Numerical Studies of Temperature Changes in Adult and Paediatric Patients in Brain Magnetic Resonance Imaging

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.