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
4. HISTOLOGIC CLASSIFICATION
OF 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 CLASSIFICATION
OF 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
9. Clinical Indications for Performing
CTC
SCREENING INDICATIONS
Asymptomatic adults at average risk
Asymptomatic patients with positive family history
Asymptomatic patients at increased risk for colonoscopy
DIAGNOSTIC 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 CONSIDERATIONS
The technique for CTC involves the following steps:
(1) Bowel preperation.
(2) Colon insufflation.
(3) Image acquisition.
(4) Image processing and interpretation.
12. Large fl at hyperplastic
polyp detected at CTC screening. 3D
endoluminal (A) and 2D transverse
(B) CTC images show a large but
relatively subtle 15-mm nonpolypypoid
lesion (arrowheads) within the
transverse colon. A central depression
is suggested on the 3D view. The
lesion was confirmed at same-day OC
(C) and proved to be hyperplastic.
17. 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
18. 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.
19. Benefits Of CT Virtual
Colonography
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.
20. Limitations of CT Virtual
Colonography
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.