Perturbation Propagation Models for Underwater Sensor Localisation using Semidefinite Programming

Real time Underwater sensor networks (UWSNs) suffer from localisation issues due to a dearth of incorporation of different geometric scenarios in UWSN scenarios. To address these issues, this paper visualises three specific scenarios of perturbation. First, small sized and large numbered particles of perturbance moving in a tangential motion to the sensor nodes; second, a single numbered and large-sized particle moving in a rectilinear motion by displacing the sensor nodes into sideward and forward direction, and third, a radially outward propagating perturbance to observe the influenced sensor nodes as the perturbance moves outwards. A novel target localisation and tracking is facilitated by including marine vehicle navigation as a source of perturbation. Using semidefinite programming, the proposed perturbation models minimise localisation errors, thereby enhancing physical security of underwater sensor nodes. By leveraging the spin, cleaving motion and radial cast-away behaviour of underwater sensor nodes, the results confirm that the proposed propagation models can be conveniently applied to real time target detection and estimation of underwater target nodes.

Vaccines against the cold chain

Vaccines require continuous refrigeration to retain their efficacy as most vaccine components are derived from mammalian or microbial origin which are thermally unstable. Continuous refrigeration, known as the vaccine cold chain, comes at a cost that directly correlates to the standard of infrastructure that is available. A break in the cold chain caused by poor infrastructure can result in direct loss of functionality in these lifesaving medicines. Therefore, several approaches have been suggested to mitigate these losses. Not only will these benefit general healthcare via improved shelf-life but also enhanced resistance to thermal fluctuations and, in some cases, improved drug target localisation. In this minireview, we highlight trends in vaccine thermal stabilisation and look to the future for cold chain logistics.

Three-dimensional guidance and control for ground moving target tracking by a quadrotor

This paper develops a three-dimensional guidance and control algorithm to ensure that a manoeuverable target is preserved by a quadrotor in a long-term tracking scenario. The proposed guidance approach determines the desired altitude of the quadrotor to adjust the field of view (FOV) to the union of two desired trusted and critical regions. The dimensions of the desired trusted region depend on the controller performance that is evaluated by the distance of the target from the center of the FOV. The critical region is a predefined margin around the trusted region that is defined by the operator based on the upper bounds of the quadrotor and target localisation errors. It also depends on the duration and magnitude of the temporal increase in the target velocity compared to the quadrotor velocity. A sufficient condition is provided for the minimum desired altitude of the quadrotor to ensure that the target is maintained in the FOV. Furthermore, a model predictive control (MPC) is employed to preserve the target at the center of the aerial image and the desired altitude determined by the guidance law. Also, the integrals of the position errors are used to achieve null steady-state errors in the presence of wind disturbances. The simulation results show the effectiveness of the proposed approach in preserving the manoeuverable target in the FOV in the presence of the wind, the uncertainty of the target and quadrotor localisation, accelerations estimation errors, and terrain altitude variation.

Towards robust, unobtrusive sensing of respiration using ultra-wideband impulse radar for the care of people living with dementia

The unobtrusive monitoring of vital signals and behaviour can be used to gather intelligence to support the care of people living with dementia. This can provide insights into the persons wellbeing and the neurogenerative process, as well as enable them to continue to live safely at home, thereby improving their quality of life. Within this context, this study investigated the deployability of non-contact respiration rate (RR) measurement based on an Ultra-Wideband (UWB) radar System-on-Chip (SoC). An algorithm was developed to simultaneously and continuously extract the respiration signal, together with the confidence level of the respiration signal and the target position, without needing any prior calibration. The radar-measured RR results were compared to the RR results obtained from a ground truth measure based on the breathing sound, and the error rates were within 8% with a mean value of 2.4%. The target localisation results match to the radarto-chest distances with a mean error rate of 5.4%. The tested measurement range was up to 5m. The results suggest that the algorithm could perform sufficiently well in non-contact stationary respiration rate detection.

Care redesign of pelvic radiotherapy using Design Thinking: An enhanced quality improvement initiative.

