Noncathartic CT colonography: Image quality assessment and performance and in a screening cohort.

OBJECTIVE: Cathartic bowel preparation is a major barrier for colorectal cancer screening. We examined noncathartic CT colonography (CTC) quality and performance using four similar bowel-tagging regimens in an asymptomatic screening cohort. SUBJECTS AND METHODS: This prospective study included 564 asymptomatic subjects who underwent noncathartic CTC without dietary modification but with 21 g of barium with or without iodinated oral contrast material (four regimens). The quality of tagging with oral agents was evaluated. A gastrointestinal radiologist evaluated examinations using primary 2D search supplemented by electronic cleansing (EC) and 3D problem solving. Results were compared with complete colonoscopy findings after bowel purgation and with retrospective unblinded evaluation in 556 of the 564 (99%) subjects. RESULTS: Of the 556 subjects, 7% (37/556) and 3% (16/556) of patients had 52 and 20 adenomatous polyps ≥ 6 and ≥ 10 mm, respectively. The addition of iodine significantly improved the percentage of labeled stool (p ≤ 0.0002) and specificity (80% vs 89-93%, respectively; p = 0.046). The overall sensitivity of noncathartic CTC for adenomatous polyps ≥ 6 mm was 76% (28/37; 95% CI, 59-88%), which is similar to the sensitivity of the iodinated regimens with most patients (sensitivity: 231 patients, 74% [14/19; 95% CI, 49-91%]; 229 patients, 80% [12/15; 95% CI, 52-96%]). The negative predictive value was 98% (481/490), and the lone cancer was detected (0.2%, 1/556). EC was thought to improve conspicuity of 10 of 21 visible polyps ≥ 10 mm. CONCLUSION: In this prospective study of asymptomatic subjects, the per-patient sensitivity of noncathartic CTC for detecting adenomas ≥ 6 mm was approximately 76%. Inclusion of oral iodine contrast material improves examination specificity and the percentage of labeled stool. EC may improve polyp conspicuity.

Does the amount of tagged stool and fluid significantly affect the radiation exposure in low-dose CT colonography performed with an automatic exposure control?

OBJECTIVE: To determine whether the amount of tagged stool and fluid significantly affects the radiation exposure in low-dose screening CT colonography performed with an automatic tube-current modulation technique. METHODS: The study included 311 patients. The tagging agent was barium (n = 271) or iodine (n = 40). Correlation was measured between mean volume CT dose index (CTDI (vol)) and the estimated x-ray attenuation of the tagged stool and fluid (ATT). Multiple linear regression analyses were performed to determine the effect of ATT on CTDI (vol ) and the effect of ATT on image noise while adjusting for other variables including abdominal circumference. RESULTS: CTDI (vol) varied from 0.88 to 2.54 mGy. There was no significant correlation between CTDI (vol) and ATT (p = 0.61). ATT did not significantly affect CTDI (vol) (p = 0.93), while abdominal circumference was the only factor significantly affecting CTDI (vol) (p < 0.001). Image noise ranged from 59.5 to 64.1 HU. The p value for the regression model explaining the noise was 0.38. CONCLUSION: The amount of stool and fluid tagging does not significantly affect radiation exposure.

Colorectal cancer screening: the role of CT colonography.

Computed tomography colonography (CTC) in colorectal cancer (CRC) screening has two roles: one present and the other potential. The present role is, without any further discussion, the integration into established screening programs as a replacement for barium enema in the case of incomplete colonoscopy. The potential role is the use of CTC as a first-line screening method together with Fecal Occult Blood Test, sigmoidoscopy and colonoscopy. However, despite the fact that CTC has been officially endorsed for CRC screening of average-risk individuals by different scientific societies including the American Cancer Society, the American College of Radiology, and the US Multisociety Task Force on Colorectal Cancer, other entities, such as the US Preventive Services Task Force, have considered the evidence insufficient to justify its use as a mass screening method. Medicare has also recently denied reimbursement for CTC as a screening test. Nevertheless, multiple advantages exist for using CTC as a CRC screening test: high accuracy, full evaluation of the colon in virtually all patients, non-invasiveness, safety, patient comfort, detection of extracolonic findings and cost-effectiveness. The main potential drawback of a CTC screening is the exposure to ionizing radiation. However, this is not a major issue, since low-dose protocols are now routinely implemented, delivering a dose comparable or slightly superior to the annual radiation exposure of any individual. Indirect evidence exists that such a radiation exposure does not induce additional cancers.

