Padraig Cantillon-Murphy

Smart Self-Assembling MagnetS for ENdoscopy (SAMSEN) for transoral endoscopic creation of immediate gastrojejunostomy (with video)

BACKGROUND Gastrojejunostomy is important for palliation of malignant gastric outlet obstruction and surgical obesity procedures. A less-invasive endoscopic technique for gastrojejunostomy creation is conceptually attractive. Our group has developed a compression anastomosis technology based on endoscopically delivered self-assembling magnets for endoscopy (SAMSEN) to create an instant, large-caliber gastrojejunostomy. OBJECTIVE To develop and evaluate an endoscopic means of gastrojejunostomy creation by using SAMSEN. SETTING Developmental laboratory and animal facility. DESIGN Animal study and human cadaveric study. SUBJECTS Yorkshire pigs (7 cadaver, 5 acute); human (1 cadaver). INTERVENTIONS A transoral procedure for SAMSEN delivery was developed in porcine and human cadaver models. Subsequently, gastrojejunostomy creation by using SAMSEN was performed in 5 acute pigs. The endoscope was advanced into the peritoneal cavity through the gastrotomy, and a segment of the small bowel was grasped and pulled closer to the stomach. An enterotomy was created, and a custom overtube was advanced into the small bowel for deployment of the first magnetic assembly. Next, a reciprocal magnetic assembly was deployed in the stomach. The 2 magnetic systems were mated under fluoroscopic and endoscopic guidance. Contrast studies assessed for gastrojejunostomy leak. Immediate necropsies were performed. MAIN OUTCOME MEASUREMENTS Technical feasibility and complications. RESULTS Gastrojejunostomy creation by using SAMSEN was successful in all 5 animals. Deep enteroscopy was performed through the stoma without difficulty. No leaks were identified on contrast evaluation. At necropsy, the magnets were properly deployed and robustly coupled together, resistant to vigorous tissue manipulation. LIMITATIONS Acute animal study. CONCLUSIONS Endoscopic creation of immediate gastrojejunostomy by using SAMSEN is technically feasible.

An active ripple filtering technique for improving common-mode inductor performance

Active ripple filtering is the replacement of large passive components in power filter circuits with smaller passive components and active control circuitry. This letter focuses on common-mode filters, where a large common-mode inductor (choke) is replaced by two smaller chokes and active op-amp control. The technique is appropriate when improved attenuation is required at relatively low frequencies and the high-frequency filtering requirements are easily met. Smaller chokes save significantly in material and winding costs. The technique is more advantageous if wire-wound chokes can be replaced by planar printed circuit board chokes. The use of the technique in an automotive electromagnetic interference (EMI) filter application is explored in detail.

Catheter Position Tracking System Using Planar Magnetics and Closed Loop Current Control

This paper presents an electromagnetic system for five degrees of freedom position and orientation sensing with application in a virtual bronchoscopy system. Planar magnetic source coils were manufactured on printed circuit boards for reproducibility and low-cost manufacturing. The exact magnetic field of each coil is calculated using a filament-based approach. A constant ac current amplifier is used to drive each coil at an independent frequency and a synchronous demodulator calculates each associated magnetic field component using the current waveform as a reference signal. Commercially available search coil sensors are used and a comparison between shielded and unshielded probes is presented. Extensive testing with two separate methods has shown the accuracy of the system to be between 1 and 2 mm. The use of a novel closed loop coil driver has been found to offer excellent magnetic field stability and significant reduction in crosstalk interference.

Convergence and translation: attitudes to inter-professional learning and teaching of creative problem-solving among medical and engineering students and staff.

BackgroundHealthcare worldwide needs translation of basic ideas from engineering into the clinic. Consequently, there is increasing demand for graduates equipped with the knowledge and skills to apply interdisciplinary medicine/engineering approaches to the development of novel solutions for healthcare. The literature provides little guidance regarding barriers to, and facilitators of, effective interdisciplinary learning for engineering and medical students in a team-based project context.MethodsA quantitative survey was distributed to engineering and medical students and staff in two universities, one in Ireland and one in Belgium, to chart knowledge and practice in interdisciplinary learning and teaching, and of the teaching of innovation.ResultsWe report important differences for staff and students between the disciplines regarding attitudes towards, and perceptions of, the relevance of interdisciplinary learning opportunities, and the role of creativity and innovation. There was agreement across groups concerning preferred learning, instructional styles, and module content. Medical students showed greater resistance to the use of structured creativity tools and interdisciplinary teams.ConclusionsThe results of this international survey will help to define the optimal learning conditions under which undergraduate engineering and medicine students can learn to consider the diverse factors which determine the success or failure of a healthcare engineering solution.

