Objective To study CT findings of sacral tuberculosis.Methods CT findings of sacral tuberculosis confirmed pathologically in 13 cases were analysed combined with literature review.Results The S 1～2 tuberculosis was most common.The types of sacrum destruction were osteolytic and bone destruction along the sacral foramen.The cold abscess were distributed at the presacral,unilateral iliac fossa and/or the gluteal region.Three patients(23.1%) were associated with sacroiliac joint tuberculosis(right 2,left 1).Conclusion In the patients with sacral tuberculosis the patterns of sacrum destruction,region of cold abscess and its relationship with the neighboring structures can be well showed by CT,and it can help surgeons to choose the appropriate surgical approach.

Objective To improve the recognition and diagnosis of pseudohypoparathyroidism (PHP). Methods Six subjects with PHP of 4 generations in one family were investigated and studied. There were 4 males (including 2 deaths) and 2 females. The age of 4 surviving patients was from 8 to 55 years. All cases were proved by clinical biochemistry tests. Plain film of hands and head CT scans were performed in 2 selected patients. Results The somatotype of Albright hereditary osteodystrophy (AHO) and short fingers and toes were found in all cases. Radiologic features were as follows:(1)short metacarpals and phalanges.(2)skull thickening and symmetrical calcification of basal ganglia. Conclusion The diagnosis of PHP can be established by close combination of radiologic findings and clinical manifestations.

European Commission (EC) has released the latest European guidelines on diagnostic reference levels for paediatric imaging (radiation protection No.185). The guidelines detailed the background, purpose, methods and uses of establishing the diagnostic reference levels (DRL) for European paediatric imaging, including radiography, fluoroscopy, computed tomography (CT) and interventional radiology (IR). The current situation, strengths and limitations of existing European paediatric national DRL (NDRL) were analyzed retrospectively. Based on the existing radiation dose data resources, some consensus was reached and the European DRL (EDRL) was issued, providing the latest guidance for the optimization of radiation protection of European children. It has positive reference significance for the domestic radiology practitioners to understand relevant knowledge.

The diagnostic reference level (DRL) for adults radiation dose in CT examination based on a large-scale national survey data is released in the form of national health industry standards (WS/T 637-2018) after more than ten years of exploration by radiologists, imaging technologists, radiation protection specialists and radiographers. Its principles and method are in line with international practices and the actual situation in China, which basically cover frequently-used CT examination items for adults. Compared with DRL in several other countries or organizations, radiation exposure to the patients as a whole is at a reasonably low level. The 50^th percentile (achievable dosimetry levels) and 25^th percentile (indicative level of unusually low dosimetry) are given as additional tools for radiation dose optimization guidance. In daily activities of radiological diagnosis, the radiation dose should be matched with image quality and clinical diagnostic tasks, and the frequency of unjustifiable high or low radiation dose should be reduced.