Abstract-Needle insertion for minimally invasive surgery is a technique explored and studied in order to adhere to the strict regulatory requirement for medical device development. While the instruments and techniques determine the success of every surgical procedure, minimal attention was given to the medium, the interaction force for testing, the development tools and surgical techniques. In this paper, we present the interaction forces involve during the needle insertion into porcine back tissue and simulated flesh-like tissue, independently measured by a testing setup developed for this purpose. The experimental setup and test procedure provides an understanding on the mechanics of needle insertion, potentially aid the design improvement on surgical instrument. Investigation on the composition of the force components helps to define the bio-mechanical properties of back abdomen tissue upon insertion. These forces comprises of stiffness, friction and cutting force. These results estimate the true insertion depth of the needle in the tissue. Needle insertion forces were measured for gelatine analogues developed to model the consistency of the tissues in the lumbar region of the back. This study was the first step in developing a force feedback controlled surgical instrument for needle insertion which will be used in kidney surgical operation.Index Terms-Needle insertion, insertion forces, porcine tissue and gelatine.
Background: There is increasing interest in examining the life space mobility and activity participation of older adults in the community using sensor technology. Objective data from these technologies may overcome the limitations of self-reported surveys especially in older adults with age-associated cognitive impairment. This paper describes the development and validation of a prototype hybrid mobility tracker for assessing life space mobility and out-of-home activities amongst 33 community-ambulant older adults in Singapore. Methods: A hybrid mobility tracker was developed by combining a passive Global Positioning System logger, triaxial accelerometer and radio-frequency identification. Objective measures of life space, derived from 1 week of tracking data using Geographic Information Systems, were the maximum Euclidean distance from home (Max Euclid) and the area of the minimum convex polygon surrounding all GPS waypoints (MCP area). Out-of-home activities were quantified by visually identifying the total number of activity nodes, or places where participants spent ≥5 min, from mobility tracks. Self-reported measure of life space in 4 weeks was obtained using the University of Alabama at Birmingham Study of Life Space Assessment (UAB-LSA) questionnaire. Self-reported out-ofhome activities were recorded daily in a travel diary for 1 week. Bivariate correlations were used to examine convergent validity between objective and subjective measures of life space and out-of-home activities. Results: The mean age of participants was 69.2 ± 7.1 years. The mean UAB-LSA total score was 79.1 ± 17.4. The median (range) Max Euclid was 2.44 km (0.26-7.50) per day, and the median (range) MCP area was 3.31 km 2 (0.03-34.23) per day. The UAB-LSA total score had good correlation with Max Euclid (r = 0.51, p = 0.002), and moderate correlation with MCP area (r = 0.46, p = 0.007). The median (range) total number of activity nodes measured by
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