Experimental And Clinical Study Of Multi-slice Spiral CT Colonography

Part One Experiment Study of Multislice CT Colonography in porcinecolonic polyp modelObjective: To evaluate the effects of different scanning parameters,different reformat modalities and different postprocessing techniques onimage quality and the detecting rate of simulated polyps. To select an optimalcombination of scanning parameters and post processing techniques.Materials and Methods: Ten polypoid lesions of varying size weresimulated with sutures on the inner face of 6 porcine colon segments (30 cm).After distending the colon segment with air, the phantoms were immerged into0.1% iodine solution. The phantom was examined using multi-detector rowCT with varying combinations of detector collimation and pitch. The CT datawere reconstructed with varying reconstruction interval and algonithms. Thenthe raw data were transmited to Advantage Windows 4.3 work station to beprocessed. The 2D and 3D images of CT virtual endoscopy (CTVE), volumerendering (VR), Raysum, multiplanar reformation (MPR) and virtualdissection (VD) were acquired. Polyp depiction was compared in varyingpitch, section thickness and method. The detecting rates of CTC affected bydifferent post processing techniques were compared as well.Results: The effect of parameters on image: a.the image qulity wasimproved with the less section thickness/reconstruction interval; b. the effectof overlap reconstruction was declined with the less section thickness; 3. the optimal protocol was section thickness 1.25mm, pitch 1.375:1, overlapreconstruction 0% and standard reconstruction algonithms. The effect ofvarying post processing techniques in polyp detection: the detection rate ofCTVE, VR+Raysum, MPR+axial image and VD was respectively 100%, 95%,95% and 100% in 10mm～12mmgroup; the rate was respectively 95%, 75%,80% and 95% in 5mm～9.9mm group; the rate was respectively 85%, 30%,50% and 80% in 2mm～4.9mmgroup. The rate of all these methods in detectingpolyps was 100%, 100% and 90% in 10～12mmgroup, 5～9.9mm group and2～4.9mm group, respectively.Conclusions: The optimal protocol of 16-row CTC was 120kV, 120mA,matrix 512×512, pitch 1.375:1, section thickness 1.25mm, overlapreconstruction 0% and standard method. CTVE and VD was suoerior to othermethods in the detection of polyps. Combine CTVE with other methods couldimprove the detection of polypsoPart Two The Diagnostic Value of CTC in colonic polyps and coloniccarcinomaObjective: To evaluate the characterstics of conlonic polyps andcarcinomas on CTC with varying process. To compare the advantages anddisadvantages of different post processing techniques and to select an optimalcombination of reconstruction to display colonic lesion better..Materials and methods: There were 44 patients who underwent opticalcolonoscopy enrolled in the present study, including 34 patients withcolorectal carcinomas and 10 patients with colorectal polyps (6 patients withsolitary polyps and 4 patients with multiple polyps, 36 polyps together), a.The image quality of four different post processing techniques includingCTVE, MPR plus axial, VR plus Raysum and VD were compared; b. Theimage quality of four different post processing techniques were also comparedwith that of optical colonoscopy, c. The detecting rates of four different post processing techniques were calculated respectively; the diagnostic rate foraccurately classcification, predicting the extent of surrounding invasion andlongitudinal extent of bowel wall involvement were compared espectively, d.The advantage and disadvantages of different post processing techniques werecompared respectively.Results: For polyps groups, the detection rate of CTVE, MPR+axial,VR+Raysum image and VD was respectively 100%, 90.9%, 81.8% and 100%in≥10 mm group; the rate was respectively 94.1%, 70.6%, 52.9% and 94.1%in 6mm～9mm group; the rate was respectively 62.5%, 25.0%, 25.0% and62.5% in＜5 mm group. The rate of all these methods in detecting polypswas 100%, 100% and 75.0% in≥10 mm group, 6～9mm group and＜5 mmgroup, respectively; For colorectal carcinoma, the diagnostic rate for accurateclassification by CTVE, MPR plus axial, VR plus Raysum and VD were 88.2%, 70.6%, 58.8% and 67.6% respectively, the diagnostic rate for accuratelypredicting the extent of surrounding invasion were 79.41%, 100%, 58.8% and73.5% respectively, the diagnostic rate for accurately predicting longitudinalextent of bowel wall involvement were 58.8%, 82.4%, 97.1% and 67.6%respectively.Conclusions: Each of the four post processing techniques has advantagesand disadvantages, the combination of all the protocols can improve theaccuracy in detecting conlonic polyps and carcinoma, and reflect the type ofcarcinoma, invasive grade and the length of invaded colon. So can afford fulland accurte image information for the operation. Moreover, on the analysis ofCTC, VD should be used first. And then combined with other methods toimprove the detection of conlonic polyps, it is benefitful to check conlonicpolyps.