enhanced CT examinations were performed to rule out biopsy-related bleeding. Animals were euthanised and coagulation areas macroscopically explored. RESULTS: The mean diameters of the coagulated area around the ex vivo biopsy tract were 4.2 +/- 1.1 mm (5 W), 6.0 +/- 2.0 mm (10 W) and 5.2 +/- 0.51 mm (20 W) in liver and 5.0 +/- 0.7 mm (5 W), 6.6 +/- 0.9 (10 W) and 6.0 +/- 2.0 mm (20 W) in kidney. After biopsies CT revealed no bleeding. Mean maximum coagulation diameters were 10.1 +/- 4.6 mm (10 W) in liver and 6.0 +/- 2.5 mm (10 W) in kidney. Mean length of the specimens was 12.2 +/- 4.4 mm in kidney and 11.1 +/- 3.6 mm in liver tissue. CONCLUSION: Bipolar RF biopsy is a promising tool for tract coagulation after percutaneous biopsy.

Introduction of a dedicated circulation phantom for comprehensive in vitro analysis of intravascular contrast material application.

OBJECTIVES: To develop a circulation phantom with physiologic circulation parameters, including a pulmonary and a body circulation for the evaluation of intravascular contrast material (CM) application. MATERIALS AND METHODS: The circulation phantom consists of a low-pressure venous system into which CM is injected, a pulmonary circulation, and high-pressure body circulation with an anthropometric aorta and coronary arteries. The phantom is driven by a pulsatile Harvard heart pump. Venous and arterial pressure were set to physiologic values with heart rate (60 beats/min), stroke volume (60 mL), and ratio of diastole to systole (60/40) also were within physiologic limits. CM with different iodine concentrations (300, 370, and 400 mg iodine/mL) were injected at a flow rate of 4 mL/s (iodine delivery rate: 1.2 g, 1.48 g, and 1.6 g iodine/s, respectively; total iodine load for all protocols: 36 g). Serial computed tomography scans at the level of the pulmonary artery, the ascending and the descending aorta replica were obtained. Dynamic pressure in the phantom and true injection system parameters (flow rate, injection pressure, and CM volume) was continuously monitored. Time-enhancement curves were calculated, and pulmonary and aortic peak time and enhancement were determined. Results were compared using nonparametric unpaired Wilcoxon tests. RESULTS: The pressure in the phantom showed physiologic values for the low (mean pressure: 15 mm Hg) and high pressure part (125/75 mm Hg). Programmed injection values (flow rate, pressure, and volume) were reached for all injections. Using CM with 400 mg iodine/mL, the shortest pulmonary and aortic peak times and the highest pulmonary and aortic peak enhancement values were obtained compared with CM with 300 and 370 mg iodine/mL. CONCLUSIONS: We developed a flow phantom with physiologic circulation parameters for measurement of contrast enhancement. The phantom is suitable for further evaluation of CM injection protocols for pulmonary and aortic enhancement.

A newly developed perfused umbrella electrode for radiofrequency ablation: an ex vivo evaluation study in bovine liver.

The purpose of this study was to evaluate the effectiveness of a newly developed perfused monopolar radiofrequency (RF) probe with an umbrella-shaped array. A perfused umbrella-shaped monopolar RF probe based on a LeVeen electrode (Boston Scientific Corp., Natick, MA, USA) with a 3-cm array diameter was developed. Five different configurations of this electrode were tested: (a) perfusion channel/endhole, (b) perfusion channel/endhole + sideholes, (c) 1 cm insulation removed at the tip, (d) 1 cm insulation removed at the tip + perfusion channel/endhole, and (e) 1 cm insulation removed at the tip + perfusion channel/endhole + sideholes. An unmodified LeVeen electrode served as a reference standard. RF ablations were performed in freshly excised bovine liver using a commercial monopolar RF system with a 200-W generator (RF 3000; Boston Scientific Corp.). Each electrode was tested 10 times applying the vendor's recommended ablation protocol combined with the preinjection of 2 ml 0.9% saline. Volumes and shapes of the lesions were compared. Lesions generated with the original LeVeen electrode showed a mean volume of 12.74 +/- 0.52 cm(3). Removing parts of the insulation led to larger coagulation volumes (22.65 +/- 2.12 cm(3)). Depending on the configuration, saline preinjection resulted in a further increase in coagulation volume (25.22 +/- 3.37 to 31.28 +/- 2.32 cm(3)). Besides lesion volume, the shape of the ablation zone was influenced by the configuration of the electrode used. We conclude that saline preinjection in combination with increasing the active tip length of the umbrella-shaped LeVeen RF probe allows the reliable ablation of larger volumes in comparison to the originally configured electrode.

In vitro evaluation of optionally retrievable and permanent IVC filters.

