由於科技的進步，電腦斷層攝影由以前的單一切面螺旋式電腦斷層掃描，進步至 多切面（multi-slice)，並朝向體積式電腦斷層掃描的方式邁進，不僅切面變細提高解析 度，更因為掃描與組像的速度增進，而有效地克服因病人無法合作閉氣所產生的假影； 經三度空間成像或多方位影像重組技術，使我們可以提高影像品質，此外應用於三度 空間攝影後處理技術，我們得以建構虚擬内視鏡的影像來診斷，以減少非必要性或較 侵襲性的内視鏡檢查。虛擬大腸鏡是最新的影像診斷技術，它以超快速螺旋電腦斷層 及電腦虛擬的影像來檢查充滿空氣的大腸。可使用於診斷大腸痣肉，大腸癌，及大腸憩室 等疾病，與傳統的大腸内視鏡比較，虚擬大腸鏡的優點是安全性較高，只需在肛門放 置一條小管，不須像内視鏡般通過整條大腸；此外，經電腦技術組合的圖像可以順行 或逆行，不會因為腫瘤阻塞而無法顯示前面的大腸，傳統的内視鏡只能向前順行，當 遇上腫瘤或其他阻塞即無法前行。虚擬大腸鏡具有避免大腸内視鏡因重複使用檢體夾 或消毒不完全所導致血液感染之可能性，同時降低大腸鋇劑攝影在檢查過程中，需灌 入高對比顯影劑時所導致腫瘤或腸道破裂之風險，因此虚擬大腸内視鏡不失為一項既 安全又為低危險性之檢查。本文目的是應用電腦斷層大腸攝影以偵測大腸病灶，並藉 由虚擬大腸鏡與大腸鋇劑攝影及大腸内視鏡做比較，以介紹並分析是否適合推廣為偵 測大腸病灶的檢查項目之一。

As the technology has matured, computed tomography (CT) has continued to undergo development, and single-slice spiral scanners have evolved into multislice scanners. Future generations will be based on volumetric CT technology. Multislice CT provides a higher scanner performance that can be used on thinner sections, which reduces the scan time and for longer ranges, which reduce motion or respiratory artifacts, especially in uncooperative patients. Furthermore, CT has truly been transformed from a transaxial cross-sectional modality into multiplanar reformation and various types of 3D imaging as the basis for an expanding variety of 3D visualization techniques to develop virtual endoscopy. We suggest virtual colonoscopy as a screening tool for colorectal entities so as to reduce unnecessary invasive colonoscopic examinations. Virtual colonoscopy is a recently developed technique that uses an ultrafast spiral CT scanner and computer virtual reality software to look at a completely air-filled colon and detect polyps, colorectal neoplasms, and diverticular disease. There are numerous benefits of virtual colonoscopy over conventional colonoscopy. It is more comfortable without having to insert a long tube into the colon. Unlike conventional colonoscopy, virtual colonoscopy is not limited by view direction. By providing both direct antegrade and retrograde visualization perspectives, virtual colonoscopy allows detection of abnormalities proximal to an obstructed segment. It is a safe, non-invasive procedure with low infection and perforation risks. The aim of this study was to compare the detection accuracy of CT colonography and virtual colonoscopy with conventional colonoscopy and a double-contrast barium enema study and discuss evidence of the effectiveness of virtual colonoscopy as an alternative to colonoscopy for the purpose of colon lesion screening offered in a diagnostic setting.