Abstract:
Magnetic Resonance Imaging (MRI) of the brain has seen a rising clinical
request during diagnosis. The ohmic heating of tissue results in rising human
temperature during MRI. This may be as a result of the unintentional heating
which seems to be an under-appreciated risk especially of high-field-strength
MRI. This study modelled Penne‘s bio-heat equation and used Matlab
programming language to predict in-vivo power deposition in brain tissues
during brain MRI of Radiofrequency (RF) above 100 kHz. Experimental
thermal dosimetry was carried out on 114 patients. These patients were
referred for (head) brain MRI at field strength of 0.3 tesla and 1.5 tesla at the
same scanning protocols of specific absorption rate (SAR) of 3.2 W/kg. The
experimental results showed that the highest change in temperature of 0.3 tesla
is 1.2 °C and 1.5 tesla is 1.9 °C. The average change confirmed that the
temperature distributions during MRI do not correlate well with SAR limit but
rather showed a positive correlation with patients‘ body mass index, scan
duration and the field strength. The lowest temperature during MRI from the
simulated results was 37.5 °C and the highest temperature was 42.5 °C during
brain scan of duration less than sixty minutes; this revealed that brain
temperature increased as scan duration increased. The highest estimated brain
temperature during brain MRI of the study was 43 °C and this depicted brain
hyperthermia since the temperature value was above 41 °C. This might
contribute to the causes of profuse localize sweating of some patients during
MRI in the acceptable ambient MRI environment. It is, therefore,
recommended that continuous temperature monitoring during MRI scan
should be the most paramount, particularly if the scan durations are prolonged.
