Ct colonography
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  • 1. ByDr/ Mahmoud Elshamy MD
  • 2. INTRODUCTION Colorectal carcinoma (CRC) is the Second most common cancer in United States and second leading cause of cancer related death Colorectal Cancer Incidence & Mortality 2000-2003 United States Kentucky African Americans Caucasians Incidence 64.4 53.1 61.2 Per 100,000 Mortality 28.4 19.8 23
  • 3. INTRODUCTION The benign colorectal polyp is the core of colorectal cancer
  • 4. HISTOLOGIC CLASSIFICATIONOF POLYPS Adenomas are one histologic subtype of colorectal polyps. Other histologic subtypes include mucosal polyps, hyperplastic/ serrated polyps, juvenile polyps, and inflammatory polyps. In addition, certain types of polyps can arise from layers deeper than the mucosa, including lipomas, carcinoid tumors, gastrointestinal stromal tumors (GIST), and serosal lesions.
  • 5. HISTOLOGIC CLASSIFICATIONOF POLYPS. Adenomas constitute approximately half of colorectal polyps; hyperplastic and serrated lesions make up about one third or more; and mucosal polyps make up approximately 10%. The remaining histologic subtypes constitute only a tiny percentage. The histologic classification of polyps cannot be reliably determined by gross evaluation either at endoscopy or at CTC; they require pathologic examination for final diagnosis.
  • 6. POLYP MORPHOLOGY. Polyps measuring 3 cm are generally divided into three major morphologic categories: sessile, pedunculated, and flat. Invasive masses are generally bulky annular or semiannular tumors.
  • 7.  The ideal target for screening and prevention of colorectal cancer is the “advanced adenoma,” which is defined as an adenoma that is large (10 mm) and/or contains histologic findings of either high-grade dysplasia or a prominent villous component
  • 8. Methods for Screening Colonoscopy Air contrast barium enema CT colonoscopy
  • 9. Clinical Indications for PerformingCTCSCREENING INDICATIONS Asymptomatic adults at average risk Asymptomatic patients with positive family history Asymptomatic patients at increased risk for colonoscopyDIAGNOSTIC INDICATIONS Following incomplete optical colonoscopy Evaluation of suspected submucosal lesions Surveillance of unresected 6-9-mm polyps detected at previous CTC Unexplained GI bleeding, iron deficiency anemia, or other GI symptoms Symptomatic patients at increased risk for colonoscopy Surveillance following resection of polyps or cancer
  • 10. CTC TECHNICAL CONSIDERATIONSThe technique for CTC involves the following steps: (1) Bowel preperation. (2) Colon insufflation. (3) Image acquisition. (4) Image processing and interpretation.
  • 11. IMAGE PROCESSING ANDINTERPRETATION
  • 12. Large fl at hyperplasticpolyp detected at CTC screening. 3Dendoluminal (A) and 2D transverse(B) CTC images show a large butrelatively subtle 15-mm nonpolypypoidlesion (arrowheads) within thetransverse colon. A central depressionis suggested on the 3D view. Thelesion was confirmed at same-day OC(C) and proved to be hyperplastic.
  • 13. 3D RECONSTRUCTION
  • 14. 3 D VIRTUAL Recontruction
  • 15. 3D RECONSTRUCTION
  • 16. Detection Rates Colonoscopy: Sensitivity of 88.2 (>10mm) Sensitivity of 90.0 (<6mm) CT colonoscopy: Sensitivity of 92.2 (>10mm) Sensitivity of 85.7 (<6mm) Air contrast barium enema: failed to identify up to 50% of polyps greater than 10mm in diameter
  • 17. Virtual vs. Optical Colonoscopy Patients reported less discomfort with virtual colonoscopy Shorter examination time with VC 72.3% of patients preferred VC as screening technique compared to 5% preferred CC as screening technique More patients were willing to repeat a VC at shorter intervals than CC.
  • 18. Benefits Of CT VirtualColonography Faster examination time and this is a non invasive test. It provides three-dimensional images that can depict many polyps and other lesions as clearly as when they are directly seen by optical Colonoscopy. Reduced patient risk, CT Colonography has a markedly lower risk of perforating the colon than conventional Colonoscopy.
  • 19. Limitations of CT VirtualColonography CT Virtual Colonography is strictly a diagnostic procedure. If any significant polyps are found, they will have to be removed by conventional colonoscopy. The immediate risks of CTC include a small rate of perforation related to gas distension, which is lower than the risk from colonoscopy. Potential long-term risk from radiation exposure.