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Abstract

Abstract.

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Abstract

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  1. Abstract Our objective was to design an infusion pump that will be used to deliver contrast agents during a MRI exam. Currently used is a syringe pump injector system that delivers fluids at the rates our client desires. However, it is limited in its sequence capability and saline/gadolinium capacities. Our client would like a new pump that is more programmable and large enough to hold the amount of gadolinium and saline needed for the entirety of one study. A replacement would reduce the total time needed to complete imaging and consequently, produce more accurate results. We propose a design where the movement of a ratchet and pawl due to an air-driven solenoid valve/linear actuator rotates a peristaltic pump to deliver fluids to the patient.

  2. Background • To be used with MRI to study cerebral hemodyanmics in stroke patients • Contrast agent (gadolinium) injected in blood stream to create image. • Saline used to “flush” contrast agent out of circulation system

  3. Pump Currently Used • Medrad’s Spectris Solaris MR Injection System • Specifications: • Syringe driven • 0.1 mL/s – 10.0 mL/s • 50 mL capacity for each compartment

  4. Problem Statement Design a MRI-compatible infusion pump that is: • Easily programmable • Made of non-ferrous materials • Capable of delivering fluids at the desired flow rates • Large enough to hold amount of gadolinium and saline needed for entirety of one study

  5. Motivation • A new infusion pump will: • Save client’s time • No need to constantly refill the solutions between bolus and infusion • Give accurate results • Patient movements are minimized with less scan interruptions • Typical interruption time: ~7 min • Eliminates image inaccuracies

  6. Design Specifications • The infusion pumps must: • Be made of a non-ferrous material • Deliver accurate flow rates • (0.2-4 mL/s, ± 0.02 mL/s) • Be easily sterilized • Be durable • Be programmable • Sequence: saline→bolus→saline →infusion →saline • Should be done quickly so interruption time is minimized • Connect to containers that can hold at least 60 mL of gadolinium and 180 mL of saline

  7. Initial Designs • Specifications: • Peristaltic pump • Stepping motor • Control with LabView • Problems: • Few pumps can achieve 0.2 - 4 mL/sec • Issues with shielding motor and pump

  8. Final Design • Proposed Mechanism consists of: • 5-way solenoid valve • Double action linear actuator • Ratchet and pawl • Peristaltic pump

  9. Final Design – Role of Solenoid Valve • Air is directed into the solenoid valve • 2 exit tubes with a vent for each 1. Solenoid - charged • air from one exit tube pushes piston in • Air on other side of piston is pushed back through valve and out the vent 2. Solenoid - discharged • air flow redirected to other exit tube and pushes piston out (opposite) • Air originally pushing piston in is now venting to valve and out the vent

  10. Final Design/Solenoid Valve (cont.) • On/off cycle of solenoid causes back and forth movement of piston within chamber. • Same motion translates to attached linear actuator (cylinder tube) • Shaft attached to pawl, which drives ratchet Circuit schematic of solenoid valve

  11. Rotational views of solenoid valve (b) Bottom of solenoid valve • Additional Specifications • Body width – 15 mm • 2 position single • Metal seal • 24 V DC / 110 V AC • L plug connector with lead wire • Also with light and surge voltage suppressor • Operating Pressure: 0.1 - 0.7 MPa (a) 3D view of solenoid valve

  12. Final Design (cont.) • Shaft attached to pawl, which drives ratchet • Ratchet connected to rod that rotates peristaltic pump • Rotation of peristaltic pump delivers fluid to patient

  13. Final Design/Cylinder Tube

  14. Final Design/Cylinder tube (b) Side view of cylinder tube (linear actuator) • Additional Specifications • Front nose mount • Double acting actuation • Bore size: 1.5” • Operating pressure: 8 - 250 PSI • 3D view of cylinder tube • (linear actuator)

  15. Future Work

  16. Possible Modifications of Prototype • Develop sensors to detect and control amount of air at: • Air source • Peristaltic pump • Non-ferrous linear actuator • Casing for solenoid valve • Separate casing for ratchet, pawl, linear actuator, and peristaltic pump

  17. Acknowledgements • Prof. Frank J. Fronczak Dept. of Mechanical Engineering • Prof. John G. Webster Dept. of Biomedical Engineering

  18. References Fronczak, Frank. Personal Interview. April 16, 2004 Hospod, Frank. Personal Interview. February 2, 2004. Medrad. (2003). Spectris Solaris MR injection system. Retrieved Dec. 4, 2003, from http://www.medrad.com/systems-and-products/magnetic-resonance/spectris-solaris.html Newman, George C. Personal Interview. April 2, 2004. SMC Corporation of America (2004). Retrieved April 27, 2004, from http://www.smcusa.com

  19. TEAM MEMBERS Aman Ghotra – Leader Can Pi – Communicator Miguel Benson – BSAC Prakash Rao - BWIG

  20. Client Dr. George C. Newman, MD, PhD Frank Hospod Dept. of Neurology Advisor Prof. John G. Webster Biomedical Engineering

  21. MRI

  22. COM

  23. PATI

  24. BLE

  25. INFU

  26. SION

  27. PUM

  28. P

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