[Recent progress in the x-ray diagnosis of colorectal cancer]

Double contrast method is very important for the early detection of the colorectal cancer. Early cancer is divided into four types macroscopically, that is I p, I s, II a and II c. Type II c is very rare. Therefore, almost all early colorectal cancer cases are the sessile and flat elevated lesions. Most important point in the diagnosis of the early cancer is the diagnosis of the depth invasion of the cancer. The lateral view of the cancer in the X-ray images are very useful for the diagnosis of the cancer invasion. By the way, a new radiographic method has been developed in Japan recently, that is computed radiography (CR). Very clear double contrast images can be obtained by the new method with the low dosages of X-ray. For example, even the dosages are one-third or one-fourth of the conventional method, also X-ray images are very clear. Therefore, the new method will be useful for mass screening of the colorectal cancer. Furthermore, computed tomography (CT) is very useful for the diagnosis of the colorectal cancer, especially concerning to depth invasion of the cancer, permeation into the neighboring organs, and lymph node metastasis.