title: Temperature-induced changes of magnetic resonance relaxation times in the human brain: a postmortem study.
abstract: OBJECTIVE
  Magnetic resonance relaxation times of most tissues are expected to depend on temperature, which can impact findings in postmortem magnetic resonance imaging or when using magnetic resonance imaging for relaxation-based thermometry. The purpose of this study was to investigate the exact temperature dependency of the relaxation times T(1), T(2), T(2) *, and the magnetization transfer ratio in different structures of the human brain.
  
  
  METHODS
  To prevent fixation and autolysis effects, this study was performed with fresh postmortem brain tissues. Following autopsy, coronal brain slices from five deceased subjects were subjected to relaxometry at 3T in a temperature range between 4°C and 37°C. Heating of the tissue was achieved by flushing the vacuum packed brain slices with water at a predefined temperature.
  
  
  RESULTS
  T1 showed a linear dependency on temperature with the highest temperature coefficient in the cortex (17.4 ms/°C) and the lowest in the white matter (3.4 ms/°C). T(2) did not depend on temperature. T(2) * and magnetization transfer ratio scaled with temperature only in deep gray matter.
  
  
  CONCLUSIONS
  The temperature coefficient for T(1) is higher than expected from previous reports and varies across brain structures. The coefficients obtained in this study can serve as reference for thermometry or for correcting quantitative postmortem magnetic resonance imaging.
authors.affiliation: Department of Neurology, Medical University of Graz, Austria.
authors.forename: Christoph
authors.initials: C
authors.lastname: Birkl
authors.forename: Christian
authors.initials: C
authors.lastname: Langkammer
authors.forename: Johannes
authors.initials: J
authors.lastname: Haybaeck
authors.forename: Christina
authors.initials: C
authors.lastname: Ernst
authors.forename: Rudolf
authors.initials: R
authors.lastname: Stollberger
authors.forename: Franz
authors.initials: F
authors.lastname: Fazekas
authors.forename: Stefan
authors.initials: S
authors.lastname: Ropele
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001831:Body Temperature; D001921:Brain / Q000473:pathology* / Q000502:physiology*; D002102:Cadaver; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011180:Postmortem Changes; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: brain; magnetic resonance imaging; postmortem; relaxation; temperature dependency; thermometry