***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: The purpose was to evaluate low-dose CT colonography without cathartic cleansing in terms of image quality , polyp visualization and patient acceptance .  Sixty-one patients scheduled for colonoscopy  started a  low-fiber diet , lactulose and amidotrizoic-acid for fecal tagging 2 days prior to the CT scan ( st and ard dose , 5.8–8.2 mSv ) . The original raw data of 51 patients were modified and reconstructed at simulated 2.3 and 0.7 mSv levels . Two observers evaluated the st and ard dose scan regarding image quality and polyps . A third evaluated the presence of polyps at all three mSv levels in a blinded prospect i ve way . All observers were blinded to the reference st and ard : colonoscopy . At three times patients were given question naires relating to their experiences and preference . Image quality was sufficient in all patients , but significantly lower in the cecum , sigmoid and rectum . The two observers correctly identified respectively 10/15 ( 67 % ) and 9/15 ( 60 % ) polyps ≥10 mm , with 5 and 8 false-positive lesions ( st and ard dose scan ) . Dose reduction down to 0.7 mSv was not associated with significant changes in diagnostic value ( polyps ≥10 mm ) . Eighty percent of patients preferred CT colonography and 13 % preferred colonoscopy ( P<0.001 ) . CT colonography without cleansing is preferred to colonoscopy and shows sufficient image quality and moderate sensitivity , without impaired diagnostic value at dose-levels as low as 0.7 mSv PURPOSE To prospect ively evaluate the diagnostic performance of magnetic resonance ( MR ) colonography by using limited bowel preparation in patients with polyps of 10 mm or larger in diameter in a population at increased risk for colorectal cancer , with optical colonoscopy as the reference st and ard . MATERIAL S AND METHODS The institutional review boards of all three hospitals approved the study . All patients provided written informed consent . In this multicenter study , patients undergoing colonoscopy because of a personal or family history of colorectal cancer or adenomatous polyps were included . Two blinded observers independently evaluated T1- and T2-weighted MR colonographic images obtained with limited bowel preparation ( bright-lumen fecal tagging ) for the presence of polyps . The limited bowel preparation consisted of a low-fiber diet , with ingestion of lactulose and an oral gadolinium-based contrast agent ( with all three major meals ) starting 48 hours prior to imaging . Results were verified with colonoscopic outcomes . Patient sensitivity , patient specificity , polyp sensitivity , and interobserver agreement for lesions of 10 mm or larger were calculated for both observers individually and combined . RESULTS Two hundred patients ( mean age , 58 years ; 128 male patients ) were included ; 41 patients had coexistent symptoms . At colonoscopy , 12 patients had 22 polyps of 10 mm or larger . Per-patient sensitivity was 58 % ( seven of 12 ) for observer 1 , 67 % ( eight of 12 ) for observer 2 , and 75 % ( nine of 12 ) for both observers combined for polyps of 10 mm or larger . Per-patient specificity was 95 % ( 178 of 188 ) for observer 1 , 97 % ( 183 of 188 ) for observer 2 , and 93 % ( 175 of 188 ) for both observers combined . Per-polyp sensitivity was 55 % ( 12 of 22 ) for observer 1 , 50 % ( 11 of 22 ) for observer 2 , and 77 % ( 17 of 22 ) for both observers combined . Interobserver agreement was 93 % for identification of patients with lesions of 10 mm or larger . CONCLUSION In patients at increased risk for colorectal cancer , specificity of MR colonography by using limited bowel preparation was high , but sensitivity was modest PURPOSE To investigate the sensitivity and specificity of polyp detection and the image quality of computed tomographic ( CT ) colonography at different radiation dose levels and to study effective doses reported in literature on CT colonography . MATERIAL S AND METHODS CT colonography and colonoscopy were performed with 100 mAs in 50 consecutive patients at high risk for colorectal cancer ;  50- and 30-mAs CT colonographic examinations were simulated with controlled addition of noise to raw transmission measurements . One radiologist r and omly evaluated all original and simulated images for the presence of polyps and scored image quality . Differences in image quality were assessed with the Wilcoxon rank test . Scan protocol s from the literature and recent ( unpublished ) up date s were collected . RESULTS In nine of 10 patients with polyps 5 