Comparing the diagnostic yields of technologists and radiologists in an invitational colorectal cancer screening program performed with CT colonography.

PURPOSE: To compare the diagnostic yields of a radiologist and trained technologists in the detection of advanced neoplasia within a population-based computed tomographic (CT) colonography screening program. MATERIALS AND METHODS: Ethical approval was obtained from the Dutch Health Council, and written informed consent was obtained from all participants. Nine hundred eighty-two participants (507 men, 475 women) underwent low-dose CT colonography after noncathartic bowel preparation (iodine tagging) between July 13, 2009, and January 21, 2011. Each scan was evaluated by one of three experienced radiologists (≥800 examinations) by using primary two-dimensional (2D) reading followed by secondary computer-aided detection (CAD) and by two of four trained technologists (≥200 examinations, with colonoscopic verification) by using primary 2D reading followed by three-dimensional analysis and CAD. Immediate colonoscopy was recommended for participants with lesions measuring at least 10 mm, and surveillance was recommended for participants with lesions measuring 6-9 mm. Consensus between technologists was achieved in case of discordant recommendations. Detection of advanced neoplasia (classified by a pathologist) was defined as a true-positive (TP) finding. Relative TP and false-positive (FP) fractions were calculated along with 95% confidence intervals (CIs). RESULTS: Overall, 96 of the 982 participants were referred for colonoscopy and 104 were scheduled for surveillance. Sixty of 84 participants (71%) referred for colonoscopy by the radiologist had advanced neoplasia, compared with 55 of 64 participants (86%) referred by two technologists. Both the radiologist and technologists detected all colorectal cancers (n = 5). The relative TP fraction (for technologists vs radiologist) for advanced neoplasia was 0.92 (95% CI: 0.78, 1.07), and the relative FP fraction was 0.38 (95% CI: 0.21, 0.67). CONCLUSION: Two technologists serving as a primary reader of CT colonographic images can achieve a comparable sensitivity to that of a radiologist for the detection of advanced neoplasia, with far fewer FP referrals for colonoscopy.

Low-fiber diet in limited bowel preparation for CT colonography: Influence on image quality and patient acceptance.

OBJECTIVE: The purpose of this study was to determine whether a low-fiber diet is necessary for optimal tagging-only bowel preparation for CT colonography. SUBJECTS AND METHODS: Fifty consecutively enrolled patients received an iodine bowel preparation: 25 patients used a low-fiber diet and 25 used no special diet. One observer determined the tagging quality per segment on a 5-point scale (1, inhomogeneous tagging; 5, excellent preparation) and the largest size of untagged feces. Semiautomatic measurements of density and homogeneity of residual feces were performed. Patient acceptance was assessed with questionnaires. Per polyp sensitivity for polyps 6 mm in diameter and larger was calculated for two experienced observers. RESULTS: Tagging quality was scored less than grade 5 in 15 segments (10%) in the low-fiber diet group and in 25 segments (17%) in the unrestricted diet group (p = 0.098). One piece of untagged feces 10 mm in diameter or larger was found in the low-fiber diet group, and 12 were found in the unrestricted diet group (p < 0.001). Automatic measurement of attenuation resulted in a mean value of 594 HU in the low-fiber diet group and 630 HU in the unrestricted diet group (p = 0.297). In the low-fiber diet group, 22% of patients indicated that the bowel preparation was extremely or severely burdensome; 8% of patients in the unrestricted diet group had this response (p = 0.19). Thirty-two polyps 6 mm in diameter or larger were found in the low-fiber diet group and 30 in the unrestricted diet group. Observer 1 had 84% and 77% sensitivity in detecting polyps 6 mm in diameter or larger in the low-fiber diet and unrestricted diet groups, respectively (p = 0.443), and observer 2 had 97% and 83% sensitivity (p = 0.099). CONCLUSION: Use of a low-fiber diet in bowel preparation for CT colonography results in significantly less untagged feces and shows a trend toward better residue homogeneity.

Polyp measurement based on CT colonography and colonoscopy: variability and systematic differences.

