CT 是一种利用X 线作能源,计算机辅助而形成的体层显像技术。CT 机于六十年代末期设计和制造成功,七十年代初期应用于临床,八十年代完备,至今已成为医学影像技术中的主要成员。B 型超声、核磁共振成像和发射—CT—(E—CT)也属体层技术。由于超声穿透能力差,很难通过骨骼和空气,使用范围受到限制:核磁共振成像虽不受深度、骨骼和气体的限制,成像参数也较多,且价格昂贵,超出一般患者经济能力。E—CT 是将放射核素注入人体,被组织吸收,放射出的r 线被接收,形成体层像。眼和眼眶组织吸收核素较少,发射出的能量也较小,目前尚难以形成可供诊断用的优质发射体层像。CT 成像不受深度限制,软组织,骨骼和气体均可显示,且成像清晰,被誉为活体解剖技术。由 CT is a use of X-ray energy, computer-assisted tomography. The CT machine was designed and manufactured successfully in the late 1960s. It was applied to the clinic in the early 1970s and was complete in the 1980s. It has become a major member of medical imaging technology so far. B-mode ultrasound, magnetic resonance imaging and emission-CT- (E-CT) are also body-layer technologies. Due to poor ultrasound penetration, it is difficult to pass through the bones and the air, limiting the scope of use: Although MRI is not limited by depth, bone and gas, imaging parameters are more, and expensive, beyond the general economic ability of patients. E-CT is the radionuclide injected into the body, absorbed by the organization, the r-ray radiation is received, the formation of tomostars. Eye and orbital tissue to absorb less radionuclides, the energy emitted is also small, it is still difficult to form a diagnostic for the use of high-quality emitter layer image. CT imaging without depth restrictions, soft tissue, bone and gas can be displayed, and imaging clear, known as living anatomy. by