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Torres F, Basaran AC, Schuller IK. Thermal Management in Neuromorphic Materials, Devices, and Networks. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2205098. [PMID: 36067752 DOI: 10.1002/adma.202205098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Revised: 08/30/2022] [Indexed: 06/15/2023]
Abstract
Machine learning has experienced unprecedented growth in recent years, often referred to as an "artificial intelligence revolution." Biological systems inspire the fundamental approach for this new computing paradigm: using neural networks to classify large amounts of data into sorting categories. Current machine-learning schemes implement simulated neurons and synapses on standard computers based on a von Neumann architecture. This approach is inefficient in energy consumption, and thermal management, motivating the search for hardware-based systems that imitate the brain. Here, the present state of thermal management of neuromorphic computing technology and the challenges and opportunities of the energy-efficient implementation of neuromorphic devices are considered. The main features of brain-inspired computing and quantum materials for implementing neuromorphic devices are briefly described, the brain criticality and resistive switching-based neuromorphic devices are discussed, the energy and electrical considerations for spiking-based computation are presented, the fundamental features of the brain's thermal regulation are addressed, the physical mechanisms for thermal management and thermoelectric control of materials and neuromorphic devices are analyzed, and challenges and new avenues for implementing energy-efficient computing are described.
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Affiliation(s)
- Felipe Torres
- Physics Department, Faculty of Science, University of Chile, 653, Santiago, 7800024, Chile
- Center of Nanoscience and Nanotechnology (CEDENNA), Av. Ecuador 3493, Santiago, 9170124, Chile
| | - Ali C Basaran
- Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla, CA, 92093, USA
| | - Ivan K Schuller
- Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla, CA, 92093, USA
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Zhao Y, Ning J, Sun Z. Establishment and experimental verification of temperature prediction model for quick‐frozen strawberry jetted with dry ice. J FOOD PROCESS ENG 2022. [DOI: 10.1111/jfpe.14098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yanfeng Zhao
- Tianjin Key Laboratory of Refrigeration Technology Tianjin University of Commerce Tianjin China
| | - Jinghong Ning
- Tianjin Key Laboratory of Refrigeration Technology Tianjin University of Commerce Tianjin China
| | - Zhaoyang Sun
- Tianjin Key Laboratory of Refrigeration Technology Tianjin University of Commerce Tianjin China
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Lu D, Li S, Yang Q, Arafa HM, Xu Y, Yan Y, Ostojich D, Bai W, Guo H, Wu C, Li S, Jacobson L, Westman AM, MacEwan MR, Huang Y, Pet M, Rogers JA. Implantable, wireless, self-fixing thermal sensors for continuous measurements of microvascular blood flow in flaps and organ grafts. Biosens Bioelectron 2022; 206:114145. [DOI: 10.1016/j.bios.2022.114145] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 02/09/2022] [Accepted: 02/28/2022] [Indexed: 11/02/2022]
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Okabe T, Fujimura T, Okajima J, Kambayashi Y, Aiba S, Maruyama S. First-in-human clinical study of novel technique to diagnose malignant melanoma via thermal conductivity measurements. Sci Rep 2019; 9:3853. [PMID: 30846837 PMCID: PMC6405870 DOI: 10.1038/s41598-019-40444-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 02/14/2019] [Indexed: 11/21/2022] Open
Abstract
Melanoma is an aggressive skin cancer that originates from melanocytes and, especially in the case of early-stage melanoma, is distributed adjacent to the epidermis and superficial dermis. Although early-stage melanoma can be distinguished from benign nevus via a dermoscopy, it is difficult to distinguish invasive melanoma in its early stages from in situ melanoma. Because invasive melanoma must undergo a sentinel lymph node biopsy to be diagnosed, a non-invasive method to detect the micro-invasion of early-stage melanoma is needed for dermato-oncologists. This paper proposes a novel quantitative melanoma identification method based on accurate measurements of thermal conductivity using a pen-shaped device. This method requires skin temperature data for one minute to determine the effective thermal conductivity of the skin, allowing it to distinguish melanoma lesions from healthy skin. Results suggest that effective thermal conductivity was negative for in situ melanoma. However, in accordance with tumour progression, effective thermal conductivity was larger in invasive melanoma. The proposed thermal conductivity measurement is a novel tool that detects the micro-invasion of melanoma.
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Affiliation(s)
- Takahiro Okabe
- Graduate School of Science and Technology, Hirosaki University, Hirosaki, Japan.
| | - Taku Fujimura
- Graduate School of Medicine, Tohoku University, Sendai, Japan.
| | | | - Yumi Kambayashi
- Graduate School of Medicine, Tohoku University, Sendai, Japan
| | - Setsuya Aiba
- Graduate School of Medicine, Tohoku University, Sendai, Japan
| | - Shigenao Maruyama
- National Institute of Technology, Hachinohe College, Hachinohe, Japan
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Krishnan SR, Su CJ, Xie Z, Patel M, Madhvapathy SR, Xu Y, Freudman J, Ng B, Heo SY, Wang H, Ray TR, Leshock J, Stankiewicz I, Feng X, Huang Y, Gutruf P, Rogers JA. Wireless, Battery-Free Epidermal Electronics for Continuous, Quantitative, Multimodal Thermal Characterization of Skin. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2018; 14:e1803192. [PMID: 30369049 DOI: 10.1002/smll.201803192] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Revised: 09/03/2018] [Indexed: 05/26/2023]
Abstract
Precise, quantitative measurements of the thermal properties of human skin can yield insights into thermoregulatory function, hydration, blood perfusion, wound healing, and other parameters of clinical interest. The need for wired power supply systems and data communication hardware limits, however, practical applicability of existing devices designed for measurements of this type. Here, a set of advanced materials, mechanics designs, integration schemes, and wireless circuits is reported as the basis for wireless, battery-free sensors that softly interface to the skin to enable precise measurements of its temperature and thermal transport properties. Calibration processes connect these parameters to the hydration state of the skin, the dynamics of near-surface flow through blood vessels and implanted catheters, and to recovery processes following trauma. Systematic engineering studies yield quantitative metrics in precision and reliability in real-world conditions. Evaluations on five human subjects demonstrate the capabilities in measurements of skin hydration and injury, including examples of continuous wear and monitoring over a period of 1 week, without disrupting natural daily activities.