OBJECTIVE: To assess the variability and systematic differences in polyp measurements on optical colonoscopy and CT colonography. MATERIALS: Gastroenterologists measured 51 polyps by visual estimation, forceps comparison and linear probe. CT colonography observers randomly assessed polyp size two-dimensionally (abdominal and intermediate window) and three-dimensionally (manually and semi-automatically). Linear mixed models were used to assess the variability and systematic differences between CT colonography and optical colonoscopy techniques. RESULTS: The variability of forceps and linear probe measurements was comparable and both showed less variability than measurement by visual assessment. Measurements by linear probe were 0.7 mm smaller than measurements by visual assessment or by forceps. The variability of all CT colonography techniques was lower than for measurements by forceps or visual assessment and sometimes lower (only 2D intermediate window and manual 3D) compared with measurements by linear probe. All CT colonography measurements judged polyps to be larger than optical colonoscopy, with differences ranging from 0.7 to 2.3 mm. CONCLUSION: A linear probe does not reduce the measurement variability of endoscopists compared with the forceps. Measurement differences between observers on CT colonography were usually smaller than at optical colonoscopy. Polyps appeared larger when using various CT colonography techniques than when measured during optical colonoscopy.

CT colonography with limited bowel preparation: prospective assessment of patient experience and preference in comparison to optical colonoscopy with cathartic bowel preparation.

The purpose of this study was to prospectively compare participant experience and preference of limited preparation computed tomography colonography (CTC) with full-preparation colonoscopy in a consecutive series of patients at increased risk of colorectal cancer. CTC preparation comprised 180 ml diatrizoate meglumine, 80 ml barium and 30 mg bisacodyl. For the colonoscopy preparation 4 l of polyethylene glycol solution was used. Participants' experience and preference were compared using the Wilcoxon signed rank test and the chi-squared test, respectively. Associations between preference and experience parameters for the 173 participants were determined by logistic regression. Diarrhoea occurred in 94% of participants during CTC preparation. This side effect was perceived as severely or extremely burdensome by 29%. Nonetheless, the total burden was significantly lower for the CTC preparation than for colonoscopy (9% rated the CTC preparation as severely or extremely burdensome compared with 59% for colonoscopy; p < 0.001). Participants experienced significantly more pain, discomfort and total burden with the colonoscopy procedure than with CTC (p < 0.001). After 5 weeks, 69% preferred CTC, 8% were indifferent and 23% preferred colonoscopy (p < 0.001). A burdensome colonoscopy preparation and pain at colonoscopy were associated with CTC preference (p < 0.04). In conclusion, participants' experience and preference were rated in favour of CTC with limited bowel preparation compared with full-preparation colonoscopy.

CT colonography with limited bowel preparation for the detection of colorectal neoplasia in an FOBT positive screening population.

PURPOSE: Aim was to evaluate the accuracy of computed tomography colonography (CTC) for detection of colorectal neoplasia in a Fecal Occult Blood Test (FOBT) positive screening population. METHODS: In three different institutions, consecutive FOBT positives underwent CTC after laxative free iodine tagging bowel preparation followed by colonoscopy with segmental unblinding. Each CTC was read by two experienced observers. For CTC and for colonoscopy the per-polyp sensitivity and per-patient sensitivity and specificity were calculated for detection of carcinomas, advanced adenomas, and adenomas. RESULTS: In total 22 of 302 included FOBT positive participants had a carcinoma (7%) and 137 had an adenoma or carcinoma ≥10 mm (45%). CTC sensitivity for carcinoma was 95% with one rectal carcinoma as false negative finding. CTC sensitivity for advanced adenomas was 92% (95% CI: 88-96) vs. 96% (95% CI: 93-99) for colonoscopy (P = 0.26). For adenomas and carcinomas ≥10 mm the CTC per-polyp sensitivity was 93% (95% CI: 89-97) vs. 97% (95% CI: 94-99) for colonoscopy (P = 0.17). The per-patient sensitivity for the detection of adenomas and carcinomas ≥10 mm was 95% (95% CI: 91-99) for CTC vs. 99% (95% CI: 98-100) for colonoscopy (P = 0.07), while the per-patient specificity was 90% (95% CI: 86-95) and 96% (95% CI: 94-99), respectively (P < 0.001). CONCLUSION: CTC with limited bowel preparation performed in an FOBT positive screening population has high diagnostic accuracy for the detection of adenomas and carcinomas and a sensitivity similar to that of colonoscopy for relevant lesions.

