[MRI of the abdomen combined with enteroclysis in Crohn disease using oral and intravenous Gd-DTPA]

Update imaging in inflammatory bowel diseases

Imaging is a central component of the diagnostic process in inflammatory bowel diseases. This review summarizes the recent progress of various most commonly used imaging modalities including computed tomography enterography, magnetic resonance enterography and capsule endoscopy. Advantages and disadvantages of each imaging protocol in suspected and established inflammatory bowel diseases are reviewed and brought into context in proposed diagnostic algorithms.

18F-Fluorodeoxyglucose positron-emission tomography (PET) can be used to assess inflammation non-invasively in Crohn's disease

BACKGROUND

Differential therapy requires repeated diagnostic assessment for mapping and monitoring of disease activity in Crohn's disease (CD).

PURPOSE

The purpose of this prospective study was to evaluate the accuracy of (18)F-fluorodexyglucose positron-emission tomography (FDG-PET) for non-invasive assessment of disease activity in CD.

METHODS

Forty-three patients with CD underwent ileocolonoscopy and hydromagnetic resonance imaging (hydro-MRI) as reference standards. In addition, FDG-PET was performed and correlated with clinical data, hydro-MRI, and endoscopy findings. Diagnostic accuracy was determined for all methods.

RESULTS

Two-hundred and forty-one bowel segments could be analyzed by all methods. Of 80 endoscopically inflamed segments in CD, FDG-PET detected 72 and hydro-MRI 53 segments. Overall sensitivity was 90 % (FDG-PET) versus 66 % (hydro-MRI), and specificity was 92.6 % versus 99 %. In the proximal ileum, hydro-MRI revealed inflammation in eight out of 49 patients and FDG-PET, also, detected all of these inflamed segments. Seventeen stenoses could be identified in 43 CD patients. With regard to assessment as inflammatory or fibrotic stenosis, there was good concordance between colonoscopy, hydro-MRI, and FDG-PET. In one case only, the nature of the stenosis was assessed differently. In contrast with leukocyte numbers and CDAI, there was significant correlation of FDG-PET activity with C-reactive protein and CDEIS levels (P = 0.019 and P = 0.007, respectively).

CONCLUSION

FDG-PET is able to detect mucosal inflammation in CD with high sensitivity and specificity and to enable proper assessment of inflammatory activity in stenoses. FDG-PET is, thus, a promising non-invasive technique for clinical management of CD.

Frequency and nature of incidental extra-enteric lesions found on magnetic resonance enterography (MR-E) in patients with inflammatory bowel diseases (IBD)

Background

The aim of this study was to determine the occurrence of extra-enteric findings in a large cohort of patients undergoing magnetic resonance enterography (MR-E) and to classify the clinical significance of these findings.

Materials and Methods

We retrospectively analyzed 1154 MR-E performed in 1006 patients referred to our radiological department between 1999–2005. The reasons for referral were suspected or proven inflammatory bowel diseases (IBD) (n = 710), further diagnostic work-up for small bowel disease because of non-specific abdominal symptoms (SBD; n = 182) or suspected small bowel malignancies (SBM; n = 114). All extra-enteric findings were reviewed by a radiologist and a gastroenterologist and were classified as having high, moderate, or low significance for further diagnostic or therapeutic procedures.

Results

The average age of all patients was 40±16 (Mean±SD) years (y) (IBD 35±13 y; SBD 49±16 y; SBM 57±15 y). A total of 1113 extra-enteric findings were detected in 600 of 1006 patients (59.6%). Of these findings 180 (16.2%) were judged as having a high, 212 (19.0%) a moderate and 721 (64.8%) a low significance. On a per group basis in patients with IBD 12.0% of the findings were of major clinical significance compared to 13.7% and 33.3% in patients with SBD and SBM, respectively. The most common major findings were abscesses (69.9%) in the IBD group and extraintestinal tumors, metastases or masses in the SBD and SBM groups (41.9% and 74.2%, respectively).

Conclusions

MR-E reveals a substantial number of extra-enteric findings, supporting the role of a cross-sectional imaging method for the evaluation of the small bowel.

Assessment of dynamic contrast enhancement of the small bowel in active Crohn's disease using 3D MR enterography

PURPOSE

To retrospectively compare the dynamic contrast enhancement of the small bowel segments with and without active Crohn's disease at 3D MR enterography (MRE).

MATERIALS AND METHODS

Thirteen patients (five men, eight women; mean age 41.2 years; range 29-56) were imaged on a 1.5-T MR scanner (Sonata, Siemens Medical) with standard MR sequences after having ingested 1000 ml of a 3% mannitol solution. Subsequently, high resolution 3D gradient-echo (volumetric interpolated breath-hold examination=VIBE) data sets were obtained pre-contrast and 20-40s, 60-80s, and 120-140 s after i.v. Gd-DOTA administration (0.2 mmol/kg). Signal enhancement was measured on single slices both in normal and histologically confirmed (12/13) inflamed small bowel wall segments as well as in the aorta, the psoas muscle, and the background to calculate signal-to-noise (SNR) and contrast-to-noise ratios (CNR).

