188 Chapter 7 Figure 7. Repeated measures correlations of the post-radiotherapy changes and the dose in the healthy-appearing brain. Each color represents a different patient and the lines represent the common linear relationship between the MRI metrics when all participants are taken into account. Statistics for each relationship are provided for each plot separately. Case-analysis As group analysis indicates significant heterogeneity in the post-radiotherapy changes in OEF, CBF, CMRO2 and CVR, a case-study analysis was performed. Three diverse cases were chosen, based on their response to the radiotherapy: growth of new brain metastases, shrinkage of brain metastases or a mixed response three months after SRS (Figure 8). Besides changes in the physiological MRI parameter maps, the cognitive changes post-radiotherapy were assessed. For the patient that had new tumor growth after radiotherapy, the MRI differences and cognitive changes aligned; there was a general worsening of the physiological MRI parameters and cognitive decline in the majority of the cognitive domains. The largest changes in physiological MRI values were near the tumor area. For the patient with tumor shrinkage, the improvement in physiological MRI parameters is most pronounced for OEF where a post-radiotherapy increase of OEF was visible in the areas surrounding the tumor area. This improvement was also reflected in the cognitive changes, with improvement or stability on the majority of the cognitive domains. For the patient with a mixed response after radiotherapy, no clear pattern emerges from the MRI and cognitive data. See Supplementary Figure 5 for a visual representation of all included patients.
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