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CT and MR of new technologies in colorectal lesions

Author: ZhangShuai
Tutor: PengWeiJun;ZhouZhengRong;GuYaJia;ZhouLiangPing
School: Fudan University
Course: Medical Imaging and Nuclear Medicine
Keywords: Contrast agent Tomography , X-ray computer Colonography Magnetic resonance imaging Polyp Colorectal mass Tumor stage Cancer , rectal Diffusion imaging Tumor grade Chemoradiotherapy Magnetic resonance imaging Apparent diffusion coefficient
CLC: R445
Type: PhD thesis
Year: 2007
Downloads: 242
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Objective To assess the sensitivity of CT Colonography and MR. Colonography with several kinds of contrast medium in detection of stimulated polyp in pig colon.Methods Three pig colon specimens with 18 simulated polyps underwent MDCT Colonography(CTC)after insufflation of air,iodine-water mixture (4:100)and fat contrast medium and MR Colonography(MRC)after insufflation of air,gadolinium-water mixture(1:100)and fat contrast medium,respectively.All data set were transported to workstation and post-processed by software.Results were analyzed statistically according to polyp size,contrast medium,method of examination and angle of colon segment to the gantry.Results For all 18 simulated polyps,the sensitivities of CTC with air,iodine-water mixture and fat contrast medium enema were the same(100%,18/18)and the sensitivities of MRC with air, gadolinium-water mixture and fat contrast medium enema were 61.11%(11/18)、77.77%(14/18)and 72.22%(13/18),respectively.Most small(<5mm-diameter) polyps were overlooked at MRC.For polyps,with air and fat contrast medium enema, the sensitivities were significantly higher in CTC than in MRC(P<0.025).The significant difference was not found in the sensitivity of polyp-detection between CTC with air enema and MRC with gadolinium-water mixture.In CTC or MRC, whatever angle of colon segment to the gantry,the sensitivities of polyp-detection had no significant difference.Image quality of CTC with air enema is the best. Conclusion For polyps,the sensitivity of CTC was higher than the sensitivity of MRC and the sensitivities of CTC and MRC were not affected by contrast medium. But image quality of CTC was influenced by contrast medium.The angle of colon segment to the gantry has no influence on the sensitivities of polyp-detection. Objective To evaluate the feasibility of helical CT colonography with fat contrast medium enema and its role for preoperative staging of colorectal carcinoma.Materials and Methods 33 patients with known and suspected colorectal carcinoma underwent helical CT colonography with fat contrast medium enema.Imaging quality of 2D and 3D,examinee’s tolerance and side effects of fat contrast medium were evaluated.Compared with colonoscopical and histopathological results,detection rates of masses and accuracy rates of staging of colorectal carcinoma using helical CT colonography were calculated.Result Patients have good tolerance and have not apparent side effects.The percentage of colonic segments with grade 1 distention and preparation was 81.44%(215/264)and 51.51%(136/264),respectively.Detection rate of masses larger than 5mm was 88%. All small masses(<5mm-diameter)were overlooked at CT colonography.All 29 colorectal carcinomas were detected and exactly located.The overall accuracy rate of CT colonography was 62.7%(18/29).For T staging and N staging,the accuracy rates were 79.31%(23/29)and 72.41%(21/29),respectively.Sensitivity and specificity for serosal infiltration were 90%(18/20)and 66.67%(6/9),respectively.Sensitivity and specificity for lymph node involvement were 76.92%(10/13)and 81.25% (13/16),respectively.Conclusion Helical CT colonography with fat contrast medium enema is a promising modality for help in detecting colorectal masses larger than 10mm in diameter and preoperative staging of colorectal carcinoma.Objective To assess magnetic resonance colonography with fat contrast medium enema as a method for detection of colorectal masses and staging of colorectal carcinoma.Methods 30 patients underwent MR colonography(MRC), after bowel preparation,administration of anisodamine and rectal administration of fat contrast medium.All patients were imaged with T1-weighted three-dimensional fast spoiled gradient-echo with inversion recovery(liver acquisition volume acceleration,LAVA)sequence in the supine position.Entire colon was covered in one contiguous coronal breath-hold acquisition lasting for average 25 seconds.Axial T1WI and T2WI of suspected masses were performed in all patients by FSPGR sequence.Images were acquired 25s and 70s after Gd-DTPA administration by T1WI axial and coronal sequence.Two radiologists reviewed patient’s tolerance,image quality,and sensitivity of colorectal masses.Compared with colonoscopical and histopathological results,detection rate of masses and accuracy rate of staging of colorectal carcinoma were calculated.Results All patients completed the MR examination.203 of 240(84.58%)colonic segments were well distended and 197 of 240(82.08%)colonic segments had not artefacts.For the post contrast scans,mean CNR of colorectal wall and lumen was 18.2±4.0,and Mean CNR of colorectal masses and lumen was 20.2±4.3.Sensitivity of masses larger than 5mm was 89.64%(39/44). For T staging and N staging,the accuracy rates were 79.17%(19/24)and 75%(18/24), respectively.Sensitivity and specificity for serosal infiltration were 87.5%(14/16) and 62.5%(5/8),respectively.Sensitivity and specificity