Cyber-physical needle steering setup
Control software for needle steering in a physical lab. Hardware and software provided by Institute for Medical Technology and Intelligent Systems (MTEC).
The experimental setup consists of a gelatin block mimicking a tissue phantom, a flexible needle design with a 45° beveled needle tip and two Basler acA1300-200uc cameras at an angle of approximately 90° to each other tracking the needle tip within the gelatin block. An Arduino controls two stepper motors guiding the flexible needle. One stepper motor rotates the needle around its axis. the other stepper motor moves the needle forward or backward. A force tenor is attached to the needle.
The experimental setup is connected to several computer systems executing different software artifacts:
Architecture of the system software
- The force server regularly reads force data and sends the data to the MTEC computer.
- The MTEC computer serves as an interface between the experimental hardware and the needle control by the STS computer. It regularly reads image data, calculates the three-dimensional positions of the needle tip by image processing, and sends the position data and force data to the STS computer. Furthermore, it executes the needle movement instructions of the online strategy workflow.
- With the goal to reach a certain position within the phantom, the STS computer calculates the needle instructions by online (or offline) strategy synthesis.
- Our experimental setup adaptions:
- We replaced the plastic needle tip with a sharper steel tip.
- We introduced a tube from the motor until the gelatin phantom guiding the flexible needle to prevent distraction before needle insertion.
- Changing parameters during the experiments:
- Gelatin phantom model: different gelatin to water concentrations (7%, 10%, 15%), obstacles (glass, cling film, metal? pipe)
- Velocity: we only used 0.7 mm/sec
- Force tenor averaging (over 0, 50, 100 data points)
- Max allowed position deviation from computed needle trace (between 0 mm - 10 mm), minimum number of deviated points to detect deviation
- Max allowed force delta (between 0.1 and 0.2, depends on the gelatin), minimum number of deviated points to detect deviation
- Position and size of the one target region
- Positions and sizes of the unsafe regions (multiple regions possible)
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Two hollow shaft steppers motor with digital oscilloscopes (Saleae, Logic Analyzer)
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Flexible needle design with a 45◦ beveled needle tip with a steel ball located at the needle tip center
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Gelatin (here 10%)
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Two Basler acA1300-200uc cameras
