Some experts tend to believe that this examination technique, provided further optimisation, could become the ideal preventative examination for large bowel cancer. Unlike the traditional colonoscopy, which requires a scope to be inserted into your rectum and advanced through your colon, virtual colonoscopy uses a CT scan to provide hundreds of cross sectional images of your abdominal organs. The images are combined and digitally manipulated to provide a detailed view of the inside of the colon and the rectum. So even small polyps can be detected. Actual problems with this examination, however, are (1) the high costs, (2) the requirement for cleaning the large bowel before the examination like with conventional colonoscopy, and (3) the considerable time requirement due to presently suboptimal software programs. In addition, as with previous radiological examinations of the large bowel (irrigoscopy), in case of a pathological finding conventional colonoscopy (with another cleaning of the large bowel procedure) has to be performed subsequently (for biopsy or polypectomy).