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Affiliation(s)
- Siddharth R Krishnan
- Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
- Simpson Querrey Institute for BioNanotechnology, Center for Bio-Integrated Electronics, Northwestern University, Evanston, IL, 60208, USA
| | - Chun-Ju Su
- Department of Materials Science and Engineering, Simpson Querrey Institute for BioNanotechnology, Center for Bio-Integrated Electronics, Northwestern University, Evanston, IL, 60208, USA
| | - Zhaoqian Xie
- Department of Civil and Environmental Engineering, Mechanical Engineering, Materials Science and Engineering, Northwestern University, Evanston, IL, 60208, USA
| | - Manish Patel
- Department of Materials Science and Engineering, Simpson Querrey Institute for BioNanotechnology, Center for Bio-Integrated Electronics, Northwestern University, Evanston, IL, 60208, USA
| | - Surabhi R Madhvapathy
- Department of Materials Science and Engineering, Simpson Querrey Institute for BioNanotechnology, Center for Bio-Integrated Electronics, Northwestern University, Evanston, IL, 60208, USA
| | - Yeshou Xu
- Department of Civil and Environmental Engineering, Mechanical Engineering, Materials Science and Engineering, Northwestern University, Evanston, IL, 60208, USA
- Key Laboratory of C&PC Structures of the Ministry of Education, Southeast University, Nanjing, 210096, China
| | - Juliet Freudman
- Department of Biomedical Engineering, Simpson Querrey Institute for BioNanotechnology, Center for Bio-Integrated Electronics, Northwestern University, Evanston, IL, 60208, USA
| | - Barry Ng
- Department of Materials Science and Engineering, Simpson Querrey Institute for BioNanotechnology, Center for Bio-Integrated Electronics, Northwestern University, Evanston, IL, 60208, USA
| | - Seung Yun Heo
- Department of Biomedical Engineering, Simpson Querrey Institute for BioNanotechnology, Center for Bio-Integrated Electronics, Northwestern University, Evanston, IL, 60208, USA
| | - Heling Wang
- Department of Civil and Environmental Engineering, Mechanical Engineering, Materials Science and Engineering, Northwestern University, Evanston, IL, 60208, USA
| | - Tyler R Ray
- Department of Materials Science and Engineering, Simpson Querrey Institute for BioNanotechnology, Center for Bio-Integrated Electronics, Northwestern University, Evanston, IL, 60208, USA
| | - John Leshock
- Department of Biomedical Engineering, Simpson Querrey Institute for BioNanotechnology, Center for Bio-Integrated Electronics, Northwestern University, Evanston, IL, 60208, USA
| | - Izabela Stankiewicz
- Department of Biomedical Engineering, Simpson Querrey Institute for BioNanotechnology, Center for Bio-Integrated Electronics, Northwestern University, Evanston, IL, 60208, USA
| | - Xue Feng
- AML, Department of Engineering Mechanics, Center for Mechanics and Materials, Tsinghua University, Beijing, 100084, China
| | - Yonggang Huang
- Department of Civil and Environmental Engineering, Mechanical Engineering, Materials Science and Engineering, Center of Bio-integrated electronics, Northwestern University, Evanston, IL, 60208, USA
| | - Philipp Gutruf
- Department of Biomedical Engineering, University of Arizona, Tucson, AZ, 85721, USA
| | - John A Rogers
- Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
- Department of Materials Science and Engineering, Biomedical Engineering, Chemistry, Mechanical Engineering, Electrical Engineering and Computer Science and Neurological Surgery, McCormick School of Engineering and Feinberg School of Medicine, Simpson Querrey Institute for BioNanotechnology, Center for Bio-Integrated Electronics, Northwestern University, Evanston, IL, 60208, USA
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Brionizio JD, Orlando ADF, Bonnier G. Characterization of a spherical heat source for measuring thermal conductivity and water content of ethanol and water mixtures. INTERNATIONAL JOURNAL OF METROLOGY AND QUALITY ENGINEERING 2017. [DOI: 10.1051/ijmqe/2017007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Dutta J, Kundu B. A revised approach for an exact analytical solution for thermal response in biological tissues significant in therapeutic treatments. J Therm Biol 2017; 66:33-48. [DOI: 10.1016/j.jtherbio.2017.03.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Revised: 03/03/2017] [Accepted: 03/27/2017] [Indexed: 12/27/2022]
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Natesan H, Bischof JC. Multiscale Thermal Property Measurements for Biomedical Applications. ACS Biomater Sci Eng 2017; 3:2669-2691. [PMID: 33418696 DOI: 10.1021/acsbiomaterials.6b00565] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Bioheat transfer-based innovations in health care include applications such as focal treatments for cancer and cardiovascular disease and the preservation of tissues and organs for transplantation. In these applications, the ability to preserve or destroy a biomaterial is directly dependent on its temperature history. Thus, thermal measurement and modeling are necessary to either avoid or induce the injury required. In this review paper, we will first define and discuss thermal conductivity and calorimetric measurements of biomaterials in the cryogenic (<-40 °C), subzero (<0 °C), hypothermic (<37 °C), and hyperthermic (>37 °C) regimes. For thermal conductivity measurements, we review the use of 3ω and laser flash techniques for measurement of thermal conductivity in thin (1 μm-2 mm thick), anisotropic, and/or multilayered tissues. At the nanoscale, we review the use of pump-probe and scanning probe methods to measure thermal conductivity at short temporal scales (10 ps-100 ns) and spatial scales (1 nm-1 μm), particularly in the coating and surrounding medium around metallic nanoparticles (1 nm-20 nm). For calorimetric techniques, we review differential scanning calorimetry (DSC), which is intrinsically at the microscale (e.g., tissue pieces or millions of cells in media). DSC is used with large sample mass (∼3-100 mg) over wide temperature ranges (-180 to 750 °C) with low-temperature scanning rates (<750 °C/min). The need to assess smaller samples at higher rates has led to the development of nanocalorimetry on a silicon based membrane. Here the sample weight is as low as 10 ng, thereby allowing ultra-rapid heating rates (∼1 × 107 C/min). Finally, we discuss various opportunities that are driving the need for new micro- and nanoscale thermal measurements.
