Conventional CT scans sometimes have difficulty showing the lesion or making a qualitative diagnosis of the lesion, which requires a CT-enhanced scan. Enhancement scan refers to the administration of water-soluble iodine contrast agent through the vein and then scanning, so that the density difference between the lesion tissue and the adjacent normal tissue increases, thus improving the lesion display rate; the mechanism is that the lesion tissue is rich in blood vessels or slow blood flow, the blood-brain barrier is broken, the contrast agent stagnates and accumulates in the pathological tissue, and then the tissue density increases and intensifies, so the enhancement scan can reflect the nature of pathological tissue. The purpose is to: 1. improve the detection rate of lesions, especially small lesions. With enhancement scans, the degree of enhancement of lesions and parenchyma or surrounding tissues is often inconsistent, and the difference in density between the two is large, which can be used to detect lesions that are missed on plain scan. These lesions are isointense or have little density difference on plain scan, or cannot be distinguished from vascular cross-sectional images. Practice has shown that small lesions in the brain, liver, pancreas, spleen, kidney and other parenchymal organs, especially substantial occupancies, abound with equal density on the plain scan image, and it is inevitable and undesirable to rely on plain scan alone to miss the diagnosis. CT scan not only has a low detection rate, but also has a limited ability to characterize and identify lesions. dynamic enhancement scan can improve the qualitative ability of lesions according to the presence or absence of lesion enhancement, degree and enhancement mode or type, and it is not difficult to make a qualitative diagnosis in typical cases. 3.In the case of established malignant tumor, the purpose of enhancement scan is to improve the accuracy of tumor staging or to judge the possibility of tumor surgical resection. 4.For the diagnosis and display of vascular lesions, dynamic enhancement scan is even more essential; for the differentiation of vascular and non-vascular lesions, enhancement scan is equally important, such as the differentiation of blood vessels and small lymph nodes is an obvious example. The identification of lymph nodes and blood vessels in the lung hilum, neck, pelvis, etc. often encounters difficulties in images, which can be easily distinguished by the increased density difference between blood vessels with high concentration and lymph nodes with insignificant enhancement through enhancement scans. Therefore, CT-enhanced scans are necessary and essential in CT examinations.