Small Bowel MRI Research Articles

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 Crohn's disease. A total of 40 patients with known Crohn's disease were analyzed retrospectively: 20 patients only ingested an oral contrast agent (group A), the other 20 subjects obtained an additional rectal water enema (group B). For small bowel distension, a solution containing 0.2% locust bean gum (LBG) and 2.5% mannitol was used. In all patients, a breathhold contrast-enhanced T1w three-dimensional volumetric interpolated breathhold examination (VIBE) sequence was acquired. Comparative analysis was based on image quality and bowel distension as well as signal-to-noise ratio (SNR) measurements. MR findings were compared with those of conventional colonoscopy, as available (N = 25). The terminal ileum and rectum showed a significantly higher distension following the rectal administration of water. Furthermore, fewer artifacts were seen within group B. This resulted in a higher reader confidence for the diagnosis of bowel disease, not only in the colon, but also in the ileocecal region. Diagnostic accuracy in diagnosing inflammation of the terminal ileum was 100% in group B; in the nonenema group there were three false-negative diagnoses of terminal ileitis. Our data show that the additional administration of a rectal enema is useful in small bowel MRI for the visualization of the terminal ileum. The additional time needed for the enema administration was minimal, and small and large bowel pathologies could be diagnosed with high accuracy. Thus, we suggest that a rectal enema in small bowel MR imaging be considered.

Dark Lumen Magnetic Resonance Enteroclysis in Combination With Mri Colonography for Whole Bowel Assessment in Patients With Crohnʼs Disease: First Clinical Experience

Magnetic resonance enteroclysis (MRE) is a recently introduced imaging technique that assesses the small bowel with similar sensitivity and specificity as the fluoroscopically performed conventional enteroclysis. Magnetic resonance imaging colonography (MRC) seems to be a promising technique for polyp assessment in the colon. In this feasibility study, we evaluated the combination of small bowel MRI with unprepared MRC as an integrative diagnostic approach of the whole bowel in patients with Crohn's disease. Thirty patients with known Crohn's disease were prospectively examined. No particular colonic preparation was applied. Applying the dark lumen technique in all patients, MRE and MRC were performed within 1 session using an integrative examination protocol. T2-weighted and contrast-enhanced T1-weighted sequences were acquired. Inflammation assessment (grades 0 to 2) of the colon was compared with conventional colonoscopy in 29 patient and with surgery in 1 patient. The entire colon was graded fair to good distended in all patients. In 11 of 210 evaluated colonic segments, feces hindered an adequate intraluminal bowel assessment. Twenty-three of 30 patients had complete colonoscopy as the gold standard. In 7 patients, complete colonoscopy could not be performed because of an inflamed stenosis. Correct grading of colonic inflammation was performed with 55.1% sensitivity and 98.2% specificity in all segments. Considering only more extensive inflammation (grade 2), the sensitivity of MRC increased to 70.2% with a specificity of 99.2%. The combination of MRE and MRC could improve the diagnostic value of abdominal MRI evaluation in patients with Crohn's disease. However, MRC can not replace conventional colonoscopy in subtle inflammation assessment.

CO2 as a distending medium for gastric and small bowel MRI: a feasibility study

This work evaluates carbon dioxide as a contrast medium for magnetic resonance imaging of the stomach and small bowel. Twelve healthy volunteers underwent rapid magnetic resonance imaging after oral administration of a carbon dioxide generating agent using a combination of breath-hold and interactive fluoroscopic imaging during breathing. Diagnostic-quality images were obtained in 100% of cases for the stomach and in 92, 75, 67 and 42% of cases for the duodenal segments 1-4, respectively. Visualisation of the jejunum and ileum proved unacceptable for clinical use and anti-peristaltic agents did not significantly influence the results. Further development of fast imaging and magnetic resonance interactive fluoroscopic methods may allow the use of carbon dioxide as a contrast medium for clinical imaging of the stomach and duodenum.

Dose optimization of mannitol solution for small bowel distension in MRI.

To optimize the dose of a hydro solution containing 2.5% mannitol and 0.2% locust bean gum (LBG) for small bowel MRI in terms of bowel distension and patient acceptance. A total of 10 healthy volunteers ingested a hydro solution containing 2.5% mannitol and 0.2% LBG. Four different volumes (1500, 1200, 1000, and 800 ml) were assessed on four different examination days. Small bowel distension was quantified on coronal two-dimensional TrueFISP images by measuring the diameter of eight bowel loops throughout the jejunum and the ileum. In addition, volunteer acceptance was evaluated for every single examination by using a questionnaire. Optimal distension was obtained with either, 1000, 1200, or 1500 ml, with no statistically significant differences in distension between these groups. Administration of 800 ml led to significantly less distension of the small bowel. Significantly less side effects were noted using either 800 or 1000 ml compared to using larger volumes. We recommend a dose of 1000 ml mannitol/LBG solution as an oral contrast agent for optimal bowel distension and minimal side effects.

What’s up in abdominal radiology?

The advent of multi-detector array CT (MDCT) has turned many things in abdominal radiology upside down. MDCT is a technique with great possibilities for several specific applications in the abdomen. For example, the results of many well-performed clinical studies on MDCT colonography for polyp detection were presented at the ECR in Vienna and at the joint meeting of the ESGAR and SGR in Orlando. MDCT colonography achieves excellent sensitivity for the detection of polyps as small as 5 mm, but is still not reliable for the visualization of smaller polyps. Thus, the debate continues about how to proceed in patients with tiny polyps found or suspected at CT colonography. The risk of malignant transformation of such tiny polyps is virtually zero and it is probably reasonable to simply follow these patients. The amount of ionizing radiation, which has been cited as a barrier to the use of MDCT as a colorectal cancer-screening tool, can be vastly reduced. A low dose technique, with noise-reduction algorithm using edge-preserving, yields comparable results, and it brings the amount of radiation delivered during a CT colonography scan into the range of a few chest X-rays. This may open the potential for the use of MDCT in screening, similar to current screening for lung cancer. For pancreatic imaging the pendulum swings toward CT. The exquisite 3D-display of tumors and their relation to the vasculature is of real benefit to pancreatic surgeons. In several centers, studies have begun to examine preoperative chemotherapy for locally inoperable pancreatic cancer. With MDCT alone, it is not possible to assess treatment response accurately, but the combination of PET/CT to assess the biological activity of tumors is a method that offers promise for every oncologic radiologist. Is there still a role for MRI in abdominal radiology? Oh, yes. MRI has matured into a widely accepted technique for liver imaging. There are several MR contrast agents for liver imaging that can optimize studies for every indication. Even the registration of second-generation ultrasound contrast agents in the European Union is not likely to win against MRI and MDCT. Another example is dynamic MR imaging of the small bowel, which has indeed recovered ground from CT and barium radiography for imaging of patients with small bowel obstruction. So the days of ‘old-fashioned’ enteroclysis seem to be numbered. Functional MRI is the first imaging modality ever to show intra-abdominal adhesions reliably, and small bowel MRI can delineate all tumors. So there is life after MDCT. Since the EURATOM directive 97/43 took effect, the radiology community is committed to reducing radiation exposure to the population. More than ever, we are now asked to choose the most effective and least invasive imaging technique from a whole range of imaging modalities we have at our fingertips.