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Affiliation(s)
- Harishankar Natesan
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - John C Bischof
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
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Liang XM, Sekar PK, Zhao G, Zhou X, Shu Z, Huang Z, Ding W, Zhang Q, Gao D. High accuracy thermal conductivity measurement of aqueous cryoprotective agents and semi-rigid biological tissues using a microfabricated thermal sensor. Sci Rep 2015; 5:10377. [PMID: 25993037 PMCID: PMC4438607 DOI: 10.1038/srep10377] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Accepted: 04/07/2015] [Indexed: 11/09/2022] Open
Abstract
An improved thermal-needle approach for accurate and fast measurement of thermal conductivity of aqueous and soft biomaterials was developed using microfabricated thermal conductivity sensors. This microscopic measuring device was comprehensively characterized at temperatures from 0 °C to 40 °C. Despite the previous belief, system calibration constant was observed to be highly temperature-dependent. Dynamic thermal conductivity response during cooling (40 °C to -40 °C) was observed using the miniaturized single tip sensor for various concentrations of CPAs, i.e., glycerol, ethylene glycol and dimethyl sulfoxide. Chicken breast, chicken skin, porcine limb, and bovine liver were assayed to investigate the effect of anatomical heterogeneity on thermal conductivity using the arrayed multi-tip sensor at 20 °C. Experimental results revealed distinctive differences in localized thermal conductivity, which suggests the use of approximated or constant property values is expected to bring about results with largely inflated uncertainties when investigating bio-heat transfer mechanisms and/or performing sophisticated thermal modeling with complex biological tissues. Overall, the presented micro thermal sensor with automated data analysis algorithm is a promising approach for direct thermal conductivity measurement of aqueous solutions and soft biomaterials and is of great value to cryopreservation of tissues, hyperthermia or cryogenic, and other thermal-based clinical diagnostics and treatments.
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Affiliation(s)
- Xin M Liang
- 1] Centre for Biomedical Engineering, Department of Electronic Science and Technology, University of Science and Technology of China, Hefei, Anhui 230027, China [2] USTC Center for Micro- and Nanoscale Research and Fabrication, University of Science and Technology of China, Hefei, Anhui 230027, China [3] Department of Mechanical Engineering, University of Washington, Seattle, WA 98195, USA [4] CAS Key Laboratory of Mechanical Behavior and Design of Material, Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230027, China
| | - Praveen K Sekar
- Department of Mechanical Engineering, University of Washington, Seattle, WA 98195, USA
| | - Gang Zhao
- Centre for Biomedical Engineering, Department of Electronic Science and Technology, University of Science and Technology of China, Hefei, Anhui 230027, China
| | - Xiaoming Zhou
- School of Mechanical, Electronic, and Industrial Engineering, University of Electronic Science and Technology of China, Chengdu, Sichuan 611731, China
| | - Zhiquan Shu
- Department of Mechanical Engineering, University of Washington, Seattle, WA 98195, USA
| | - Zhongping Huang
- Department of Biomedical Engineering, Widener University, Chester, PA 19013, USA
| | - Weiping Ding
- Centre for Biomedical Engineering, Department of Electronic Science and Technology, University of Science and Technology of China, Hefei, Anhui 230027, China
| | - Qingchuan Zhang
- CAS Key Laboratory of Mechanical Behavior and Design of Material, Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230027, China
| | - Dayong Gao
- Department of Mechanical Engineering, University of Washington, Seattle, WA 98195, USA
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Dillon CR, Payne A, Christensen DA, Roemer RB. The accuracy and precision of two non-invasive, magnetic resonance-guided focused ultrasound-based thermal diffusivity estimation methods. Int J Hyperthermia 2014; 30:362-71. [PMID: 25198092 DOI: 10.3109/02656736.2014.945497] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
PURPOSE The use of correct tissue thermal diffusivity values is necessary for making accurate thermal modelling predictions during magnetic resonance-guided focused ultrasound (MRgFUS) treatment planning. This study evaluates the accuracy and precision of two non-invasive thermal diffusivity estimation methods, a Gaussian temperature method and a Gaussian specific absorption rate (SAR) method. MATERIALS AND METHODS Both methods utilise MRgFUS temperature data obtained during cooling following a short (<25 s) heating pulse. The Gaussian SAR method can also use temperatures obtained during heating. Experiments were performed at low heating levels (ΔT∼10 °C) in ex vivo pork muscle and in vivo rabbit back muscle. The non-invasive MRgFUS thermal diffusivity estimates were compared with measurements from two standard invasive methods. RESULTS Both non-invasive methods accurately estimated thermal diffusivity when using MR temperature cooling data (overall ex vivo error <6%, in vivo <12%). Including heating data in the Gaussian SAR method further reduced errors (ex vivo error <2%, in vivo <3%). The significantly lower standard deviation values (p < 0.03) of the Gaussian SAR method indicated that it had better precision than the Gaussian temperature method. CONCLUSIONS With repeated sonications, either MR-based method could provide accurate thermal diffusivity values for MRgFUS therapies. Fitting to more data simultaneously likely made the Gaussian SAR method less susceptible to noise, and using heating data helped it converge more consistently to the FUS fitting parameters and thermal diffusivity. These effects led to the improved precision of the Gaussian SAR method.
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Guntur SR, Lee KI, Paeng DG, Coleman AJ, Choi MJ. Temperature-dependent thermal properties of ex vivo liver undergoing thermal ablation. ULTRASOUND IN MEDICINE & BIOLOGY 2013; 39:1771-84. [PMID: 23932271 DOI: 10.1016/j.ultrasmedbio.2013.04.014] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2012] [Revised: 04/17/2013] [Accepted: 04/18/2013] [Indexed: 05/08/2023]
Abstract
Thermotherapy uses a heat source that raises temperatures in the target tissue, and the temperature rise depends on the thermal properties of the tissue. Little is known about the temperature-dependent thermal properties of tissue, which prevents us from accurately predicting the temperature distribution of the target tissue undergoing thermotherapy. The present study reports the key thermal parameters (specific heat capacity, thermal conductivity and heat diffusivity) measured in ex vivo porcine liver while being heated from 20 ° C to 90 ° C and then naturally cooled down to 20 ° C. The study indicates that as the tissue was heated, all the thermal parameters resulted in plots with asymmetric quasi-parabolic curves with temperature, being convex downward with their minima at the turning temperature of 35-40 ° C. The largest change was observed for thermal conductivity, which decreased by 9.6% from its initial value (at 20 ° C) at the turning temperature (35 ° C) and rose by 45% at 90 ° C from its minimum (at 35 ° C). The minima were 3.567 mJ/(m(3) ∙ K) for specific heat capacity, 0.520 W/(m.K) for thermal conductivity and 0.141 mm(2)/s for thermal diffusivity. The minimum at the turning temperature was unique, and it is suggested that it be taken as a characteristic value of the thermal parameter of the tissue. On the other hand, the thermal parameters were insensitive to temperature and remained almost unchanged when the tissue cooled down, indicating that their variations with temperature were irreversible. The rate of the irreversible rise at 35 ° C was 18% in specific heat capacity, 40% in thermal conductivity and 38.3% in thermal diffusivity. The study indicates that the key thermal parameters of ex vivo porcine liver vary largely with temperature when heated, as described by asymmetric quasi-parabolic curves of the thermal parameters with temperature, and therefore, substantial influence on the temperature distribution of the tissue undergoing thermotherapy is expected.
