Virtual Palpation Gripper

In the middle of difficulty lies opportunity Summary This thesis presents the design and performance of the Virtual Palpation Gripper, an early prototype of a remote palpation instrument intended for laparoscopic surgery. Psychophysical experiments related to this prototype are also described. In minimally invasive techniques, such as laparoscopic surgery, the interventions are performed with instruments inserted into the body through small incisions. This technique has become increasingly popular and is now considered the gold standard for many surgical procedures, such as cholecystectomy. The main advantages compared to open surgery are smaller scars, reduction in pain and faster recovery. Despite the advantages, la-paroscopic surgery introduces many restrictions for the surgeon, such as reduced dexterity, fewer degrees of freedom and awkward positioning of the hands. Additionally, the visual and tactile perception is severely degraded. The aim of the Virtual Palpation Gripper is to compensate for some of the lost perception by feeding tactile information back to the surgeon. The ultimate goal is to make the remote palpation instrument serve as an extension of the surgeon's fingers. This is accomplished by attaching a tac-tile sensor array to the end effector of a laparoscopic grasper and a tactile display to the handle of the grasper. The sensor array then aids as the tac-tile sense, and the tactile information is sent to the surgeon's fingers via the tactile display to provide him with a feeling of the shape,hardness, or size of an object grasped with the laparoscopic instrument. Two different sensor arrays are discussed. The first one is based on piezoelectricity and is made from scratch in our laboratory. The second sensor is the custom made TactArray, which is based on a mature capaci-tive technology. Both sensor arrays are small enough to fit through a 12 mm trocar. Due to crosstalk in the piezoelectric array, the TactArray sensor array is chosen for the prototype of the Virtual Palpation Gripper. The performance and usefulness of the sensor array is tested and documented through an experiment where 15 surgeons with varying experience participate. The main goal is to compare direct palpation (with gloved fingers i as in open surgery), palpation with a conventional laparoscopic grasper and palpation with a laparoscopic grasper with visually presented tactile information. Results show that direct palpation is superior to both the la-paroscopic graspers, but that the grasper with visual feedback of the tactile image seems to be useful for subjects who fully …