Primary uncleansed 2D versus primary electronically cleansed 3D in limited bowel preparation CT-colonography. Is there a difference for novices and experienced readers?

The purpose of this study was to compare a primary uncleansed 2D and a primary electronically cleansed 3D reading strategy in CTC in limited prepped patients. Seventy-two patients received a low-fibre diet with oral iodine before CT-colonography. Six novices and two experienced observers reviewed both cleansed and uncleansed examinations in randomized order. Mean per-polyp sensitivity was compared between the methods by using generalized estimating equations. Mean per-patient sensitivity, and specificity were compared using the McNemar test. Results were stratified for experience (experienced observers versus novice observers). Mean per-polyp sensitivity for polyps 6 mm or larger was significantly higher for novices using cleansed 3D (65%; 95%CI 57-73%) compared with uncleansed 2D (51%; 95%CI 44-59%). For experienced observers there was no significant difference. Mean per-patient sensitivity for polyps 6 mm or larger was significantly higher for novices as well: respectively 75% (95%CI 70-80%) versus 64% (95%CI 59-70%). For experienced observers there was no statistically significant difference. Specificity for both novices and experienced observers was not significantly different. For novices primary electronically cleansed 3D is better for polyp detection than primary uncleansed 2D.

CT colonography polyp matching: differences between experienced readers.

The purpose of this study was to investigate if experienced readers differ when matching polyps shown by both CT colonography (CTC) and optical colonoscopy (OC) and to explore the reasons for discrepancy. Twenty-eight CTC cases with corresponding OC were presented to eight experienced CTC readers. Cases represented a broad spectrum of findings, not completely fulfilling typical matching criteria. In 21 cases there was a single polyp on CTC and OC; in seven there were multiple polyps. Agreement between readers for matching was analyzed. For the 21 single-polyp cases, the number of correct matches per reader varied from 13 to 19. Almost complete agreement between readers was observed in 15 cases (71%), but substantial discrepancy was found for the remaining six (29%) probably due to large perceived differences in polyp size between CT and OC. Readers were able to match between 27 (71%) and 35 (92%) of the 38 CTC detected polyps in the seven cases with multiple polyps. Experienced CTC readers agree to a considerable extent when matching polyps between CTC and subsequent OC, but non-negligible disagreement exists.

Does a computer-aided detection algorithm in a second read paradigm enhance the performance of experienced computed tomography colonography readers in a population of increased risk?

We prospectively determined whether computer-aided detection (CAD) could improve the performance characteristics of computed tomography colonography (CTC) in a population of increased risk for colorectal cancer. Therefore, we included 170 consecutive patients that underwent both CTC and colonoscopy. All findings >or=6 mm were evaluated at colonoscopy by segmental unblinding. We determined per-patient sensitivity and specificity for polyps >or=6 mm and >or=10 mm without and with computer-aided detection (CAD). The McNemar test was used for comparison the results without and with CAD. Unblinded colonoscopy detected 50 patients with lesions >or=6 mm and 25 patients with lesions >or=10 mm. Sensitivity of CTC without CAD for these size categories was 80% (40/50, 95% CI: 69-81%) and 64% (16/25, 95% CI: 45-83%), respectively. CTC with CAD detected one additional patient with a lesion >or=6 mm and two with a lesion >or=10 mm, resulting in a sensitivity of 82% (41/50, 95% CI: 71-93%) (p = 0.50) and 72% (18/25, 95% CI: 54-90%) (p = 1.0), respectively. Specificity without CAD for polyps >or=6 mm and >or=10 mm was 84% (101/120, 95% CI: 78-91%) and 94% (136/145, 95% CI: 90-98%), respectively. With CAD, the specificity remained (nearly) unchanged: 83% (99/120, 95% CI: 76-89%) and 94% (136/145, 95% CI: 90-98%), respectively. Thus, although CTC with CAD detected a few more patients than CTC without CAD, it had no statistically significant positive influence on CTC performance.

