Recent developments in CT colonography

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.

A feasibility study of unidirectional 240°-angle 3D CT colonography

In three-dimensional (3D) CT colonography (CTC), a wider viewing angle provides a larger field of view. The purpose of this study was to investigate the polyp detection rate and time efficiency of unidirectional 240°-angle 3D CTC compared with bidirectional 120°-angle CTC. CTC data sets of 40 patients were reviewed by two readers using the two methods. The unidirectional 240°-angle CTC showed a performance in polyp detection similar to the bidirectional 120°-angle CTC with improved time efficiency.

From point to local neighborhood: polyp detection in CT colonography using geodesic ring neighborhoods

Existing polyp detection methods rely heavily on curvature-based characteristics to differentiate between lesions. These assume that the discrete triangulated surface mesh or volume closely approximates a smooth continuous surface. However, this is often not the case and because curvature is computed as a local feature and a second-order differential quantity, the presence of noise significantly affects its estimation. For this reason, a more global feature is required to provide an accurate description of the surface at hand. In this paper, a novel method incorporating a local neighborhood around the centroid of a surface patch is proposed. This is done using geodesic rings which accumulate curvature information in a neighborhood around this centroid. This geodesic-ring neighborhood approximates a single smooth, continuous surface upon which curvature and orientation estimation methods can be applied. A new global shape index, S is also introduced and computed. These curvature and orientation values will be used to classify the surface as either a bulbous polyp, ridge-like fold or semiplanar structure. Experimental results show that this method is promising (100% sensitivity, 100% specificity for lesions > 10 mm) for distinguishing between bulbous polyps, folds and planar-like structures in the colon.

Routine preoperative abdominal computed tomography in colon cancer: a utility study

BACKGROUND

There is no proven utility for preoperative scanning of intraperitoneal colonic cancer with computed tomography (CT). A prospective study was conducted where CT was preoperatively incorporated into the management algorithm to ascertain its role in patient treatment.

METHODS

Thoraco-abdominal CT was performed in both the elective and emergency settings in an unselected group of 73 patients referred to a coloproctology unit established over the last 30 months at the Queen Elizabeth Hospital, Barbados. CT and operative findings were compared to determine the influence that the preoperative CT had on surgical decision making.

RESULTS

Unexpected additional pathology was found in 6.8% of patients. Sensitivity for the detection of visceral metastatic disease was 84.6%. Preoperative CT was deemed to be of clinical value in 24.7% of cases and to definitively alter surgical management in 13.7% of patients. These alterations in management included several types of multivisceral resections, the need for ureteric stenting or reimplantation, the utilization of stomas alone and the avoidance of resection in known metastatic disease.

CONCLUSIONS

Preoperative CT of intraperitoneal colonic cancer adds important technical information to the conduct of the surgery and alters therapy in a selected patient group.

CT colonography versus colonoscopy in the follow-up of patients after diverticulitis - a prospective, comparative study

AIM

To assess whether computed tomography colonography (CTC) is a viable alternative to colonoscopy or double contrast barium enema in the follow-up of patients after diverticulitis.

MATERIAL AND METHODS

Fifty patients underwent CTC followed immediately by colonoscopy. Results were blinded to the examiners. Findings of diverticular disease and patient acceptance were evaluated.

RESULTS

Bowel preparation and distension were good in the majority of CTC and colonoscopy examinations. Diverticular disease was found in 96% of patients at CTC and in 90% at colonoscopy. The rate of agreement between CTC and colonoscopy for diverticular findings in the sigmoid colon was good (kappa=0.64). No complications were seen. Patients found colonoscopy more uncomfortable (p<0.03), more painful (p<0.001), and more difficult (p<0.01) than CTC. Of the patients favouring one examination, 74% preferred CTC.

CONCLUSION

CTC appears to have a better diagnostic potential for imaging of diverticular disease-specific findings, when compared with colonoscopy. Also, CTC was less uncomfortable and was preferred by a majority of patients. CTC seems to be a reasonable alternative in follow-up of patients with symptomatic diverticular disease.

Magnetic resonance colonography vs computed tomography colonography for the diagnosis of colorectal cancer: an indirect comparison

OBJECTIVE

The primary aim of this study was to use meta-regression techniques to compare the diagnostic accuracy of computed tomography colonography (CTC) and magnetic resonance colonography (MRC), compared with conventional colonoscopy for patients presenting with colorectal cancer (CRC).

METHOD

Quantitative meta-analysis was performed using prospective studies reporting comparative data between CTC and MRC individually to conventional colonoscopy. Study quality was assessed and sensitivities, specificities, diagnostic odds ratios (DOR) were calculated. Summary receiver operating characteristic (SROC) curves and sensitivity analysis were utilized. Meta-regression was used to indirectly compare the two modalities following adjustment for patient and study characteristics.

RESULTS

Overall sensitivity and specificity for CTC (0.96, 95% CI 0.92-0.99; 1.00, 95% CI 0.99-1.00 respectively) and MRC (0.91, 95% CI 0.79-0.97; 0.98, 95% CI 0.96-0.99 respectively) for the detection of CRC was similar. Meta-regression analysis showed no significant difference in the diagnostic accuracy of both modalities (beta=-0.64, P=0.37 and 95% CI of 0.12-2.39). Both tests showed high area under the SROC curve (CTC=0.99; MRC=0.98), with high DORs (CTC=1461.90, 95% CI 544.89-3922.30; MRC=576.41, 95% CI 135.00-2448.56). Factors that enhanced the overall accuracy of MRC were the use intravenous contrast, faecal tagging and exclusion of low-quality studies. No factors improved diagnostic accuracy from CTC except studies with more than 100 patients (AUC=1.00, DOR=2938.35, 95%CI 701.84-12 302.91).

CONCLUSION

This meta-analysis suggested that CTC and MRC have similar diagnostic accuracy for detecting CRC. Study quality, size and intravenous/intra-luminal contrast agents affect diagnostic accuracies. For an exact comparison to be made, studies evaluating CTC, MRC and colonoscopy in the same patient cohort would be necessary.

An update on imaging of colorectal cancer

Screening of asymptomatic average-risk patients for presence of colon cancer and early detection in precursor stages is of great interest to general population. Comprehensive evaluation of symptomatic or high-risk patients represents another important clinical focus. Available techniques for total colon imaging, rectal cancer staging and the role of positron emission tomography are discussed.

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.