Optimizing parameters of an open-source airway segmentation algorithm using different CT images

Background Computed tomography (CT) helps physicians locate and diagnose pathological conditions. In some conditions, having an airway segmentation method which facilitates reconstruction of the airway from chest CT images can help hugely in the assessment of lung diseases. Many efforts have been made to develop airway segmentation algorithms, but methods are usually not optimized to be reliable across different CT scan parameters.MethodsIn this paper, we present a simple and reliable semi-automatic algorithm which can segment tracheal and bronchial anatomy using the open-source 3D Slicer platform. The method is based on a region growing approach where trachea, right and left bronchi are cropped and segmented independently using three different thresholds. The algorithm and its parameters have been optimized to be efficient across different CT scan acquisition parameters. The performance of the proposed method has been evaluated on EXACT’09 cases and local clinical cases as well as on a breathing pig lung phantom using multiple scans and changing parameters. In particular, to investigate multiple scan parameters reconstruction kernel, radiation dose and slice thickness have been considered. Volume, branch count, branch length and leakage presence have been evaluated. A new method for leakage evaluation has been developed and correlation between segmentation metrics and CT acquisition parameters has been considered.ResultsAll the considered cases have been segmented successfully with good results in terms of leakage presence. Results on clinical data are comparable to other teams’ methods, as obtained by evaluation against the EXACT09 challenge, whereas results obtained from the phantom prove the reliability of the method across multiple CT platforms and acquisition parameters. As expected, slice thickness is the parameter affecting the results the most, whereas reconstruction kernel and radiation dose seem not to particularly affect airway segmentation.ConclusionThe system represents the first open-source airway segmentation platform. The quantitative evaluation approach presented represents the first repeatable system evaluation tool for like-for-like comparison between different airway segmentation platforms. Results suggest that the algorithm can be considered stable across multiple CT platforms and acquisition parameters and can be considered as a starting point for the development of a complete airway segmentation algorithm.

Navigational Bronchoscopy for Early Lung Cancer: A Road to Therapy

Peripheral lung nodules remain challenging for accurate localization and diagnosis. Once identified, there are many strategies for diagnosis with heterogeneous risk benefit analysis. Traditional strategies such as conventional bronchoscopy have poor performance in locating and acquiring the required tissue. Similarly, while computerized-assisted transthoracic needle biopsy is currently the favored diagnostic procedure, it is associated with complications such as pneumothorax and hemorrhage. Video-assisted thoracoscopic and open surgical biopsies are invasive, require general anesthesia and are therefore not a first-line approach. New techniques such as ultrathin bronchoscopy and image-based guidance technologies are evolving to improve the diagnosis of peripheral lung lesions. Virtual bronchoscopy and electromagnetic navigation systems are novel technologies based on assisted-computerized tomography images that guide the bronchoscopist toward the target peripheral lesion. This article provides a comprehensive review of these emerging technologies.

Planar Magnetic Shielding for Use With Electromagnetic Tracking Systems

This paper evaluates the use of planar magnetic shielding with electromagnetic (EM) tracking systems to prevent field distortion from ferromagnetic objects below a magnetic-field transmitter. A comparison of the shielding performance of MuMetal, ferrite, aluminum, and steel is presented over a frequency range of 1 Hz to 1 MHz. Both simulation and experimental results show the merits of each shield material. MuMetal and ferrite were found to give excellent shielding performance over a wide frequency range. The use of a ferrite and MuMetal shield is also demonstrated in a full 5 degree of freedom EM tracking system and is shown to successfully operate with position errors of 1.8 and 2.3 mm, respectively, in a volume of 25 cm × 25 cm × 25 cm. This is compared with a mean position error 67.3 mm without shielding. The orientation error for each shield was found to be 1.9° and 2.1° for the ferrite and MuMetal, respectively, in comparison with an error of 115.1° without shielding.