246 Background: Cone Beam Computed Tomography(CBCT) is the cornerstone of image guided radiotherapy(IGRT) which is an integral part of pelvic cancers like prostate cancer. Each pelvic radiotherapy (RT) session is preceded by a planned CBCT to ensure target localisation and organ at risk avoidance. When these criteria are not met, an unplanned CBCT is performed until the CBCT is satisfactory. Possible reasons for an unsatisfactory CBCT include an under filled bladder, distended rectum or prostate gland movement. Repeated unplanned CBCT results in unnecessary excess radiation for patients. We aimed to reduce the incidence of unplanned CBCT from a baseline of 21% to 9% over 5 months. Methods: We conducted the project using both conventional quality improvement methodology and the design thinking methodology. In the diagnostic phase up to March 2017, the baseline incidence of CBCT in patients receiving pelvic RT was 21%. We hypothesized that there were reversible factors leading to a higher incidence of unplanned CBCT and sought to identify and rectify these reversible factors to reduce the incidence of unplanned CBCT. Using human centred design, we designed a new process of performing a bladder ultrasound prior to CBCT to ensure a full bladder prior to RT using the steps empathy, define, ideation, prototype, testing, sharing. Results: A total of 97 patients that underwent pelvic radiotherapy were included in this study, 40 patients were pre intervention and 61 patients received the bladder ultrasound intervention implemented from April 2017 onwards. After intervention, incidence of unplanned decreased from 21% to 5.8%. A 2 sample t test was used to compare the unplanned CBCT pre and post intervention. We found the mean pre and post intervention difference in pooled mean incidence of unplanned CBCT to be significantly different by 13.3%. The reduction in unplanned CBCT translated to saving each patient on average equivalent to 3000 chest x rays worth of unnecessary radiation. Conclusions: Design Thinking is a feasible strategy in quality improvement. We report the first design thinking project in radiation oncology quality improvement. An automated ultrasound bladder is a feasible strategy to screen for bladder filling prior to each CBCT to reduce reliance on CBCT and also patient exposure to radiation in IGRT of pelvic cancers.

Role of fiducial markers in the assessment of prostate bed motion in post-prostatectomy patients treated with volumetric modulated arc therapy

Aim:Accurate localisation of target position is crucial when using techniques with sharp dose fall off such as volumetric modulated arc therapy (VMAT). Gold seed fiducial markers have been used for target localisation in image-guided radiation therapy for various tumors including intact prostate cancers. However, their role for target localisation in post-prostatectomy radiotherapy is unclear. This study was undertaken to determine the feasibility and effectiveness of gold seed fiducial markers in patients undergoing prostate bed VMAT.Materials and methods:The institutional radiation oncology database was used to analyse the treatment data of 18 post-prostatectomy patients with implanted gold seed fiducial markers. The shifts of the fiducial markers were reviewed, tabulated and statistically analysed.Results:Three hundred and eighty-six orthogonal pair images for 18 patients were reviewed. Specifically, the average gold seed fiducial shifts were 0·34 cm in the superior–inferior (S/I) axis (0·31 SD), 0·31 cm (0·29 SD) in the anterior–posterior (A/P) axis and 0·28 cm (0·25 SD) in the lateral axis (R/L). As a result, the 95% probability of fiducial marker displacement was 0·96 cm in the S/I, 0·89 cm in the A/P and 0·78 cm in the R/L axes. The most frequent shifts occurred in the inferior, left and posterior directions. The percentage of shifts more than 0·5 cm were 19·74, 21·56 and 12·47% for the S/I, A/P and R/L axes, respectively.Conclusion:In the absence of fiducial markers, non-uniform planning target volume (PTV) margins of 1 cm for S/I, 9 mm for A/P and 8 mm for the lateral direction are necessary for target localisation in post-prostatectomy radiotherapy. By improving prostate bed localisation, gold seed fiducial markers can decrease PTV margins, reduce normal tissue radiation exposure and allow for dose-escalated and/or hypofractionated radiotherapy to be considered in appropriate clinical scenarios.