CT的基本知识文件材料教学稿件.ppt

In this unit system, water is assigned a value of zero and air is assigned a value of -1000. 加灰度标 (number of detector rows available) peripheral nodular enhancement and progressive centripetal fill-in Plain scan Arterial phase Venous phase Multiphase scan Acquiring a series of CT images of the same slice locations in (rapid) succession such that time dependent changes of contrast enhancement can be studied. HCC Arterial phase Venous phase Late venous phase Plain scan Focal Nodular Hyperplasia Multiphase scan Nodular enhancement appears in the rim of the lesion(A)，showing similar density with blood vessel. With the time passing by, enhancement spreads to the center and fill the whole lesion(C) A B C Hemangioma Delay phase Arterial phase Venous phase Multiphase scan: CT Myelography involves opacification of the subarachnoid space by injection of contrast media and followed by CT scanning. Currently, only non-ionic iodinated contrast material is recommended for intrathecal injection. 3. CT Myelography CT myelography Axial and sagittal reformation images show excellent bone detail and the outline of the subarachnoid space. 4. Target CT scan Using small field of view to provide enhanced spatial resolution over a small area of interest. They are commonly used for the imaging of inner ear, larynx, sella turcica, adrenal gland, vertebrae, and so on. Target scan of vertebrae Target scan of sella turcica 5. High resolution CT (HRCT) A CT technique using thin collimation and image reconstruction with a high resolution algorithm in order to obtain detailed images of areas of interest. HRCT is commonly used to image diffuse lung diseases and focal lung lesions as well as structures of mastoid and inner-middle ear. Lobes of lung segments of lung Conventional High resolution scan (HRCT) Conventional spiral CT scan High resolution spiral CT scan 2.5 CT Image post-processing Multiplanar reformation (MPR) Maximum of minimum intensity projection (MIP) Surfa