Group Members:

1

• Group Members
• Ryan Augustine
• Brian Frederick
• Nate Gaeckle
• Gordy Lawrence
• Advisor
• Professor Willis Tompkins
• Client
• Dr. Myron Pozniak

2
Abstract

• A robotic arm has previously been developed to
  integrate
• information provided from a CT scan in order to
  place a
• biopsy needle in the proper trajectory. A
  prototype has
• been constructed that uses air pressure to drive
  a biopsy
• needle into a patient via a piston/cylinder
  assembly with
• a compression spring to retract the needle. This
  prototype
• has been tested on specimens that have comparable
  tissue
• to humans to see if there was noticeable
  deflection of the
• needle. No deflection was observed. The biopsy
• mechanism will be activated upon impact with the
  end of
• the cylinder in a fully automatic fashion. In
  the future, the
• needle will also be able to be retracted
  automatically by the
• combination of an LED and photodiode sensor, or
  an
• electrode sensor.

3
Motivation

• Problems with current drive mechanism
• Slow needle advancement 2 cm/s
• Slower biopsies increases risk of internal damage
• Creates tumor movement
• Makes use of the robotic arm infeasible

4
Problem Definition

• Biopsies are used in conjunction with a CT scan
• Many dilemmas with manual biopsy needle injection
• Inaccurate
• Physician exposure to radiation
• Sometimes multiple attempts at tumor capture
• Robotic Arm created to eliminate these problems

5
Problem Statement

• Our goal is to create a needle driver that
• Drives a needle fast to counter tumor movement
  and patient injury
• Retracts the needle with speed and ease with a
  sample of the tumor
• Is compatible with CT scanners
• Preserves Imageguide Inc.s Remote Center of
  Motion for the Robotic Arm

6
Design Criteria

• Device must not be any longer than 30 cm
• Needle must be able to travel 22 cm
• Minimize radio-opaque materials
• Must have redundant safety checks
• Needle must be extracted rapidly with tissue
  sample
• Needle must be fired fast enough to utilize
  inertia of body tissue
• Biopsy should be completely automatic

7
Final Design

• Needle contained inside piston/cylinder assembly
• Needle injected by pneumatic power controlled by
  a solenoid valve
• Needle retracted by a compression spring
• Biopsy mechanism activated by impact of needle at
  the end of the cylinder
• Gasket around piston to create seal
• Most parts may be constructed from radiolucent
  material

8
Prototype Testing

• Tested on a turkey breast
• Needle entered easily sans deflection
• Pressurized to 30 psi
• Varying heights and angles of entry tested
  successfully
• Tested on a pig to simulate skin resistance
• Qualitative assessment to determine if distance
  away from skin affects deflection
• Increasing the pressure improved entry

9
Solenoid Valve

• Directs air flow greater than 50 psi
• Will be implemented on the robotic arm so that it
  is close to the biopsy needle
• Located outside plane of CT scan
• Pneumatic devices are best in low humidity so
  nitrogen gas will be used

10
Needle Retraction

• Pressure applied to the needle to propel it
  forward
• Piston compresses the spring while it is injected
  into the body
• Once biopsy taken, pressure is released and
  spring extends, retracting the needle
• Retraction rate correlates with spring constant
  according to Hookes Law
• Spring may affect CT image

11
Biopsy Mechanism

• Cannula retracts by impact with end of cylinder
• Flexor pegs lock into place once spring is
  compressed
• Pinching the pegs extends the spring and ejects
  tumor cells

12
Future Work

• Automate the retraction mechanism
• LED and photodiode
• Electrode sensor
• Connect to a computer with LabView to integrate
  sensor signal
• Apply radiolucent material to prototype
• Attach to ImageGuides robotic arm

13
Methods to Automate System

• LED and photodiode located opposite each other at
  the end of the cylinder
• Opaque piston holding the needle breaks light
  path on the photodiode
• This signals pressure to be released

14
Methods to Automate System

• Spaced electrodes are placed at the bottom of the
  cylinder
• Piston has a conducting ring that will pass
  current between electrodes
• This signals pressure to be released

15
Box Diagram of Air Control
Robotic Arm
16
Circuit Controlling Solenoid Valve
17
References

• Professor Frank Fronczak
• Professor Willis Tompkins
• Steve Polishinski
• Professor John Webster
• ECB Machine Shop