A 64-element, 1 MHz prototype dual-mode array (DMUA) with therapeutic and imaging capabilities is described. Simulation and experimental results for the characterization of the therapeutic operating field (ThxOF) and imaging field-of-view (IxFOV) for a DMUA are given. In addition, some of the special considerations for imaging with DMUAs are given and illustrated experimentally using wire-target arrays and commercial, quality-assurance phantoms. These results demonstrate what is potentially the most powerful advantage of the use of DMUAs in image-guided surgery; namely, inherent registration between the imaging and therapeutic coordinate systems. We also present imaging results before and after discrete and volumetric HIFU-induced lesions in freshly-excised tissues. DMUA images consistently show changes in echogenicity after lesion formation with shape and extent reflecting the actual shape of the lesion. While changes in echogenicity cannot be used as an indicator of irreversible HIFU-induced tissue damage, they provide important feedback on the location and extent of the expected lesion. Thus, together with the self-registration property of DMUAs, lesion images can be expected to provide immediate and spatially-accurate feedback on the tissue response to the therapeutic HIFU beams. Based on the results provided here, the imaging capabilities of DMUAs can add unique features to other forms of image guidance, e.g. MRI, CT and diagnostic ultrasound.
Genetic Algorithm (GA) is a metaheuristic used in solving combinatorial optimization problems. Inspired by evolutionary biology, GA uses selection, crossover, and mutation operators to efficiently traverse the solution search space. This paper proposes nature inspired fine-tuning to the crossover operator using the untapped idea of Mitochondrial DNA (mtDNA). mtDNA is a small subset of the overall DNA. It differentiates itself by inheriting entirely from the female, while the rest of the DNA is inherited equally from both parents. This unique characteristic of mtDNA can be an effective mechanism to identify members with similar genes and restrict crossover between them. It can reduce the rate of dilution of diversity and result in delayed convergence. In addition, we scale the well-known Island Model, where instances of GA are run independently and population members exchanged periodically, to a Continental Model. In this model, multiple web services are executed with each web service running an island model. We applied the concept of mtDNA in solving Traveling Salesman Problem and to train Neural Network for function approximation. Our implementation tests show that leveraging these new concepts of mtDNA and Continental Model results in relative improvement of the optimization quality of GA.
In this paper, we present temperature imaging data obtained before and after HIFU-induced lesions in implanted tumors in the hind limb of nude mice in vivo. The RF data was acquired using a 9 MHz 192-element linear probe on a diagnostic scanner at 90 frames per second. Approximately 2 seconds of frame data was collected before, during and after sub-therapeutic exposures of 0.2 second duration. The frame rates were sufficiently high to capture the effects of local tissue deformation due to breathing and pulsation near blood vessel. Using a physics-based spatial-temporal filtering of tissue displacement, we were able to produce accurate spatial-temporal maps of the temperature change with fine spatial and temporal resolution. These results are in good agreement with directly measured temperatures using fine temperature sensors near the HIFU focal spot. The results show that robust temperature estimation in the presence of tissue motion/deformation is feasible. Applications of this method in measuring the local thermal properties of tissue will be addressed. In particular, tissue absorption can be estimated and it appears to increase by a factor of 2-4 after lesion formation.
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