mm in diameter or larger ( sensitivity , 90 % ) and in seven of 17 patients with polyps smaller than 5 mm , polyps were correctly identified with CT colonography at all dose levels . Specificity for patients without polyps 5 mm or larger was 53%-60 % at all dose levels and for patients without any polyps was 26 % ( at 100 and 50 mAs ) and 48 % ( at 30 mAs ) . Image quality decreased significantly as the dose level decreased . The median effective doses ( supine and prone positions ) calculated from protocol s reported in the literature and up date s were 7.8 and 8.8 mSv , respectively . CONCLUSION Although image quality decreases significantly at 30 mAs ( 3.6 mSv ) , polyp detection remains unimpaired . The median dose for CT colonography at institutions that perform CT colonographic research is currently 8.8 mSv The aim of this prospect i ve trial was to evaluate sensitivity and specificity of bright lumen magnetic resonance colonography ( MRC ) in comparison with conventional colonoscopy ( CC ) . A total of 120 consecutive patients with clinical indications for CC were prospect ively examined using MRC ( 1.5 Tesla ) which was then followed by CC . Prior to MRC , the cleansed colon was filled with a gadolinium-water solution . A 3D GRE sequence was performed with the patient in the prone and supine position , each acquired during one breathhold period . After division of the colon into five segments , interactive data analysis was carried out using three-dimensional post-processing , including a virtual intraluminal view . The results of CC served as a reference st and ard . In all patients MRC was performed successfully and no complications occurred . Image quality was diagnostic in 92 % ( 574/620 colonic segments ) . On a per-patient basis , the results of MRC were as follows : sensitivity 84 % ( 95 % CI 71.7 - 92.3 % ) , specificity 97 % ( 95 % CI 89.0 - 99.6 % ) . Five flat adenomas and 6/16 small polyps ( < or = 5 mm ) were not identified by MRC . MRC offers high sensitivity and excellent specificity rates in patients with clinical indications for CC . Improved MRC techniques are needed to detect small polyps and flat adenomas BACKGROUND AND STUDY AIMS The purpose of this study was to evaluate dark-lumen magnetic resonance ( MR ) colonography prospect ively in patients with incomplete conventional colonoscopy . PATIENTS AND METHODS Thirty-two patients with incomplete conventional colonoscopy underwent same-day dark-lumen MR colonography on the basis of a st and ard protocol . The depiction of colorectal diseases was assessed in the following colon segments : cecum , ascending colon , transverse colon , descending colon , sigmoid colon , and rectum . The reasons for incomplete colonoscopy included high- grade stenosis in 26 patients ( four with occlusive cancer , 12 with fibrotic stenosis based on recurrent sigmoid diverticulitis , eight with Crohn's-induced stenosis , and two with nonsteroidal anti-inflammatory drug colonopathy ) , extreme patient intolerance in one patient , and technical challenges associated with an elongated colon in five patients . The results of MR colonography were compared with the findings of the initial conventional colonoscopy , the histopathological outcome , and follow-up colonoscopy when possible . RESULTS All high- grade stenoses were confirmed on MR colonographic data sets . Of the 26 patients with high- grade stenosis , 19 underwent surgery with histopathological confirmation of the initial diagnosis . Follow-up colonoscopy was carried out in 14 patients with surgically treated high- grade stenosis . In six of these 14 patients , nine polyps identified at the initial MR colonography were confirmed and removed during a postoperative conventional colonoscopy . Two polyps ( 5 mm and 8 mm in diameter ) identified on postoperative conventional colonoscopy had not been seen preoperatively at MR colonography . One polyp seen on MR colonography was not identified in the follow-up colonoscopy . CONCLUSION Dark-lumen MR colonography is a feasible and useful method of evaluating the entire colon in patients with incomplete conventional colonoscopy PURPOSE To prove the feasibility of air-distended magnetic resonance colonography ( MRC ) and compare it with water-based distention . MATERIAL S AND METHODS In five volunteers , the colon was imaged twice : once after distending the colon with air and a second time after distending the colon with water . A total of 50 patients , who had been referred to colonoscopy for a suspected colorectal pathology were r and omized into