Image-guided 1H NMR spectroscopical and histological characterization of a human brain tumor model in the nude rat; a new approach to monitor changes in tumor metabolism.

In this study a human glioma-derived intracerebral tumor model was analyzed histologically and examined by image-guided 1H NMR spectroscopy. It was shown that histological characteristics such as cellular subpopulation and necrosis of the primary tumor were preserved in the implants. Usually circumscript tumor growth was present with tumor cells invading the surrounding brain parenchyma. It was demonstrated that tumor growth and tumor metabolism could be monitored by image-guided 1H NMR spectroscopy in a longitudinal study. One of the initial changes noticed was the rise of the lactate signal in the tumor region followed by an increase of the choline and a decrease of N-acetyl-aspartate and phosphocreatine signals. Even before tumor invasion in brain adjacent to the central tumor area could be demonstrated by NMR imaging increased lactate and moderately increased choline signals were measured in these regions. By histopathological examination these areas were shown to be infiltrated by single tumor cells. These observations indicate that image-guided 1H NMR spectroscopy could play an important role in the study of brain tumor biology, especially in the case of changing tumor metabolism during growth.