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Affiliation(s)
- Sitaramanjaneya Reddy Guntur
- Interdisciplinary Postgraduate Program of Biomedical Engineering, Jeju National University, Jeju Special Self-Governing Province, Jeju-Si, Republic of Korea
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13
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Liang XM, Ding W, Chen HH, Shu Z, Zhao G, Zhang HF, Gao D. Microfabricated thermal conductivity sensor: a high resolution tool for quantitative thermal property measurement of biomaterials and solutions. Biomed Microdevices 2011; 13:923-8. [DOI: 10.1007/s10544-011-9561-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Sarkar S, Zimmermann K, Leng W, Vikesland P, Zhang J, Dorn H, Diller T, Rylander C, Rylander MN. Measurement of the thermal conductivity of carbon nanotube--tissue phantom composites with the hot wire probe method. Ann Biomed Eng 2011; 39:1745-58. [PMID: 21360225 DOI: 10.1007/s10439-011-0268-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Accepted: 02/03/2011] [Indexed: 11/26/2022]
Abstract
Developing combinatorial treatments involving laser irradiation and nanoparticles require an understanding of the effect of nanoparticle inclusion on tissue thermal properties, such as thermal conductivity. This information will permit a more accurate prediction of temperature distribution and tumor response following therapy, as well as provide additional information to aid in the selection of the appropriate type and concentration of nanoparticles. This study measured the thermal conductivity of tissue representative phantoms containing varying types and concentrations of carbon nanotubes (CNTs). Multi-walled carbon nanotubes (MWNTs, length of 900-1200 nm and diameter of 40-60 nm), single-walled carbon nanotubes (SWNTs, length of 900-1200 nm and diameter <2 nm), and a novel embodiment of SWNTs referred to as single-walled carbon nanohorns (SWNHs, length of 25-50 nm and diameter of 3-5 nm) of varying concentrations (0.1, 0.5, and 1.0 mg/mL) were uniformly dispersed in sodium alginate tissue representative phantoms. The thermal conductivity of phantoms containing CNTs was measured using a hot wire probe method. Increasing CNT concentration from 0 to 1.0 mg/mL caused the thermal conductivity of phantoms containing SWNTs, SWNHs, and MWNTs to increase by 24, 30, and 66%, respectively. For identical CNT concentrations, phantoms containing MWNTs possessed the highest thermal conductivity.
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Affiliation(s)
- Saugata Sarkar
- Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
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Park BK, Park J, Kim D. Note: Three-omega method to measure thermal properties of subnanoliter liquid samples. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2010; 81:066104. [PMID: 20590275 DOI: 10.1063/1.3441963] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
There are growing needs to measure the thermal properties of small-volume liquid samples in various fields of bioengineering and microfluidics. Accordingly, there have been efforts toward miniaturization of the sensing device without substantially sacrificing the sensitivity. The minimum sample volume required for quantitative thermal analysis is currently in the 10 nl scale. In this work, we describe microfabricated sensors and a modified three-omega data-analysis scheme to determine the thermal conductivity k and volumetric heat capacity rhoc(p) of samples of a few hundred picoliters. In experiments using several reference liquids, the technique measured k and rhoc(p) of 750 and 375 pl samples. The measurement accuracies were approximately 10% for k and approximately 15% for rhoc(p).
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Affiliation(s)
- Byoung Kyoo Park
- Department of Mechanical Engineering, POSTECH, Pohang 790-784, Republic of Korea
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Choi J, Bischof JC. Review of biomaterial thermal property measurements in the cryogenic regime and their use for prediction of equilibrium and non-equilibrium freezing applications in cryobiology. Cryobiology 2009; 60:52-70. [PMID: 19948163 DOI: 10.1016/j.cryobiol.2009.11.004] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2009] [Revised: 11/16/2009] [Accepted: 11/24/2009] [Indexed: 01/06/2023]
Abstract
It is well accepted in cryobiology that the temperature history and cooling rates experienced in biomaterials during freezing procedures correlate strongly with biological outcome. Therefore, heat transfer measurement and prediction in the cryogenic regime is central to the field. Although direct measurement of temperature history (i.e. heat transfer) can be performed, accuracy is usually achieved only for local measurements within a given system and cannot be readily generalized to another system without the aid of predictive models. The accuracy of these models rely upon thermal properties which are known to be highly dependent on temperature, and in the case of significant cryoprotectant loading, also on crystallized fraction. In this work, we review the available thermal properties of biomaterials in the cryogenic regime. The review shows a lack of properties for many biomaterials in the subzero temperature domain, and especially for systems with cryoprotective agents. Unfortunately, use of values from the limited data available (usually only down to -40 degrees C) lead to an underestimation of thermal property change (i.e. conductivity rise and specific heat drop due to ice crystallization) with lower temperatures. Conversely, use of surrogate values based solely on ice thermal properties lead to an overestimation of thermal property change for most biomaterials. Additionally, recent work extending the range of available thermal properties to -150 degrees C has shown that the thermal conductivity will drop in both PBS and tissue (liver) due to amorphous/glassy phases (versus crystalline) of biomaterials with the addition of cryoprotective additives such as glycerol. Thus, we investigated the implications of using approximated or constant property values versus measured temperature-dependent values for predicting temperature history during freezing in PBS (phosphate-buffered saline) and porcine liver with and without cryoprotectants (glycerol). Using measured property values (thermal conductivity, specific heat, and latent heat of phase change) of porcine liver, a standard was created which showed that values based on surrogate ice properties under-predicted cooling times, while constant properties (i.e. based on limited data reported near the freezing point) over-predicted cooling times. Additionally, a new iterative numerical method that accommodates non-equilibrium cooling effects as a function of time and position (i.e. crystallization versus amorphous phase) was used to predict temperature history during freezing in glycerol loaded systems. Results indicate that in addition to the increase in cooling times due to the lowering of thermal diffusivity with more glycerol, non-equilibrium effects such as the prevention of maximal crystallization (i.e. amorphous phases) will further increase required cooling times. It was also found that the amplified effect of non-equilibrium cooling and crystallization with system size prevents the thermal history to be described with non-dimensional lengths, such as was possible under equilibrium cooling. These results affirm the need to use accurate thermal properties that incorporate temperature dependence and crystallized fraction. Further studies are needed to extract thermal properties of other important biomaterials in the subzero temperature domain and to develop accurate numerical methods which take into account non-equilibrium cooling events encountered in cryobiology when partial or total vitrification occurs.
