Virtual Colonoscopy: Technique and Accuracy

Colonic distention at screening CT colonography: role of spasmolytic agents and body habitus

Sufficient colonic dilation is important when using CT colonography (CTC) for colorectal cancer screening. We investigated the effect of antispasmodic agents and the patient body habitus on the degree of colonic dilation in screening CTC.We assessed the effect of clinical characteristics [age, gender, body mass index (BMI), and the presence of diverticula] and the use of antispasmodics on colonic distention in 140 patients who underwent CTC for colorectal cancer screening. The CTC was performed in both the supine- and prone positions. Seventy patients received antispasmodics prior to CT examination and the other 70 did not. Colonic distention was scored using a 5-point scale: 1=collapsed, 2=poorly visualized, 3=visualized but underdistended, 4=acceptable, and 5=excellent. Images scored as 4 or 5 were considered to be of diagnostic quality. The mean visual evaluation score was significantly higher in the supine- than the prone position (4.2±0.5 vs. 4.0±0.5, p<0.01). For the supine position, only the use of antispasmodic was statistically associated with sufficient colonic dilation by univariate logistic analysis (odds ratio=2.365, p=0.03). For the prone position, age, BMI, and the use of antispasmodic were statistically associated with sufficient colonic dilation by multivariate analysis. The odds ratio of these parameters was 0.955 (p=0.02), 0.874 (p=0.03), and 2.391 (p=0.02), respectively.We obtained sufficient colonic dilation with an antispasmodic for CTC in both positions. Younger age and a lower BMI were also associated with better colonic dilation in the prone position.

Small intestinal tumors: diagnostic accuracy of enhanced multi-detector CT virtual endoscopy

OBJECTIVE

To study the diagnostic accuracy of enhanced multi-detector CT virtual endoscopy (MDCT-VE) for small intestinal tumors.

MATERIALS AND METHODS

125 patients were examined by multi-detector CT (MDCT: 54 on 4-slice; 71 on 64-slice) following standard gastrointestinal tract cleansing, oral double contrast aerogenesis agent, and rectal gas administration. Unenhanced CT was performed, followed by enhanced CT in supine (30 and 80s delay after 100 mL standard intravenous contrast medium) and prone positions (180s delay). Supplementary CT in the lateral position was performed if small bowel was not well-filled. Images were reviewed on post-processing workstations with Virtual Endoscopy software.

RESULTS

33/125 patients had proven small intestinal tumors: ten stromal tumors, nine lymphoma, eight adenocarcinomas, three hemangiomas, one each lipoma, Brunner gland adenoma, and hamartoma. 92 were nontumors. MDCT-VE correctly identified 30/33 cases with one false-positive diagnosis: sensitivity 90.9%, specificity 98.9% and accuracy 96.8%.

CONCLUSION

Small intestinal MDCT-VE technique has high diagnostic accuracy for the detection of intestinal tumors. Contrast enhancement and adequate intestinal tract gas-filling can improve the detection rate for small intestinal tumors.

CT colonography can be an adjunct to optical colonoscopy in CRC screening

CT colonography or virtual colonoscopy is a fairly new modality that has the potential to play a significant role in screening for colon cancer. CT colonography is an attractive option for two specific reasons. First, it is non-invasive and, second, it obviates the need for sedation. It thus overcomes the two major drawbacks of optical colonoscopy. CT colonography cannot be a stand-alone technique for colorectal cancer screening because, unlike conventional colonoscopy, it does not possess a therapeutic option or a definite diagnostic capability. However, CT colonography can be a cost-effective complement to traditional colonoscopy if it is reasonably priced and if appropriate cut-off levels (>6 mm polyp) are used to increase its sensitivity.

Comparison of polyp distance on CT colonography between supine and prone scans using an automated path-distance measurement tool: correlation with colonoscopy

OBJECTIVE

To investigate the proximity of polyp distance on CT colonography (CTC) between supine and prone scans using an automated path-distance measurement tool and to correlate the path distance of polyps with that of colonoscopy.

METHODS

Of 196 polyps in 85 patients, 98 polyps (25 <6 mm, 42 6-9.9 mm, 31 > or =10 mm) detected on supine and prone positions in 72 patients, were included. The location of each polyp, which was expressed as the distance from the tip of the rectum, was measured using an automated path-distance measurement tool and was compared between the two positions. The effect of colonic collapse on the proximity of polyp distance between the two scans was analyzed. The automated path distance of 50 polyps in the rectosigmoid colon was correlated with that of colonoscopy.

RESULTS

Mean difference of the automated path distances of polyps between the two positions was 2.6 cm and was not significantly different between the two positions (P > 0.05). Correlation coefficient (gamma) between the two positions was 0.9977. The difference of the distance of polyps between the groups with or without colonic collapse was not significant (P > 0.05). Automated path distance of 50 polyps in the sigmoid colon or rectum was generally well correlated with that on colonoscopy (gamma = 0.8005, P < 0.0001) and the mean difference was 5.1 cm. The mean difference increased as the polyp distance from the point of reference became further located, and reached significance when the distance was further than 30 cm from the tip of the rectum (P = 0.002).

CONCLUSION

Automated path distance of polyps matches closely between the two positions and is not influenced by the presence of collapsed segments. Polyps located 30 cm or further from the tip of the rectum on CTC do not match closely with that on colonoscopy.

Screening CT colonography in an asymptomatic average-risk Asian population: a 2-year experience in a single institution

OBJECTIVE

The purpose of our study was to report the results of screening CT colonography (CTC) in an asymptomatic average-risk Asian population.

