Public Health Concern
134,000 new cases and 55,000 deaths in 1996
3rd most common cancer and 2nd leading cause cancer death in the USA
Average lifetime incidence is 6%
Natural history permits the recognition and curative treatment of precursor polyps and
SCREENING SAVES LIVES!
Fecal Occult Blood Tests (FOBT): low sensitivity and specificity. 30% sensitivity for
asymptomatic CRC. However, there is small mortality reduction due to earlier detection
of localized cancers (not polyps).
Proctosigmoidoscopy: effective for region that is covered but limited naturally for the
portions of colon not examined. Half of all CRC’s will be missed as a result.
Barium Enema: low sensitivity. Only 44% of clinically important (>10mm polyps) are
(Optical) Colonoscopy: Trials have shown reduction of both CRC mortality and
incidence particularly in high risk population. Invasive and moderately expensive and
carries a small risk for morbidity.
CT (Virtual) Colonography: non-invasive technique requiring only bowel prep, greater
comfort and convenience. It is safe, more comfortable and convenient compared with
optical colonoscopy. High sensitivity and specificity. Prospects for future for minimal
preparation without laxatives.
CT Colonography Colon Preparation: low residue meals, laxatives, stool and liquid
Extra Colonic Findings: 10-13% have significant extra colonic findings based on several
Summary of the “National Trial” ACRIN 6664 Study.
2600 participants (data available on 2531), 50 yoa or older, 15 centers
All had CT colonography and optical colonoscopy
All lesions 5mm or greater in diameter were reported
Sensitivity 90, Specificity 86, PPV 23, NPV 99.
Benefits From CTC Screening Every 5 Years From the Age of 50 to 80 Outweigh Radiation Risks
The benefits of screenings with CT colonography (CTC) scans every five years from age 50 to 80 outweigh
the radiation-related cancer risks of the screenings, according to a recent study. Using the... (More)
From "Radiation-Related Cancer Risks From CT Colonography Screening: A Risk-Benefit Analysis"
American Journal of Roentgenology (04/11) Vol. 196, No. 4, P. 816 Berrington de González, Amy ; Kim, Kwang Pyo ;
Knudsen, Amy B.; et al.
Web Link | Return to Headlines
CTC May Be More Suitable for Initial Colorectal Screening
Researchers carried out a systematic review and meta-analysis of published studies evaluating the
sensitivity of both computed tomographic colonography (CTC) and optical colonoscopy (OC) for the...
From "Colorectal Cancer: CT Colonography and Colonoscopy for Detection—Systematic Review and Meta-Analysis"
Radiology (05/01/11) Vol. 259, No. 2, P. 393 Pickhardt, Perry J.; Hassan, Cesare; Halligan, Steve; et al.
Web Link | Return to Headlines
CT Colonography Equal to Optical
Colonoscopy, says Study
By Deborah Abrams Kaplan | May 4, 2011
CT colonography is a better screening test than optical colonoscopy (OC), according to a
new study published in the MayRadiology print issue. Using meta-analysis of studies done
over a 15 year period, authors found that the sensitivity of CT colonography for
colorectal cancer detection was 96.1 percent, compared with 94.7 percent for OC.
Authors noted that their study supported the clinical equivalence of CTC and OC for
screening invasive cancers. They felt the CTC was mature enough to be seen as a
Aside from the sensitivity rates being roughly equal, there are other reasons that the CTC
can be better for screening, including cost and the minimal invasiveness. One potential
downside, however, is that CTC exposes the patient to radiation, though lead author Perry
J. Pickhardt, MD, a professor of radiology at the University of Wisconsin School of
Medicine doesn’t think the amount is concerning. “CTC is a low-dose exam applied to
adult patients,” he said. “There are no meaningful implications related to the radiation
The meta-analysis ultimately included 49 studies covering 11,551 patients, done from
January 1994 (the year that CT colonography was first mentioned), through 2009. All the
CTC studies were for screening, to diagnose colorectal polyps and cancer, and all
positive results were proven histologically. Six studies, encompassing 42 percent of the
participants, focused on asymptomatic patients typical in a screening setting. The
remaining 43 studies included symptomatic patients and/or a disease-enriched population.
Authors note the low prevalence of invasive colon cancer in screenings, citing a
cumulative 3.6 percent rate from the meta-analysis. A total of 414 colorectal cancers
were found in the studies, including 20 in the screening group (less than a 0.5 percent
prevalence rate) and 394 in the disease-enriched group (almost a 6 percent prevalence
As for the cost, Pickhardt says that using CTC is less expensive. “Our work has shown
that CTC is considerably more cost-effective as a primary screening test compared with
One reported reason that patients are less likely to get a colonscopy is because the
evacuatory and uncomfortable nature of the bowel preparation. Plus, OC requires the use
of some anesthesia or medication for patient comfort. With CTC, those issues are
diminished, according to Pickhardt. “CTC is much less invasive, requires no IV for
sedation or pain medication, and requires no recovery time,” said Pickhardt, adding that
patients don’t need a driver to take them home. “In addition, our low-volume bowel prep
is much better tolerated than the typical colonoscopy preps in use.”
