CT colonography using different reconstruction modi

Comparison of 64-Detector CT Colonography and Conventional Colonoscopy in the Detection of Colorectal Lesions

Background:

Colon cancer is a leading cause of morbidity and mortality in developed countries. The early detection of colorectal cancer using screening programs is important for managing early-stage colorectal cancers and polyps. Modalities that allow examination of the entire colon are conventional colonoscopy, double contrast barium enema examination and multi-detector computed tomography (MDCT) colonography.

Objectives:

To compare CT colonography and conventional colonoscopy results and to evaluate the accuracy of CT colonography for detecting colorectal lesions.

Patients and Methods:

In a prospective study performed at Gastroenterology and Radiology Departments of Medical Faculty of Eskisehir Osmangazi University, CT colonography and colonoscopy results of 31 patients with family history of colorectal carcinoma, personal or family history of colorectal polyps, lower gastrointestinal tract bleeding, change in bowel habits, iron deficiency anemia and abdominal pain were compared. Regardless of the size, CT colonography and conventional colonoscopy findings for all the lesions were cross - tabulated and the sensitivity, specificity, and positive and negative predictive values were calculated. To assess the agreement between CT colonography and conventional colonoscopy examinations, the Kappa coefficient of agreementt was used. Statistical analysis was performed by SPSS ver 15.0.

Results:

Regardless of the size, MDCT colonography showed 83% sensitivity and 95% specificity, with a positive predictive value of 95% and a negative predictive value of 83% for the detection of colorectal polyps and masses. MDCT colonography displayed 92% sensitivity and 95% specificity, with a positive predictive value of 92% and a negative predictive value of 95% for polyps ≥ 10 mm. For polyps between 6mm and 9 mm, MDCT colonography displayed 75% sensitivity and 100% specificity, with a positive predictive value of 100% and a negative predictive value of 90%. For polyps ≤ 5 mm MDCT colonography displayed 88% sensitivity and 100% specificity with a positive predictive value of 100% and a negative predictive value of 95%.

Conclusions:

CT colonography is a safe and minimally invasive technique, a valuable diagnostic tool for examining the entire colon and a good alternative compared to other colorectal cancer screening tests because of its high sensitivity values in colorectal lesions over 1 cm.

Current techniques in the performance, interpretation, and reporting of CT colonography

The technical objective of computed tomographic colonography (CTC) is to acquire high-quality computed tomography images of the cleansed, well-distended colon for polyp detection. In this article the authors provide an overview of the technical components of CTC, from preparation of the patient to acquisition of the imaging data and basic methods of interpretation. In each section, the best evidence for current practices and recommendations is reviewed. Each of the technical components must be optimized to achieve high sensitivity in polyp detection.

Electronic colon-cleansing for CT colonography: diagnostic performance

BACKGROUND

The purpose of this study was to evaluate whether an electronic-colonic-cleansing (ECC) algorithm is beneficial for the diagnostic performance compared to a CT colonography (CTC) evaluation without electronic cleansing in tagged datasets.

METHODS

Two blinded readers evaluated CTC datasets from 79 patients with 153 colorectal polyps confirmed by optical colonoscopy. Cases were read in a randomized order with and without the use of electronic colon-cleansing software. Per-polyp sensitivity, per-polyp/per-patient specificity and reading times (with and without ECC) have been calculated and reported.

RESULTS

Per-polyp sensitivity for polyps >6 mm without using ECC was 60.4% (Reader 1: 59.7%, Reader 2: 61.1%), while polyps >10 mm were detected with a sensitivity of 58.3% (Reader 1: 66.7%, Reader 2: 50%). On electronically cleansed datasets, the sensitivity was 73.6% (Reader 1: 76.4%; Reader 2: 70.8%) for polyps >6 mm and 83.3% (Reader 1: 83.3%; Reader 2: 83.3%), respectively. Per-patient specificity was 75% without using cleansing (Reader 1: 68%, Reader 2: 82%) and 81.5% using ECC (Reader 1: 86%, Reader 2: 77%).

CONCLUSION

Reading CTC cases using ECC software improves sensitivity in detecting clinically relevant colorectal polyps.

Virtual dissection CT colonography: evaluation of learning curves and reading times with and without computer-aided detection

PURPOSE

To prospectively evaluate the learning curves and reading times of inexperienced readers who used the virtual dissection reading method for retrospective computed tomographic (CT) colonography data sets, with and without concurrent computer-aided detection (CAD).

