1. CT examination shortcomings of existing artifacts and image noise. CT bone area in the vicinity of beam hardening artifacts can be seen, high-density structures such as the occipital tuberosity and the anterior cranial fossa within the comb-like or strip such as caused by radiation of high density and low density; threat in the skull bone inside the board and is also common in the inner surface of strip low density. With MRI of the central nervous system lesions have a better contrast resolution between the organizations. Therefore, in the cerebral cortex, posterior fossa, middle cranial fossa, skull base and spinal parts of the tumor diagnosis, MRI replaced CT play a leading role. Since swallowing and breathing exercises cause throat and chest, abdomen scan artifacts of CT examination often shows lesions, the latest spiral appears CT, every 0.5 seconds to scan 1, 4 floors each received image, than single helical CT scan has greatly enhanced the speed, you can eliminate the motion artifacts, is conducive to early detection of lesions in these areas. But expensive, yet popular.
2. Regular meal examination of the gastrointestinal mucosa lock the display and the diagnosis of early lesions than CT is superior.CT examination in the detection of mesenteric lesions, the distinction between bar and not filling the bowel cancer has been difficult. In recent years, the improvement of CT scanning technology, such as the use of colon cleansing preparation, transformation, such as the rectum in the prone position scanning bit scanning, oral contrast agent to form a good bowel contrast Dengjun help distinguish between the two.
3. Helical CT that the introduction of many new diagnostic techniques, but a wide range of diseases, different among the histological types of disease, identification of difficult. Therefore, to emphasize that the specificity of CT in the diagnosis of histologically significant limitations exist, must be combined with clinical data, or other means. For example, in determining aspects of benign and malignant thyroid lesions, ultrasound and nuclear medicine techniques are generally more effective than the CT examination. MRI is a better soft tissue resolution than CT imaging technology, but CT examination has its advantages, such as calcium deposited on the tissue sensitivity to determine small amounts of tumor calcification and bone destruction was absolutely is the preferred method, reflecting the abnormal cortical bone particularly helpful.
4. CT can not reliably find the transfer of small diffuse lesions, such as CT examination can not show diffuse liver, spleen and bone marrow tumor invasion, and pleural cavity, peritoneal cavity samples of disseminated miliary lesions, thus limiting its role in tumor staging.
Advantages and disadvantages of CT examination, 5. Identification of tumor recurrence and residual issues. Because spiral CT scanning can provide a good level of repeatability, in most cancer centers have been widely used as a tumor (especially abdominal, pelvic) observed after treatment were followed up for dissipation of the primary means of mass, but CT of the local tumor recurrence and stage of the primary lesion has the same limitations. Residual tumor was most often kill the tumor tissue fibrosis after residues, but may have residual active tumor tissue, CT differential diagnosis of such changes and tumor recurrence after treatment or residues are often difficult.