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Affiliation(s)
- Jeunghwan Choi
- Department of Mechanical Engineering, University of Minnesota, 111 Church St. SE, Minneapolis, MN 55455, USA
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Kharalkar NM, Bauserman SC, Valvano JW. Effect of formalin fixation on thermal conductivity of the biological tissue. J Biomech Eng 2009; 131:074508. [PMID: 19640144 DOI: 10.1115/1.3147745] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Effect of formalin fixation on thermal conductivity of the biological tissues is presented. A self-heated thermistor probe was used to measure the tissue thermal conductivity. The thermal conductivity of porcine aorta, fat, heart, and liver was measured before the formalin fixation and then 1 day, 4 days, and 11 days after formalin fixation. The results indicate that the formalin fixation does not cause a significant change in the tissue thermal conductivity of the tissues studied. In the clinical setting, tissues removed surgically are often fixed in formalin for subsequent pathological analysis. These results suggest that, in terms of thermal properties, it is equally appropriate to perform in vitro studies in either fresh tissue or formalin-fixed tissue.
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Affiliation(s)
- Nachiket M Kharalkar
- Department of Electrical and Computer Engineering, University of Texas at Austin, 1 University Station C0803, Austin, TX 78712, USA.
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Ladurner R, Feilitzsch M, Steurer W, Coerper S, Königsrainer A, Beckert S. The impact of a micro-lightguide spectrophotometer on the intraoperative assessment of hepatic microcirculation: a pilot study. Microvasc Res 2009; 77:387-8. [PMID: 19323973 DOI: 10.1016/j.mvr.2009.01.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2008] [Revised: 01/19/2009] [Accepted: 01/21/2009] [Indexed: 11/25/2022]
Abstract
INTRODUCTION The intraoperative measurement of the peripheral microperfusion after liver transplantation is connected with quite an effort and a continuous evaluation in the postoperative follow up is not possible till now. PATIENTS AND METHODS Before mobilization of the liver during surgical intervention the following parameters were measured on the surface of the right (segment 7/8) and the left (segment 2/3) liver lobe with a probe, combining laser-Doppler-flowmetry and tissue-spectrometry: the oxygen saturation (SO2), the relative capillary hemoglobin concentration (rHB), the blood flow (flow) and the blood flow velocity (velo). In addition the peripheral oxygen saturation (SPO2), the central venous pressure (ZVP), the positive endexspiratory pressure (PEEP) and the hemoglobin (HB) were documented. RESULTS 9 patients (median age 75 years) were included in the study. SPO2, ZVP, PEEP and HB were regular. The parameters SO2, rHB, flow and velo showed no significant changes between the right and the left liver lobe. CONCLUSIONS The O2C-method allows a reproducible intraoperative evaluation of the hepatic microcirculation.
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Affiliation(s)
- Ruth Ladurner
- Department of General, Visceral and Transplant Surgery, University Hospital Tübingen, Hoppe-Seyler-Str. 3, D-72076 Tübingen, Germany.
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Harikrishnan G, Macosko CW, Jeung Hwan Choi, Bischof JC, Singh SN. A Simple Transient Method for Measurement of Thermal Conductivity of Rigid Polyurethane Foams. J CELL PLAST 2008. [DOI: 10.1177/0021955x08096532] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Rigid polyurethane foams (PU) are widely used as thermal insulators in various applications. The thermal conductivity of the foam is the key parameter that governs the efficiency of thermal insulation provided by the foam. The usual technique employed to measure thermal conductivity is based on the rate of steady state heat transfer across a known thickness, induced by two different known temperatures at two opposite surfaces of the foam. We introduce a technique based on the transient measurement of heat transfer measured by an embedded needle probe. This technique is not only rapid but the instrumentation required for such a measurement is simple and the cost is only a fraction of the steady state counterpart. The values of thermal conductivity obtained by both methods are compared and found to agree within 4% over the range of 0.02—0.03 W/mK, which is the usual range of thermal conductivity for commercial rigid PU foams. The sensitivity of the needle probe technique is demonstrated by measuring the thermal conductivity values of foams made with various concentrations of chemical blowing agent (water). The present technique is also shown to be effective for measuring the thermal conductivity of small samples, especially, free rise cup foams for which the steady state technique can not be used.
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Affiliation(s)
- G. Harikrishnan
- Department of Chemical Engineering and Material Science University of Minnesota, Minneapolis, MN, 55455, USA,
| | - Christopher W. Macosko
- Department of Chemical Engineering and Material Science University of Minnesota, Minneapolis, MN, 55455, USA
| | - Jeung Hwan Choi
- Department of Mechanical Engineering University of Minnesota Minneapolis, MN, 55455, USA
| | - John C. Bischof
- Department of Mechanical Engineering University of Minnesota Minneapolis, MN, 55455, USA
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Saxena V, Marcu L, Karunasiri G. A novel noninvasive all optical technique to monitor physiology of an exercising muscle. Phys Med Biol 2008; 53:6211-25. [DOI: 10.1088/0031-9155/53/21/021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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21
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A quantitative analysis of the thermal properties of porcine liver with glycerol at subzero and cryogenic temperatures. Cryobiology 2008; 57:79-83. [DOI: 10.1016/j.cryobiol.2008.05.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2007] [Revised: 05/14/2008] [Accepted: 05/20/2008] [Indexed: 11/19/2022]
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22
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Mehrabi A, Golling M, Kashfi A, Boucsein T, Schemmer P, Gutt CN, Schmidt J, Büchler MW, Kraus TW. Negative impact of systemic catecholamine administration on hepatic blood perfusion after porcine liver transplantation. Liver Transpl 2005; 11:174-87. [PMID: 15666391 DOI: 10.1002/lt.20299] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Catecholamines are often administered during and after liver transplantation (LTx) to support systemic perfusion and to increase organ oxygen supply. Some vasoactive agents can compromise visceral organ perfusion. We followed the hypothesis that the vasculature of transplanted livers presents with a higher sensitivity, which leads to an increased vulnerability for flow derangement after application of epinephrine (Epi) or norepinephrine (NorEpi). Hepatic macroperfusion and microperfusion during systemic Epi or NorEpi infusion were measured by Doppler flow and thermodiffusion probes in porcine native, denervated, and transplanted livers (n = 16 in each group). Epi or NorEpi were infused (n = 8 in each subgroup) in predefined dosages (low dose = 5 microg/kg/minute and high dose = 10 microg/kg/minute) over 240 minutes. Systemic cardiocirculatory parameters were monitored continuously. Hepatic perfusion data were compared between all groups at comparable time points and dosages. In all native, denervated, and transplanted liver groups, Epi and NorEpi induced an inconsistent rise of mean arterial pressure and heart rate shortly after onset of infusion in both dosages compared with baseline. No significant differences of cardiovascular parameters at comparable time points were observed. In native livers, Epi and NorEpi induced only temporary alterations of hepatic macrocirculation and microcirculation, which returned to baseline 2 hours after onset of infusion. No significant alterations of hepatic blood flow were detected after isolated surgical denervation of the liver. By contrast, transplanted livers showed a progressive decline of hepatic macrocirculation (33-75% reduction) and microcirculation (39-58% reduction) during catecholamine infusions in a dose-dependent fashion. Characteristics of liver blood flow impairment were comparable for both vasoactive agents. In conclusion, pronounced disturbances of hepatic macrocirculation and microcirculation were observed during systemic Epi and NorEpi infusion after LTx compared with native and denervated livers. Microcirculation disturbances after LTx might be explained by impairment of hepatic blood flow regulation caused by an increased sensitivity of hepatic vasculature after ischemia-reperfusion and by lengthening of vasopressor effects caused by reduced hepatocyte metabolism. Clinicians should be aware of this potentially hazardous effect. Therefore, application of catecholamines after clinical LTx should be indicated carefully.
