Estimation of heat transfer and temperature rise in partial-body regions during MR procedures: an analytical approach with respect to safety considerations

Brix, Gunnar; Seebass, M.; Hellwig, Gesine; Griebel, Jürgen

doi:10.1016/s0730-725x(02)00483-6

Cited by 86 publications

(50 citation statements)

References 27 publications

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“…Each zone respectively corresponds to insulator (polystyrene), PVA hydrogel, and PVA hydrogel dispersing magnetite nanoparticles in the experiments. Thermal conductivity, specific heat capacity, and mass density of each material 45) are shown in Table 2. Values of heat release rate at different concentrations of nanoparticles are also shown in Table 2 and added to the energy equation in the spherical zone as heat source term.…”

Section: Heat Diffusion Characteristics Of Magnetitementioning

confidence: 99%

Present status and prospects of magnetite nanoparticles-based hyperthermia

Jeyadevan

2010

J. Ceram. Soc. Japan

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Magnetic fluid hyperthermia is a cancer treatment technique that utilizes the heat dissipated by magnetic nanoparticles exposed to an alternating current magnetic field. The heat dissipated is consequence of the conversion of the magnetic energy through different relaxation mechanisms, which depends on the physical properties of the magnetic particles. Particularly, in the case of magnetic nanoparticles, the magnetic energy is converted to heat energy either by the resistive response of the rotation of the magnetic particles (Brownian relaxation) or the rotation of the magnetic moment within the particles (Néel relaxation) to the alternating magnetic field. In this article, the main focus has been on the progress of theoretical and experimental investigations towards the realization of magnetic fluid hyperthermia (MFH) through heat dissipation by Néel relaxation of magnetite particles. We discuss about the present status and prospects of magnetite nanoparticles-based hyperthermia focusing mainly on the dissipation of heat through Néel relaxation mechanism. In doing so, an attempt has been made to review and deepen the understanding on specific topics such as (a) specific heat absorption characteristics of magnetite, especially the physical properties of particles that generate heat through Néel relaxation, (b) the preparation techniques available to synthesize particles with required properties, (c) experimental investigations carried out to determine the relative contribution of Néel relaxation to dissipate heat and their potential for in vivo application, and (d) the theoretical estimation of and experimental verification of heat diffusion characteristics of magnetite. The theoretical and experimental studies have suggested that the development of case specific treatment technologies based on an integrated approach considering both the physical constraints of the magnetic particles to be used as thermal seeds and practically feasible alternating magnetic field generators is a must for the establishment of MFH therapy in the foreseeable future.

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Section: Heat Diffusion Characteristics Of Magnetitementioning

confidence: 99%

Present status and prospects of magnetite nanoparticles-based hyperthermia

Jeyadevan

2010

J. Ceram. Soc. Japan

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“…4 According to the IEC recommendation, the upper limit in the Japanese Industrial Standards (JIS) was also reviewed in 1999 5 and provided for an upper limit of 2.0 W/kg for 6 min average as the usual operation mode and 4.0 W/kg for 15 min average as theˆrst-level operation mode, which is the same as the IEC standard. However, risk of burn accidents remains during MR imaging following these standards, [6][7][8][9] most resulting from contact between the skin of the human body and the cable of the electrocardiography monitor, oxygen color saturation monitor, or RF receiving coil. 10 Knopp's group has also reported cases where burning occurred during MR imaging procedures without such environmental conditions.…”

Section: Introductionmentioning

confidence: 99%

Dependence of RF Heating on SAR and Implant Position in a 1.5T MR System

Muranaka

Horiguchi

Usui

et al. 2007

MRMS

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Purpose: We evaluated radiofrequency (RF) heating of a humerus implant embedded in a gel phantom during magnetic resonance (MR) imaging for the speciˆc absorption rate (SAR), angle between the implant and static magneticˆeld (B 0 ), and position of the implant in the irradiation coil.Methods: We embedded a stainless steel humerus implant 2 cm deep in tissue-equivalent loop and mass phantoms, placed it parallel to the static magneticˆeld of a 1.5T MR scanner, and recorded the temperatures of the implant surface with RF-transparentˆberoptic sensors. We measured rises in temperature at the tips of the implant by varying the SAR from 0.2 to 4.0 W/kg and evaluated RF heating of the implant for its angle to B 0 and its displacement along B 0 from the center of the RF irradiation coil.Results: RF heating was similar for the loop and mass phantoms because the eddy current ‰ows through the periphery of both. As the SAR increased, the temperature at the implant tip increased, and there was a linear relationship between the SAR and temperature rise. The values were 6.49 C at 2.0 W/kg and 12.79 C at 4.0 W/kg. Rise in temperature decreased steeply as the angle between the implant and B 0 surpassed 459 . In addition, as the implant was displaced from the center of the RF coil to both ends, the rise in temperature decreased.Conclusion: The rise in temperature in deep tissue was estimated to be higher than 1.09 C for SAR above 0.4 W/kg. RF heating was greatest when the implant was set parallel to B 0 . In MR imaging of patients with implants, there is a risk of RF heating when the loop of the eddy current is formed inside the body.

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“…The need for high RF deposition, in order to produce the MR images at any particular field, however, is subject of extensive research in experimental as well as computational aspects [20 -22]. In a recent CEM modeling of tissue heating, no temperature increases in any of the tissues investigated were observed above 0.58C/(W kg) of RF power input [23].…”

Section: Discussionmentioning

confidence: 99%