NMR imaging of central nervous system diseases before and after radiotherapy.

Two brain tumors, a foramen magnum tumor and an arterio-venous malformation (AVM) were treated with radiation but without chemotherapy or surgical removal. These cases were monitored by NMR imaging for a period of 16 months after radiotherapy to detect the response of the tumors and brain tissue to radiation. The T1 and T2 of the tumors behaved independently. T1 decreased after radiation related to clinical improvement. T2 did not change to the same degree as T1. An increased T2 area around the tumors and along the lateral ventricle developed about six months in one case and 16 months in the other case after radiotherapy, without associated clinical change in either case.