| Colonic polyp and colon cancer are the common disease and frequently occurring illness in China.And colonic polyps are strongly related to colon cancer.The detection of colorectal lesions is mainly relied on the performance of colonoscolpy,which is often described as the golden standard for colonic evaluation.However,some patients are reluctant to comply with colonoscopy because of the physically and mentally suffering process.The introduction of the multi-row detector CT and the software advances of CT virtual colonoscopy have allowed MSCT(multi-slice spiral CT) to be a noninvasive option for colorectal examination and be accepted by more and more people.But CT equipment and detection techniques limit the widespread use of colonoscoply.This study is aimed at applying this new imaging technique into early detection of colon polyp and preoperative staging of colon cancer,evaluating the detection of the colon polyps and popularizing its application.Purposes1.To study the bowel preparation before multi-detector row CT examination,scanning techniques,and the effect of imaging post-process methods on the sensitivity of space-occupying lesion;to provide clinical data for multi-detector row CT as a colon polyp screening examination and for preoperative staging of colon cancer.2.In experimental conditions,to investigate the feasibility of fecal tagging for CT colonography and fix on the optimal attenuation.Methods1.Eighty-two cases suspected as space-occupying lesions were divided into two groups.The first group,including 41 patients,underwent colonoscopy followed by MSCT. The second group,including 25 patients,underwent MSCT followed by colonoscopy.The data of all patients were employed in imaging reconstruction by using CTVC,MPR,VR and SSD.The results obtained from both groups compared with the results of colonoscopy and pathology respectively. 2.Polyps measuring 3mm-10mm were created in porcine colon.Peanut butter and saline were used as fecal and fluid substitute with uniform mixing of positive contrast medium to produce different attenuation values.In experimental conditions,before and after subtraction,polyps were respectively measured and compared with control group to analyze the influence of different viewing windows and different attenuation value on polyps measurement,and to analyze the ability of differentiating the polyps and faeces with MSCT.Results1.For 1cm or smaller polyps,the sensitivity of MSCT is inferior to that of colonoscopy;for polyps(＞1cm),the sensitivity of MSCT is 100%,same as colonoscopy; Optimal scanning parameter and well-bowel preparation before examination may observably improve the sensitivity of detecting small polyps.2.For the patients of colon cancer,the sensitivity of MSCT is 100%,which is the same as colonoscopy;For the preoperative staging of colon cancer patients with MSCT,the accuracy is 80%and in the M staging system the accuracy is 100%,superior to colonoscopy.3.The optimal attenuation value of fecal tagging is 800HU;before subtraction the optimal viewing window is colon(-150HU,1500 HU) and bone(500HU,2500HU).Fecal tagging is conducive to improving the sensitivity of small colon and decrease false positive.Conclusion1.With the development of computer software and hardware,the improvement of the CT density and time resolution,and the performance of fecal tagging,MSCT will be a new screening method for colon polyp and it will decrease the morbidity and mortality associated with colorectal cancer.2.MSCT is a noninvasive,safe and reliable way of examination for colonic tumor.It is not only a supplementary technique when colonoscopy is obstructed,but also superior to colonoscopy in depicting colon tumors and in displaying the invasion of adjacent tissues and distant metastasis.MSCT is very important for clinical staging of preoperative colonic cancer and for arranging operations. |
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