Survey update on implementation, indications, and technical performance of computed tomography colonography in Sweden.

BACKGROUND: Computed tomographic colonography (CTC) has gained increased acceptance in the last few years as a valid substitute for double-contrast barium enema (DCBE). However, implementation of new technologies is complex, since several factors may influence the process. PURPOSE: To evaluate the current situation in Sweden concerning implementation of CTC, as compared to a previous national survey in 2005. MATERIAL AND METHODS: In December 2008, a structured, self-assessed questionnaire regarding implementation and technical performance of CTC was mailed to all radiology departments in Sweden. In March 2009, departments who had not replied were contacted by e-mail or by telephone. All (100%, 119/119) departments answered the questionnaire. RESULTS: CTC is currently performed in 50/119 (42%) departments, i.e., 18 additional departments compared to 2005. Twenty-three out of 60 (38%) responding departments stated that they intend to start to perform CTC in the near future. DCBE is currently performed in 77/119 (65%) departments, 12 departments less compared to 2005. The most common reasons for non-implementation of CTC are non-availability of spiral CT scanner (41%, 26/64) and/or multidetector-row CT scanner (39%, 25/64), and lack of doctors' time (34%, 22/64). Only 3% (2/64) of departments are "awaiting further scientific documentation" on CTC, a significant reduction compared to 2005 (P=0.002). Until 2009, 59% (29/49) of CTC centers had performed more than 200 CTCs compared to 13% (4/32) of CTC centers in 2005. Intravenous contrast material is routinely administered in 86% (42/49), and carbon dioxide is used to distend the colon in 90% (44/49). Almost all radiology departments (93%, 93/100) currently believe that CTC will "absolutely" or "probably" replace barium enema in the future, while in 2005 only 56% (55/99) gave similar answers. CONCLUSION: The survey reflects a further transition process from DCBE to CTC, with attitudes of radiologists increasingly in favor of CTC, although DCBE is still performed by the majority of radiology departments. DCBE should be replaced by colonoscopy and CTC, but the transition requires both human and economic resources.

Audit of the introduction of CT colonography for detection of colorectal carcinoma in a non-academic environment and its implications for the national bowel cancer screening programme.

AIM: To compare the sensitivity of double-contrast barium enema (DCBE) with computed tomography colonography (CTC) to determine whether CTC is superior for the detection of colorectal cancer (CRC) locally, and to compare the results to those of a national barium enema audit. MATERIALS AND METHODS: All patients undergoing diagnostic DCBE or CTC between January 2003 and December 2005 were identified from the picture archiving communication system (PACS). Patients with a confirmed diagnosis of CRC were identified from the local cancer registry. Patients who were not diagnosed as having CRC on imaging were assumed true negatives if they were not listed in the cancer registry by December 2007, giving a minimum of 2 years follow-up. DCBE and CTC reports of all patients with CRC were analysed, and cancer detection was considered to have occurred (positive test result) if the report stated the definite presence of CRC or possible CRC requiring further investigation. RESULTS: 2520 DCBEs and 604 CTCs were included. Twenty-one of 33 patients with CRC were detected using DCBE (incidence 1.31%, sensitivity 63.7%). Thirty-two of 33 patients with CRC were -detected using CTC (incidence 5.46%, sensitivity 97.7%). CONCLUSION: CTC is more sensitive for the detection of CRC, and its introduction in a district general hospital is justified. However, there has been a consequent decline in DCBE sensitivity, which, if reflected nationally, suggests CTC is the preferential screening test for CRC.

Critical analysis of the performance of double-contrast barium enema for detecting colorectal polyps > or = 6 mm in the era of CT colonography.