Effective 7/40, must use Category II CPT codes:
0066T- CT colonography screening
0067T- CT colonography diagnostic
these are tracking codes and not reimbursed.
NHIC may adopt North East policy: reimbursable in patients in whom colonoscopy incomplete
due to obstructing lesion (DB 11/04)
LCD- reimburse for failed colonoscopy & history of neoplasm
Elimination of bowel prep (fecal tagging) & CAD needed before widespread adoption.
Viatronix V3D System-FDA approved
On-line CT Colonography Database-
E. Neri- Pisa.
CT Colonography CAD- Torino
Digital subtraction bowel cleansing algorithm. Give oral contrast 48hrs prior but no bowel prep.
Automated Polyp Detection (R2)
3D: Superiority of Viatronix V3D-Colon (v1.2.4)- Pickhardt, AJR2003;181:1599.
Colon Cancer Screening with Virtual Colonoscopy
-48 hr conventional prep (phospho-soda: 1.5oz @ 2pm & 7pm day before exam- (contraindicated
if CHF, renal failure, angina, electrolyte imbalance) or 24hr Fleets kit.
-colon insufflated with room air (over 2-3min) by pt. (40-50 puffs)- start R side down (20puffs),
then supine (20puffs), check CT topogram
-5mm collimation, 2-3mm reconstruction intervals. (2.5mm @ 1.25mm intervals if using quad)
-supine & prone.
-CT tube current 100-140 mA, possibly lower. (120 kVp & 48 mAs, pitch 3- 40s scan, or use
96mAs, pitch 6- 20s scan).
-review 2D axial images, 2D MPR, also 3D volume rendering display helpful, best if there is 2D-
3D interactive display.
-90% sens for polyps >10 mm (80% sens 5-10mm).
-per patient sens 100% for >10mm
-false positives: diverticular ds, poor distention, undissolved meds, stool.
- only 1% of all adenomas < 10mm will harbor invasive CA.
-likelihood of therapeutic colonoscopy required about 10%.
-potentially important, malignant, or surgical ds as incidental extraluminal findings in 4%.
-appropriate remibursement about $500-750.
-important developments: low-dose multidetector protocols, CAD, prepless methods.
Thin Section Low Dose MDCT:
-minimum 40 puffs
-supine scout image to verify adequate distention
-supine scan first, turn prone, several additional puffs air & scan.
-4 x 1 mm section collimation
-120kV, 0.5 sec rotation, effective 50 mAs, pitch 6-7 for 30 sec scan time.
-reconstructions 1.25mm sections with 1mm interval.
-effective dose: 5.0mSv men, 7.8mSv women.
-Interpretation: use axial images, if abn- do coronal & sagittal MPR images & volume rendered
endoluminal views: lesions with irregular geometric borders & internal heterogeneities in central
portion consistent with stool. Polyps and small tumors have smooth, round borders. Coronal &
endoluminal views used to differentiate linear (fold) from round (polyp) features.
Pitfalls: carpet lesions vs stool, bulbous fold vs polyp on fold, ileocecal valve.
Report by colonic segment (assess adequacy of distention, location & size (probably report
polyps >= 8mm, ignore lesions < 5mm) of lesions. Extra-colonic findings.
Thin section (1.25mm every 1mm) has same sensitivity but better specificity than 5mm sections
every 2mm. Rad2003;229:791
-easy to miss, may mimic stool coating a fold.
-predominantly in cecum, ascending colon and rectum.
-can become malignant.
Missed lesions; AJR2004182:881
-flat & pedunculated (esp if long stalk) morphology & irregular surface contour.
-location at the convergence of folds or adjacent to thickened colonic wall or suboptimal local
-lesions seen only on 1 position should not be disregarded unless corresponding colonic segment
in opposite position is well visualized and normal.
Positional change in polyps- 27% of polyps moved from ventral to dorsal location between supine
& prone positions, can't assume mobile lesion is stool. Rad2004;231:761
-if normal: 5yr
-if lesion <6mm: 3-5yr
-if lesion 6mm or >: colonoscopy
Reporting & Data System- A Consensus Proposal, Rad2005;236:3
-looking at 2D vs 3D
-stool & fluid tagging