MR determined brain metabolic pattern in patients with brain metastases and adolescents with low birth weight

Abstract

The clinical applications of MRS have become a supplement to MR imaging (MRI) for diagnosis and treatment monitoring of several pathologies. In this thesis MR spectroscopy (MRS) has been used to assess brain metastases in adult cancer patients and cerebral metabolites in frontal lobe of adolescents.

Children born with very low birth weight are at risk of later neurodevelopment problems. Adolescents with different birth weight were examined using MRI and MRS and multivariate analyses for assessing differences in cerebral metabolites. The results from the multivariate analyses were consistent with observations in earlier published MRI findings, motor skills, psychiatric symptoms and disorders detected in the same participants. The classification of the adolescents was based on metabolic pattern differences which were only explored by the multivariate analyses. When the spectral information shows small or complex differences the interpretations become a challenge. In three of the four papers in this thesis, multivariate analyses were used as a tool to interpret the spectral information.

Brain metastasis is the dominating type of brain tumors which represent an oncologic challenge. The incidence of brain metastases is probably increasing due to improved treatment strategy of patient with primary cancer, prolonging their survival and brain metastases get time to develop. In some cases patients have an unknown primary cancer or several primary cancers. If MRS could provide metabolic information about brain metastases especially in differentiating it from the primary cancer, it might be a supplement to the conventional diagnostics and could help to optimize the cancer treatment. In the two last papers in vivo and ex vivo MRS of brain metastases were obtained before treatment and the spectra were analysed by using both principal component analysis and regression analysis. The spectra were classified according to primary cancer and clinical outcome five months after start of treatment. The results showed a significant correlation of spectral findings and clinical outcome of brain metastases patients.

From the MR theory, signal-to-noise ratio and resolution in MR spectra should increase by a factor of two with double the magnetic field strength. Different studies using in vivo MRS have shown that the situation varies. In Paper II the effect of increased magnetic field from 1.5T to 3T was investigated in spectra obtained in patients with brain metastases. The comparisons of spectral improvements in SNR and spectral resolution were made by ratio calculations. The gain was smaller than expected probably caused by various definitions of effective volume size at different clinical scanners.

In conclusion, in vivo and ex vivo MR spectroscopy can determine metabolic pattern on clinically highly relevant questions.