water-distention ( N = 25 ) and air-distention ( N = 25 ) groups . A contrast-enhanced T1-weighted three-dimensional volume interpolated breath-hold ( VIBE ) sequence was collected . Comparative analysis was based on qualitative ratings of image quality and bowel distention , as well as contrast-to-noise ratio ( CNR ) measurements for the colonic wall with respect to the colonic lumen . In addition , patient acceptance was evaluated . RESULTS Inflammatory changes and colorectal masses were correctly identified on MRC in eight patients each . One 4-mm polyp identified at colonoscopy was missed on water-distended MRC . There were no false positive findings . No significant differences were found between air- and water-distention regarding discomfort levels and image quality . The presence of air in the colonic lumen was not associated with susceptibility artifacts . CNR of the contrast-enhanced colonic wall , as well as bowel distention , were superior on air-distended three-dimensional data sets . CONCLUSION MRC can be performed using either water or air for colonic distention . Both techniques permit assessment of the colonic wall and identification of colorectal masses . While discomfort levels are similar for both agents , MRC with air provides higher CNR and better colonic distention Recent improvements in hardware and software , lack of side effects , as well as diagnostic accuracy make magnetic resonance imaging a natural c and i date for preventative imaging . Thus , the purpose of the study was to evaluate the feasibility of a comprehensive 60-min MR-based screening examination in healthy volunteers and a limited number of patients with known target disease . In ten healthy volunteers ( 7 men , 3 women ; mean age , 32.4 years ) and five patients ( 4 men , 1 woman ; mean age , 56.2 years ) with proven target disease we evaluated the performance of a comprehensive MR screening strategy by combining well-established organ-based MR examination components encompassing the brain , the arterial system , the heart , the lungs , and the colon . All ten volunteers and five patients  tolerated the comprehensive MR examination well . The mean in-room time was 63 min . In one volunteer , insufficient colonic cleansing on the part of the volunteer diminished the diagnostic reliability of MR colonography . All remaining components of the comprehensive MR examination were considered diagnostic in all volunteers and patients . In the five patients , the examination revealed the known pathologies [ aneurysm of the anterior communicating artery ( n=1 ) , renal artery stenosis ( n=1 ) , myocardial infa rct ( n=1 ) , and colonic polyp ( n=2 ) ] . The outlined MR screening strategy encompassing the brain , the arterial system , the heart , the lung , and the colon is feasible . Further studies have to show that MR-based screening programs are cost-effective in terms of the life-years saved AIM To assess Magnetic resonance colonography with fat enema as a method for detection of  colorectal neoplasm .  METHODS Consecutive twenty-two patients underwent MR colonography with fat enema before colonoscopy . T1-weighted three-dimensional fast spoiled gradient-echo with inversion recovery sequence was acquired with the patient in the supine position before and 75 s after Gadopentetate Dimelumine administration . Where by , pre and post MR coronal images were obtained with a single breath hold for about 20 s to cover the entire colon . The quality of MR colonographs and patients ' tolerance to fat contrast medium was investigated . Colorectal neoplasms identified by MR colonography were compared with those identified on colonoscopy and sensitivity of detecting the lesions was calculated accordingly . RESULTS MR colonography with fat enema was well tolerated without sedation and analgesia . 120 out of 132 ( 90.9 % ) colonic segments were well distended and only 1 ( 0.8 % ) colonic segment was poor distension . After contrast enhancement scan , mean contrast-to-noise ratio ( CNR ) value between the normal colonic wall and lumen was 18.5 + /- 2.9 while mean CNR value between colorectal neoplasm and lumen was 20.2 + /- 3.1 . By Magnetic resonance colonography , 26 of 35 neoplasms ( sensitivity 74.3 % ) were detected . However , sensitivity of MRC was 95.5 % ( 21 of 22 ) for neoplasm larger than 10 mm and 55.6 % ( 5 of 9 ) for 5 - 10 mm neoplasm 
    Output:
    
Significant heterogeneity was found for overall per patient sensitivity and specificity .
Conclusion MR-colonography can accurately detect colorectal polyps more than 10 mm in