This paper presents a multi-slot coaxial antenna with a pi impedance matching network for liver tumor ablation. A multi-slot radiating probe was optimized by using the modified genetic algorithm to produce a near-spherical heating zone with significantly increased possibility of conformal treatment. A pi impedance matching network was designed to match the feeding transmission line and antenna without increasing antenna size. The reflection coefficient, ablation zone shape, specific absorption rate, and temperature were determined by a finite element electromagnetic simulation using COMSOL. Experimental validations were designed to evaluate the proposed antenna. Both simulation and experimental results show that the proposed antenna has the ability for liver tumor ablation, which offers faster heating rates in the heating center and more localized heating distribution than the conventional single-slot antenna.

Re-establishing compromised periodontium to its original structure, properties and function is demanding, but also challenging, for successful orthodontic treatment. In this study, the periodontal regeneration capability of collagenhydroxyapatite scaffolds, seeded with bone marrow stem cells, was investigated in a canine labial alveolar bone defect model. Bone marrow stem cells were isolated, expanded and characterized. Porous collagen-hydroxyapatite scaffold and cross-linked collagen-hydroxyapatite scaffold were prepared. Attachment, migration, proliferation and morphology of bone marrow stem cells, co-cultured with porous collagen-hydroxyapatite or cross-linked collagen-hydroxyapatite, were evaluated in vitro. The periodontal regeneration capability of collagen-hydroxyapatite scaffold with or without bone marrow stem cells was tested in six beagle dogs, with each dog carrying one sham-operated site as healthy control, and three labial alveolar bone defects untreated to allow natural healing, treated with bone marrow stem cells -collagenhydroxyapatite scaffold implant or collagen-hydroxyapatite scaffold implant, respectively. Animals were euthanized at 3 and 6 months (3 animals per group) after implantation and the resected maxillary and mandibular segments were examined using micro-computed tomography scan, H&E staining, Masson's staining and histometric evaluation. Bone marrow stem cells were successfully isolated and demonstrated self-renewal and multi-potency in vitro. The porous collagen-hydroxyapatite and cross-linked collagen-hydroxyapatite had average pore sizes of 415 AE 20 mm and 203 AE 18 mm and porosity of 69 AE 0.5% and 50 AE 0.2%, respectively. The attachment, proliferation and migration of bone marrow stem cells were satisfactory on both porous collagen-hydroxyapatite and cross-linked collagen-hydroxyapatite scaffolds. Implantation of bone marrow stem cells -collagen-hydroxyapatite or collagen-hydroxyapatite scaffold in beagle dogs with experimental periodontal defects resulted in significantly enhanced periodontal regeneration characterized by formation of new bone, periodontal ligament and cementum, compared with the untreated defects, as evidenced by histological and micro-computed tomography examinations. The prepared collagen-hydroxyapatite scaffolds possess favorable bio-compatibility. The bone marrow stem cells -collagen-hydroxyapatite and collagen-hydroxyapatite scaffold -induced periodontal regeneration, with no aberrant events complicating the regenerative process. Further research is necessary to improve the bone marrow stem cells behavior in collagen-hydroxyapatite scaffolds after implantation.

BackgroundNoninvasive magnetic resonance thermometry (MRT) at low-field using proton resonance frequency shift (PRFS) is a promising technique for monitoring ablation temperature, since low-field MR scanners with open-configuration are more suitable for interventional procedures than closed systems. In this study, phase-drift correction PRFS with first-order polynomial fitting method was proposed to investigate the feasibility and accuracy of quantitative MR thermography during hyperthermia procedures in a 0.35 T open MR scanner.MethodsUnheated phantom and ex vivo porcine liver experiments were performed to evaluate the optimal polynomial order for phase-drift correction PRFS. The temperature estimation approach was tested in brain temperature experiments of three healthy volunteers at room temperature, and in ex vivo porcine liver microwave ablation experiments. The output power of the microwave generator was set at 40 W for 330 s. In the unheated experiments, the temperature root mean square error (RMSE) in the inner region of interest was calculated to assess the best-fitting order for polynomial fit. For ablation experiments, relative temperature difference profile measured by the phase-drift correction PRFS was compared with the temperature changes recorded by fiber optic temperature probe around the microwave ablation antenna within the target thermal region.ResultsThe phase-drift correction PRFS using first-order polynomial fitting could achieve the smallest temperature RMSE in unheated phantom, ex vivo porcine liver and in vivo human brain experiments. In the ex vivo porcine liver microwave ablation procedure, the temperature error between MRT and fiber optic probe of all but six temperature points were less than 2 °C. Overall, the RMSE of all temperature points was 1.49 °C.ConclusionsBoth in vivo and ex vivo experiments showed that MR thermometry based on the phase-drift correction PRFS with first-order polynomial fitting could be applied to monitor temperature changes during microwave ablation in a low-field open-configuration whole-body MR scanner.

The Network-on-Chips based communication architecture is a promising candidate for addressing communication bottlenecks in many-core processors and neural network processors. In this work, we consider the generalized fault-tolerance topology generation problem, where the link (physical channel) or switch failures can happen, for application-specific network-onchips (ASNoC). With a user-defined maximum number of faults, K, we propose an integer linear programming (ILP) based method to generate ASNoC topologies, which can tolerate at most K faults in switches or links. Given the communication requirements between cores and their floorplan, we first propose a convexcost flow based method to solve a core mapping problem for building connections between the cores and switches. Second, an ILP based method is proposed to solve the routing path allocation problem, where K + 1 switch-disjoint routing paths are allocated for every communication flow between the cores. Finally, to reduce switch sizes, we propose sharing the switch ports for the connections between the cores and switches and formulate the port sharing problem as a clique-partitioning problem, which is solved by iteratively finding the maximum cliques. Additionally, we propose an ILP-based method to simultaneously solve the core mapping and routing path allocation problems when only physical link failures are considered. Experimental results show that the power consumptions of fault-tolerance topologies increase almost linearly with K because of the routing path redundancy for fault tolerance. When both switch faults and link faults are considered, port sharing can reduce the average power consumption of faulttolerance topologies with K = 1, K = 2 and K = 3 by 18.08%, 28.88%, and 34.20%, respectively. When considering only the physical link faults, the experimental results show that compared to the FTTG (fault-tolerant topology generation) algorithm, the proposed method reduces power consumption and hop count by 10.58% and 6.25%, respectively; compared to the DBG (de Bruijn Digraph) based method, the proposed method reduces power consumption and hop count by 21.72% and 9.35%, respectively.

No abstract