Magnetic Compression in Gastrointestinal and Bilioenteric Anastomosis How Much Force

Aim. The concept of compression alimentary anastomosis is well established. Recently, magnetic axial alignment pressures have been encompassed within such device constructs. We quantify the magnetic compression force and pressure required to successfully achieve gastrointestinal and bilioenteric anastomosis by in-depth interrogation of the reported literature. Methods. Reports of successful deployment and proof of anastomotic patency on survival were scrutinized to quantify the necessary dimensions and strengths of magnetic devices in (a) gastroenteral anastomosis in live porcine models and (b) bilioenteric anastomosis in the clinical setting. Using a calculatory tool developed for this work (magnetic force determination algorithm, MAGDA), ideal magnetic force and compression pressure were quantified from successful reports with regard to their variance by intermagnet separation. Results. Optimized ranges for both compression force and pressure were determined for successful porcine gastroenteral and clinical bilioenteric anastomoses. For gastroenteral anastomoses (porcine investigations), an optimized compression force between 2.55 and 3.57 kg at 2-mm intermagnet separation is recommended. The associated compression pressure should not exceed 60 N/cm2. Successful bilioenteric anastomoses is best clinically achieved with intermagnet compression of 18 to 31 g and associated pressures between 1 and 3.5 N/mm2 (at 2-mm intermagnet separation). Conclusion. The creation of magnetic compression anastomoses using permanent magnets demonstrates a remarkable resilience to variations in magnetic force and pressure exertion. However, inappropriate selection of compression characteristics and magnet dimensions may incur difficulties. Recommendations of this work and the availability of the free online tool (http://magda.ucc.ie/) may facilitate a factor of robustness in the design and refinement of future devices.

Magnetic pancreaticobiliary stents and retrieval system: obviating the need for repeat endoscopy (with video).

BACKGROUND Plastic stents are routinely placed in the pancreaticobiliary system to facilitate drainage. A second endoscopy is often required for stent removal. We have developed magnetic pancreaticobiliary stents that can be removed by using an external hand-held magnet, thereby obviating the need for a second endoscopy. OBJECTIVE To develop and test magnetic pancreaticobiliary stents and retrieval system in ex-vivo and in-vivo porcine models. SETTING Animal laboratory. DESIGN Benchtop and animal study. ANIMALS 5 pigs. INTERVENTIONS Design: Computer simulations determined both the optimal design of cylindrical magnets attached to the distal aspect of existing plastic stents and the optimal design of the external hand-held magnet. Benchtop ex-vivo experiments measured magnetic force to validate the design. In-vivo analysis: In 5 Yorkshire pigs, magnetic stents were deployed into the common bile duct by using a conventional duodenoscope. An external hand-held magnet was applied for stent removal. Stent insertion and removal times were recorded. MAIN OUTCOME MEASUREMENTS Technical feasibility. RESULTS Magnetic stents of varying lengths and calibers were successfully created. In ex-vivo testing, the capture distance was 10.0 cm. During in-vivo testing, the magnetic stents were inserted and removed easily. The mean insertion and removal times were 3.2 minutes and 33 seconds, respectively. LIMITATIONS Animal study, small numbers. CONCLUSIONS Magnetic pancreaticobiliary stents and associated retrieval system were successfully designed and tested in the acute porcine model. An external, noninvasive means of stent removal potentially obviates the need for a second endoscopy, which could represent a major gain both for patients and in health care savings.

Low Cost Super-Nyquist Asynchronous Demodulation for Use in EM Tracking Systems

We present a novel method for demodulating multiple frequency components of an ac magnetic field for use in electromagnetic tracking systems. Our undersampling method allows for a low sampling rate to acquire signals of interest in a range of 20-30 kHz without significant loss of precision. Lower sample rates give additional computation time between each sample, allowing for real-time demodulation without expensive high speed data acquisition and processing hardware. This also allows the use of low speed high precision analog-to-digital converters (ADCs) for sampling high frequency signals. The presented system demodulates 16 frequency components from two signals using an Arduino Due microcontroller and a two channel 16-bit ADC. The demodulated signals are then used to accurately determine the position of a magnetic sensor to within 1 mm in a volume 25 cm × 25 cm × 25 cm. The system accuracy compares well with both commercial and research systems in terms of accuracy, but at a dramatically lower cost.