MATERIALS AND METHODS

An Institutional Review Board approved this study; informed consent was waived. Four radiologists without experience in CT colonography evaluated 100 optical colonoscopy-proved data sets of 100 patients (49 men, 51 women; mean age, 59 years +/- 13 [standard deviation]; range, 21-85 years) by using the virtual dissection reading method. Two readers used concurrent CAD. Data sets were read during five consecutive 1-day sessions (20 data sets per session). Polyp detection and false-positive rates, receiver operating characteristics (ROCs), and reading times were calculated for individual, CAD group, and non-CAD group readings. Diagnostic values were compared by calculating the 95% confidence intervals (CIs) around the relative risk. Areas under ROC curves (AUCs) (Hanley and McNeil for paired analysis and z statistics for unpaired analysis) and reading times (Wilcoxon signed rank test) were compared across the sessions, within each session and for the whole study.

RESULTS

The range of detection rates was 79 of 111 (.71 [95% CI: .61, .79]) to 91 of 111 (.82 [95% CI: .73, .88]). The range of false-positive rates was 17 of 111 (.15 [95% CI: .09, .23]) to 22 of 111 (.20 [95% CI: .12, .28]). All readers' AUCs rose from session 1 to session 4; this rise was significant (P < .05) for the non-CAD group. Only during session 1 was the CAD group AUC (.83) higher than the non-CAD group AUC (.54) (P < .05). Comparison of CAD and non-CAD reading times showed no significant difference for the whole study or during each session (P > .05).

CONCLUSION

The virtual dissection reading technique allows short learning curves, which may be improved by the concurrent use of CAD, without significant effect on average reading time.

[CT colonography: techniques of visualization and findings]

Evaluation and interpretation of CT colonography is based on both 2D and 3D techniques. The 2D techniques are popular mainly because the time needed for evaluation is short. The 3D techniques allow better definition than the 2D techniques, especially of polyps close to folds or at the base of a fold. The evaluation strategies generally accepted so far (primarily 2D, with 3D for problem cases, or vice versa) demand knowledge of both 2D and 3D techniques. Newer 3D visualization techniques help make it possible to acquire more complete and faster recording particularly of areas that are not easily accessible to endoscopic examination. These user-friendly developments are thus well suited to improving the detection and the security of detection of polyps. It must be remembered that experience and the knowledge of associated artifacts and the limitations they can impose on diagnosis are prime requirements for the implementation of such visualization techniques.

Two- versus Three-dimensional Colon Evaluation with Recently Developed Virtual Dissection Software for CT Colonography

This retrospective study was institutional review board approved; the requirement for informed patient consent was waived. The purpose of this study was to retrospectively compare a two-dimensional (2D) data interpretation technique with a three-dimensional (3D) colon dissection technique in terms of interpretation time and sensitivity for colonic polyp detection, with colonoscopy as the reference standard. Ninety-six patients (56 men, 40 women; mean age, 54.8 years) underwent colonoscopy and multidetector computed tomographic (CT) colonography on the same day. Two radiologists independently analyzed the data on a per-polyp and per-patient basis. The sensitivity of both approaches was compared by using the McNemar test. The time required to interpret CT colonographic data with each technique was also assessed. Compared with the conventional 2D colonic polyp detection method, primary 3D interpretation with use of virtual dissection software for CT colonography revealed comparable per-polyp (77% and 69% for two readers) and per-patient (77% and 73% for two readers) sensitivities and comparable per-patient specificity (99% and 89% for two readers) for the detection of polyps 6 mm in diameter or larger and involved a shorter interpretation time.

Three-dimensional virtual dissection at CT colonography: unraveling the colon to search for lesions

Computed tomographic (CT) colonography is a promising noninvasive examination for colorectal cancer screening; however, the optimal interpretation strategy remains undecided. Virtual dissection is an innovative technique whereby the three-dimensional (3D) model of the colon is virtually unrolled, sliced open, and displayed as a flat 3D rendering of the mucosal surface, similar to a gross pathologic specimen. This technique has the potential to reduce evaluation time by providing a more rapid 3D image assessment than is possible with an antegrade and retrograde 3D endoluminal fly-through. It may also ultimately improve accuracy by reducing blind spots present with 3D endoluminal displays and by reducing reader fatigue. A disadvantage of virtual dissection is the potential for distortion of colonic lesions and normal anatomy. To avoid potential pitfalls in image interpretation, the radiologist must be familiar with the unique appearance of the normal colon anatomy and of various pathologic findings when using virtual dissection with two-dimensional axial and 3D endoluminal CT colonographic image data sets.

Multislice CT Colonography: Current Status and Limitations

CT colonography (CTC) is a promising method for colorectal cancer screening because it provides a full structural evaluation of the entire colon. It has a superior safety profile, a low rate of complications, and high patient acceptance. In addition, CTC offers the real possibility of eliminating the cathartic bowel preparation, one of the biggest obstacles to patient compliance with colorectal cancer screening. Results of CTC studies in recently published literature are extremely encouraging, demonstrating that this method of screening can detect lesions equal to or larger than 8 mm with few false-positive findings.