CT colonography: an update

Computed tomography colonography for the practicing radiologist: A review of current recommendations on methodology and clinical indications

Colorectal cancer (CRC) represents one of the most relevant causes of morbidity and mortality in Western societies. CRC screening is actually based on faecal occult blood testing, and optical colonoscopy still remains the gold standard screening test for cancer detection. However, computed tomography colonography (CT colonography) constitutes a reliable, minimally-invasive method to rapidly and effectively evaluate the entire colon for clinically relevant lesions. Furthermore, even if the benefits of its employment in CRC mass screening have not fully established yet, CT colonography may represent a reasonable alternative screening test in patients who cannot undergo or refuse colonoscopy. Therefore, the purpose of our review is to illustrate the most updated recommendations on methodology and the current clinical indications of CT colonography, according to the data of the existing relevant literature.

A COMPLETE SYSTEM FOR CANDIDATE POLYPS DETECTION IN VIRTUAL COLONOSCOPY

We present a computer-aided detection pipeline for polyp detection in Computer tomographic colonography. The first stage of the pipeline consists of a simple colon segmentation technique that enhances polyps, which is followed by an adaptive-scale candidate polyp delineation, in order to capture the appropriate polyp size. In the last step, candidates are classified based on new texture and geometric features that consider both the information in the candidate polyp location and its immediate surrounding area. The system is tested with ground truth data, including flat and small polyps which are hard to detect even with optical colonoscopy. We achieve 100% sensitivity for polyps larger than 6 mm in size with just 0.9 false positives per case, and 93% sensitivity with 2.8 false positives per case for polyps larger than 3 mm in size.

Diagnosis of bowel diseases: The role of imaging and ultrasonography

Examinations with a visualisation of the anatomy and pathology of the gastrointestinal (GI) tract are often necessary for the diagnosis of GI diseases. Traditional radiology played a crucial role for many years. Endoscopy, despite some limitations, remains the main technique in the differential diagnosis and treatment of GI diseases. In the last decades, the introduction of, and advances in, non-invasive cross-sectional imaging modalities, including ultrasound (US), computed tomography (CT), positron-emission tomography (PET), and magnetic resonance imaging, as well as improvements in the resolution of imaging data, the acquisition of 3D images, and the introduction of contrast-enhancement, have modified the approach to the examination of the GI tract. Moreover, additional co-registration techniques, such as PET-CT and PET-MRI, allow multimodal data acquisition with better sensitivity and specificity in the study of tissue pathology. US has had a growing role in the development and application of the techniques for diagnosis and management of GI diseases because it is inexpensive, non-invasive, and more comfortable for the patient, and it has sufficient diagnostic accuracy to provide the clinician with image data of high temporal and spatial resolution. Moreover, Doppler and contrast-enhanced ultrasound (CEUS) add important information about blood flow. This article provides a general review of the current literature regarding imaging modalities used for the evaluation of bowel diseases, highlighting the role of US and recent developments in CEUS.

Magnetic air capsule robotic system: proof of concept of a novel approach for painless colonoscopy

BACKGROUND

Despite being considered the most effective method for colorectal cancer diagnosis, colonoscopy take-up as a mass-screening procedure is limited mainly due to invasiveness, patient discomfort, fear of pain, and the need for sedation. In an effort to mitigate some of the disadvantages associated with colonoscopy, this work provides a preliminary assessment of a novel endoscopic device consisting in a softly tethered capsule for painless colonoscopy under robotic magnetic steering.

METHODS

The proposed platform consists of the endoscopic device, a robotic unit, and a control box. In contrast to the traditional insertion method (i.e., pushing from behind), a "front-wheel" propulsion approach is proposed. A compliant tether connecting the device to an external box is used to provide insufflation, passing a flexible operative tool, enabling lens cleaning, and operating the vision module. To assess the diagnostic and treatment ability of the platform, 12 users were asked to find and remove artificially implanted beads as polyp surrogates in an ex vivo model. In vivo testing consisted of a qualitative study of the platform in pigs, focusing on active locomotion, diagnostic and therapeutic capabilities, safety, and usability.

