In vivo measurement of the size of lipid droplets in an intracerebral glioma in the rat

Pulsed field gradient NMR was used to measure the root mean square displace ment lambda of the NMR visible lipid molecules in C6 brain tumors in the ra t at different diffusion times. For a distribution of spherical droplets of diameter with volume fraction xi(Phi (i)), the mean characteristic droplet diameter Phi (c) = root Sigma (i)xi(Phi (i))Phi (2)(i) was shown to be rel ated to the root mean square displacement at long diffusion times by the si mple relationship Phi (2)(c) = 10 lambda (2). In the range of diffusion tim es 100-530 msec, lambda was found to be independent of the diffusion time a nd equal to 1.35 +/- 0.22 mum and Phi (c) to 4.27 +/- 0.71 mum. The data re inforce the notion that the presence of lipid resonances in NMR spectra of tumors is due to lipid droplets. Light microscopy of histologic slices show ed the presence of lipid droplets mainly in the necrotic region and in a la yer of tumor cells surrounding the necrosis. (C) 2001 Wiley-Liss, Inc.