Objective    To evaluate the diagnostic value of several 16-slice CT colonography (CTC) for colorectal tumors.     Methods    Forty-two patients with colorectal tumors underwent transverse scan using 16-slice spiral CT. The size

the circumferential extension and the pathologic patterns of tumors were compared among the images obtained by different techniques

including the original transverse images

the images of the multiplanar reformation (MPR)

shaded surface display (SSD)

Raysum

CT virtual colonoscopy (CTVC)

Wall View and virtual dissection (VD)

most of which were obtained from the postprocessing in the workstation. All the tumors were confirmed by the conventional colonography (CC) and/or histologically.     Results    The correction rates of the tumor size evaluation by Wall View

SSD and Raysum (97.6%

95.2%

95.2%) were higher than CTVC (78.6%) and original transverse images (73.8%). The correction rate in evaluating the circumferential extension of colorectal tumors by VD (100%) was higher than by CTVC

SSD

Raysum and original transverse images (85.7%

80.9%

80.9%

78.6%). The correction rate in evaluating the pathologic pattern by CTVC (90.5%) was higher than by SSD

Raysum and VD (71.4%

71.4%

61.9%); Futhermore

that by Wall View (88.1%) was higher than by VD (61.9%).     Conclusion    Seven display methods of CT colonography have their own advantages and disadvantages in diagnosis of the colorectal tumors. Proper choice of display methods and their combination can improve the diagnostic accuracy.