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Affiliation(s)
- Arianeb Mehrabi
- Division of Liver Transplantation, Department of General, Visceral, and Transplant Surgery, University of Heidelberg, 69120 Heidelberg, Germany.
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Abstract
In this paper, we present our experimental results on the determination of the thermal conductivity of biological tissues using a transient technique based on the principles of the cylindrical hot-wire method. A novel, 1.45 mm diameter, 50 mm long hot-wire probe was deployed. Initial measurements were made on sponge, gelatin and Styrofoam insulation to test the accuracy of the probe. Subsequent experiments conducted on sheep collagen in the range of 25 degrees C < T < 55 degrees C showed the thermal conductivity to be a linear function of temperature. Further, these changes in the thermal conductivity were found to be reversible. However, when the tissue was heated beyond 55 degrees C, irreversible changes in thermal conductivity were observed. Similar experiments were also conducted for determining the thermal conductivity of cow liver. In this case, the irreversible effects were found to set in much later at around 90 degrees C. Below this temperature, in the range of 25 degrees C < T < 90 degrees C, the thermal conductivity, as for sheep collagen, varied linearly with temperature. In the second part of our study, in vivo measurements were taken on the different organs of a living pig. Comparison with reported values for dead tissues shows the thermal conductivities of living organs to be higher, indicating thereby the dominant role played by blood perfusion in enhancing the net heat transfer in living tissues. The degree of enhancement is different in different organs and shows a direct dependence on the blood flow rate.
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Affiliation(s)
- A Bhattacharya
- Mechanical Engineering Department, University of Colorado at Boulder, Boulder, CO 80309-0427, USA
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25
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Deng ZS, Liu J. Analytical study on bioheat transfer problems with spatial or transient heating on skin surface or inside biological bodies. J Biomech Eng 2002; 124:638-49. [PMID: 12596630 DOI: 10.1115/1.1516810] [Citation(s) in RCA: 135] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Several closed form analytical solutions to the bioheat transfer problems with space or transient heating on skin surface or inside biological bodies were obtained using Green's function method. The solutions were applied to study several selected typical bioheat transfer processes, which are often encountered in cancer hyperthermia, laser surgery, thermal comfort analysis, and tissue thermal parameter estimation. Thus a straightforward way to quantitatively interpret the temperature behavior of living tissues subject to constant, sinusoidal, step, point or stochastic heatings etc. both in volume and on boundary were established. Further solution to the three-dimensional bioheat transfer problems was also given to illustrate the versatility of the present method. Implementations of this study to the practical problems were addressed.
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Affiliation(s)
- Zhong-Shan Deng
- Cryogenics Laboratory, P.O. Box 2711, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100080, P.R. China
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26
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Liu J, Zhou YX, Deng ZS. Sinusoidal heating method to noninvasively measure tissue perfusion. IEEE Trans Biomed Eng 2002; 49:867-77. [PMID: 12148826 DOI: 10.1109/tbme.2002.800769] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Noninvasively measuring the tissue blood perfusion has been an important however difficult problem in the biomedical engineering field. Based on the newly developed phase-shift principle, an improved sinusoidal heating method to estimate the perfusion was proposed in this paper to replace the original heating algorithm. The phase shift between the sinusoidal heat flux and the surface temperature response was both theoretically and experimentally revealed to be a time-dependent value which however will approach a constant value after a sufficiently long time. Only using this constant phase shift can the perfusion be properly estimated. Following the theory, an instrument consisting of low-frequency sinusoidal signal generator, power amplifier, heating plate, temperature and heat flux monitoring unit, as well as the data-acquisition system was carefully constructed. It allows generating a high-quality sinusoidal heat flux whose frequency and magnitude can be easily regulated. An auxiliary heat-conducting plate was introduced to simultaneously measure the surface temperature and the heat flux, which are hard to do otherwise. Experiments on human bodies were performed and the forearm perfusion was estimated and then validated through a constant surface heating experiment. Several issues related to the instrument integration and perfusion measurement were discussed. The instrument was also tested through experiments on nonperfused materials and good results were obtained. These efforts will help to build a compact device for noninvasively measuring the human perfusion, which may have significant applications in future clinics.
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Affiliation(s)
- Jing Liu
- Cryogenic Laboratory, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, P. R. China.
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Bhavaraju NC, Cao H, Yuan DY, Valvano JW, Webster JG. Measurement of directional thermal properties of biomaterials. IEEE Trans Biomed Eng 2001; 48:261-7. [PMID: 11296882 DOI: 10.1109/10.909647] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This paper presents an experimental technique to measure the directional thermal conductivity and thermal diffusivity of materials. A heated thermistor heats the sample and a sensing thermistor placed about 2.5 mm away measures the temperature rise due the heating pulse at the heated thermistor. An empirical relation between the power delivered by the first thermistor and the temperature rise recorded by the sensing thermistor is used to measure the thermal conductivity of the material along the line joining the thermistors. Diffusivity of the material is determined from the delay between the power pulse in the heated thermistor and the temperature pulse at the sensing thermistor. Signal processing was done to eliminate errors in the measurement due to change of base line temperature. Uncertainty of the measurement technique was found to be 5% when tested in media of known thermal properties. The thermal conductivity and thermal diffusivity of swine left ventricle in normal and ablated conditions were measured using this technique. The thermal conductivity of the tissue dropped significantly from 0.61 to 0.50 W.m(-1).K(-1) after ablation while the diffusivity dropped from 2.1 x 10(-7) to 1.7 x 10(-7)m2.s(-1).
