MR Colonography and MR Enterography

The bowel is a common site for pathologic processes, including malignancies and inflammatory disease. Colorectal cancer accounts for 10% of all new cancers and 9% of cancer deaths. A significant decrease in the incidence of colorectal cancer and cancer death rates has been attributed to screening measures, earlier detection, and improved therapies. Virtual colonoscopy (VC), also known as computed tomography colonography, is an effective method for detecting polyps. However, in light of increasing concerns about ionizing radiation exposure from medical imaging and potential increased risk of future radiation-induced malignancies, magnetic resonance imaging (MRI) is seen as an increasingly attractive alternative. Improvements in MRI technology now permit three-dimensional volumetric imaging of the entire colon in a single breath hold at high spatial resolution, making VC with MRI possible.

The bowel is a common site for pathologic processes, including malignancies and inflammatory disease. The American Cancer Society estimated 146,970 new cases of colorectal cancer with 49,920 deaths in 2009. Colorectal cancer accounts for 10% of all new cancers and 9% of cancer deaths. From the early 1990s to 2005, there was a significant decrease in the incidence of colorectal cancer and cancer death rates, which has been attributed to screening measures, earlier detection, and improved therapies.

Virtual colonoscopy (VC), also known as computed tomography colonography (CTC), is an effective method for detecting small (6–9 mm) and larger (≥10 mm) polyps. However, in light of increasing concerns about ionizing radiation exposure from medical imaging and potential increased risk of future radiation-induced malignancies, magnetic resonance imaging (MRI) is seen as an increasingly attractive alternative. Improvements in MRI technology, which include multicoil designs with parallel imaging and higher field strength magnets, now permit three-dimensional (3D) volumetric imaging of the entire colon in a single breath hold at high spatial resolution, making VC with MRI possible.

MR colonography techniques

Early research in the late 1990s on MR colonography (MRC) showed the feasibility of this technique. Two major imaging strategies have evolved: dark-lumen MRC ( Fig. 1 ) and bright-lumen MRC. As the respective names suggest, there terms refer to the intraluminal signal intensity. Regardless of which technique is chosen, adequate colonic distension is mandatory for accurate evaluation.