An-Najah Staff

Dark-lumen magnetic resonance colonography has been shown to be an appropriate diagnostic tool for the detection of colorectal pathologies. This review describes the underlying techniques of dark-lumen magnetic resonance colonography concerning data acquisition, image interpretation and diagnostic accuracy for the detection of colorectal pathologies. In addition, techniques to improve patients' acceptance are discussed.

Magnet resonance colonography (MRC) is a promising method for the depiction of colorectal pathologies. For colorectal masses exceeding 10mm, high accuracy values (92% to 100%) have been reported (1). However, due to limited spatial resolution, the detection rate of smaller pathologies is only fair. Another limitation of current MRC protocols is related to relatively long data acquisition of up to 25 seconds, which need to be performed under breath-hold conditions. Especially in elderly patients or patients with diseases of the respiratory tract, this can result in severe motion artefacts hampering a reliable assessment of the colon. The underlying problems may be solved by new image acquisition techniques providing a higher spatial resolution and / or a decreased acquisition time. These parallel acquisition techniques (PAT) have recently been successfully applied for MR colonography in an in-vitro study (2). Aim of the current trial was to prove the practicability of PAT imaging for MR colonography in-vivo.

The aim of the study was to evaluate the utility of dark-lumen MR colonography (MRC) for the assessment of extra-colonic organs. Three hundred seventy-five subjects with suspected colonic disease underwent a complete MRC examination. MRC data were evaluated by two radiologists in a blinded fashion. In addition to the large bowel, the extra-intestinal organs from the lung bases to the pelvis were assessed for the presence of pathologies. All findings were divided into known or unknown findings and therapeutically relevant or irrelevant findings. If deemed necessary, other diagnostic imaging tests to further assess those findings were performed. In total, 510 extracolonic findings were found in 260 (69%) of the 375 subjects. Known extra-colonic findings were found in 140 subjects (54%) and unknown findings in 120 subjects (46%). Thirty-one (12%) of the 260 subjects had therapeutically relevant findings (45 findings); 229 patients (88%) had irrelevant findings (465 findings). Dark-lumen MRC is a useful tool not only for the assessment of the entire colon, but also for the evaluation of extra-colonic organs. Thus, intra- and extra-colonic pathologies can be diagnosed within the same examination.

In the last few years virtual colonography using MR imaging has shown a proceeding development regarding detection and quantification of colorectal pathologies. Dark-lumen MR colonography (MRC) has been a leading tool for the diagnosis of the entire colon and their pathologies. This review article describes some of the underlying techniques of MRC concerning data acquisition, the need for intravenously applied paramagnetic contrast agent, as well as indications, results and limitations of MRC for the detection of colorectal pathologies. In addition, new techniques to improve patient acceptance are discussed.