Quantitative kinetic modelling and mapping of cerebral glucose transport and metabolism using glucoCESL MRI.

Chemical-exchange spin-lock (CESL) MRI can map regional uptake and utilisation of glucose in the brain at high spatial resolution (i.e sub 0.2 mm³ voxels). We propose two quantitative kinetic models to describe glucose-induced changes in tissue <i>R</i>_1ρ and apply them to glucoCESL MRI data acquired in tumour-bearing and healthy rats. When assuming glucose transport is saturable, the maximal transport capacity (<i>T</i>_max) measured in normal tissue was 3.2 ± 0.6 µmol/min/mL, the half saturation constant (<i>K</i>_t) was 8.8 ± 2.2 mM, the metabolic rate of glucose consumption (<i>MR</i>_glc) was 0.21 ± 0.13 µmol/min/mL, and the cerebral blood volume (<i>v</i>_b) was 0.006 ± 0.005 mL/mL. Values in tumour were: <i>T</i>_max = 7.1 ± 2.7 µmol/min/mL, <i>K</i>_t = 14 ± 1.7 mM, <i>MR</i>_glc = 0.22 ± 0.09 µmol/min/mL, <i>v</i>_b = 0.030 ± 0.035 mL/mL. <i>T</i>_max and <i>K</i>_t were significantly higher in tumour tissue than normal tissue (p = 0.006 and p = 0.011, respectively). When assuming glucose uptake also occurs via free diffusion, the free diffusion rate (<i>k</i>_d) was 0.061 ± 0.017 mL/min/mL in normal tissue and 0.12 ± 0.042 mL/min/mL in tumour. These parameter estimates agree well with literature values obtained using other approaches (e.g. NMR spectroscopy).