Robert R. Christensen

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The Sarcos Treadport is a locomotion interface comprised of a large tilting treadmill, an active mechanical tether, and a CAVElike visual display. This paper presents the design specifications for the second-generation Sarcos Treadport. INTRODUCTION There have been various approaches towards the design of locomotion interfaces, including powered pedaling(More)
Percutaneous drainage of 101 pancreatic pseudocysts (51 infected, 50 noninfected) in 77 patients is described. In this group of patients, 91 of 101 pseudocysts were cured by means of catheter drainage (90.1%) (noninfected, 43 of 50 [86%]; infected, 48 of 51 [94.1%]). Six patients underwent operation after percutaneous treatment due to persistent drainage.(More)
Computed tomography (CT) was used to guide percutaneous fine-needle biopsy in 150 cases of difficult thoracic lesions; in 76 cases, nondiagnostic bronchoscopy (n = 62) and fluoroscopic biopsy (n = 14) had previously been performed. CT was indicated for guidance when the pulmonary or pleural lesions were small (0.3-2.5 cm); in a juxta-vascular location,(More)
The inertial force due to the acceleration of a locomotion interface is identified as a difference between virtual and real-world locomotion. To counter the inertial force, inertial-force feedback was implemented for the Treadport, a locomotion interface. A force controller was designed for a mechanical tether to apply the feedback force to the user. For(More)
Perforation of hepatic amebic abscess is associated with high morbidity and may result in death. Traditional treatment has been emergency surgery. The authors report successful percutaneous drainage of perforated hepatic amebic abscesses in five severely ill patients. These perforations resulted in abscesses in the subhepatic space, pelvis, chest, right and(More)
This paper investigates whether torso force feedback on treadmillstyle locomotion interfaces can substitute for treadmill tilt to simulate walking on smooth inclines. The experimental platform is the Sarcos Treadport, whose active mechanical tether can apply horizontal forces to the user to simulate the gravity forces experienced in slope walking. The(More)
On the basis of laboratory experiments, we devised a wire-sheath system for MR-guided biopsy and drainage and then evaluated that system in 10 patients. The localizing system consisted of a 20-gauge plastic sheath into which a stainless-steel alloy wire had been inserted. In laboratory studies, we compared this wire-sheath assembly with other materials to(More)
Smooth slopes can be displayed on treadmills through tilt mechanisms , but these mechanisms are typically too slow to present sudden slope changes. The Sarcos Treadport utilizes a mechanical tether that can apply horizontal forces to the user to simulate gravity forces. Psychophys-ical results are presented to show that slope display via tether forces is a(More)
This report summarizes diagnostic and therapeutic radiologic procedures in 45 patients who suffered major complications from cholecystectomy. Complications were divided into (1) bile duct injury or ligation and (2) a variety of pathologic fluid collections. Specific lesions were bile duct injury (n = 6), accidental bile duct ligation (n = 12), ductal(More)
This paper investigates whether torso force feedback on treadmillstyle locomotion interfaces can substitute for treadmill tilt to simulate walking on smooth inclines. The experimental platform is the Sarcos Treadport, whose active mechanical tether can apply horizontal forces to the user to simulate the gravity forces experienced in slope walking. The(More)
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