| CT scans are indicated to detect or confirm the characteristics, size, and involvement of abnormal structural changes. Wherever the location, a tumor can be evaluated before definitive treatment is begun. A head CT can provide direct information about bruises (contusions) or blood clots (hematomas) within or outside (epidural or subdural hematomas) the brain. CT of the spine is indicated in cases of suspected disc herniation, spinal infection, trauma, or intraspinal tumor. A face or neck CT is indicated for inflammation or infection, fractures of the facial structures, or for assessing foreign bodies within the eye socket (orbit). Chest CTs are most commonly used to detect suspected cancers (malignancies) and to determine the extent to which the cancer has spread (metastasis). CT is used to define the presence and extent of the ballooning of a vessel due to weakness of the vessel wall (traumatic aneurysms) and the splitting of an aortic vessel wall (aortic dissections). High-resolution CT can help evaluate lung diseases and, when used with dye (intravenous contrast), can be used to confirm an inflammation of the pancreas (acute pancreatitis).
CT may also be useful in differentiating a kidney tumor from a faintly calcified stone that may not be visible on plain x-ray. It can also help in the classification of kidney injuries by defining the extent of lacerations, hematomas, or urine leaking into the abdominal cavity. In the pelvis, CT can provide information regarding the extent of tumors in the lymphatic system and their relationship to normal structures. While bone fractures are usually evaluated by standard x-ray, CT scan provides more precise information about the presence, location, orientation, and relationship of fracture fragments in complex anatomic regions such as the pelvis, shoulder, foot, and ankle. CT can provide precise locations and help guide the needle to sample of cells withdrawn through a needle for microscopic examination (aspiration biopsies), to withdraw a core of tissue withdrawn through a large-bore needle, for microscopic examination (core biopsy), for through the skin (percutaneous) drainage of abdominal abscesses, or for other fluid collections. CT can also be used to guide the placement of various catheters or surgical instruments. The CT may not be diagnostically helpful for people who cannot lie still (due to some neurological diseases), for the extremely obese, or for those who have a fear of being surrounded by or contained within a machine (this later would be unusual because of the openness of the scanner).
It's important to note that MRI scanning also creates an image of body structures by combining a series of pictures taken at different levels and angles. However, MRI uses a different technology to create the images. MRIs have replaced CT scans for many soft tissue conditions, but CT continues to be the best imaging test in select situations. |
Source: Medical Disability Advisor