Abstract
In these years, CT colonography had shown a rapid spreading in Japan, because of the progress of CT devises and workstations, the improvement of bowel preparation, and an approval of the automatic Co2 gas infusion-pomp. The conventional bowel preparation protocol is utilized for CT colonography. Other bowel preparation method, which is called as fecal tagging, can distinguish the lesion from the labeled fecal mass using the positive contrast agent with diet. Another advantage of fecal tagging is to extract high density bowel content in the images, using the image segmentation method of digital technology, which is called an electronic colon cleansing.
There are many varieties of the image renderings, the MPR as two dimensional image, air image looks like a barium enema image, virtual endoscopy and dissecting image of the bowel lumen as three dimensional images. The combined images of virtual endoscopy and MPR are also available. Recently the study of CAD in the detection of colorectal cancer is investigated. In our experience, the detection rate of CAD for elevated lesions is 100%, while it is still low for superficial type lesions. Major assignment of CT colonography is how to detect the superficial colorectal tumor.
The advantages of CT colonography for colorectal cancer screening are as follows: 1) the throughput of CT colonography is better than other modalities, 2) the image data is really objective and the quality of examination is not depend on the examiners, 3) the bowel cleansing is not necessary to perform completely, 4) CAD is also available to utilize, 5) the procedure of CT colonography itself is quite safe. According to these advantages, CT colonography should be carried out in the screening for colorectal cancer. At least it will be able to decrease the number of patient without a close examination in the colorectal cancer screening.
