ABSTRACT
Objective To study the value of multi-slice spiral CT virtual colonoscopy(CTVC) in diagnosing colorectal neoplasms.Methods Forty-one patients with colorectal neoplasms proven by colonoscopy were further scanned successively by a 16-slice spiral CT with thin-section after intra-anal air insufflation.Then the data were 3D reconstructed simulating in virtual endoscopy and the results were compared with what seen with the conventional colonoscopy and the clinic pathological findings.Results A total of 21 polyps in 12 patients were discovered by colonoscopy,while 15 polyps in 10 patients by CTVC.In addition,29 cases of colorectal cancer were diagnosed by colonoscopy,and 27 cases of colorectal cancer were discovered by CTVC.Besides,two cases of liver metastasis and one case of lymph node metastasis in posterior peritoneal cavity were demonstrated in colonic cancer by CTVC.Conclusion CTVC is a non-invasive and valid technique for colonic occupying lesion,which can demonstrate not only the location and the size of colorectal neoplasms,but also the invasive depth and extracolonic metastasis.CTVC has an important value in clinical stage and choice of surgery for colorectal cancer.
ABSTRACT
Objective To investigate the effects of tagged fluid and substraction in CT virtual colonoscopy (CTVC) on the conspicuity of polyps and to confirm the optimal attenuation value and the optimal viewing window. Methods Polyps measured 3-10 mm were created in fresh porcine colon in vitro and submerged in saline and mixed with positive contrast medium for the CT values of 200 HU, 400 Hu, 600 HU, and 800 HU. Polyps were measured before and after substraction and compared with those in the control group. The effects of different viewing windows and different attenuation values on the measurement and conspicuity of polyps were analyzed. Results The optimal attenuation value of tagged fluid was 800 HU and the optimal viewing window was colon (-150 HU, 1 500 HU) and bone (500 HU, 2 500 HU). Conclusion The combination of tagged fluid and CT substraction can improve the conspicuity of small polyps covered by colonic fluid.