MRI detection of brown adipose tissue with low fat content in newborns with hypothermia.
OBJECTIVE
To report the observation of brown adipose tissue (BAT) with low fat content in neonates with hypoxic-ischemic encephalopathy (HIE) after they have undergone hypothermia therapy.


METHODS
The local ethics committee approved the imaging study. Ten HIE neonates (3 males, 7 females, age range: 2-3days) were studied on a 3-T MRI system using a low-flip-angle (3°) six-echo proton-density-weighted chemical-shift-encoded water-fat pulse sequence. Fat-signal fraction (FF) measurements of supraclavicular and interscapular (nape) BAT and adjacent subcutaneous white adipose tissues (WAT) were compared to those from five non-HIE neonates, two recruited for the present investigation and three from a previous study.


RESULTS
In HIE neonates, the FF range for the supraclavicular, interscapular, and subcutaneous regions was 10.3%-29.9%, 28.0%-57.9%, and 62.6%-88.0%, respectively. In non-HIE neonates, the values were 23.7%-42.2% (p=0.01), 45.4%-59.5% (p=0.06), and 67.8%-86.3% (p=0.38), respectively. On an individual basis, supraclavicular BAT FF was consistently the lowest, interscapular BAT values were higher, and subcutaneous WAT values were the highest (p<0.01).


CONCLUSIONS
We speculate that hypothermia therapy in HIE neonates likely promotes BAT-mediated non-shivering thermogenesis, which subsequently leads to a depletion of the tissue's intracellular fat stores. We believe that this is consequently reflected in lower FF values, particularly in the supraclavicular BAT depot, in contrast to non-HIE neonates.
Radiology, Children's Hospital Los Angeles, Los Angeles, CA, USA. Electronic address: hhu@chla.usc.edu.
Houchun H
HH
Hu
Neonatology, Children's Hospital Los Angeles, Los Angeles, CA, USA.
Tai-Wei
TW
Wu
Pediatrics, Children's Hospital Los Angeles, Los Angeles, CA, USA.
Larry
L
Yin
Pediatrics, Children's Hospital Los Angeles, Los Angeles, CA, USA.
Mimi S
MS
Kim
Philips Healthcare, Cleveland, OH, USA.
Jonathan M
JM
Chia
Philips Healthcare, Cleveland, OH, USA.
Thomas G
TG
Perkins
Radiology, Children's Hospital Los Angeles, Los Angeles, CA, USA; Pediatrics, Children's Hospital Los Angeles, Los Angeles, CA, USA.
Vicente
V
Gilsanz
D002001:Adipose Tissue, Brown / Q000473:pathology*; D005260:Female; D006801:Humans; D007035:Hypothermia / Q000473:pathology*; D007036:Hypothermia, Induced; D020925:Hypoxia-Ischemia, Brain / Q000628:therapy*; D007231:Infant, Newborn; D016014:Linear Models; D008279:Magnetic Resonance Imaging; D008297:Male; D015203:Reproducibility of Results; D014867:Water / Q000737:chemistry
D014867:Water
Brown adipose tissue; Fat-signal fraction; Hypothermia; Infants; Water-fat MRI