Laparoscopic ultrasound offers noninvasive, real-time, and low-cost intraoperative monitoring of the intra-abdominal organs. However, because of the lack of degrees of freedom in the positioning of the laparoscopic ultrasound probe, it is difficult to align an ultrasound imaging plane with the longitudinal section of a blood vessel in the liver. This paper proposes a handheld laparoscopic ultrasound manipulator with three degrees of freedom designed to manipulate a miniature laparoscopic ultrasound probe. First, an ideal range of motion, measured using sensors and quantified as the required minimum range of motion of the laparoscopic ultrasound probe, was demonstrated by a surgeon. Thereafter, a double-bevel-gear mechanism enabling a pitch motion of ±40° and a yaw motion of ±30° and a wire-driven mechanism enabling a roll motion of ±60° were designed and implemented to the laparoscopic ultrasound manipulator with three degrees of freedom. A mechanism for assembling the miniature laparoscopic ultrasound probe with the shaft of the manipulator under a laparoscopic view was also designed to minimize the number and size of incisions in the abdomen. A prototype of the manipulator with a drive unit was fabricated and tested on an ultrasound liver phantom. A successful assembly, as well as successful visualization of the longitudinal section of a blood vessel in the liver model was demonstrated in a simulated laparoscopic environment. In future, the design will be revised, and the handheld laparoscopic ultrasound manipulator with three degrees of freedom will be tested for in vivo experiments.
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