What is your differential diagnosis?
Differentials include a pineal parenchymal tumour (e.g. pineoblastoma), high grade tectal astrocytoma, metastasis and even lymphoma. Germinoma is though unlikely due to A) peripheral calcification B) female gender.
What does the DWI / ADC signal suggest?
Restricted diffusion suggests tightly packed cells. This is usually therefore a feature of more aggressive, cellular tumours.
There is a mass in the quadrigeminal plate cistern which is homogeneously mildly T2 hyper- and T1 hypointense to grey matter which demonstrates avid heterogeneous contrast enhancement. There is abnormal signal also extending into the thalami, more marked on the right. It diffusion restricts.
There is increased blood volume in the lesion. The MRS shows increased choline-creatine ratio with reduced NAA peak in keeping with a high-grade tumour trace.
There is obstruction of the cerebral aqueduct with hydrocephalus involving the lateral and third ventricles. Mild periventricular T2 hyperintensity suggests a degree of transependymal oedema.