RESULTS

Small bowel wall enhancement was significantly higher (p<0.05) in inflamed compared to normal segments at 20-40s (SNR inflamed: 58.7+/-33.8 vs normal: 36.0+/-19.8; p=0.048; CNR inflamed: 34.8+/-23.4 vs normal: 16.3+/-11.2; p=0.017) and at 60-80s (SNR: 60.3+/-25.1 vs 41.9+/-20.0; p=0.049; CNR: 34.9+/-15.1 vs 19.3+/-13.2; p=0.01) after i.v. contrast administration, respectively. Even at 120-140 s CNR was still increased in inflamed segments (33.7+/-16.0 vs 18.1+/-13.2; p=0.04), while differences in SNR did not attain statistical significance (63.0+/-26.2 vs 45.3+/-23.3; p=0.15).

CONCLUSION

In active Crohn's disease, histologically confirmed inflamed small bowel wall segments demonstrate a significantly increased early uptake of gadolinium on 3D VIBE sequences compared to normal small bowel segments.

Updating magnetic resonance imaging of small bowel: Imaging protocols and clinical indications

High soft tissue contrast resolution, acquisition of multi-planar images and the possibility to obtain functional information make magnetic resonance an interesting imaging technique to evaluate the small bowel disease. The absence of ionizing radiation is an important feature of magnetic resonance imaging (MRI) examinations because inflammatory diseases such as Crohn’s disease (CD) are studied most frequently, which are prevalent among children and young adults. MRI, using modern equipment and a rigorous technical approach, can offer detailed morphologic information and functional data on the small bowel. This article discusses the MRI protocols for small bowel and the MR imaging findings of small bowel diseases, such as CD and small bowel neoplasms.

Adult celiac disease: MRI findings

The purpose of our report is to describe a spectrum of findings of celiac disease at MR enterography. MR enterography is a non-invasive, feasible, and reproducible imaging technique for the evaluation of small bowel. Findings on MR enterography, similar to those of conventional barium studies, may suggest a diagnosis of celiac disease.

Feasibility of evaluating Crohn's disease activity at 3.0 Tesla

PURPOSE

To determine whether abdominal 3.0T MRI can be used for evaluation of Crohn's disease (CD) compared with ileocolonoscopy (CS), and to determine patient preference for MRI as opposed to CS.

MATERIALS AND METHODS

Twenty patients scheduled for CS underwent MRI. At CS, disease severity was graded and the Crohn's Disease Endoscopic Index of Severity (CDEIS) was determined. Radiological grading (by two observers) was compared with endoscopic grading and CDEIS. Patient experience and preference were determined.

RESULTS

In respectively 10 (observer 1) and 13 patients (observer 2) exact agreement between radiological and endoscopic grading was found. In respectively 10 and 7 patients radiological and endoscopic grading differed one level. No statistically significant correlation was found between radiological grading and CDEIS. Between bowel wall thickness and CDEIS weak to moderate correlations were found, and between bowel wall enhancement and CDEIS weak correlations were found. All patients preferred MRI over CS.

CONCLUSION

It is feasible to perform abdominal 3.0T MRI using orally administered contrast medium for evaluation of CD, and this method can be considered a patient-friendly alternative to CS.

[Value of contrast-enhanced MR enterography in pediatric Crohn's disease: preliminary study]

OBJECTIVE

Feasibility study of contrast enhanced MR enterography without enteroclysis as a new diagnostic tool for children with known or suspected Crohn's disease.

METHODS

We prospectively included 15 children, 8-18 years old, with clinical suspicion of Crohn's disease. MR enterography without enteroclysis was performed on a 1,5 T clinical MR system. A total of 1000 ml of mannitol 5% was orally administered 60 minutes prior to MRI. Coronal and axial breath-hold sequences were acquired. The following sequences were obtained: True-FISP, FLASH T1 2D/3D with Fat saturation before and after gadolinium injection. Two radiologists, blinded to patient information, independently reviewed all examinations to record image quality, the degree of distension of the distal ileum, the presence of abnormal bowel segments and the presence of extra-intestinal complications. MRI findings were correlated to sonographic, endoscopic and biological results (sensitivity, specificity, Kappa test).

RESULTS

The examinations were considered of satisfactory diagnostic quality in 93.3% of patients. Respiratory artifacts were present in one case. The entire GI tract could be identified on all sequences. Distention of the distal ileum was recorded as good to excellent in 89% of healthy subjects. Five MR examinations were considered abnormal with isolated ileal involvement in 2 cases, ileocolic involvement in 2 cases, and isolated colonic involvement in 1 case. The sensitivity and specificity of MR for the positive diagnosis of Crohn's disease were 100% and 83% respectively. Three extra-intestinal complications were detected: one case of ileo-ileal fistula, not identified on ultrasonography, an asymptomatic anal fistula and a symptomatic inflammatory stricture.

CONCLUSION

MR enterography without enteroclysis is a well tolerated, effective non invasive method in the evaluation of known or suspected Crohn's disease. Because of the absence of ionizing radiation, MR enterography should become the gold standard in pediatric patients.

