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Neuroendoscopy is a surgical procedure that uses endoscopes or tube-like instruments to view the internal surface of the brain. A continuous (non-peristaltic) flow of saline is necessary to visualize and navigate throughout the surgical field. If not maintained, variable saline pressures may lead to flooding of the brain or visibility issues with the endoscope lens. Currently, this continuous flow of saline is created through a pressurized bag of saline; however, due to lengthy procedures, the saline bags must be replaced frequently causing disruptions during the surgery. Our client, Dr. Joshua Medow, would like to use a centrifugal pump to control the constant flow of saline. The pump that has been chosen was originally designed for cardiac surgery, having a saline flow of 5.0 L/min, much higher than the 150-mL/min flow required for the rinsing the brain. Dr. Medow would like us to design the circuitry for the centrifugal pump as to create a negative feedback system to control the saline flow when instruments are inserted and removed from the endoscope during the procedure and to reduce the overall flow rate to the appropriate level.
At present, we have decided to pursue a negative feedback circuit design employing a magnitude comparator and bipolar transistors to achieve feedback voltage to the biopump. To begin selection of the proper components, we have conducted preliminary testing of the system’s voltage relationships.
| Week | Reporting Period Beginning | Activities |
|---|---|---|
| 1 | September 5 | To begin, we established team roles, contacted our client and set a date for first meeting. We also began background research into neuroendoscopy and centrifugal pumps. |
| 2 | September 12 | This week, we met with our client and received project overview, scope, and expectations. Additionally, we continued individual research into the system with emphasis on negative feedback circuitry. |
| 3 | September 19 | We began the week with our first advisor meeting through which we established a timeline and expectations for the semester. Additionally, we conducted a team meeting to corroborate the information that we had gleaned from our client meeting to create a solid foundation from which to attack the project. |
| 4 | September 26 | We conducted another meeting with Dr. Medow and began preliminary characterization of the current pump system in his electronics lab. We also assembled the first draft of the Product Design Specification document and continued individual research. |
| 5 | October 3 | As we were able to gain further familiarity with the system last week, we began this week by brainstorming specific design solutions and then tested these concepts in the BME electronics lab. |
| 6 | October 10 | This week, we prepared our midsemester Powerpoint presentation, met with our client to discuss the design alternatives that we had produced, and conducted further testing to characterize the voltage relationships among the system’s components. |
| 7 | October 17 | Following midsemester presentations, we met as a team to select the design alternative that we will optimize and construct for the remainder of the semester - the magnitude comparator design. In addition, we laid down a plan for progress during remaining weeks of the semester. |
| 8 | October 24 | Throughout this week we prepared for an invention disclosure meeting with WARF, which we attended on Friday, October 31. We also met with BME 310 teaching assistant Amit Nimunkar to discuss the feasibility of our circuit design and the remaining system characterization that had to be completed prior to assembly. |
| 9 | October 31 | Following Amit’s advice, we spent much of this week gathering the remaining data to complete our understanding of the voltage and current relationships within our system. We also began construction of a preliminary circuit in the BME Electronics Lab. |
| 10 | November 7 | This week, we continued assembly and troubleshooting of the circuit design within the Electronics Lab where we were able to achieve real-time feedback using LabVIEW. From the information gathered here, we made a significant modification to our design in that we substituted the magnitude comparator for differential and summing amplifiers. |
| 11 | November 14 | Having made as many observations of the circuit’s efficacy in the Electronics Lab, we began incorporation of the controller into our client’s Medtronic system in the Neurosurgery Lab at the VA hospital. |
| 12 | November 21 | Throughout this week, we were able to continue integration and troubleshooting of our design. With the assistance of Professor John Webster, we again realized we had to make a modification to our implemented circuit, this time removing the summing amplifier and readjusting the voltage attenuation and amplification factors. |
| 13 | November 28 | Construction of the final prototype, which involved miniaturization of the circuit that we developed on a breadboard down to four separate phases that were confined to a project box, was begun this week and completed over the Thanksgiving holiday. |
| 14 | December 5 | With construction of the prototype completed, we spent this week collecting data to support the effectiveness of our design including tests that utilized the neuroendoscope as well as LabVIEW software for data acquisition. Following this analysis, we prepared ourselves for the final poster presentation. |
| 15 | December 12 | This week, we completed work on our final written report detailing our progress throughout the semester. In addition, we conducted our self- and peer-evaluations and tied up the remaining loose ends of the semester. |
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Product Design Specifications (Dec 12 2008, 158 kb) |
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Midsemester PowerPoint Presentation (Dec 12 2008, 3685 kb) |
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Final Poster Presentation (Dec 12 2008, 500 kb) |
