Non‐invasive In Vivo localized 1H spectroscopy of human astrocytoma implanted in rat brain: Regional differences followed in time

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Abstract
Human astrocytoma cells were cultured and inoculated into the rat brain. From the pre‐clinical to the terminal state, tumour growth was monitored by in vivo MR imaging and by localized water‐suppressed 1H spectroscopy (0.12‐0.15 cm3 volumes) and spectroscopic imaging (0.01 cm3 voxels) employing the ACE localization technique. The MR experiments were conducted completely non‐invasively, leaving the scalp intact. Brain spectra were obtained, showing distinct resonances for more than five different brain metabolites; they were not contaminated with lipid signals because of the adequate localization. Tumour progression, monitored in a selected volume of interest, was reflected in the corresponding spectra by decreasing intensities for resonances of N‐acetyl aspartate and (phospho)creatine and increasing intensities for resonances of choline compounds and lactate. From spectroscopic imaging experiments metabolic heterogeneity could be deduced within the tumorous region. At particular times during tumour development spectra were obtained greatly resembling localized 1H MR spectra obtained from patients with astrocytomas by the use of similar localization methods. This emphasizes the relevance of animal model study for the evaluation of MR spectroscopic investigations in human brain tumour diagnosis and therapy evaluation.