PURPOSE: To systematically evaluate different optionally retrievable and permanent inferior vena cava (IVC)-filters with respect to their capture rates. MATERIAL AND METHODS: Seven optionally retrievable and permanent IVC filters were tested in an in vitro flow model with a tube size of 22 mm in horizontal and vertical positions. To analyze the capture efficiency the IVC filters were implanted in concentric and eccentric positions and subsequently exposed to single and multiple blood clots of different sizes (3x5, 3x10, 5x10, 5x20, 7x20, 10x24 mm). Capture rates and pressure changes were measured and compared between the different IVC filters. RESULTS: There were significant differences between the tested IVC filters. In general, the capture rate improved with increasing clot size (P<0.0001). In the single-clot exposure the highest mean capture rate was achieved with the Celect filter (90.4%+/-15.7%), whereas the Günther Tulip filter achieved best results in the multi-clot exposure (76.7%+/-12.5%). Capture rates differed significantly between the various IVC filters (single-clot: P<0.0001; multi-clot: P=0.0016). The position (horizontal or vertical) did not show a significant influence, whereas capture rates significantly decreased in the multi-clot test with eccentric filter positions (P=0.0299). In this study optionally retrievable IVC filters were more efficient than the tested permanent IVC filters (single-clot: P<0.0001; multi-clot: P=0.0002). CONCLUSIONS: Optionally retrievable IVC filters are efficient. Clot size, IVC filter type, and position significantly influence capture rate. Deliberate selection of the most efficient IVC filter and concentric positioning are important to ensure optimal results.

Evaluation of a newly developed percutaneous thrombectomy basket device in sheep with central pulmonary embolisms.

OBJECTIVE: The authors studied the development of a thrombectomy device that is adequately steerable and quickly placeable in case of extensive pulmonary embolism. MATERIALS AND METHODS: The device consists of a self-expandable nitinol basket mounted at a catheter-tip, which allows suction and extraction of thrombus material. Five in vitro tests were performed followed by tests in 6 sheep. In vivo thrombus material was introduced through a jugular vein to produce pulmonary embolism. After catheter insertion over the right femoral vein, the basket was placed adjacent to the pulmonary embolus and the extraction procedure was performed. RESULTS: In in vitro tests, the extracted thrombus amount varied between 60% and 95%. In animal experiments, the extracted amount varied between 30% and 95% as determined angiographically. Limiting factors were steerability and optimal positioning of the basket in relation to the embolus. CONCLUSIONS: Extraction of pulmonary embolism with the self-expanding suction basket is feasible. However, successful recanalization is limited by catheter maneuverability in the pulmonary arterial system.

Use of a nonmetallic guide wire for magnetic resonance-guided coronary artery catheterization.

RATIONALE AND OBJECTIVES: Metallic guide wires can be subject to substantial heating when used in the magnetic resonance (MR) environment. Therefore, animal experiments were performed to test the feasibility of a non-metallic and MR-safe guide wire with passive markers for catheterization of coronary arteries under MR guidance. MATERIALS AND METHODS: Self-made guide wires consisting of a resin-microparticle compound covered by polytetrafluoroethylene were used to catheterize both coronary arteries of swine together with a non-braided catheter. Time needed for catheterization was recorded. RESULTS: MR-guided coronary artery catheterization with passive visualization of a self-made non-metallic guide wire is possible. In average 141 seconds (SD 68) were needed to manipulate the guide wire together with a catheter from the carotid artery into the left or right coronary artery ostium. CONCLUSION: Standard nitinol guide wires have to be considered unsafe for MR-guided interventions due to possible heating of electrical conducting structures in the MR environment. Passive visualization techniques allow MR-guided catheterization of small arteries like coronaries. However, there is the substantial disadvantage of obscuring the underlying anatomy of small vessels by the passive markers needed for real-time MR guidance.

Gadolinium containing contrast agents for pulmonary ventilation magnetic resonance imaging: preliminary results.

RATIONALE AND OBJECTIVES: Five gadolinium containing contrast media (gadopentetate dimeglumine [Magnevist; Berlex Imaging, Montville, NJ, USA], gadobutrol [Gadovist; Schering, Järfälla, Sweden], gadoteridol [ProHance; Bracco-Byk Gulden, Konstanz, Germany], gadobenate dimeglumine [MultiHance; Bracco-Byk Gulden, Konstanz, Germany], and gadopentetate dimeglumine added with mannitol and a surface active detergent) were evaluated for their efficacy in magnetic resonance depiction of lung ventilation. METHODS: All contrast agent aerosols were generated by a jet nebulizer. Twelve intubated domestic pigs were mechanically ventilated with the respective aerosolized contrast agent and studied on a 1.5 T MR imager. T1-weighted TSE images using respiratory gating were obtained before and after a 10-minute ventilation period. Pulmonary signal intensity (SI) and signal-to-noise (SNR) changes were measured for both lungs. RESULTS: Mean SI increases ranged between 13.5% and 45.8% (right lung) and 14% and 39.8% (left lung). SNR changes ranged from +14.7% to +46.8% and from +13.1% to +40.5% for the right and left lung, respectively. The highest SI and SNR increases were observed in the gadoteridol group. CONCLUSIONS: The use of gadolinium for MR ventilation imaging is primarily hindered by its viscosity properties and thus, its capability of aerosolization. Of the five agents tested, the medium with the lowest viscosity at room temperature (gadoteridol) showed the most promising enhancement results. The results reaffirm the potential of gadolinium-based contrast agents as a pulmonary imaging alternative. With a reduction of ventilation duration down to ten minutes, the method appears tolerable in a clinical setting.