Comparison of Specific Absorption Ratio Monitoring Values on Various MRI Systems

Ishikuro, Akihiro; Ogura, Akio; Hongou, Takaharu; Inoue, Hiroshi; Yamazaki, Masaru

doi:10.6009/jjrt.kj00001356926

Cited by 2 publications

(2 citation statements)

References 2 publications

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“…Therefore, the value of SAR was thought to be an important factor and a good index of RF heating, although there may be greater or lesser diŠerences according to the SAR calculation method of the MR scanner. 20 RF heating of the implant can be suppressed by decreasing SAR within the permissible range. However, the use of largediameter transmit whole-body coil built into the MR scanner makes SAR large, except a transmit/receive coil with small diameter such as a knee coil.…”

Section: Discussionmentioning

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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Section: Discussionmentioning

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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“…Even with the same parameter settings in MR imaging, large variations in the displayed SAR ave values were reported among different MRI systems, 39 , 40 suggesting that the displayed SAR ave does not always guarantee the safety of MR examination. Another preliminary study indicated that large errors in the displayed SAR ave values were observed in experiments based on the standard F2182 provided by ASTM International (see subsection “ Assessment standards of RF heating due to implants ”).…”

Section: Safety Standardmentioning

confidence: 99%

Progress in Understanding Radiofrequency Heating and Burn Injuries for Safer MR Imaging

Tang

Yamamoto

2023

MRMS

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RF electromagnetic wave exposure during MRI scans induces heat and occasionally causes burn injuries to patients. Among all the types of physical injuries that have occurred during MRI examinations, RF burn injuries are the most common ones. The number of RF burn injuries increases as the static magnetic field of MRI systems increases because higher RFs lead to higher heating. The commonly believed mechanisms of RF burn injuries are the formation of a conductive loop by the patient's posture or cables, such as an electrocardiogram lead; however, the mechanisms of RF burn injuries that occur at the contact points, such as the bore wall and the elbow, remain unclear. A comprehensive understanding of RF heating is needed to address effective countermeasures against all RF burn injuries for safe MRI examinations. In this review, we summarize the occurrence of RF burn injury cases by categorizing RF burn injuries reported worldwide in recent decades. Safety standards and regulations governing RF heating that occurs during MRI examinations are presented, along with their theoretical and physiological backgrounds. The experimental assessment techniques for RF heating are then reviewed, and the development of numerical simulation techniques is explained. In addition, a comprehensive theoretical interpretation of RF burn injuries is presented. By including the results of recent experimental and numerical simulation studies on RF heating, this review describes the progress achieved in understanding RF heating from the standpoint of MRI burn injury prevention.

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Comparison of Specific Absorption Ratio Monitoring Values on Various MRI Systems

Cited by 2 publications

References 2 publications

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

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

Progress in Understanding Radiofrequency Heating and Burn Injuries for Safer MR Imaging

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