Physics-Based Modelling and Simulation of Multibeam Echosounder Perception for Autonomous Underwater Manipulation.

One of the key distinguishing aspects of underwater manipulation tasks is the perception challenges of the ocean environment, including turbidity, backscatter, and lighting effects. Consequently, underwater perception often relies on sonar-based measurements to estimate the vehicle's state and surroundings, either standalone or in concert with other sensing modalities, to support the perception necessary to plan and control manipulation tasks. Simulation of the multibeam echosounder, while not a substitute for in-water testing, is a critical capability for developing manipulation strategies in the complex and variable ocean environment. Although several approaches exist in the literature to simulate synthetic sonar images, the methods in the robotics community typically use image processing and video rendering software to comply with real-time execution requirements. In addition to a lack of physics-based interaction model between sound and the scene of interest, several basic properties are absent in these rendered sonar images-notably the coherent imaging system and coherent speckle that cause distortion of the object geometry in the sonar image. To address this deficiency, we present a physics-based multibeam echosounder simulation method to capture these fundamental aspects of sonar perception. A point-based scattering model is implemented to calculate the acoustic interaction between the target and the environment. This is a simplified representation of target scattering but can produce realistic coherent image speckle and the correct point spread function. The results demonstrate that this multibeam echosounder simulator generates qualitatively realistic images with high efficiency to provide the sonar image and the physical time series signal data. This synthetic sonar data is a key enabler for developing, testing, and evaluating autonomous underwater manipulation strategies that use sonar as a component of perception.

Immediate breast reconstruction in locally advanced breast cancer: is it safe?

PURPOSE: Immediate breast reconstruction (IBR) following mastectomy remains controversial for locally advanced breast cancer over concerns regarding recurrence and complications which may delay adjuvant therapies. This study aimed to compare the oncologic outcomes and surgical safety of IBR following mastectomy with mastectomy alone (MA) for locally advanced breast cancer. METHODS: All patients treated at the Providence Breast Center between 2012 and 2017 for biopsy-proven locally advanced breast cancer, AJCC (8th edition) clinical stages (IIB-IIIC), were included. Primary outcomes were overall survival (OS), disease-specific survival (DSS), and disease-free survival (DFS). Secondary outcomes included recurrence rate, adjuvant therapy use, and reoperation. RESULTS: 267 patients (112 IBR, 155 MA) were included. On average, IBR patients were younger (48.82 years vs 61.42 years, P < 0.001). Median study follow-up was 50.7 months. OS was higher among IBR patients (86.6% vs 73.5%, P < 0.05). However, no significant differences were found in DSS (87.5% vs 84.5%, P = 0.34), DFS (79.5% vs 78.7%, P = 0.55), local recurrence (0% vs 1.9%, P = 0.194), adjuvant therapy use (95.5% vs 91.6%, P = 0.155), or reoperation (1.8% vs 1.3%, P = 0.559). CONCLUSION: IBR is a safe option for patients with locally advanced breast cancer and does not negatively impact survival, cancer recurrence rates, and use of adjuvant therapy.