A New Method For Fiber Bragg Grating Based Needle Shape Sensing Calibration Accurate placement of the needle is critical in percutaneous surgery. Needle shape reconstruction technology based on fiber Bragg gratings (FBGs) sensor is considered to have the potential to achieve this goal. In this paper, we present a temperatureinsensitive calibration model for calibrating needles with FBG sensors to accurately estimate its deformation. In addition, we have designed a device for simultaneously calibrating the loading direction and shape. Preliminary results indicate that the proposed model is theoretically insensitive to temperature, but in fact it can only be used within a certain temperature range. The resolution of the loading direction increases as the degree of bending increases, with a maximum error of 8.58xc2xb0. Shape reconstruction error can be less than 1.5mm with small needle bending. This calibration method can meet clinical applications.

Estimating and Localizing External Forces Applied on Flexible Instruments by Shape Sensing Force sensing is highly desirable in medical applications showing great potential to reduce tissue damage and enhance manipulation safety. Embedding force sensors in medical devices is however challenging and costly. Provided that the medical device is long, slender and largely compliant, we show in this paper that it is possible to estimate multiple loads along the length of the flexible instrument using a Cosseratrod model and Fiber Bragg Grating sensors, which allows simultaneous shape and force sensing. We perform experiments that illustrate the feasibility of using this method to locate multiple contact forces along the instrument, and to estimate the magnitudes of the forces that are applied along the length of the instrument. Results show that onedirectional force magnitude and location can be estimated with an average error of 6.3% and 5.4 mm (3.0% of rod length), respectively. In the worst case, the error for magnitude and location can go up to 22.6% and 13.9 mm (7.7% of rod length), respectively. For twodirectional forces, results show an average error of 9.8% for magnitude and 6.4 mm (3.6% of rod length) for the location. The errors on magnitude and location do not exceed 27.4% and 17.4 mm (9.7% of rod length), respectively.