Authors: Jasper Florie Rogier E van Gelder Michiel P Schutter Adrienne van Randen Henk W Venema Steven de Jager Victor P M van der Hulst Anna Prent Shandra Bipat Patrick M M Bossuyt Lubbertus C Baak Jaap Stoker
Publish Date: 2007/06/05
Volume: 17, Issue: 12, Pages: 3112-3122
Abstract
The purpose was to evaluate lowdose CT colonography without cathartic cleansing in terms of image quality polyp visualization and patient acceptance Sixtyone patients scheduled for colonoscopy started a lowfiber diet lactulose and amidotrizoicacid for fecal tagging 2 days prior to the CT scan standard dose 58–82 mSv The original raw data of 51 patients were modified and reconstructed at simulated 23 and 07 mSv levels Two observers evaluated the standard dose scan regarding image quality and polyps A third evaluated the presence of polyps at all three mSv levels in a blinded prospective way All observers were blinded to the reference standard colonoscopy At three times patients were given questionnaires 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 falsepositive lesions standard dose scan Dose reduction down to 07 mSv was not associated with significant changes in diagnostic value polyps ≥10 mm Eighty percent of patients preferred CT colonography and 13 preferred colonoscopy P0001 CT colonography without cleansing is preferred to colonoscopy and shows sufficient image quality and moderate sensitivity without impaired diagnostic value at doselevels as low as 07 mSvSince computed tomography colonography CTC has shown good results in detecting clinically relevant polyps 1 2 3 4 5 6 studies have been performed focusing on increasing patient acceptance by reducing the bowel preparation This can be done by adding an oral contrast agent to meals fecal tagging 7 8 9 10 11 12 in combination with a lowfiber diet and sometimes lactulose for stool softening thereby obviating extensive cleansingDifferent studies have been performed using barium iodine or a combination of both as tagging material However only a limited number of these studies on CTC have used limited bowel preparation Few have evaluated the diagnostic value and patient acceptance of CTC In parallel with the development of limited bowel preparation strategies ultra lowdose protocols have been evaluated 13 14 15To our knowledge to date no studies have evaluated the effect of dose reduction on sensitivity and specificity in patients with a limited bowel preparation Only one study 7 has evaluated limited bowel preparation at a relatively low dose level 140 kVp 10 mAs This study has shown very good results however these data have not been reproduced yet Moreover as only one doselevel was studied the effect of dose reduction remains unknownThe purpose of this study was to evaluate limited bowelpreparation CTC using an oral contrast agent amidotrizoic acid in terms of image quality patient acceptance and polyp visualization using conventional colonoscopy CC as a reference standard A second objective was to determine the effect of substantially reducing the radiation dose levels on the diagnostic accuracy of limited bowel preparation CTC again using CC as the reference standardPatients of the Onze Lieve Vrouwe Gasthuis at increased risk for colorectal cancer personal or family history of colorectal polyps or cancer 16 who were scheduled to undergo CC between April 2002 and August 2003 were invited to participate in the study Exclusion criteria were impossibility to understand the information/informed consent age below 18 years pregnancy and inflammatory bowel disease The study was approved by the institutional review board of the Onze Lieve Vrouwe Gasthuis and Academic Medical Center All patients gave written informed consent
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