Radiation-induced brain calcification: Paradoxical high signal intensity in T1-weighted MR images

Background. Irradiation to the central nervous system (CNS) in childhood is known to induce cerebral calcification after a latent period. Calcification has been generally found to show nil or a reduction in signal intensity in magnetic resonance (MR) images. However, we have studied three patients with radiation-induced brain calcification, who manifested increased signal intensity on T1-weighted MR images. Method. Three girls had each been diagnosed as having a suprasellar germ cell tumour and were treated with conventional fractionated radiotherapy in their childhood. In one case, chemotherapy was given prior to the CNS irradiation. Findings. All three patients survived their disease, and a follow-up CT scan revealed calcification in the brain, which has shown an increased signal intensity in the T1-weighted images of MR. Interpretation. Cerebral calcification may be presented as a high signal intensity in the T1-weighted MR images. This may be explained by a surface-relaxation effect by the calcium salt particle, precipitated in the brain due to radiation-induced mineralising microangiopathy.