影像 整理.docVIP

总论 流空效应: In the case of rapid arterial flow, the protons leave the imaging volume between the two RF pulses, no signal is collected, and the arteries are displayed dark on the MR image. 根尖片分角线投照技术X-ray beam perpendicular to line bisecting angle formed by film and long axis of tooth。It may cause imaging distorted during posterior teeth projection. 远距平行投照技术牙颈部buruout征Diffuse radiolucent areas with ill-defined borders may be apparent radiographically on the medial or distal aspects of teeth in the cervical regions between the edge of the enamel cap and the crest of alveolar，which results in decrease x-ray absorption in these areas . T1加权像 *long TR(2000msec), long TE(60msec)----T2-weighted image（T2WI，T2加权图） T1-weighted imaging: the contrast between tissues is due mainly to their T1 relaxation properties. 牙科线数字影像技术X-ray machine，Sensor(CCD)，Computer，Monitor，Printer 牙体牙周病变 根尖周脓肿，根尖周囊肿，根尖周肉芽肿的影像学表现? Chronic periapical abscess（脓肿） Periapical granuloma （肉芽肿） Peiapical cyst （囊肿） Size uncertain ﹤1cm 1-2cm,or larger shap Irregularity round or oval round or oval Opical density Low and uneven Soft tissue density, uneven Low and even periphery ill-defined, Without cortical boundary Well define, Without cortical boundary well defined, With cortical boundary Surrounding bone May increase the bone formation Normal Normal  假性牙瘤与真性牙瘤的鉴别Cemental hypoplasia and benign cementoblastoma : Age and Sex Location Radiographic feature Cemental hypoplasia 40 years old female Mandibular incisor Multiple foci A radiopaque mass of comparatively high density, which is encircled by a thin,radiolucent line . The lamina dura and periodontal ligament is intact. Benign cementoblastoma 25years old male Mandibular molar region , single focus An uneven radiopaque attached to the root of affected tooth, surrounded by a radiolucent band. Root absorbtion and fusion may occur. 颌骨炎症 线状骨膜反应Appears as a thin , faint , radiopaque line adjacent to and almost parallel or slightly convex to the surfac