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The use of Computed Tomography (CT) is commonly used to locate tumors for biopsy procedures. However, the process is vulnerable to human error; consequently, robotic design has been implemented to eliminate said human error. Our client feels that the leading design in robotic image guided biopsy is flawed in that the process of driving the biopsy needle is too slow. We developed several ideas, within the constraints set, that could feasibly drive the needle faster. Evaluation of these ideas allowed us to select a single design: the pneumatic driver. Prototypes have been constructed to test if the needle deflects at all upon contact with tissue. No visible deflection was observed when the needle was inserted into a pig. A solenoid valve has been implemented in order to direct airflow of the pneumatic cylinder, and a spring is being used to eject the needle from the subject. Future work includes automating the whole system and attaching it to ImageGuide’s robotic arm.
Images from left to right: CAD diagram of the idea behind our device, our second prototype, and the second prototype in testing (failed).
Following successful testing of the pneumatic needle injection phase with our third, and now fourth, prototypes, we have successfully designed a needle capture mechanism. This mechanism has not yet been tested, but the design is simple, effective, and should work well. We have also designed a mechanism within the fourth prototype that retracts the needle well, but will be improved upon next semester in order to dampen the impact produced on return. Additionally, our device is much closer to being fully automated, as we have integrated a solenoid valve to control needle insertion and retraction. As of now the valve is manually turned on and off, but in the future we will be adding a sensor that will automatically turn the solenoid valve off once the needle is fully inserted.
Images of our third prototype in testing on a porcine subject:
This is a schematic of our newest prototype design:
In operation the device would undergo the following sequence: A switch is thrown and a solenoid valve (not in image) allows air pressure to enter the cylinder, pushing the piston and needle forward at high velocity. As the piston and needle reach the full-insertion position, the two pegs at the front of the piston are depressed, pushing the stylet back inside the cannula. This will hopefully allow the targeted tissue to enter, and become trapped in, the cannula. While this happens, and as the piston is in contact with the front of the cylinder, a sensor will be triggered, and the solenoid valve will be commanded to shut off the pressure. This will allow the spring to push the piston back, hopefully retracting the needle with a tissue sample.
This is a closer look at the design of our tissue capture mechanism:
| Week | Reporting Period Beginning | Activities |
|---|---|---|
| 1 | September 3 | Formed group, contacted client and advisor, reviewed progress from last semester and goals for this semester. |
| 2 | September 10 | Began collecting materials for our third prototype design. |
| 3 | September 17 | Production of third prototype nearly completed. |
| 4 | September 24 | Production of prototype completed and is ready for testing. |
| 5 | October 1 | Prototype successfully tested on turkey breast. Testing was done at differing pressures, distances, and angles, all successfully with no apparent deflection. |
| 6 | October 8 | Tested prototype on fresh pig specimen. Test through realistic specimen revealed our goal should be to the highest pressure that our device design will allow. |
| 7 | October 15 | Prepared and executed mid-semester presentation. Beginning designs for biopsy capture mechanism and computer-controlled flow valve. |
| 8 | October 22 | Design for biopsy capture mechanism is finished after correcting small flaw, researched retrorelectors and LEDs for sensing needle position and controlling needle direction. |
| 9 | October 29 | Obtained information about three- and four-way solenoid valves for controlling needle deflection; obtained more needles. |
| 10 | November 5 | Obtained approval from client for purchasing needed parts and finished fabrication of the biopsy capture mechanism. |
| 11 | November 12 | Worked on design on retraction mechanism; updated website. |
| 12 | November 19 | After meeting with Dr. Fronczak, we considered using a spring force to retract the needle or a combination of a second pneumatic sequence with a spring. |
| 13 | November 26 | Finished our final prototype for the semester, which included the new spring design for retracting the needle and solenoid-controlled airflow. |
| 14 | December 3 | Finished final paper and all design deliverables; posted final paper on website. |
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Problem Design Specification Sheet (Oct 7 2004, 25 kb) |
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Mid Semester Presentation, Fall 2004 (Nov 21 2004, 3777 kb) |
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End of Semester Poster Presentation Slides (Dec 6 2004, 756 kb) |
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Final Report Fall 2004 (Dec 8 2004, 536 kb) |
