共查询到20条相似文献,搜索用时 15 毫秒
1.
Cheolkyun Kim O'Rourke A.P. Mahvi D.M. Webster J.G. 《IEEE transactions on bio-medical engineering》2007,54(7):1177-1185
Cryoablation is a widely used method for the treatment of nonresectable primary and metastatic liver tumors. A model that can accurately predict the size of a cryolesion may allow more effective treatment of tumor, while sparing normal liver tissue. We generated a computer model of tissue cryoablation using the finite-element method (FEM). In our model, we considered the heat transfer mechanism inside the cryoprobe and also cryoprobe surfaces so our model could incorporate the effect of heat transfer along the cryoprobe from the environment at room temperature. The modeling of the phase shift from liquid to solid was a key factor in the accurate development of this model. The model was verified initially in an ex vivo liver model. Temperature history at three locations around one cryoprobe and between two cryoprobes was measured. The comparison between the ex vivo result and the FEM modeling result at each location showed a good match, where the maximum difference was within the error range acquired in the experiment (< 5 degC). The FEM model prediction of the lesion size was within 0.7 mm of experimental results. We then validated our FEM in an in vivo experimental porcine model. We considered blood perfusion in conjunction with blood viscosity depending on temperature. The in vivo iceball size was smaller than the ex vivo iceball size due to blood perfusion as predicted in our model. The FEM results predicted this size within 0.1-mm error. The FEM model we report can accurately predict the extent of cryoablation in the liver. 相似文献
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《IEEE transactions on medical imaging》2010,29(1):44-54
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Niedre M. Ntziachristos V. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2008,96(3):382-396
While the mathematics, physics, and technology behind magnetic resonance (MR) and fluorescence image formation are distinctively different, the two modalities have significant complementary features to impart strong preclinical and clinical application synergies. Traditionally, hybrid MR and fluorescence imaging implied the use of a system where optical and MR signals can be concurrently acquired. In this case, the common geometry allows for the superposition of fluorescence images of cellular and subcellular processes onto anatomical and functional MR images. More recently, a different hybrid imaging paradigm is strongly evolving by utilizing hybrid MR-fluorescence nanoparticles. This approach offers a second paradigm of hybrid visualization where the common underlying contrast enables the coregistration of MR and fluorescence images acquired under different geometries. We review herein progress with the evolving field of multimodality MR and fluorescence imaging and discuss how these strategies offer a highly promising outlook in established and in novel preclinical and clinical applications. 相似文献
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《IEEE transactions on bio-medical engineering》2009,56(6):1700-1710
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Cox M.P. Hongtao Ma Bahlke M.E. Beck J.H. Schwartz T.H. Kymissis I. 《Electron Devices, IEEE Transactions on》2010,57(1):174-177
We demonstrate a reflectivity-based cerebral blood volume sensor comprised of surface-mount light-emitting diodes on a flexible substrate with integrated photodetectors in a form factor suitable for direct brain contact and chronic implantation. This reflectivity monitor is able to measure blood flow through the change of the surface reflectivity and, through this mechanism, detect the cerebral-blood-volume changes associated with epileptic seizures with a signal-to-noise (SNR) response of 42 dB. The device is tested in an in vivo model confirming its compatibility and sensitivity. The data taken demonstrate that placing the sensor into direct brain contact improves the SNR by more than four orders of magnitude over current noncontact technologies. 相似文献
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Fingerprint recognition is one of the dominant methods among all biometric techniques. However, current commercial fingerprint reader systems are based on analysis of surface topography of a finger and, thus, have tremendous security vulnerability for simply made artificial fingerprint dummies. In this letter, we demonstrate that a novel optical coherence tomography-based method for depth-resolved 2-D and 3-D imaging and assessment of artificial and real fingerprints could significantly enhance spoof-proofing of fingerprint reader systems as well as provide information of both artificial and real ridge and furrow patterns (that form the fingerprint patterns) simultaneously. 相似文献
