Transcript Abstract

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.
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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

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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
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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
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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
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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
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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
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Final Design

Proposed
Mechanism
consists of:
– 5-way solenoid
valve
– Double action
linear actuator
– Ratchet and
pawl
– Peristaltic pump
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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
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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
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Rotational views of solenoid valve
(b) Bottom of solenoid valve
Additional Specifications
(a) 3D view of solenoid valve
-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
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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

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Final Design/Cylinder Tube
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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
(a) 3D view of cylinder tube
(linear actuator)
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Future Work
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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

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Acknowledgements

Prof. Frank J. Fronczak
Dept. of Mechanical Engineering

Prof. John G. Webster
Dept. of Biomedical Engineering
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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-andproducts/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
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TEAM MEMBERS
Aman Ghotra – Leader
Can Pi – Communicator
Miguel Benson – BSAC
Prakash Rao - BWIG
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Client
Dr. George C. Newman, MD, PhD
Frank Hospod
Dept. of Neurology
Advisor
Prof. John G. Webster
Biomedical Engineering
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