Christiane A. Kuehle

Hydro-MRI of the Small Bowel: Effect of Contrast Volume, Timing of Contrast Administration, and Data Acquisition on Bowel Distention

OBJECTIVE The purpose of this study was to assess oral contrast agents, volumes of the agents, and time points of data acquisition in regard to small-bowel distention and patient acceptance. SUBJECTS AND METHODS Six healthy volunteers underwent imaging on 16 different days. Four volumes (450, 900, 1,350, and 1,800 mL) of each of the four contrast compounds (0.2% locust bean gum plus 2.5% mannitol, VoLumen containing 2.0% sorbitol, VoLumen containing 1.4% sorbitol, and tap water) were used. Two-dimensional true fast imaging with steady-state free precession data sets were acquired at 5-minute intervals after contrast ingestion. Distention values for small-bowel segments (duodenum, proximal and distal jejunum, ileum) and occurrence of side effects were documented. RESULTS Analysis of bowel distention revealed significantly greater distention for all carbohydrate sugar alcohol-containing solutions compared with water but no significant difference among the three contrast agents. Sufficient duodenal distention was achieved with 900 mL of any of the contrast agents, but imaging had to be performed soon after ingestion. For MRI of the distal jejunum and ileum, a volume of 1,350 mL is preferable, and the time point of data acquisition plays a minor role. Ingestion of 1,800 mL of the carbohydrate sugar alcohol solutions led to a significantly higher rate of side effects such as abdominal cramps than did ingestion of smaller volumes. CONCLUSION The data indicate that sufficient contrast consumption and optimal timing of data acquisition are essential to distention of the small bowel. Oral contrast agent protocols should be adapted to the bowel region in question.

Magnetic resonance colonography without bowel cleansing: a prospective cross sectional study in a screening population

Background and aim: To evaluate the diagnostic accuracy of magnetic resonance colonography (MRC) without bowel cleansing in a screening population and compare the results to colonoscopy as a standard of reference. Methods: 315 screening patients, older than 50 years with a normal risk profile for colorectal cancer, were included in this study. For MRC, a tagging agent (5.0% Gastrografin, 1.0% barium sulphate, 0.2% locust bean gum) was ingested with each main meal within 2 days prior to MRC. No bowel cleansing was applied. For the magnetic resonance examination, a rectal water enema was administered. Data collection was based on contrast enhanced T1 weighted images and TrueFISP images. Magnetic resonance data were analysed for image quality and the presence of colorectal lesions. Conventional colonoscopy and histopathological samples served as reference. Results: In 4% of all colonic segments, magnetic resonance image quality was insufficient because of untagged faecal material. Adenomatous polyps >5 mm were detected by means of MRC, with a sensitivity of 83.0%. Overall specificity was 90.2% (false positive findings in 19 patients). However, only 16 of 153 lesions <5 mm and 9 of 127 hyperplastic polyps could be visualised on magnetic resonance images. Conclusions: Faecal tagging MRC is applicable for screening purposes. It provides good accuracy for the detection of relevant (ie, adenomatous) colorectal lesions >5 mm in a screening population. However, refinements to optimise image quality of faecal tagging are needed.

Small bowel hydro-MR imaging for optimized ileocecal distension in Crohn's disease: Should an additional rectal enema filling be performed?

To assess the impact of an additional rectal enema filling in small bowel hydro‐MRI in patients with Crohns disease.

Magnetic resonance colonography: Comparison of contrast-enhanced three-dimensional vibe with two-dimensional FISP sequences: Preliminary experience

Purpose:The purpose of this study was to compare a dark-lumen magnetic resonance colonography (MRC) approach with a True FISP-based bright-lumen technique concerning presence of artifacts and the detection rate of colorectal pathologies. Materials and Methods:Thirty-seven patients with suspected colorectal lesions were included in this trial. The colon was filled with 2500 mL of tap water. Two-dimensional True FISP datasets as well as T1-weighted GRE sequences (pre- and post intravenous contrast) were acquired. The detection rate of colorectal masses and inflammatory lesions was determined for both techniques separately. Besides, image quality was assessed. All patients underwent conventional colonoscopy as the standard of reference. Results:By means of dark-lumen MRC datasets, all polyps >5 mm were correctly diagnosed, whereas 4 polyps <5 mm were missed. Sensitivity of dark-lumen MRC amounted to 78.9%. There were no false-positive results: residual stool could correctly be differentiated from colorectal masses. The True FISP-based bright-lumen MRC, however, failed to detect 2 additional polyps resulting in a sensitivity of 68.4%. Furthermore, bright-lumen MRC led to false-positive results in 5 patients. Both techniques visualized inflammatory bowel disease in 5 patients. However, image quality of True FISP was rated superior to that of dark-lumen MRC. Conclusion:Dark-lumen MRC proved to be superior over bright-lumen MRC regarding the detection of colorectal masses. However, True FISP imaging can turn out to be helpful as a result of high image quality and motion insensitivity.

Digital subtraction dark-lumen MR colonography: initial experience.

To evaluate image subtraction for the detection of colonic pathologies in a dark‐lumen MR colonography exam.

Contrast-Enhanced Dark Lumen PET/CT and MR Colonography in a Rodent Polyp Model: Initial Results with Histopathologic Correlation

OBJECTIVE The objective of this study was to assess the feasibility of PET/CT for the detection of colorectal masses in a rodent polyp model in an intraindividual comparison with dark-lumen MR colonography. CONCLUSION Detection of small tumors with PET/CT and MR colonography is possible in a rodent model. The technique thus warrants further evaluation in animal studies as well as in patients with suspected colorectal disease.

MR colonography with fecal tagging: Do individual patient characteristics influence image quality?

To evaluate if different patient characteristics influence performance of fecal tagging (a new MR colonography (MRC) technique to label stool to avoid bowel cleansing) and, consecutively, MR image quality.