Higher precision surgical devices are needed for tumor resections near critical brain structures. The goal of this study is to demonstrate feasibility of a system capable of precise and bloodless tumor ablation. An image-guided laser surgical system is presented for excision of brain tumors in vivo in a murine xenograft model. The system combines optical coherence tomography (OCT) guidance with surgical lasers for high-precision tumor ablation (Er:YAG) and microcirculation coagulation (Thulium (Tm) fiber laser). Methods: A fluorescent human glioblastoma cell line was injected into mice and allowed to grow four weeks. Craniotomies were performed and tumors were imaged with confocal fluorescence microscopy. The mice were subsequently OCT imaged prior, during and after laser coagulation and/or ablation. The prior OCT images were used to compute three-dimensional tumor margin and angiography images, which guided the coagulation and ablation steps. Histology of the treated regions was then compared to post-treatment OCT images. Results: Tumor sizing based on OCT margin detection matched histology to within experimental error. Although fluorescence microscopy imaging showed the tumors were collocated with OCT imaging, margin assessment using confocal microscopy failed to see the extent of the tumor beyond ~ 250 µm in depth, as verified by OCT and histology. The two-laser approach to surgery utilizing Tm wavelength for coagulation and Er:YAG for ablation yielded bloodless resection of tumor regions with minimal residual damage as seen in histology. Conclusion: Precise and bloodless tumor resection under OCT image guidance is demonstrated in the murine xenograft brain cancer model. Tumor margins and vasculature are accurately made visible without need for exogenous contrast agents.
Self‐sustainable energy generation represents a new frontier to significantly extend the lifetime and effectiveness of implantable biomedical devices. In this work, a piezoelectric energy harvester design is employed to utilize the bending of the lead of a cardiac pacemaker or defibrillator for generating electrical energy with minimal risk of interfering with cardiovascular functions. The proposed energy harvester combines flexible porous polyvinylidene fluoride–trifluoroethylene thin film with a buckled beam array design for potentially harvesting energy from cardiac motion. Systematic in vitro experimental evaluations are performed by considering complex parameters in practical implementations. Under various mechanical inputs and boundary conditions, the maximum electrical output of this energy harvester yields an open circuit voltage (peak to peak) of 4.5 V and a short circuit current (peak to peak) of 200 nA, and that energy is sufficient to self‐power a typical pacemaker for 1 d. A peak power output of 49 nW is delivered at an optimal resistor load of 50 MΩ. The scalability of the design is also discussed, and the reported results demonstrate the energy harvester's capability of providing significant electrical energy directly from the motions of pacemaker leads, suggesting a paradigm for biomedical energy harvesting in vivo.
ventricular dysrhythmias, and congestive heart failure. [1] Currently, lithium-based batteries provide the power for operations of implantable biomedical devices, such as cardiac pacemakers and AICD. Although the advances in microelectronics technology reduce the internal current drain concurrently allowing for a smaller volume and greater reliability of implantable biomedical devices, the batteries used in those devices only have a few years operating lifetime. Patients are still exposed to health risks associated with doing periodic surgeries to replace the depleted lithium-based batteries of the implantable biomedical devices. Therefore, energy consumption and battery replacement are key to the lifetime and effectiveness of implantable biomedical devices. This work represents an effort in tackling the challenges in extending the lifetime of the batteries for such biomedical devices as cardiac pacemakers and AICDs.Given the advances in low power consumption in implantable biomedical devices (such as 0.3 µW for cardiac activity sensing, [2] 10-100 µW for pacemakers, [3,4] 100-2000 µW for cochlear implant, [5] and 1-10 mW for neural recording [6] ), it is desirable to make them self-sustainable by having their own renewable power supply. One promising way to provide this alternative power source is by means of energy harvesting, i.e., to convert the source energy to electrical energy in order to power implantable biomedical devices. Emerging new approaches on energy harvesting for powering biomedical devices are discussed in the literature. [7][8][9][10][11] In recent development, in vivo studies have been conducted to further advance the energy harvesting capabilities of these devices in living systems. [12,13] For example, a piezoelectric energy harvesting device using single crystalline (1-x) Pb(Mg 1/3 Nb 2/3 )O 3-x PbTiO 3 (PMN-PT) was implanted into the heart of a live rat and the device was then used to show functional electrical stimulation of the heart. [14] Heartbeats of pigs were also used to power wireless communication systems, [15] of which the integration with energy harvesting devices would allow for further implementation into implantable medical devices. Moreover, implantable triboelectric nanogenerators (iTENG) have been employed to convert the mechanical energy from the contraction from breathing of a rat to electricity, which was then used to power a pacemaker. [16] In another application, Self-sustainable energy generation represents a new frontier to greatly extend the lifetime and effectiveness of implantable biomedical devices, such as cardiac pacemakers and defibrillators. However, there is a lack of promising technologies which can efficiently convert the mechanical energy of the beating heart to electrical energy with minimal risk of interfering with the cardiovascular functions. Here a unique design is presented based on existing pacemaker leads tailored for compact energy harvesting. This new design incorporates flexible porous polyvinylidene fluoride-trifluoroethylene thin film withi...
Trabeculae carneae account for a significant portion of human ventricular mass, despite being considered embryologic remnants. Recent studies have found trabeculae hypertrophy and fibrosis in hypertrophied left ventricles with various pathological conditions. The objective of this study was to investigate the passive mechanical properties and microstructural characteristics of trabeculae carneae and papillary muscles compared to the myocardium in human hearts. Uniaxial tensile tests were performed on samples of trabeculae carneae and myocardium strips, while biaxial tensile tests were performed on samples of papillary muscles and myocardium sheets. The experimental data were fitted with a Fung-type strain energy function and material coefficients were determined. The secant moduli at given diastolic stress and strain levels were determined and compared among the tissues. Following the mechanical testing, histology examinations were performed to investigate the microstructural characteristics of the tissues. Our results demonstrated that the trabeculae carneae were significantly stiffer (Secant modulus SM2 = 80.06 ± 10.04 KPa) and had higher collagen content (16.10 ± 3.80%) than the myocardium (SM2 = 55.14 ± 20.49 KPa, collagen content = 10.06 ± 4.15%) in the left ventricle. The results of this study improve our understanding of the contribution of trabeculae carneae to left ventricular compliance and will be useful for building accurate computational models of the human heart.
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