Lesion conspicuity and efficiency of CT colonography with electronic cleansing based on a three-material transition model.

OBJECTIVE: The purpose of this article is to report the effect on lesion conspicuity and the practical efficiency of electronic cleansing for CT colonography (CTC). MATERIALS AND METHODS: Patients were included from the Walter Reed Army Medical Center public database. All patients had undergone extensive bowel preparation with fecal tagging. A primary 3D display method was used. For study I, the data consisted of all patients with polyps > or = 6 mm. Two experienced CTC observers (observer 1 and observer 2) scored the lesion conspicuity considering supine and prone positions separately. For study II, data consisted of 19 randomly chosen patients from the database. The same observers evaluated the data before and after electronic cleansing. Evaluation time, assessment effort, and observer confidence were recorded. RESULTS: In study I, there were 59 lesions partly or completely covered by tagged material (to be uncovered by electronic cleansing) and 70 lesions surrounded by air (no electronic cleansing required). The conspicuity did not differ significantly between lesions that were uncovered by electronic cleansing and lesions surrounded by air (observer 1, p < 0.5; observer 2, p < 0.6). In study II, the median evaluation time per patient after electronic cleansing was significantly shorter than for original data (observer 1, 20 reduced to 12 minutes; observer 2, 17 reduced to 12 minutes). Assessment effort was significantly smaller for both observers (p < 0.0000001), and observer confidence was significantly larger (observer 1, p < 0.007; observer 2, p < 0.0002) after electronic cleansing. CONCLUSION: Lesions uncovered by electronic cleansing have comparable conspicuity with lesions surrounded by air. CTC with electronic cleansing sustains a shorter evaluation time, lower assessment effort, and larger observer confidence than without electronic cleansing.

Influence of tagged fecal material on detectability of colorectal polyps at CT: phantom study.

OBJECTIVE: The purpose of this study was to determine the influence of tagged material on the minimal radiation dose needed to detect colorectal polyps at CT. MATERIALS AND METHODS: The study was conducted in two phases. In the first, three experienced observers determined the visibility of sessile polyps (6 mm) at five contrast levels (300, 480, 790, and 1,040 HU and air) and five tube charge levels (10, 14, 20, 28, and 40 mAs) in an anthropomorphic phantom. Each polyp was present in one of eight possible locations. The mean tube charge threshold for 90% correct responses was determined for each contrast level. Blinded observers performed independent 2D readings. In the second phase of the study, three 150-cm virtual colons were evaluated at two contrast levels (300 and 480 HU) and at five tube charge levels between 20 and 80 mAs. The three colons contained 18 randomly located polyps. The mean tube charge threshold for 90% sensitivity was determined for each contrast level. RESULTS: In the first phase of the study, the estimated tube charge thresholds for 300, 480, and 790 HU were 24.0, 16.3, and 6.2 mAs. At 1,040 HU and in air, all polyps were detected at the lowest tube charge setting (10 mAs). In the second phase, the tube charge thresholds for 90% sensitivity at 300 and 480 HU were 70 and 35 mAs, respectively. CONCLUSION: If polyps are covered by fecal material, a considerably higher tube charge setting is needed for adequate visualization than is needed for polyps in a completely cleansed colon, especially when the density of the tagged residue is low.

Image quality and patient acceptance of four regimens with different amounts of mild laxatives for CT colonography.

