Fundamental Elements for Successful Performance of CT Colonography (Virtual Colonoscopy)

Abstract

There are many factors affecting the successful performance of CT colonography (CTC). Adequate colonic cleansing and distention, the optimal CT technique and interpretation with using the newest CTC software by a trained reader will help ensure high accuracy for lesion detection. Fecal and fluid tagging may improve the diagnostic accuracy and allow for reduced bowel preparation. Automated carbon dioxide insufflation is more efficient and may be safer for colonic distention as compared to manual room air insufflation. CT scanning should use thin collimation of ≤3 mm with a reconstruction interval of ≤1.5 mm and a low radiation dose. There is not any one correct method for the interpretation of CTC; therefore, readers should be well-versed with both the primary 3D and 2D reviews. Polyps detected at CTC should be measured accurately and reported following the "polyp size-based" patient management system. The time-intensive nature of CTC and the limited resources for training radiologists appear to be the major barriers for implementing CTC in Korea.

Diagnostic value of computed tomography colonography (CTC) after incomplete optical colonoscopy

“…In some cases, scanning in the right or left lateral decubitus position may be helpful to move retained fluid and optimize colonic distention [4,31]. Each scan is acquired in approximately 3e4 s. The total room time is generally less than 15 min, as in our study [4,15,31]. As in our practice, the use of dose modulation devices, adaptive statistical iterative reconstruction and model-based iterative reconstructions, are employed to reduce dose exposure up to 50% [4,6,11].…”

“…As in our practice, the use of dose modulation devices, adaptive statistical iterative reconstruction and model-based iterative reconstructions, are employed to reduce dose exposure up to 50% [4,6,11]. The data is elaborated with a dedicated software, and 2D images in multiple planes and 3D surface-rendered and endoluminal views are displayed [4,15,31]. In our practice, 3D endoluminal views and 2D multiplanar reformations are displayed side by side on two monitors to facilitate rapid interpretation; we use 3D navigation for primary detection of focal abnormalities and correlation with 2D multiplanar images to determine the nature of a focal finding and Table 1 CT colonography reporting and data system (C-RADS) criteria [29]: proposed categorization system for extracolonic findings.…”

“…Although the use of CTC as screening tool is still under evaluation, it is well established that CTC is mainly indicated when endoscopy is contraindicated, not possible, failed or incompletely performed [3], in patients reluctant to undergo OC or in cases of obstructing colonic tumors [11e14]. Abnormal colic shape or length and lumen narrowing are not limitations for CTC feasibility and this allows CTC to be able to investigate the whole colon detecting any synchronous lesions when a CCR stenosis is present [15]. At the same time, CTC can also detect extracolonic findings, which are described in up to 74% of patients older than 65 years with an incidence rate that increases with age.…”

Panoramic endoluminal display with minimal image distortion using circumferential radial ray-casting for primary three-dimensional interpretation of CT colonography

“…The sensitivity and specificity for detecting adenomatous polyps ≥6 mm did not differ, but the mean interpretation time was significantly shorter with the band view than with the conventional endoluminal view by 1.8 and 4.5 minutes in readers 1 and 2, respectively (P<0.0001). The review method, is generally less time-efficient than 2D review as the colon should be evaluated with four flythrough passes, including antegrade and retrograde flythroughs of the supine and prone datasets [2,3,[7][8][9].…”

Optimizing the degree of distension and reducing discomfort in CT colonography by means of a microprocessor interface system for air insufflation

“…However, folding of the mucosa has been reported to occur when СО 2 is used, [9,10] which results in the deterioration of the quality of CT colonography. This raises the question of an appropriate insufflation method to provide optimal conditions for CT colonography.…”