Motivation: Radiofrequency ablation (RFA) has in recent years become a popular treatment for primary tumors in the breast, kidney, liver, and etc. However, traditional approaches of guidance such as ultrasound and computed tomography (CT) fail to provide satisfactory placement precision. Although MRI guidance offers the ability to evaluate the completeness of the RFA, those procedures that are currently done using MRI are performed under “image guidance” rather than “continuous imaging”. The goal of this research is to build a multi-DOF device for breast biopsy/RFA that is MRI compatible and teleoperated with a haptic interface. We envision a “one-sitting procedure”, whereby identification of tumor boundaries, placement of the needle, assessment of placement accuracy, ablation, and assessment of ablation accuracy can be done in one sitting, without removing the patient from the scanner or disrupting tumor location, as shown in Fig. 1.
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| Fig. 1: CAD drawing of the robot inside the MRI bore [2] |
Methods:
- MRI compatible device and actuation system: To actuate the device, we chose pnematic cylinders and piezo motor to ensure MRI-compatibility and maintain MR image quality. We have build with non-ferromagnetic material a 4-DOF breast biopsy robot, as shown in Fig. 2. It consists of a parallel mechanism that is actuated with three pneumatic cylinders and a needle driver that is actuated with a piezo motor. This device is capable of adjusting needle orientation and performing the biopsy needle insertion. The prototype robot has been tested in the MRI environment, as shown in Fig. 3, and the result shows that the robot can be safely operated inside the MR bore with modest SNR loss. We are also working on integrating a X-Y stage to this robot and get a full scale prototype of the system.
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| Fig. 2: The 4-DOF MRI-compatible breast biopsy robot [2] |
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| Fig. 3: Experimental setup in the MRI [2] |
- Fiber-optic force sensor: A 3-DOF fiber-optic force sensor has been designed and developed. Optical approach is proposed because it is inherently MRI-compatible as signals are transmitted in the form of light which eliminates the existence of electrical wires inside the MRI room as illustrated in Fig. 4. Force acting on the force sensor causes a deformation in the elastic frame structure, resulting in a displacement in the reflector. By monitoring the reflected light intensity, the force acting on the loading point is computed. A topology optimization technique is also used to provide a systematic algorithm aiding engineers in designing the elastic frame structures that are needed. Fig. 5 shows a photo of the prototype and Fig. 6 illustrates the MR image quality of the force sensor.
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| Fig. 4: Overview of MRI Compatible Fiber-optic Force Sensor Using Reflective Intensity Measurement [3] | |
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| Fig. 5: Prototype of the 3-DOF MRI Compatible Fiber-optic Force Sensor [3] | Fig. 6: MR Image of the Fiber-optic Force Sensor [3] |
- Tele-operation system with haptic interface: The device in the MRI bore is a slave device and will be tele-operated by a master device placed in the MRI control room. We believe that the integration of haptic interface will improve the success rate of the procedures to some extent by helping to characterize the tissue type (normal, fat, cancerous, etc) during biopsy/RFA needle insertion tasks. Such master device is currently under development.
Relevant Publications:
- Bo Yang, U-Xuan Tan, Alan McMillan, Rao Gullapalli, and Jaydev P. Desai, “Design and control of a 1-DOF MRI compatible pneumatically actuated robot with long transmission lines”, IEEE/ASME Transactions on Mechatronics, vol. 16, no. 6, pp. 1040-1048, December 2011. [Full Text]
- Bo Yang, U-Xuan Tan, Alan McMillan, Rao Gullapalli, and Jaydev P. Desai, “Design and implementation of a pneumatically-actuated robot for breast biopsy under continuous MRI”, In IEEE International Conference on Robotics and Automation, pp. 674-679, Shanghai, China, May 2011. [Full Text]
- U-Xuan Tan, Bo Yang, Rao Gullapalli, and Jaydev P. Desai, “Tri-Axial MRI Compatible Fiber-optic Force Sensor”,IEEE Transactions on Robotics, vol. 27, no. 1, pp. 65-74, Feburary, 2011.
- U-Xuan Tan, Bo Yang, Rao Gullapalli, and Jaydev P. Desai, “Design and Development of a 3-Axis MRI-compatible Force Sensor”, In IEEE International Conference on Robotics and Automation, pp. 2586-2591, Alaska, USA, May 2010.
- Rebecca Kokes, Kevin Lister, Rao Gullapalli, Bao Zhang, Howard Richard, Jaydev P. Desai, “Towards a Needle Driver Robot for Radiofrequency Ablation of Tumors under Continuous MRI”, In IEEE