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Mercanzini A. Colin P. Bensadoun J.-C. Bertsch A. Renaud P. 《IEEE transactions on bio-medical engineering》2009,56(7):1909-1918
The goal of this experiment was to determine the electrical properties of the tissue reaction to implanted microelectrode arrays. We describe a new method of analyzing electrical impedance spectroscopy data to determine the complex impedance of the tissue reaction as a function of postimplantation time. A model is used to extract electrical model parameters of the electrode-tissue interface, and is used to isolate the impedance of the tissue immediately surrounding the microelectrode. The microelectrode arrays consist of microfabricated polyimide probes, incorporating four 50-mum-diameter platinum microelectrodes. The devices were implanted in the primary motor cortex of adult rats, and measurements were performed for 12 weeks. Histology was performed on implants at three time points in one month. Results demonstrate that the tissue reaction causes a rapid increase in bioimpedance over the first 20 days, and then stabilizes. This result is supported by histological data. 相似文献
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Ahuja A.K. Behrend M.R. Kuroda M. Humayun M.S. Weiland J.D. 《IEEE transactions on bio-medical engineering》2008,55(6):1744-1753
Epiretinal prostheses are being developed to bypass a degenerated photoreceptor layer and excite surviving ganglion and inner retinal cells. We used custom microfabricated multielectrode arrays with 200-mum-diameter stimulating electrodes and 10-mum-diameter recording electrodes to stimulate and record neural responses in isolated tiger salamander retina. Pharmacological agents were used to isolate direct excitation of ganglion cells from excitation of other inner retinal cells. Strength-duration data suggest that, if amplitude will be used for the coding of brightness or gray level in retinal prostheses, shorter pulses (200 mus) will allow for a smaller region in the area of the electrode to be excited over a larger dynamic range compared with longer pulses (1 ms). Both electrophysiological results and electrostatic finite-element modeling show that electrode-electrode interactions can lead to increased thresholds for sites half way between simultaneously stimulated electrodes (29.4 plusmn 6.6 nC) compared with monopolar stimulation (13.3 plusmn 1.7 nC, < 0.02). Presynaptic stimulation of the same ganglion cell with both 200- and 10- m-diameter electrodes yielded threshold charge densities of 12 plusmn 6 and 7.66 plusmn 1.30 nC/cm2, respectively, while the required charge was 12.5 plusmn 6.2 and 19 plusmn 3.3 nC. 相似文献
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《IEEE transactions on medical imaging》2009,28(11):1681-1687
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Tsung-Yu Chiang Tien-Sheng Chao Yi-Hong Wu Wen-Luh Yang 《Electron Device Letters, IEEE》2008,29(10):1148-1151
In this letter, for the first time, we have successfully fabricated silicon-oxide-nitride-oxide-silicon (SONOS) devices with embedded silicon nanocrystals (Si-NCs) in silicon nitride using in situ method. This process is simple and compatible to modern IC processes. Different Si-NCs deposition times by in situ method were investigated at first. SONOS devices with embedded Si-NCs in silicon nitride exhibit excellent characteristics in terms of larger memory windows (> 5.5 V), lower operation voltage, high P/E speed, and longer retention time (> 108 s for 13% charge loss). 相似文献
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Jacq J.-J. Cresson T. Burdin V. Roux C. 《IEEE transactions on bio-medical engineering》2008,55(5):1620-1633
This paper addresses the problem of the robust registration of multiple observations of the same object. Such a problem typically arises whenever it becomes necessary to recover the trajectory of an evolving object observed through standard 3-D medical imaging techniques. The instances of the tracked object are assumed to be variously truncated, locally subject to morphological evolutions throughout the sequence, and imprinted with significant segmentation errors as well as significant noise perturbations. The algorithm operates through the robust and simultaneous registration of all surface instances of a given object through median consensus. This operation consists of two interwoven processes set up to work in close collaboration. The first one progressively generates a median and implicit shape computed with respect to current estimations of the registration transformations, while the other refines these transformations with respect to the current estimation of their median shape. When compared with standard robust techniques, tests reveal significant improvements, both in robustness and precision. The algorithm is based on widely-used techniques, and proves highly effective while offering great flexibility of utilization. 相似文献
