Role of CT colonography in symptomatic assessment, surveillance and screening

Model-based iterative reconstruction in low-dose CT colonography-feasibility study in 65 patients for symptomatic investigation

RATIONALE AND OBJECTIVES

To compare image quality on computed tomographic colonography (CTC) acquired at standard dose (STD) and low dose (LD) using filtered-back projection, adaptive statistical iterative reconstruction, and model-based iterative reconstruction (MBIR) techniques.

MATERIALS AND METHODS

A total of 65 symptomatic patients were prospectively enrolled for the study and underwent STD and LD CTC with filtered-back projection, adaptive statistical iterative reconstruction, and MBIR to allow direct per-patient comparison. Objective image noise, subjective image analyses, and polyp detection were assessed.

RESULTS

Objective image noise analysis demonstrates significant noise reduction using MBIR technique (P < .05) despite being acquired at lower doses. Subjective image analyses were superior for LD MBIR in all parameters except visibility of extracolonic lesions (two-dimensional) and visibility of colonic wall (three-dimensional) where there were no significant differences. There was no significant difference in polyp detection rates (P > .05). Doses: LD (dose-length product, 257.7), STD (dose-length product, 483.6).

CONCLUSIONS

LD MBIR CTC objectively shows improved image noise using parameters in our study. Subjectively, image quality is maintained. Polyp detection shows no significant difference but because of small numbers needs further validation. Average dose reduction of 47% can be achieved. This study confirms feasibility of using MBIR in this context of CTC in symptomatic population.

CT colonography in the diagnosis and management of colorectal cancer: Emphasis on pre- and post-surgical evaluation

This article addresses the use of computed tomographic colonography (CTC) for the diagnosis and management of colorectal cancer, focusing on presurgical evaluation of the colon proximal to an occlusive cancer and surveillance after cancer resection surgery. The key evidences accumulated in the literature and future work needed are summarized. CTC is a technically robust and the most practical method to evaluate the colon proximal to an occlusive cancer, which prevents colonoscopic examination past the occlusion, either before or after metallic stent placement. The high sensitivity of CTC for detecting cancers and advanced adenomas in the proximal colon can help prevent additional surgical procedures in patients showing negative results. However, the accuracy of CTC for distinguishing intramural cancers from adenomas is low, and the technique is limited in guiding management when a medium-sized lesion that do not show invasive features such as pericolic extension or nodal metastasis is found in the proximal colon. A maximal diameter ≥ 15 mm has been proposed as a criterion for surgical removal of proximal lesions. However, this needs to be verified in a larger cohort. In addition, the influence of presurgical CTC results on the current post-cancer resection colonic surveillance timeline remains to be determined. CTC can be readily added to the routine abdominopelvic CT in the form of contrast-enhanced CTC, which can serve as an effective stand-alone tool for post-cancer resection surveillance of both the colorectum and extracolonic organs. Although the accuracy of CTC has been demonstrated, its role in the current colonoscopy-based postoperative colonic surveillance protocols remains to be determined. Readers of CTC also need to be knowledgeable on the colonic lesions that are unique to the postoperative colon.

Predictors of CT colonography utilization among asymptomatic medicare beneficiaries

BACKGROUND

Although the Centers for Medicare and Medicaid Services (CMS) denied coverage for screening computed tomography colonography (CTC) in March 2009, little is understood about whether CTC was targeted to the appropriate patient population prior to this decision.

OBJECTIVE

Evaluate patient characteristics and known relative clinical indications for screening CTC among patients who received CTC compared to optical colonoscopy (OC).

DESIGN/PARTICIPANTS

Cross-sectional study of all 10,538 asymptomatic Medicare beneficiaries who underwent CTC between January 2007 and December 2008, compared to a cohort of 160,113 asymptomatic beneficiaries who underwent OC, matched on county of residence and year of examination.

MAIN MEASURES

Patient characteristics and known relative appropriate and inappropriate clinical indications for screening CTC.