OBJECTIVE: The purpose of our study was to prospectively evaluate image quality and patient acceptance of CT colonography (CTC) with fecal tagging using different levels of catharsis. SUBJECTS AND METHODS: Forty consecutive increased-risk patients were randomized. Group 1 received orally 20 mg of bisacodyl, group 2 received 30 mg of bisacodyl, group 3 received 20 mg of bisacodyl and 8.2 g of magnesium citrate, and group 4 received 30 mg of bisacodyl and 16.4 g of magnesium citrate. All patients used a 2-day low-fiber diet and received diatrizoate meglumine and barium for fecal tagging. One reviewer blindly scored subjective image quality (fecal tagging, amount of residual feces [liquid or solid], luminal distention, and image readability) on a 5- to 6-point scale using a 2D review technique. The mean and SD of attenuation of tagging were measured as well as the relative SD as a measure of homogeneity. Furthermore, patient acceptance (burden related to diarrhea, abdominal pain, flatulence, and overall burden) was evaluated. Ordinal regression, generalized estimating equations, and parametric and nonparametric tests were used for analysis. RESULTS: Image readability was evaluated as good or excellent in all examinations except one in group 2 (nondiagnostic) and two in group 3 (moderate). Group 2 contained more feces than group 4 (p = 0.04). With regard to mean attenuation and homogeneity of tagging, no significant differences were observed between groups. Group 4 experienced more severe diarrhea than groups 1 and 2 and higher overall burden than groups 1 and 3 (p < 0.042). CONCLUSION: The mildest preparation with 20 mg of bisacodyl provided good image quality of CTC images. Increasing the amount of laxatives did not improve image quality or tagging characteristics but was associated with a lower patient acceptance.

CT colonography with limited bowel preparation: performance characteristics in an increased-risk population.

PURPOSE: To prospectively evaluate the sensitivity and specificity of computed tomographic (CT) colonography with limited bowel preparation for the depiction of colonic polyps, by using colonoscopy as the reference standard. MATERIALS AND METHODS: Institutional review board approval and written informed consent were obtained. Patients at increased risk for colorectal cancer underwent CT colonography after fecal tagging, which consisted of 80 mL of barium sulfate and 180 mL of diatrizoate meglumine. Bisacodyl was added for stool softening. A radiologist and a research fellow evaluated all data independently by using a primary two-dimensional approach. Discrepant findings for lesions 6 mm or larger in diameter were solved with consensus. Segmental unblinding was performed. Per-patient sensitivity and specificity, per-polyp sensitivity, and number of false-positive findings were found (for lesions > or = 6 mm and > or = 10 mm in diameter). Per-patient sensitivities (blinded colonoscopy vs CT colonography) were tested for significance with McNemar statistics. Interobserver variability was analyzed per segment (prevalence-adjusted bias-adjusted kappa values [kappa(p)]). RESULTS: One hundred fourteen of 168 patients (105 men, 63 women; mean age, 56 years) had polyps, with 56 polyps 6 mm or larger and 17 polyps 10 mm or larger. Per-patient sensitivities were not significantly different for CT colonography (consensus reading) and colonoscopy (P > or = .070). Sensitivity of CT colonography for patients with lesions 6 mm or larger and 10 mm or larger was 76% and 82%, respectively, and specificity of CT colonography was 79% and 97%, respectively. Blinded colonoscopy depicted 91% (lesions > or = 6 mm) and 88% (lesions > or = 10 mm) of disease in patients. Per-polyp sensitivity for CT colonography was 70% (lesions > or = 6 mm) and 82% (lesions > or = 10 mm). Number of false-positive findings was 42 (lesions > or = 6 mm) and six (lesions > or = 10 mm). kappa(p) Was 0.88 (lesions > or = 6 mm) and 0.96 (lesions > or = 10 mm). CONCLUSION: CT colonography with limited bowel preparation has a sensitivity of 82% and specificity of 97% for patients with polyps 10 mm or larger.

Detection of protrusions in curved folded surfaces applied to automated polyp detection in CT colonography.

Over the past years many computer aided diagnosis (CAD) schemes have been presented for the detection of colonic polyps in CT Colonography. The vast majority of these methods (implicitly) model polyps as approximately spherical protrusions. Polyp shape and size varies greatly, however and is often far from spherical. We propose a shape and size invariant method to detect suspicious regions. The method works by locally deforming the colon surface until the second principal curvature is smaller than or equal to zero. The amount of deformation is a quantitative measure of the 'protrudeness'. The deformation field allows for the computation of various additional features to be used in supervised pattern recognition. It is shown how only a few features are needed to achieve 95% sensitivity at 10 false positives (FP) per dataset for polyps larger than 6 mm.