A Comprehensive Tissue Properties Database Provided for the Thermal Assessment of a Human at Rest

McIntosh, R.; Anderson, Vitas

doi:10.1142/s1793048010001184

Cited by 177 publications

(106 citation statements)

References 82 publications

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“…Certainly, tissue properties play a role in where peaks occur. For example, while a peak value for averaged SAR or VAR may occur in the brain, this is not the case for DT due to the high blood perfusion levels within the brain, especially gray matter [McIntosh and Anderson, 2010b]. We must also recall that in this study only valid voxels were considered, so that while DT values were defined everywhere, average SAR and VAR values had smaller domains.…”

Section: Relationship Between the Peak Of Each Metric With The Peak Omentioning

confidence: 97%

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SAR versus VAR, and the size and shape that provide the most appropriate RF exposure metric in the range of 0.5-6 GHz

McIntosh

Anderson

2011

Bioelectromagnetics

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Basic restrictions for protecting against localized tissue heating induced from exposure to radiofrequency (RF) fields are typically specified as the specific energy absorption rate (SAR), which is mass averaged in recognition of the thermal diffusion properties of tissues. This article seeks to determine the most appropriate averaging mass (1, 3, 5, 7, or 10 g) and averaging shape (cube or sphere). We also consider an alternative metric, volumetric energy absorption rate (VAR), which uses volume averaging (over 1, 3, 5, 7, and 10 cm(3) ; cube and sphere). The SAR and VAR averaging approaches were compared by considering which was a better predictor of tissue temperature rise (ΔT) induced by near- and far-field RF exposures (0.5-6 GHz), calculated in a detailed human body model. For the exposure scenarios that we examined, VAR is better correlated with ΔT than SAR, though not at a statistically significant level for most of the metric types we studied. However, as VAR offers substantive advantages in ease of assessment we recommend this metric over SAR. Averaging over a cube or a sphere provides equivalent levels of correlation with ΔT, and so we recommend choosing the averaging shape on the basis of which is easier to assess. The optimal averaging volume is 10 cm(3) for VAR, and the optimal mass is 10 g for SAR. The correlation between VAR or SAR and ΔT diminishes substantially at 6 GHz, where incident power flux density may be a better exposure metric.

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Section: Relationship Between the Peak Of Each Metric With The Peak Omentioning

confidence: 97%

“…The dielectric properties (electrical conductivity and relative permittivity) used in this study primarily originate from Gabriel [1996]. The thermal properties and mass density values were obtained from McIntosh and Anderson [2010b].…”

Section: Computational Modeling Setupmentioning

confidence: 99%

SAR versus VAR, and the size and shape that provide the most appropriate RF exposure metric in the range of 0.5-6 GHz

McIntosh

Anderson

2011

Bioelectromagnetics

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“…The black circle represents the cortical bone boundary and the white circle represents the marrow cavity. Ambient room temperature was applied to all other surfaces of the model as a uniform temperature boundary [47] 0.53 [19,45] 0.50 0.60 [49] 1738 1800 [46] 1050 [47,48] 994 [50] 1030 [47] 1776 1800 [46] 994 [50] 1050 [47,48] 1800 [46] 1390 994 [50] 1492 1290 [47] 3600 [47] 4167 [51] 2660 [47] 1376 1290 [47] 4167 [51] 3600 [47] 1290 [47] 2300 4167 [51] condition (22 °C), to mimic the experimental environment, until the bone returned to 37 °C. The resulting 3D temperature distributions derived from the global tissue level analysis were applied as boundary conditions for the osteon submodel.…”

Section: Globalmentioning

confidence: 99%

How Bone Tissue and Cells Experience Elevated Temperatures During Orthopaedic Cutting: An Experimental and Computational Investigation

Duffy

Vaughan

Niebur

et al. 2014

Journal of Biomechanical Engineering

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During orthopaedic surgery elevated temperatures due to cutting can result in bone injury, contributing to implant failure or delayed healing. However, how resulting temperatures are experienced throughout bone tissue and cells is unknown. This study uses a combination of experiments (forward-looking infrared (FLIR)) and multiscale computational models to predict thermal elevations in bone tissue and cells. Using multiple regression analysis, analytical expressions are derived allowing a priori prediction of temperature distribution throughout bone with respect to blade geometry, feed-rate, distance from surface, and cooling time. This study offers an insight into bone thermal behavior, informing innovative cutting techniques that reduce cellular thermal damage.

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“…The indicator for heat-sink strength by blood perfusion is the blood perfusion rate (m), usually expressed in mL/min/100 g [30]. In order to consider this parameter in Eq.…”

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confidence: 99%

Computer modelling of RF ablation in cortical osteoid osteoma: Assessment of the insulating effect of the reactive zone

Irastorza

Trujillo

Martel

et al. 2016

International Journal of Hyperthermia

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2 AbstractPurpose: To study by computer simulations the insulating role of the reactive zone surrounding a cortical osteoid osteoma (OO) in terms of electrical and thermal performance during radiofrequency ablation (RFA). Material and methods:We modeled a cortical OO consisting of a nidus (10 mm diameter) enclosed by a reactive zone. The OO is near a layer of cortical bone 1.5 mm thick. Trabecular bone partially surrounds the OO and there is muscle around the cortical bone layer. We modeled RF ablations with a non-cooled-tip 17G needle electrode (300 s duration and 90ºC target temperature). Sensitivity analyses were conducted assuming a reactive zone electrical conductivity value (σ rz ) within the limits of the cortical and trabecular bone, i.e. 0.02 S/m and 0.087 S/m, respectively. In this way we were really modeling the different degrees of osteosclerosis associated with the reactive zone. Results:The presence of the reactive zone drastically reduces the maximum temperature reached outside it. The temperature drop is proportional to the thickness of the reactive zone: from 68ºC when it is absent to 44ºC when it is 7.5 mm thick. Higher nidus conductivity values (σ n ) implied higher temperatures, while lower temperatures meant higher σ rz values. Changing σ rz from 0.02 S/m to 0.087 S/m reduced lesion diameters from 2.4 cm to 1.8 cm. Conclusions:The computer results suggest that the reactive zone plays the role of insulator in terms of reducing the temperature in the surrounding area.

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A Comprehensive Tissue Properties Database Provided for the Thermal Assessment of a Human at Rest

Cited by 177 publications

References 82 publications

SAR versus VAR, and the size and shape that provide the most appropriate RF exposure metric in the range of 0.5-6 GHz

SAR versus VAR, and the size and shape that provide the most appropriate RF exposure metric in the range of 0.5-6 GHz

How Bone Tissue and Cells Experience Elevated Temperatures During Orthopaedic Cutting: An Experimental and Computational Investigation

Computer modelling of RF ablation in cortical osteoid osteoma: Assessment of the insulating effect of the reactive zone

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