for lymph node involvement were 75%(9/12)and 83.33%(10/12),respectively.Conclusion MRC with fat contrast medium enema and LAVA sequence is a promising alternative method for detection of colorectal masses and play a important role in preoperative staging of colorectal carcinoma. Objective To evaluate the accuracy of high-spatial-resolution MR imaging and contrast enhanced MR imaging in preoperative staging of rectal carcinoma and diffusion-weighted imaging(DWI)in distinguishing tumor classification.Methods Eighty patients with histologically proved rectal carcinoma underwent MR imaging including high-spatial-resolution MR imaging,contrast enhanced MR imaging(CE-MRI)and DWI.According to postoperative histopathology,the accuracies of the MRI T staging and N staging were calculated and high-spatial-resolution MRI staging and CE-MRI staging of rectal carcinoma were compared.The apparent diffusion coefficient(ADC)value and signal intensity (SI)were recorded and compared between well differentiated,intermediately differentiated and poorly differentiated rectal carcinoma.The mean ADC value and mean SI of rectal carcinoma in different b values were also analyzed.Results 1)The accuracy of high-spatial-resolution MRI T staging was 85%(68/80).Sensitivity and specificity of high-spatial-resolution MRI in detecting tumor penetration through rectal wall were 88.89%(40/45)and 88.57%(31/35),respectively.The accuracy of high-spatial-resolution MRI N staging was 64.56%(51/79).Sensitivity and specificity of high-spatial-resolution MRI in detecting lymph node involvement were 92.86%(39/42)and 64.86%(24/37),respectively.2)The accuracy of CE-MRI T staging was 82.5%(66/80).Sensitivity and specificity of CE-MRI in detecting tumor penetration through rectal wall were 95.56%(43/45)and 80%(28/35),respectively. The accuracy of CE-MRI N staging was 67.09%(53/79).Sensitivity and specificity of CE-MRI in detecting lymph node involvement were 90.48%(38/42)and 70.27% (26/37),respectively.Addition of CE-MRI to high-spatial-resolution MR imaging did not significantly improve diagnostic accuracy for prediction of T staging and N staging of rectal carcinoma,tumor penetration through rectal wall and lymph node involvement(P>0.05).3)At 500 s/mm2,the mean ADC values of well differentiated carcinomas,intermediately differentiated carcinomas and poorly differentiated carcinomas were 1.255±0.180,1.016±0.172 and 0.874±0.098.At 1000 s/mm2,the mean ADC values of well differentiated carcinomas,intermediately differentiated carcinomas and poorly differentiated carcinomas were 0.840±0.156,0.706±0.133 and 0.577±0.069.The difference in mean ADC values of the tumor classification were significant at these b values(P<0.001).The difference in the mean ADC values were significant between two types(the well differentiated and the intermediately differentiated,the well differentiated and the poorly differentiated,the intermediately differentiated and the poorly differentiated).4)For rectal carcinoma,the mean ADC value and mean SI declined with the increased b values.The significant difference was indicated in ADC value and mean SI at these b values,t=11.701(P<0.001)and t=8.851(P<0.001),respectively.At 1000 s/mm2,the quality of DWI was better for detecting rectal carcinoma.Conclusion High-spatial-resolution MR imaging accurately indicates depth of extramural tumor infiltration,but still has a low accuracy for detecting metastatic lymph node.CE-MRI did not improve accuracy of the staging of rectal carcinoma.ADC value may predict the classification of rectal carcinoma Objective To evaluate the clinical value of diffusion-weighted MRI(DW-MRI)to monitor response of primary rectal carcinoma to preoperative chemoradiation by measuring tumor apparent diffusion coefficient(ADC).Methods ADC values of sixteen patients undergoing preoperative combined chemoradiation for clinical staged T3-4N0-2M0 rectal carcinoma were analyzed.Diffusion-weighted MR images were obtained prior to and at specified intervals during chemoradiation. Surgical resection of the tumors enabled a correlation of ADC values with the pathologic results.Response group and nonresponse group were separated according to the change of T-staging.Results In four patients tumor T-downstaging was observed and in eleven patients tumor T-downstaging was not observed.One patient’ data were lost.Compared to onset of chemoradiation,the mean ADC value of all patients was higher at the 1st week of treatment,followed by a steady decrease. Compared to onset of chemoradiation,a significant increase in the mean ADC value at the 1st week(0.092±0.032,P=0.01)of therapy and a slight increase in the mean ADC value at the 2nd week(0.037±0.050,P=0.302)of therapy,followed by a slow decrease (P>0.05),was found for the response group and no significant increase of the mean ADC value was observed after the 1st week(0.012±0.056,P=0.504)of therapy,but the mean ADC values were significantly lower(P<0.05)in the nonresponse group during the remaining duration of therapy.The correlation was not observed between ADC values of all points and changes of T-staging after therapy.The mean ADC values of all points revealed no distinction between the response group and nonresponse group (P>0.05).Conclusion DW-MRI is able to detect individual changes of tumor ADC values during the course of combined chemoradiation reflecting biological changes within the rectal carcinoma and may be a valuable clinical tool to predict therapy outcome.

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