KEY RESULTS

CTC utilization was higher among women, patients > 65 years of age, white patients, and those with household income > 75 % (p = 0.001). Patients with relatively appropriate clinical indications for screening CTC were more likely to undergo CTC than OC including presumed incomplete OC (OR 80.7, 95 % CI 76.01-85.63); sedation risk (OR 1.11, 95 % CI 1.05-1.17); and chronic anticoagulation risk (OR 1.46, 95 % CI 1.38-1.54), after adjusting for patient characteristics and known clinical indications. Conversely, patients undergoing high-risk screening, an inappropriate indication, were less likely to receive CTC (OR 0.4, 95 % CI 0.37-0.42). Overall, 83 % of asymptomatic patients referred to CTC had at least one clinical indication relatively appropriate for CTC (8,772/10,538).

CONCLUSION

During the 2 years preceding CMS denial for screening, CTC was targeted to asymptomatic patients with relatively appropriate clinical indications for CTC/not receiving OC. However, CTC utilization was lower among certain demographic groups, including minority patients. These findings raise the possibility that future coverage of screening CTC might exacerbate disparities in colorectal cancer screening while increasing overall screening rates.

Cost-effectiveness analysis of 3-D computerized tomography colonography versus optical colonoscopy for imaging symptomatic gastroenterology patients

BACKGROUND

When symptomatic gastroenterology patients have an indication for colonic imaging, clinicians have a choice between optical colonoscopy (OC) and computerized tomography colonography with three-dimensional reconstruction (3-D CTC). 3-D CTC provides a minimally invasive and rapid evaluation of the entire colon, and it can be an efficient modality for diagnosing symptoms. It allows for a more targeted use of OC, which is associated with a higher risk of major adverse events and higher procedural costs. A case can be made for 3-D CTC as a primary test for colonic imaging followed if necessary by targeted therapeutic OC; however, the relative long-term costs and benefits of introducing 3-D CTC as a first-line investigation are unknown.

AIM

The aim of this study was to assess the cost effectiveness of 3-D CTC versus OC for colonic imaging of symptomatic gastroenterology patients in the UK NHS.

METHODS

We used a Markov model to follow a cohort of 100,000 symptomatic gastroenterology patients, aged 50 years or older, and estimate the expected lifetime outcomes, life years (LYs) and quality-adjusted life years (QALYs), and costs (£, 2010-2011) associated with 3-D CTC and OC. Sensitivity analyses were performed to assess the robustness of the base-case cost-effectiveness results to variation in input parameters and methodological assumptions.

RESULTS

3D-CTC provided a similar number of LYs (7.737 vs 7.739) and QALYs (7.013 vs 7.018) per individual compared with OC, and it was associated with substantially lower mean costs per patient (£467 vs £583), leading to a positive incremental net benefit. After accounting for the overall uncertainty, the probability of 3-D CTC being cost effective was around 60 %, at typical willingness-to-pay values of £20,000-£30,000 per QALY gained.

CONCLUSION

3-D CTC is a cost-saving and cost-effective option for colonic imaging of symptomatic gastroenterology patients compared with OC.

Recent advances in targeted endoscopic imaging: Early detection of gastrointestinal neoplasms

Molecular imaging has emerged as a new discipline in gastrointestinal endoscopy. This technology encompasses modalities that can visualize disease-specific morphological or functional tissue changes based on the molecular signature of individual cells. Molecular imaging has several advantages including minimal damage to tissues, repetitive visualization, and utility for conducting quantitative analyses. Advancements in basic science coupled with endoscopy have made early detection of gastrointestinal cancer possible. Molecular imaging during gastrointestinal endoscopy requires the development of safe biomarkers and exogenous probes to detect molecular changes in cells with high specificity anda high signal-to-background ratio. Additionally, a high-resolution endoscope with an accurate wide-field viewing capability must be developed. Targeted endoscopic imaging is expected to improve early diagnosis and individual therapy of gastrointestinal cancer.