EMF-Portal | Alterations in body and skin temperatures caused by magnetic resonance imaging: is the recommended exposure for radiofrequency radiation too conservative?

Alterations in body and skin temperatures caused by magnetic resonance imaging: is the recommended exposure for radiofrequency radiation too conservative? med./bio.

Aim of study (acc. to author)

To report the use of the fluoroptic thermometry system to determine body and skin temperature responses before, during and after magnetic resonance imaging (MRI) of human subjects exposed to mean SARs six to 10 times higher than the level recommended by the NRPB (UK National Radiological Protection Board).

Endpoint

thermoregulation: body and skin temperature responses

Exposure

Exposure	Parameters
Exposure 1: 64 MHz Exposure duration: 30 min	SAR: 2.8 mW/g mean (unspecified) (body weight of the subject = 69 kg.) SAR: 3.4 mW/g mean (unspecified) (body weight of the subject = 81 kg.) SAR: 4 mW/g mean (unspecified) (body weight of the subject = 61 kg.) SAR: 3.6 mW/g mean (unspecified) (body weight of the subject = 74.5 and 77 kg.) SAR: 2.7 mW/g mean (unspecified) (body weight of the subject = 90.5 kg.) magnetic flux density: 1.5 T

General information

MRI experiment.

Exposure 1

Main characteristics

Frequency	64 MHz
Exposure duration	30 min

Exposure setup

Exposure source	1.5 T superconducting magnet with a circularly polarized transmit/recieve RF coil
Setup	Each subject was positioned in the MRI scanner such that the subject`s umbilicus was at the center of the coil.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
SAR	2.8 mW/g	mean	measured and calculated	unspecified	body weight of the subject = 69 kg.
SAR	3.4 mW/g	mean	measured and calculated	unspecified	body weight of the subject = 81 kg.
SAR	4 mW/g	mean	measured and calculated	unspecified	body weight of the subject = 61 kg.
SAR	3.6 mW/g	mean	measured and calculated	unspecified	body weight of the subject = 74.5 and 77 kg.
SAR	2.7 mW/g	mean	measured and calculated	unspecified	body weight of the subject = 90.5 kg.
magnetic flux density	1.5 T	-	-	-	-

Exposed system:

human
whole body

Methods Endpoint/measurement parameters/methodology

thermoregulation: body and skin temperature (fluoroptic thermometry system)

Investigated system:

investigation on living organism

Time of investigation:

before exposure
during exposure
after exposure

Main outcome of study (acc. to author)

Body temperature was unchanged. Abdominal skin temperature increased significantly during MRI, decreased significantly post-MRI, but was still significantly higher than baseline. The highest abdominal skin temperature measured was 36°C. Upper arm, forearm and chest skin temperatures increased significantly during MRI and remained elevated post-MRI. The highest skin temperatures recorded on the upper arm, forearm and chest were 38.1, 36.0 and 34.5°C, respectively. Thigh and calf skin temperatures were not significantly changed during MRI. These changes in tissue temperatures were physiologically trivial and easily tolerated by the subjects, suggesting that the recommended exposure to radiofrequency irradiation during MRI of the body for patients with normal thermoregulatory function may be too conservative.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

National Cancer Institute (NCI; U.S. National Institutes of Health), Maryland, USA

National Institutes of Health (NIH), Maryland, USA

Public Health Service (PHS), USA

Shellock FG et al. (1994): Physiologic responses to an MR imaging procedure performed at a specific absorption rate of 6.0 W/kg

Shellock FG et al. (1988): Temperature changes caused by MR imaging of the brain with a head coil

Shellock FG et al. (1987): Temperature, heart rate, and blood pressure changes associated with clinical MR Imaging at 1.5 T