Patient-mounted robotic needle guidance is an emerging method of needle insertion in percutaneous ablation therapies. During needle insertion, patient-mounted robots can account for patient body movement, unlike gantry or floor mounted devices, and still increase the accuracy and precision of needle placement. Patient-mounted robots, however, require repeated sterilisation, which is often a difficult process with complex devices; overcoming this challenge is therefore key to the success of a patient mounted robot. To eliminate the need for repeated sterilization, we have developed a disposable patient-mounted robot with two rings as a kinematic structure: an angled upper ring both rotates and revolves about the lower ring. Using this structure, the robot has a clinically suitable range of needle insertion angles with a remote center of motion. To achieve disposability, our structure applies a disposable gear transmission component which detachably interfaces with non-disposable driving motors. With a manually driven prototype of the gear trains, we assessed whether the kinematic structure of the two rings can be operated only by using input pinions locating at outside of the kinematic structure. Our tests confirmed that the input pinions were able to rotate both upper and lower rings independently. We also determined a linear relationship of rotation transmission with the gear trains and determined that the rotation transmission between the pinions and the two rings were within 3 % of error from the designed value. Our robot introduces a novel approach to patient-mounted robots, and has potential to enable sterile and accurate needle guidance in percutaneous ablation therapies.
Current methods of needle insertion during percutaneous CT and MRI guided procedures lack precision in
needle depth sensing. The depth of the needle insertion is currently monitored through depth markers drawn on the
needle and later confirmed by intra-procedural imaging; until this confirmation, the physicians’ judgment that the target
is reached is solely based on the depth markers, which are not always clearly visible. We have therefore designed an
optical sensing device which provides continuous feedback of needle insertion depth and degree of rotation throughout
An optical mouse sensor was used in conjunction with a microcontroller board, Arduino Due, to acquire needle
position information. The device is designed to be attached to a needle guidance robot developed for MRI-guided
prostate biopsy in order to aid the manual insertion. An LCD screen and three LEDs were employed with the Arduino
Due to form a hand-held device displaying needle depth and rotation. Accuracy of the device was tested to evaluate the
impact of insertion speed and rotation.
Unlike single dimensional needle depth sensing developed by other researchers, this two dimensional sensing
device can also detect the rotation around the needle axis. The combination of depth and rotation sensing would be
greatly beneficial for the needle steering approaches that require both depth and rotation information. Our preliminary
results indicate that this sensing device can be useful in detecting needle motion when using an appropriate speed and
range of motion.