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Davis C.E. Dickherber A.J. Hunt W.D. May G.S. 《Electronics Packaging Manufacturing, IEEE Transactions on》2008,31(4):273-284
Variable-frequency microwave (VFM) curing can perform the same processing steps as conventional thermal processing in minutes, without compromising intrinsic material properties. With increasing demand for novel dielectrics, there is a corresponding demand for new processing techniques that lead to comparable or better properties than conventional methods. VFM processing can be a viable alternative to conventional thermal techniques. However, current limitations include a lack of reliable temperature measuring techniques. This research focuses on developing a reliable temperature measuring system using acoustic techniques to monitor low-k polymer dielectrics cured on silicon wafers in a VFM furnace. The acoustic sensor exhibits the capability to measure temperatures from 20degC to 300degC with an attainable accuracy of plusmn2 degrees. 相似文献
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Meng-Lin Li Jung-Taek Oh Xueyi Xie Geng Ku Wei Wang Chun Li Lungu G. Stoica G. Wang L.V. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2008,96(3):481-489
Noninvasive molecular and functional imaging in vivo is promising for detecting and monitoring various physiological conditions in animals and ultimately humans. To this end, we present a novel noninvasive technology, spectroscopic photoacoustic tomography (SPAT), which offers both strong optical absorption contrast and high ultrasonic spatial resolution. Optical contrast allows spectroscopic separation of signal contributions from multiple optical absorbers (e.g., oxyhemoglobin, deoxyhemoglobin, and a molecular contrast agent), thus enabling simultaneous molecular and functional imaging. SPAT successfully imaged with high resolution the distribution of a molecular contrast agent targeting integrin overexpressed in human U87 glioblastomas in nude mouse brains. Simultaneously, SPAT also imaged the hemoglobin oxygen saturation and the total hemoglobin concentration of the vasculature, which revealed hypoxia in tumor neovasculature. Therefore, SPAT can potentially lead to better understanding of the interrelationships between hemodynamics and specific biomarkers associated with tumor progression. 相似文献
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Tsz Ho Tse Z. Elhawary H. Zivanovic A. Rea M. Paley M. Bydder G. Davies B.L. Young I. Lamperth M.U. 《Mechatronics, IEEE/ASME Transactions on》2008,13(3):316-324
The "magic angle" effect consists of the increase in signal intensity observed at a tendon or cartilage in a magnetic resonance image, when the tissue is oriented at an angle of approximately 55deg with respect to the main magnetic field B0. The exploitation of this phenomenon is often used to assist diagnosis of tendinous and other diseases, although practical difficulties derived from positioning target tissue at the desired orientation inside closed-bore scanners has made this exploitation hard to implement. A 3-DOF MR-compatible mechatronic system has been developed to position a variety of limbs at the magic angle inside a closed- bore scanner, actuated by a custom-developed pneumatic air motor. The system is capable of locating the desired anatomy with high accuracy, and is designed to position the target tissue at a minimal distance from the isocenter. The compatibility of the system is demonstrated, producing negligible artifacts and an insignificant reduction in signal to noise of the image. Preliminary clinical trials scanning the Achilles tendon of healthy volunteers prove the functionality of the device. An increase in signal intensity of up to 21-fold has been recorded in the tendon at the magic angle. 相似文献
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《IEEE transactions on medical imaging》2009,28(8):1190-1197
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Owen N. R. Bouchoux G. Seket B. Murillo-Rincon A. Merouche S. Birer A. Paquet C. Delabrousse E. Chapelon J-.Y. Berriet R. Fleury G. Lafon C. 《IEEE transactions on bio-medical engineering》2010,57(1):80-92