Objective To evaluate the characteristics of CT, MRI, PET and histopathology of brain radiation injuries following radiotherapy for nasopharyngeal carcinoma. Methods We reviewed the imaging records of 71 patients with brain radiation injuries following radiotherapy for nasopharyngeal carcinoma examined over a 10 year period. Results The radiation injury lesions occurred in the temporal lobes, brain stems or cerebella. Their CT appears were homogeneous or heterogeneous density. If the lesions situated in temporal lobes, they presented as "finger like" hypointensity. Twenty three patients(29 lesions) undenwent contrast enhanced CT scan, 86.2 percent(25/29)of the lesions showed no enhancement. MRI demonstrated prolonged T 1 and T 2 relaxation time of the injured tissue, they might showed homogeneous or heterogeneous signal intensity. MR enhanced T 1WI were performed in 20 cases(29 lesions),and 65.5 percent(19/29)of the lesions presented "Flower lace" enhancement. Two patients were carried on PET scan. One patient′s PET appearance is similar to the CT or MRI finding. Resections and histopathologic observations of temporal lobes′ lesions were performed on 3 cases, which showed cerebral necrosis. Conclusion (1) MRI plain or contrast enhanced scan is more sensitive than that of CT or PET. (2)The heterogeneous signal intensity on T 1WI and T 2WI represent necrosis,and all are located in the radiation field. (3)"Flower lace" enhancement on contrast MRI is the characteristic of brain radionecrosis. (4)PET may serve as a complementarity in the diagnosis of radiation induced injuries.

Objective To evaluate the reasons of positive MR findings and negative radionuclide bone scan in the spinal metastasis.Methods 68 patients with spinal metastasis were undergone MR scan and radionuclide bone scan.MRI appearances including the site,location and their relation to the cortex of bone were analyzed. The relationship between MRI and radionuclide bone scan appearances were also analyzed.Results 561 lesions were detected by MRI,and only 199 lesions were found by raionuclide(199/561=35.47%).133 lesions located in the bone marrow without cortex erosion were not detected by radionuclide bone scan. The detective ratios of lesions located in the subcortex and through cortex were 25.58%(55/215) and 67.61%(144/213) on radionuclide bone scan respectively. The detective ratios in small lesions (