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28
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Deng ZS, Liu J. Parametric studies on the phase shift method to measure the blood perfusion of biological bodies. Med Eng Phys 2000; 22:693-702. [PMID: 11334755 DOI: 10.1016/s1350-4533(01)00015-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
To better understand the phase shift method to non-invasively measure the blood perfusion of living tissues in vivo, the dual reciprocity boundary element method (DRBEM) was applied to numerically solve the transient and non-linear two-dimensional bio-heat transfer in biological bodies subject to a sinusoidal heat flux at the skin surface. The influences of the heating flux, the heating oscillation magnitude, the heating frequency, the blood vessel underneath the skin, and the space or temperature dependent blood perfusion to the temperature response and the phase shift between the heat flux and the temperature response at the skin surface were comprehensively examined. The effects of the heating area to the temperature response were also investigated. And a better understanding on the heat transfer behavior of biological bodies under sinusoidal heating was thus obtained. These results are expected to be valuable for constructing the practical instrumentation to non-invasively measure the blood perfusion of biological bodies.
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Affiliation(s)
- Z S Deng
- Cryogenic Laboratory, Chinese Academy of Sciences, P.O. Box 2711, Beijing 100080, People's Republic of China
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29
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Kraus T, Mehrabi A, Golling M, Schäffer F, Bud O, Gebhard MM, Herfarth C, Klar E. Effects of exogenous endothelin-1 application on liver perfusion in native and transplanted porcine livers. J Surg Res 2000; 93:272-81. [PMID: 11027470 DOI: 10.1006/jsre.2000.5972] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
PURPOSE This study was designed to assess and differentiate the impact of progressivly increasing portal venous endothelin-1 (ET) plasma concentrations on hepatic micro- and macroperfusion of native porcine livers (Group A) and liver grafts after experimental transplantation (Group B). METHODS A standardized gradual increment in systemic ET plasma concentration (0-58 pg/ml) was induced by continuous ET-1 infusion into the portal vein in both groups (A: n = 10, B: n = 10). Control animals received only saline (n = 5, each group). Hepatic microcirculation (HMC) was quantified by thermodiffusion electrodes, hepatic artery flow (HAF), and portal venous flow (PVF) by Doppler flowmetry. RESULTS No changes in ET or perfusion parameters were observed in controls. The mean ET level after orthotopic liver transplantation (OLT) in Group B was elevated (baseline: 3.8 +/- 2.4 pg/ml) compared with Group A (2.8 +/- 1.9 pg/ml). With rising ET levels HAF decreased progressively in Group A from 205 +/- 97 (baseline) to 160 +/- 72 ml/min, and in Group B from 161 +/- 87 to 146 +/- 68 ml/min. PVF decreased in Group A from 722 +/- 253 to 370 +/- 198 ml/min, and in Group B from 846 +/- 263 to 417 +/- 203 ml/min. Baseline HMC in Group A was 86 +/- 15 and decreased significantly to 29 +/- 9 ml/100 g/min, and baseline MC in Group B was 90 +/- 22 and decreased to 44 +/- 32 ml/100 g/min. No significant alteration in systemic circulation was noted at the ET concentrations investigated. CONCLUSIONS Significant impairment of hepatic micro- and macrocirculation was detected after induction of systemic ET levels above 9.4 pg/ml both in native and in transplanted livers. Disturbance of HMC was caused predominantly by reduction of portal venous flow, while the effect of ET on HAF was less pronounced. Characteristics of flow impairment in transplanted and native livers were analogous after short cold ischemic graft storage (6 h).
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Affiliation(s)
- T Kraus
- Department of Surgery, University of Heidelberg, Heidelberg, Germany.
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30
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Liu J, Xu LX. Estimation of blood perfusion using phase shift in temperature response to sinusoidal heating at the skin surface. IEEE Trans Biomed Eng 1999; 46:1037-43. [PMID: 10493066 DOI: 10.1109/10.784134] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A closed form analytical solution of the Pennes' bio-heat equation was obtained for temperature distributions in the skin tissue subject to the sinusoidal heat flux. Phase shifts in the surface temperature response were revealed to be related to local blood perfusion rate and heating frequency. The influence of the thermal contact resistance on the perfusion estimation was investigated. It has been proved that this influence is relatively small because of the phase shift based estimation and can be effectively eliminated by application of highly conductive grease. This analysis provides the theoretical foundation for a new noninvasive modality of blood perfusion estimation based on the surface temperature measurement which can have significant applications in future clinical practices.
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Affiliation(s)
- J Liu
- School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907-1288, USA
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31
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Abstract
Thermotherapy of the uterus has emerged as an alternative to hysterectomy in the treatment of menorrhagia, from whence it follows that the thermal properties of uterine tissue have become of importance. This study presents measurements of the thermal conductivity and the water content of uterine tissue in vitro. A steady-state thermal conductivity apparatus, based on the comparison of test samples with a material with known thermal conductivity, is described. Measurements were conducted on tissue samples from eleven patients, directly after hysterectomy. Samples with and without endometrium, as well as coagulated samples, were examined. The thermal conductivity of myometrial tissue was found to be 0.536 +/- 0.012 W m(-1) K(-1) (mean +/- 1 SD) and the corresponding water content was 81.2 +/- 1.5% (mean +/- 1 SD). Measurements on samples with both endometrium and myometrium showed similar thermal conductivity (0.542 +/- 0.008 W m(-1) K(-1), mean +/- 1 SD) and water content (81.6 +/- 0.7%, mean +/- 1 SD). It was also indicated that coagulation causes dehydration, resulting in a lower thermal conductivity.
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Affiliation(s)
- J Olsrud
- Department of Radiation Physics, Lund University Hospital, Sweden
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32
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Liu J, Ren Z, Wang C. A technique for identifying the total space or temperature dependent thermal parameters (TITP) of biological materials in vivo. IEEE Trans Biomed Eng 1996; 43:847-50. [PMID: 9216157 DOI: 10.1109/10.508547] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A new algorithm for simultaneously identifying the space or temperature dependent conductivity K, blood perfusion rate Wb, metabolic rate qm, and thermal diffusibility alpha in Pennes' equation is postulated. The obtained over determined equations are solved by way of Householder's transformation. The validity of the method is tested through an example.
