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DISTRIBUTED SMA ACTUATORS FOR MULTIDIRECTIONAL MANIPULATION OF AN ACTIVE NEEDLE: INVESTIGATION ON INTERNAL PHASE TRANSFORMATION OF SMAS FOR PRECISE ASSEMBLY AND PERFORMANCE
|Title:||DISTRIBUTED SMA ACTUATORS FOR MULTIDIRECTIONAL MANIPULATION OF AN ACTIVE NEEDLE: INVESTIGATION ON INTERNAL PHASE TRANSFORMATION OF SMAS FOR PRECISE ASSEMBLY AND PERFORMANCE|
|Authors:||Padasdao, Blayton Kenji|
|Contributors:||Konh, Bardia (advisor)|
Mechanical Engineering (department)
|Publisher:||University of Hawai'i at Manoa|
|Abstract:||Today, several medical diagnosis and therapeutic cancer interventions are performed using needles via percutaneous surgical procedures. It is often challenging to guide and track the needle in a desired path to reach the target precisely, while avoiding sensitive organs or large arteries so the success of these procedures highly depends on accurate placement of the needle tip at target positions. Improving targeting accuracy necessitates improvements in medical imaging and needle steering techniques. The former provides an improved vision on the target (i.e., cancerous tissue) and the needle, while the latter enables an enhanced interventional tool. In spite of considerable advancements in the medical imaging field, the structure of the needle itself has remained unchanged. In the past decade, research works have suggested passive or active navigation of the needle inside the tissue to improve targeting accuracy. In addition, to provide actuation and control for needle steering, an active needle has been introduced that is activated by shape memory alloy (SMA) actuators. However, actuation of SMAs is complex due to their nonlinear and hysteresis behavior that depends on stress, strain, and temperature during operation.This thesis is the culmination of studies involving the rapid manufacturing (via 3D printing), precise assembly, and performance evaluation of multiple distributed SMA actuators in an active flexible needle while also introducing a robot-assisted tracking system to provide the 3D position of the needle tip during a needle insertion task. A robotic system has been developed and programmed to move the ultrasound transducer on top of the needle tip with an adjusted velocity while simultaneously controlling another system to pull the cable tendons and control the needle deflection inside tissue. The position of the needle tip is provided by applying a series of image processing techniques on transverse ultrasound images. The tracking system is tested on several needle insertion tests in a phantom tissue. The needle tip position is compared with measured data obtained via a vision-based technique (using a camera).|
Through the first study, the interactive response of the SMA actuators was investigated using experimental tests, constitutive material model, and kinematics of the active needle. It was shown that with proper installation of SMA actuators on the active needle, an effective manipulation can be realized in three dimensions. The results from the second study shows that our proposed robot-assisted ultrasound tracking method can be used to track the needle tip (average error less than 1.5 mm) in real-time since the computational time is quite low (in milliseconds).
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|Appears in Collections:||
M.S. - Mechanical Engineering|
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