Dark lumen MR colonography: can high spatial resolution VIBE imaging improve the detection of colorectal masses?

PURPOSE: To assess whether the detection of colorectal lesions can be improved using high spatial resolution VIBE imaging. MATERIALS AND METHODS: 48 patients underwent same-day dark lumen MR colonography (MRC) and conventional colonoscopy (CC) as the standard for the detection of colorectal masses. MRC was performed using contrast-enhanced standard and high spatial resolution T1-weighted 3D VIBE sequences. The findings and the image quality of the standard and high spatial resolution VIBE sequences were compared qualitatively and quantitatively. The findings of both sequences regarding colorectal lesions were compared to those of a subsequently performed colonoscopy. RESULTS: The high spatial resolution VIBE sequence significantly improved the quantitative image quality (CNR 54.0 vs. 36.8). However, high spatial resolution VIBE imaging did not detect more colorectal lesions than the standard VIBE sequence. In addition, none of the sequences employed was able to detect lesions with a diameter of less than 5 mm (CC 40 lesions). However, 13 colorectal lesions with a diameter of greater than 5 mm were detected by both sequences (CC 15). CONCLUSION: High spatial resolution VIBE imaging did not improve the detection of colorectal masses and MRC fails to detect colorectal lesions with a diameter of less than 5 mm.

[State of the art of MR colonoscopy]. / Aktuelle Standards der MR-Kolonographie.

MR colonoscopy is suitable for colorectal cancer screening. This imaging modality is non-invasive, has no harmful side effects and provides a high diagnostic accuracy. MR colonoscopy has been found to be highly sensitive and specific in detecting colorectal lesions > 10 mm in size. Since colonic polyps are difficult to differentiate from residual stool, colonic cleansing has been unavoidable but reduces patient acceptance. Cleansing of the bowel can be avoided if the signal of stool is rendered different from its surrounding. This can be achieved by adding an agent to the food that tags the feces (fecal tagging). This article describes current techniques of MR colonoscopy as well as first results with fecal tagging.

Equilibrium-phase MR angiography of the aortoiliac and renal arteries using a blood pool contrast agent.

OBJECTIVE: The purpose of this study was to determine the diagnostic usefulness of a new blood pool contrast agent, NC100150, for assessing the aortoiliac and renal arteries. SUBJECTS AND METHODS: Twenty patients with hemodynamically significant stenosis (> or =50% of luminal diameter) of the iliac or renal arteries or an aortic aneurysm documented by digital subtraction angiography underwent MR angiography at 1.5 T after administration of NC100150. Three-dimensional MR angiographic data sets were collected ill the equilibrium phase. In a prospective analysis, each vascular segment (16 segments per arterial tree) was evaluated. RESULTS: All patients tolerated the NC100150 administration well. Mean contrast-to-noise ratios of the vascular data collected in the equilibrium phase of NC100150 was 3.3+/-15.9. Compared with digital subtraction angiography, the sensitivity and specificity of MR angiography for the renal arteries were 82% and 98%, respectively; for the common iliac arteries, 86% and 97%, respectively; for the external iliac arteries, 80% and 100%, respectively; and for the internal iliac arteries, 71% and 977, respectively. All 83 aneurysmal changes revealed by digital subtraction angiograpy of the aortoiliac arteries were well displayed on the MR angiographic data sets. CONCLUSION: Equilibrium-phase NC 00150-enhanced three-dimensional MR angiography shows high specificity when evaluating the abdominal and pelvic vascular systems, but the attendant venous overlap can limit the assessment of stenosis in renal and pelvic arterial segments.

[Contrast-enhanced 3D MR-angiography of the thorax, abdomen and lower extremities]. / Kontrastverstärkte 3D-MR-Angiographie in Thorax, Abdomen und Peripherie.

Contrast-enhanced 3D MR angiography permits comprehensive assessment of the arterial system in the chest, abdomen und lower extremities. The method combines intravenous bolus application of a non-nephrotoxic, paramagnetic, extracellular contrast agent with the acquisition of a fast 3D data set. High contrast between the vascular lumen and surrounding tissues, inherent three-dimensionality and the ability to collect image data in the chest and abdomen under apnea conditions all contribute to excellent image quality. Contrast-enhanced 3D MRA is being employed in many centers throughout the world for the evaluation of various arterial pathologies. This review provides a technical overview and critically discusses the clinical applications in the chest, abdomen and lower extremities based upon the available literature and several clinical examples.