OBJECTIVE: The purpose of our study was to perform a meta-analysis comparing the performance of double-contrast barium enema (DCBE) with CT colonography (CTC) for the detection of colorectal polyps > or = 6 mm using endoscopy as the gold standard. MATERIALS AND METHODS: Prospective DCBE and CTC studies were identified. Percentages of polyps and of patients with polyps > or = 10 mm and 6-9 mm were abstracted. The performance of DCBE versus CTC was determined by separately evaluating each technique's performance versus that of endoscopy, and contrasting the techniques. The I-squared statistic and Fisher's exact test were used for heterogeneity, the Cochran-Mantel-Haenszel and the Kruskal-Wallis tests for correlation, and the A(z) test for comparing pooled weighted estimates of performance. RESULTS: Eleven studies of DCBE (5,995 patients, 1,548 polyps) and 30 studies of CTC (6,573 patients, 2,348 polyps) fulfilled inclusion criteria. For polyps > or = 10 mm, a 0.121-per-patient sensitivity difference favored CTC (p < 0.0001; DCBE, 0.702 [95% CI, 0.687-0.715]; CTC, 0.823 [0.809-0.836]). For polyps > or = 10 mm, a 0.031-per-polyp sensitivity difference favored CTC (p < 0.0001; DCBE, 0.715 [0.703-0.726]; CTC, 0.746 [0.735-0.757]). For polyps > or = 10 mm, a specificity difference of 0.104 favored CTC (p = 0.001; DCBE, 0.850 [0.847-0.855]; CTC, 0.954 [0.952-0.955]). DCBE was also significantly less sensitive for 6- to 9-mm polyps (p < 0.001). CONCLUSION: DCBE has statistically lower sensitivity and specificity than CTC for detecting colorectal polyps > or = 6 mm.

Replacing barium enema with CT colonography in patients older than 70 years: the importance of detecting extracolonic abnormalities.

OBJECTIVE: The objective of our study was to evaluate the significance of extracolonic abnormalities in patients older than 70 years referred for CT colonography (CTC). MATERIALS AND METHODS: We performed a retrospective analysis of 400 consecutive patients older than 70 years undergoing CTC over a 14-month period. All patients presented with weight loss, alteration of bowel habits, rectal blood loss, abdominal pain, or anemia; these symptoms led to clinical suspicion of lower gastrointestinal abnormalities. RESULTS: Five hundred five separate extracolonic abnormalities were detected in 268 of 400 patients (67%). One hundred thirty-nine pathologic processes were deemed significant in 116 patients. Of these, 110 lesions (79%) were previously unknown in 96 of the 400 patients (24.0%). Forty-nine of the 400 patients (12.3%) had at least one malignancy, including 23 extracolonic malignancies and 29 colorectal malignancies. Thirteen patients had early cancers (T1N0M0 or T2N0M0). Twenty of the colon cancer patients had significant previously unknown extracolonic abnormalities, half of which were related to the primary tumor and half of which were unrelated extracolonic abnormalities. CONCLUSION: In patients older than 70 years being examined because of lower gastrointestinal symptoms, CTC findings yield a high number of new significant extracolonic abnormalities. This finding makes a compelling case for targeting this group of patients for a CTC service.

Availability, indications, and technical performance of computed tomographic colonography: a national survey.

PURPOSE: To determine the availability, indications, and technique of computed tomographic colonography (CTC) in Sweden and to investigate opinions on its future role in colon imaging. MATERIAL AND METHODS: In May 2004, a questionnaire on CTC was mailed to all Departments of Radiology in Sweden, and one year later a telephone interview was conducted with the departments that intended to start a CTC service. RESULTS: Ninety-nine departments (83%) answered the questionnaire, indicating that 23/ 99 (23.2%) offered a CTC service. Reasons for non-implementation of CTC were lack of CTC training in 34/73 (46.6%) and non-availability of multi-detector row CT scanners in 33/73 (45.2%), while 26% were awaiting further scientific documentation on CTC. Incomplete colonoscopy was the main indication for CTC in 21/23 (91.3%) departments performing CTC. Dual positioning, room air insufflation, and thin-slice collimation were used in all the responding departments. The number of CTC studies performed varied from 1-5 (26.1%) to more than 200 (17.4%). Intravenous contrast material was routinely administered by 9/23 (39.1%) departments. Out of 30 (39.5%) departments that in 2004 intended to start CTC, 9 (30%) had done so by June 2005. A total of 32/99 (32.3%) departments had therefore started CTC by June 2005. Half of the departments that replied believed that CTC would absolutely or probably replace barium enema in the future. CONCLUSION: The survey shows relatively limited diffusion of CTC practice in Sweden, with approximately one-third of radiology departments offering a CTC service, mostly on a small scale. A wider dissemination of CTC requires further scientific documentation of its capability, intensified educational efforts, and additional funding.