Heating effects of RF pulses

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Heating effects of RF pulses

Post by makyina » Thu Oct 01, 2015 4:27 pm

Hello! Does anybody know how parameters of RF pulses influence the measurement object temperatrue? I experiment with 9,4T magnetic resonance and I would like to know WHICH RF pulses and WHICH parametres od this RF pulses sould be important to examinate measurement object temperatrue changes :-( I am really confused :-( (Sorry for my English)

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Re: Heating effects of RF pulses

Post by myridm » Tue Nov 14, 2017 8:47 pm

Hello there,

Below the answer to your question:

Tissue Heating - An RF pulse (a short burst of an electromagnetic wave originating from the RF coils) is used in MRI to "excite" protons by an exchange of energy. This absorption of RF energy can potentially cause heating of the tissue. Absorption of RF power by the tissue is described in terms of Specific Absorption Rate (SAR), which is expressed in Watts/kg. (In the US, the recommended SAR level for head imaging is 3.2 Watts/kg.) SAR in MRI is a function of many variables including pulse sequence and coil parameters and the subject’s weight. However, the actual increase in tissue temperature caused by exposure to RF radiation is dependent on the persons’ thermoregulatory system. This is why when using the 3T magnet we do not allow the use of blankets or restrictive (such as large sweaters) clothing. The participant must be able to dissipate heat properly.

Electrical Burns - RF fields can cause burns by producing electrical currents in conductive loops. When using equipment such as surface coils, EEG leads, and response cables the investigator must be extremely careful not to allow the wire or cable to form a conductive loop with itself or with the participant.

Resource: http://cbs.fas.harvard.edu/science/core ... mr-hazards


Myri :D

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Re: Heating effects of RF pulses

Post by Dave Higgins » Wed Nov 15, 2017 8:30 am

You can reduce energy deposition, and therefore heating, with a reduction of flip angle. But this also affects image contrast.

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Re: Heating effects of RF pulses

Post by ThomasStokes » Wed Mar 21, 2018 6:08 am

Changes of the RF electromagnetic fields resulting from the changes in tissue electrical properties during an MR scan may affect, for example, both the efficacy of RF pulses and the MRI-induced specific absorption rate.The thermal and electrical effects of pulsed radiofrequency (PRF) for pain relief can be controlled by modifying the characteristics of the RF pulses applied. Our goal was to evaluate the influence of such modifications on the thermal and electric performance in tissue.

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Re: Heating effects of RF pulses

Post by Wolkins » Fri Aug 10, 2018 11:23 am

Hi Thomas, is there a place online where I can see the results of those experiments btw?

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