Needle access required for percutaneous renal surgery is a challenging art. A steep learning curve characterizes the acquisition of skill necessary to gain access safely and routinely.
It is presently performed by manually inserting the needle under single-view flu-oroscopic radiological guidance. To improve on this approach, several researchers have investigated the use of robotic systems in assisting in the needle placement.
Potaminos et al. have proposed a stereopair of two X-ray views registered to a common fiducial system with a five-degrees-of-freedom passive linkage that is equipped with position encoders to position a passive needle guide (11,12). Bzostek et al. used an active robot, LARS, for a similar application. Although these robotic systems successfully address the issues of image-to-robot registration and provide a very convenient means of defining target anatomy, they are expensive and their large size makes them cumbersome for routine use in the operating room. Stoianovici et al., from Johns Hopkins University, developed the simple, noncomputerized system—Percutaneous Access of the Kidney—for this purpose (13,14). Percutaneous Access of the Kidney is a radiolucent needle driver actuated by an electrical motor. The surgeon manually orients the driver and therefore the needle using the technique of "superimposed needle registration" (13). Percutaneous Access of the Kidney is then locked into the desired orientation and needle insertion is manually controlled by a joystick. Using the Percutaneous Access of the Kidney device in nine patients, percutaneous access to the desired calyx was attained in the first attempt in each case. Percutaneous Access of the Kidney appeared to be safe and effective, with no perioperative complications attributable to needle access, and even offered a reduction in procedure time (15). Encouraged by these preliminary results, the same group later reported the development of a remote center of motion actuator module called the "MINI-remote center of motion." This module is reported to integrate both with Percutaneous Access of the Kidney and a wide variety of additional end effectors, which are under development. The idea is to simplify the orientation procedure, increase accuracy, reduce radiation exposure, and to achieve Percutaneous Access of the Kidney's compatibility with computerized tomography. The MINI-remote center of motion is an extremely compact robot that utilizes the remote center of motion principle of the LARS robot (16).
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