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CT Hounsfield Units of Brown Adipose Tissue Increase with Activation: Preclinical and Clinical Studies

Shingo Baba, Heather A. Jacene, James M. Engles, Hiroshi Honda and Richard L. Wahl
Journal of Nuclear Medicine February 2010, 51 (2) 246-250; DOI: https://doi.org/10.2967/jnumed.109.068775

Article Figures & Data

Figures

  • FIGURE 1. 
    FIGURE 1. 

    (A) Sagittal CT HU of subcutaneous paraspinal BAT (arrow) in rodent is greater under activated conditions than under control conditions. 18F-FDG uptake of BAT is also increased under activated conditions. CT shows that BAT with increased fat density (right) fuses precisely to area of increased 18F-FDG uptake. (B) CT image of resected BAT with surrounding WAT subjected to 4 h of cold-stimulation shows greater CT density that is closer to water (top) than control kept at room temperature (bottom). Under control conditions, BAT is difficult to distinguish from surrounding WAT. On CT, higher CT HUs are shown as areas of increased whiteness, whereas low HUs are increasingly black. Areas of WAT and BAT as seen on direct visual inspection are shown in schematic at right.

  • FIGURE 2. 
    FIGURE 2. 

    On light microscopy, major structural changes can be seen in BAT cells stained with hematoxylin–eosin. Many large lipid vacuoles are seen in control BAT cells (A), but vacuoles are almost nonexistent in BAT cells exposed to cold (B). Lipid content is much lower in cold-stimulated BAT.

  • FIGURE 3. 
    FIGURE 3. 

    (A) Average CT HUs of BAT (46 regions from 23 patients) between high SUV for 18F-FDG and low SUV for 18F-FDG is shown. CT HUs in scans with high SUV were significantly higher than CT HUs in scans with low SUV (−71.6 ± 18.0 vs. −104.4 ± 16.8; P < 0.05). (B) When we plotted CT HUs against 18F-FDG uptake in all 92 ROIs, there was significant positive correlation between the 2 values (R = 0.66, P < 0.01).

  • FIGURE 4. 
    FIGURE 4. 

    Representative study of patient in whom CT HU of BAT is increased in parallel with increase in 18F-FDG uptake. A 20-y-old man with malignant lymphoma displayed bilateral cloudy BAT (increased CT HUs of −53 and −56) with avid 18F-FDG uptake (SUVmax = 3.4 and 3.2) (B), whereas baseline scan showed low-attenuation BAT (CT HUs of −87 and −85) with low 18F-FDG uptake (SUVmax = 0.9 and 1.0) (A). Both CT images are displayed with same window level (−20) and narrow window width (300) of CT HU to emphasize small difference of CT density in BAT.

Tables

  • TABLE 1

    Patient and Disease Characteristics (BAT-Avid Cohort)

    CharacteristicValue
    Age (y)
     Mean ± SD34 ± 17
     Range17–54
    Men/women (n)5/18
    Disease (n)
     Ovarian carcinoma5
     Non-Hodgkin lymphoma3
     Hodgkin disease2
     Thyroid carcinoma3
     Breast carcinoma2
     Malignant melanoma2
     Other6
  • TABLE 2

    Summary of In Vivo Imaging Studies

    Study typeFirst parameterSecond parameterP
    RatCold-activatedControl
     18F-FDG uptake (Bq/cm3 of BAT)1,982.8 ± 361.3892.9 ± 357.7<0.05
     CT HU (BAT)−12.4 ± 22.4−27.9 ± 9.6<0.05
     CT HU (WAT)−69.3 ± 9.7−75.6 ± 9.0NS
     CT HU (liver)19.8 ± 4.223.6 ± 9.9NS
    HumanHigh SUVLow SUV
     18F-FDG uptake (SUVmax of BAT)6.6 ± 2.80.9 ± 0.5<0.05
     CT HU (BAT)−71.6 ± 18.0−104.4 ± 16.8<0.05
     CT HU (WAT)−101.8 ± 6.4−102.6 ± 5.1NS
     CT HU (liver)56.0 ± 7.756.2 ± 7.4NS
     Frequency during cold season*19/234/23<0.05

    • ↵* Number of scans obtained between November and March of a total of 23 human scans.

    • NS = not statistically significant.

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