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Affiliation(s)
- J Liu
- Thermal Engineering Department, Tsinghua University, Beijing, PRC
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Abstract
A thermal method has been developed to quantify continuous perfusion changes with self-calibration. A dynamic, one-dimensional bio-heat transfer model of the thermal probe and tissue describes the system response to either continuous or transient heating. A nonlinear least-squares fit of the model to experimental data yields estimates of the baseline perfusion and other model parameters. With a partial analytical solution of the model, the optimal estimation procedure is two orders of magnitude more efficient than with a total numerical solution of the model system. Experimental data is used to estimate the operating relations between perfusion and the temperature measurement. A new procedure has also been presented to obtain the dynamic response of the system for continuous measurement of perfusion.
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Affiliation(s)
- D Wei
- Department of Neurosciences, Cleveland Clinic Foundation, OH 44195-5283, USA
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Wei D, Saidel GM, Jones SC. Thermal method for continuous measurement of cerebral perfusion. Med Biol Eng Comput 1994; 32:481-8. [PMID: 7845063 DOI: 10.1007/bf02515305] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A new thermal system using constant heating power for continuous measurement of cerebral perfusion is presented. It is designed and implemented for optimal perfusion sensitivity and dynamic response based on heat-transfer analysis of perfused brain tissue with thermistors on the cortical surface. Two matched thermistors are used, one to serve as a perfusion sensor and the other to compensate for the base-line temperature changes. To improve the signal-to-noise ratio of the measurement system, lock-in amplifiers are used to minimise long-term drift and low-frequency noise. Errors in the measurement caused by electrical and thermal fluctuations are tested and analysed. In vitro tests show that the measurement accuracy of temperature change is better than 10(-3) degrees C, and the temperature resolution is even greater. In vivo evaluation confirms that the system is responsive to cerebral perfusion changes associated with sudden changes in mean arterial blood pressure caused by bolus injection of norepinephrine, blood withdrawal and blood infusion. The dynamic response of the system is sufficient to detect the autoregulatory perfusion changes in response to arterial blood pressure alteration and the oscillations of cerebral blood flow.
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Affiliation(s)
- D Wei
- Department of Neurosciences, Cleveland Clinic Foundation, OH 44195-5283
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A View of the History of Heat Transfer in Bioengineering. ACTA ACUST UNITED AC 1992. [DOI: 10.1016/s0065-2717(08)70343-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Wei DT, Saidel GM, Jones SC. Optimal design of a thermistor probe for surface measurement of cerebral blood flow. IEEE Trans Biomed Eng 1990; 37:1159-72. [PMID: 2289790 DOI: 10.1109/10.64457] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Microthermistors are put on the surface of cerebral cortex to monitor local cerebral blood flow (CBF) continuously with minimal tissue damage and disturbance to the normal physiological state. Using a distributed, dynamic model of the measurement system, we simulated the effects of this flow measurement method under isothermal and adiabatic boundary conditions. Numerical results show that the adiabatic boundary condition can provide maximal sensitivity to perfusion changes at physiological perfusion levels. The constant power and constant temperature operating modes are compared in terms of output relation, sensitivity, and frequency response through analytical and numerical solutions. While the steady-state relations between thermistor measurements and perfusion for the two modes do not differ significantly, the constant temperature mode has better frequency response. Analytical results show that the relative sensitivity is the same for the two modes and is approximately proportional to the radius of thermistor. If there is an unperfused layer surrounding the thermistor, the sensitivity will decrease as the thickness of the layer increases. Simulations predict that the thermal measurement has a low-pass frequency response and the cutoff frequency is inversely proportional to the probe surface area. The results provide a theoretical foundation to the optimal design of thermistor probe for continuous CBF measurement from tissue surface.
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Affiliation(s)
- D T Wei
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106
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37
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Adams T, Spielman WS, Holmes KR, Heisey SR, Chen MM. Proposed methods for the measurement of regional renal blood flow using heat transfer analysis. Ann Biomed Eng 1985; 13:237-58. [PMID: 3898927 DOI: 10.1007/bf02584242] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The kidney, with its heterogeneous regional perfusion in the two anatomically and functionally distinct vascular beds of the renal cortex and medulla, and with its non-uniform blood vessel geometries, presents a unique challenge for measuring intrarenal blood flow distribution. Determining whole organ perfusion, on the other hand, is comparatively simple for the kidney, but it provides relatively little information about the suspected dependency of renal excretory function on local perfusion rate. Among the variety of methods proposed for gauging regional renal blood flow, some depend on measuring one or more of the tissue's thermal properties. The most straightforward, but least reliable, involve measurements either of focal tissue temperature alone, or of regional tissue thermal gradients. Simply using heat as a diffusible indicator, however, is unreliable as a measure of blood flow, for many of the same reasons that using an inert gas in a dilution technique is unreliable. Recently developed thermal analytical methods, though, hold promise for measuring local tissue blood flow with accuracy and precision. Two of them are reviewed here. One depends on measurement of the effective thermal conductivity of a small mass of tissue by evaluating the steady state ratio between regional unidirectional heat flux across it and the associated temperature gradient in one vector along a segment of it through an imposed spheroidal heat field. The other depends on analyses of tissue temperature decay subsequent to a controlled pulse of heat delivered through a small inserted thermistor bead. Both techniques use bioheat transfer equations to deduce regional blood flow by differentiating between heat dissipation due to local thermal conductivity and that attributable to the effects of regional convection. Although both methods are unavoidably invasive, neither produces debilitating damage in the tissue volume in which perfusion is measured, nor increases local temperature or metabolism enough to affect blood flow itself. Both techniques quantify local blood flow in small volumes of tissue by detailed evaluation of the many properties of tissue and blood which affect heat transfer, and both allow for a virtually unlimited number of nearly continuous sequential measurements at short (nom. 1 min) time intervals.
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Abstract
Drinking water that does not equilibrate with ruminal fluid, i.e., bypasses the rumen, was studied qualitatively and quantitatively in eight rumen-fistulated lactating Holstein cows. Decreased temperatures in the sulcus omasi and abomasum shortly after initiation of drinking indicated that water had bypassed the rumen. Recovery of a water-soluble marker, included in drinking water offered after water was withheld for 4.5 or 9 h following feeding, was used to estimate ruminal bypass. For respective treatments, 18 and 5% of drinking water was calculated to have bypassed the rumen. Ruminal bypass in lactating cows drinking relatively large amounts of water could affect comparisons of water intake with total ruminal fluid outflow as measured by dilution of a water-soluble marker. Drinking water should not be assumed to equilibrate with ruminal fluid.
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Holmes KR, Ryan W, Chen MM. Thermal conductivity and H2O content in rabbit kidney cortex and medulla. J Therm Biol 1983. [DOI: 10.1016/0306-4565(83)90014-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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