Courtesy of Dr Karla Suchacki and Dr Will Cawthorn, this image comes from the first study to use PET/CT to assess bone marrow adipose tissue (BMAT) glucose metabolism in vivo. BMAT is the fat-storing cells found within bone marrow, which accumulating evidence shows to differ from the two typically recognised subtypes of white adipose tissue (WAT) and brown adipose tissue (BAT).
To identify BMAT from clinical PET/CT scans, Hounsfield Units (HU) of subcutaneous fat, yellow marrow and red marrow were determined based on data from patients who had undergone paired MR and CT scans. The MR and CT scans were co-registered and volumes of interest were manually drawn around the sternum, vertebrae and subcutaneous adipose tissue. HU were extracted on a per voxel basis, and data underwent post-processing to measure the total number of voxels across all patient HU. ROC analysis was conducted on per voxel HU to determine threshold values with the greatest sensitivity and specificity to detect bone, yellow marrow and red marrow.
As shown in the image above, the volume of BMAT (yellow) is high in the arms, legs and sternum but is markedly lower in the clavicle, ribs and vertebrae, where red marrow (RM; red) predominates. The new method can be applied to identify BMAT from CT scans, allowing its functional analysis by PET/CT; assessing 18F-FDG uptake in co-registered PET and CT scans showed that BMAT has high basal glucose uptake.
The image is taken from a recent study available as a preprint on bioRxiv:
Suchacki KJ, Tavares AAS, Mattiucci D, Scheller EL, Papanastasiou G, Gray C, Sinton MC, Ramage LE, McDougald WA, Lovdel A, Sulston RJ, Thomas BJ, Nicholson BM, Drake AJ, Alcaide-Corral CJ, Said D, Poloni A, Cinti S, MacPherson GJ, Dweck MR, Andrews JPM, Williams MC, Wallace RJ, van Beek EJR, MacDougald OA, Morton NM, Stimson RH, Cawthorn WP. Bone marrow adipose tissue is a unique adipose subtype with distinct roles in systemic glucose homeostasis.