Introduction.
OPPORTUNITIES FOR VIRTUAL COLONOSCOPY
Virtual colonoscopy or computed tomographic (CT) colonography is a recent radiologic technique enabling detection of tumoral lesions in the colon.
CT colonography constitutes a real opportunity for the gastrointestinal radiologists to play a preponderant role in the diagnosis and treatment of colorectal cancer and its benign precursor.
Since its introduction by David Vining in 1994, CT colonography has very rapidly shown its virtues as a possible substitution to the DCBE.
The first important study on CT colonography by Helen Fenlon from the Boston Medical Center, published in 1999 in the New England Journal of Medicine, reporting very good results of lesion detection, underscored this aspiration.
Since then CT colonography has dramatically evolved by the refinement of existing techniques and the introduction of new ones:
* fecal tagging with the option of reducing the cathartic or laxative part of the preparation,
* the use of carbon dioxide to inflate the colon,
* the introduction of multi-detector CT scanners producing spectacular images with isotropic resolution and reducing the examination time for the patient,
* the use of ultra low-dose scan protocols reducing the radiation dose, improvement of the image post-processing with fast three-dimensional functions and computer aided diagnosis (CAD).
These technical improvements help both the radiologist and the patient.
For the radiologists there is an improvement of the reading conditions possibly improving diagnostic accuracy.
For the patients the preparation and examination are more comfortable.
Despite these improvements in technique, CT colonography has however not yet been able to break through as an acceptable tool to screen for colorectal cancer.
This was caused by the disappointing results produced in some recent large multi-centre trials.
Most probably sub-optimal technique concerning preparation, colonic distension, scanning parameters and image post-processing was the main cause of this failure.
The ACRIN II trial additionally showed the importance of reader experience.
In fact technique as well as reader experience need a rigorous attention to boost a maximum of results as was obtained in another momentous study, performed by Perry Pickhardt and published in the New England Journal of Medicine in 2003.
Based upon a meticulous technique of preparation with fecal tagging, colonic inflation, scanning parameters and reading conditions, CT colonography obtained better scores than optical colonoscopy in this study.
Furthermore, the examinations were interpreted by a team of radiologists experienced in CT colonography.
In experienced hands CT colonography seems to be ready for prime time colorectal cancer screening. However it is not yet ready for widespread application of colorectal cancer screening because of the aforementioned reasons. CT colonography is now at an important crossroads and serious efforts should be undertaken to take it to the level of being a widely accepted method to screen for colorectal cancer. To fulfil this goal tremendous efforts are being performed in both Europe an d the United States to give a high level of education to the radiologists with workshops, data banks and numerous scientific publications.
VIRTUAL COLONOSCOPY TEACHING CENTRE
The main purpose of our VIRTUAL COLONOSCOPY TEACHING CENTRE is to teach Virtual Colonoscopy:
by theoretical advise, practical advise and reading advise (second readings e.g. over-reads)
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