RESULTS

The mean percentage of beads identified by each user during ex vivo trials was 85 ± 11%. All the identified beads were removed successfully using the polypectomy loop. The mean completion time for accomplishing the entire procedure was 678 ± 179 s. No immediate mucosal damage, acute complications such as perforation, or delayed adverse consequences were observed following application of the proposed method in vivo.

CONCLUSIONS

Use of the proposed platform in ex vivo and preliminary animal studies indicates that it is safe and operates effectively in a manner similar to a standard colonoscope. These studies served to demonstrate the platform's added advantages of reduced size, front-wheel drive strategy, and robotic control over locomotion and orientation.

Development of an Automatic Adjustable Colonoscope

Colonoscopy can be associated with many problems, such as mechanical trauma due to the distal tip contacting the colon wall or health issues due to the extended use of anesthesia. In order to eliminate these complications, an automatic adjustable colonoscope was designed. This device uses sensors, actuators, and a control system to automatically position the distal tip in the center of the colon lumen. The sensors were tested to determine their ability to accurately sense the distance from the tip to the surface. The actuators were tested to determine the correlation between motor rotation and displacement of the distal tip. The control system was tested to assess the ability of the device to position the tip in the center of the test tube and the ability to navigate through a flat test course. It was determined that the sensors could accurately determine distances from 0 to 15 mm from the test surface in all test conditions. The motors for up-down movement and left-right movement of the colonoscope had response times of 0.57 s and 0.69 s, respectively, when the motors were rotated from 0 deg to 90 deg. The control system was able to safely move the colonoscope tip away from all walls of the test apparatus. It was also able to navigate through the flat test course without coming in contact with the walls. The automatic adjustable colonoscope has demonstrated that it can safely and effectively position the distal tip to avoid contact with the walls of the test surface.

[CT colonography: what radiologists need to know]

In 2008, CT colonography was approved by the American Cancer Society as a technique for screening for colorectal cancer. This approval should be considered an important step in the recognition of the technique, which although still relatively new is already changing some diagnostic algorithms. This update about CT colonography reports the quality parameters necessary for a CT colonographic study to be diagnostic and reviews the technical innovations and colonic preparation for the study. We provide a brief review of the signs and close with a discussion of the current indications for and controversies about the technique.

Development of a colonoscopy add-on device for improvement of the intubation process

A colonoscopy add-on device has been developed to reduce intubation time without modification of the current colonoscope and peripheral devices. One of the main purposes of the system is to minimize trauma caused by the distal tip of the colonoscope. The detachable sensory fixture at the end of the distal tip measures the distance between the distal tip and the colon wall in three directions, and the actuation system attached at the base of the colonoscope controls the distal tip by rotating two dial knobs. The device controls the distal tip to minimize contact between the distal tip and the colon wall, and the distal tip ideally points out the next possible lumen. A compatibility test of the infrared sensory system was carried out, and the design of the actuation system was accomplished. The system is integrated and controlled by a microprocessor. The device was tested in a silicon colon and porcine intestine. The results showed that a colonoscopist successfully reached the cecum with the aid of the colonoscopy add-on device without significant contact between the colon wall and the distal tip. The colonoscopy aid device was very helpful for the novice colonoscopist.

Imaging of the gastrointestinal tract-novel technologies

Imaging of the gastrointestinal tract is very useful for research and clinical studies of patients with symptoms arising from the gastrointestinal tract and in visualising anatomy and pathology. Traditional radiological techniques played a leading role in such studies for a long time. However, advances in non-invasive modalities including ultrasound (US), computed tomography (CT), positron emission tomography (PET), magnetic resonance imaging (MRI), etc, have in the last decades revolutionised the way in which the gastrointestinal tract is studied. The resolution of imaging data is constantly being improved and 3D acquisition, tools for filtering, enhancement, segmentation and tissue classification are continually being developed. Additional co-registration techniques allow multimodal data acquisition with improved classification of tissue pathology. Furthermore, new functional imaging techniques have become available. Altogether, the future of gastrointestinal imaging looks very promising which will be of great benefit in clinical and research studies of gastrointestinal diseases. The purpose of this review is to highlight the capabilities of the newest techniques to explore the detailed morphology, biomechanical properties, function and pathology of the gastrointestinal tract.