When was the VP shunt inserted? How can you tell?
Recently as one can still see a little pneumocephalus on the right anteriorly.
Where is the mass located? Is the epicentre of a mass a good guide to origin in the brain?
The mass is centered on the pineal region. The epicentre of a mass is only a reasonable guide as to site of origin provided the mass does not abut the bone. When this occurs as the mass grows it is restricted at the bony interface and the epicentre migrates inwards as the mass enlarges.
What is the pattern of calcification? How is this helpful?
The calcification is peripherally distributed ("blasted") rather than engulfed. This is a feature of pineal parenchymal tumours. Germ cell tumours tend to engulf the pineal calcifications.
Axial brain CT images show a large hyperdense lobulated mass in the pineal region with peripheral foci of calcification and associated hydrocephalus. A VP shunt has recently been inserted (note the small amount of pneumocephalus). Hyperdense material is seen coating the frontal horns of the lateral ventricle and filling the floor of the third ventricle.