MATERIALS AND METHODS

In 2005 and 2006, 1,015 Korean adults (609 men and 406 women; mean age, 51 years) underwent screening CTC using a 16-MDCT scanner and an automated CO2 delivery system. During the study period, the protocols were changed to use less vigorous purgation and lower radiation doses; fecal tagging (n = 890) and primary 3D interpretation (n = 966) were generally used. CTC results were categorized as C0, inadequate; C1, no significant polyp; C2, one or two 6- to 9-mm polyps; C3, polyps > or = 10 mm or > or = three 6- to 9-mm polyps; and C4, mass. Patients with positive CTC results were referred to gastroenterologists for follow-up or management planning.

RESULTS

Categories C0-C4 were assigned to 21 (2.1%), 916 (90.2%), 54 (5.3%), 23 (2.3%), and one (0.1%) patients, respectively. Fifty-four patients with C4 (n = 1), C3 (n = 20), or C2 (n = 33) underwent subsequent optical colonoscopy: complete (n = 53) and incomplete (n = 1). Per-patient positive predictive values (PPVs) for categories C3-C4 and C2-C4 were 90% (18/20) and 74% (39/53), respectively. Per-polyp PPVs at 10- and 6-mm thresholds were 92% (22/24) and 69% (45/65), respectively. The diagnostic yield for advanced neoplasm was 1.5% (15/1,015).

CONCLUSION

Our results seem comparable to Western experiences, showing that a successful screening CTC program can be reproduced in an Asian population.

Computed tomographic colonography

Computed tomographic colonography is a modern technique to evaluate the colon, which may be more appealing to patients than invasive methods. The potential of this test, including current and future developments are presented in this review. The essential steps required to perform a diagnostic quality computed tomographic colonography are discussed as well as different methods of study interpretation. The current status and promising areas of future investigation are also discussed.

[Virtual pleuroscopy of diaphragmatic pleura: myth or reality?]

PURPOSE

Evaluate the feasibility of the virtual pleuroscopy (VP) in the detection of the pleural plaques.

METHOD AND MATERIALS

Twenty consecutive patients, having asbestos exposure, explored by unenhanced multidetector CT-scan (Siemens, Sensation 16). The imaging parameters were as follows: beam width, 12 mm; beam pitch, 1; and reconstruction thickness, 1mm every 0.8mm at 120 kV and 180 mA. The image display used a surface-rendering algorithm and produced perspective red-scale images with a matrix of 512 x 512. Each VP image simulated a coned-down view, with a variable cone angle to explore the diaphragmatic pleura. The camera was placed 1 to 2 cm above the diaphragmatic dome. Four views are studied by diaphragm: crâniocaudal, lateral tangential, anterior and posterior. The observed virtual pleura aspect was classified in 5 groups (gr): gr 1: Rib band, gr 2: lobulated pleural thickening, gr 3: spicular, gr 4: plaques and gr 5: nodules. The results were compared to the other MDCT images using multiplanar reformatting.

RESULTS

The visualization of each diaphragm was optimal (35/40; 87.5%), limited (3/40; round atelectasis and asbestosis) or impossible (2/40; asbestosis). The classifications of the studied 38 diaphragmatic pleura were: gr 1 (n=15), gr 2 (n=5), gr 3 (n=11), gr 4 (n=7), gr 5 (n=0). The MDCT analysis showed normal pleura for both gr 1 and gr 2, a confirmed or beginning of fibrosis for gr 3 and confirmed the presence of pleural plaques on the diaphragmatic pleura in all cases of gr 4.

CONCLUSION

The virtual pleuroscopy is a reality. It is a feasible technique. Other studies are necessary to confirm these preliminary results.

Single-center study comparing computed tomography colonography with conventional colonoscopy

AIM: To compare the results from computed tomography (CT) colonography with conventional colonoscopy in symptomatic patients referred for colonoscopy.

METHODS: The study included 227 adult outpatients, mean age 60 years, with appropriate indications for colonoscopy. CT colonography and colonoscopy were performed on the same day in a metropolitan teaching hospital. Colonoscopists were initially blinded to the results of CT colonography but there was segmental unblinding during the procedure. The primary outcome measures were the sensitivity and specificity of CT colonography for the identification of polyps seen at colonoscopy (i.e. analysis by polyp). Secondary outcome measures included an analysis by patient, extracolonic findings at CT colonography, adverse events with both procedures and patient acceptance and preference.

RESULTS: Twenty-five patients (11%) were excluded from the analysis because of incomplete colonoscopy or poor bowel preparation that affected either CT colonography, colonoscopy or both procedures. Polyps and masses (usually cancers) were detected at colonoscopy and CT colonography in 35% and 42% of patients, respectively. Of nine patients with a final diagnosis of cancer, eight (89%) were identified by CT colonography as masses (5) or polyps (3). For polyps analyzed according to polyp, the overall sensitivity of CT colonography was 50% (95% CI, 39%-61%) but this increased to 71% (95% CI, 52%-85%) for polyps ≥ 6 mm in size. Similarly, specificity for all polyps was 48% (95% CI, 39%-58%) increasing to 67% (95% CI, 56%-76%) for polyps ≥ 6 mm. Adverse events were uncommon but included one colonic perforation at colonoscopy. Patient acceptance was high for both procedures but preference favoured CT colonography.

CONCLUSION: Although CT colonography was more sensitive in this study than in some previous studies, the procedure is not yet sensitive enough for widespread application in symptomatic patients.