MR imaging in patients with Crohn disease: value of T2- versus T1-weighted gadolinium-enhanced MR sequences with use of an oral superparamagnetic contrast agent

PURPOSE

To prospectively compare oral contrast-enhanced T2-weighted half-Fourier rapid acquisition with relaxation enhancement (RARE) magnetic resonance (MR) imaging with T1-weighted gadolinium-enhanced fast low-angle shot (FLASH) MR and standard examinations in the evaluation of Crohn disease.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. Fifty-nine patients with Crohn disease underwent MR imaging after oral administration of a superparamagnetic contrast agent; RARE plain and fat-suppressed sequences and FLASH sequences were performed before and after intravenous injection of gadolinium chelate. References were endoscopic, small-bowel barium, computed tomographic, ultrasonographic, and clinical-biochemical scoring of disease activity. Two radiologists analyzed MR images for presence and extent of Crohn disease lesions, presence of strictures or other complications, and degree of local inflammation. MR findings were correlated with endoscopic, radiologic, and clinical data (kappa statistic and Spearman rank correlation test).

RESULTS

T2-weighted MR was 95% accurate, 98% sensitive, and 78% specific for detection of ileal lesions. Agreement between T1- and T2-weighted images ranged from 0.77 for ileal lesions to 1.00 for colic lesions. T2-weighted MR enabled detection of 26 of 29 severe strictures, 17 of 24 enteroenteric fistulas, and all adhesions and abscesses; T1-weighted MR enabled detection of 20 of 29 severe strictures, 16 of 24 enteroenteric fistulas, and all adhesions and abscesses. Complications leading to surgery were found in 12 (20%) patients; these were assessed correctly with either T1- or T2-weighted images. T2-weighted signal intensities of the wall and mesentery correlated with biologic activity (P < .001, r of 0.774 and 0.712, respectively). Interobserver agreement was 0.642-1.00 for T2-weighted and 0.711-1.00 for T1-weighted images.

CONCLUSION

T2-weighted MR can depict Crohn disease lesions and help assess mural and transmural inflammation with the same accuracy as gadolinium-enhanced T1-weighted MR. Combination of gadolinium-enhanced T1- and T2-weighted sequences is useful in the assessment of Crohn disease.

Small bowel

MR imaging, using modern equipment and a rigorous technical approach, can offer detailed morphologic information and functional data on the small bowel. The optimal study technique is debatable, although the oral administration of contrast material as a first-line approach is less expensive, faster, easier to perform, and better tolerated by patients. MR enteroclysis might be reserved for selected cases as a second-line study. The major clinical indication is the evaluation of patients who have suspected or known Crohn's disease. The absence of ionizing radiation, considering the young age of most of the patients and the frequency of the examinations, is an important advantage over other techniques (radiograph and CT enteroclysis).

Magnetic resonance imaging in Crohn's disease

AIM

To evaluate the value of gadolinium enhanced MRI with oral opacification using a 5% mannitol solution (CE-Mannitol-MRI) to reveal bowel inflammation in pediatric patients with known or suspected Crohn's disease (CD).

MATERIALS AND METHODS

Sixty-two consecutive children (median age 13.9 years) with known or suspected CD underwent ileocolonoscopy with biopsy, ultrasonography and CE-Mannitol-MRI. CD activity was measured with the Pediatric Crohn's Disease Activity Index (PCDAI). Image quality, wall thickness, bowel wall enhancement and complications identified on CE-Mannitol-MRI were evaluated by two blinded radiologists.

RESULTS

The sensitivity and specificity of CE-Mannitol-MRI for the diagnosis of CD were 83% and 100%, respectively. Bowel wall enhancement was higher in the group of patients with abnormal small bowel loops versus control group (P = 0.001). In patients with known CD, there was a positive correlation between wall thickness and PCDAI (P = 0.003). However, no significant correlation was demonstrated between parietal contrast enhancement and PCDAI (P = 0.497). CE-Mannitol-MRI enabled identification of complications in 18 patients (9 fistulae, 8 strictures and 1 intussusception).

CONCLUSION

In pediatric patients with CD, CE-Mannitol-MRI contributes significantly to the identification of disease extension, severity and intestinal complications with adequate diagnostic accuracy. This technique could also be useful as the first line diagnostic exploration in young patients with suspected CD.

Magnetic Resonance Enteroclysis

MR enteroclysis (MRE) is an emerging technique for the evaluation of small intestinal diseases. Administration of an iso-osmotic water solution through a nasojejunal catheter can guarantee adequate luminal distention, and in combination with ultrafast sequences, such as single shot TSE, true FISP, HASTE and 3D FLASH, results in excellent anatomic demonstration of the small intestine. MR fluoroscopy can be performed during MRE examination to monitor the filling process and might be useful in studying low-grade stenosis or motility related disorders. MRE is a very promising technique for the detection and characterization of involved small bowel segments in patients with Crohn's disease while its diagnostic performance in disclosing lumen narrowing and extramural manifestations and complications of the disease is outstanding. Initial experience shows that MRE is very efficient in the diagnosis of small bowel tumors and can be used in the evaluation of small bowel obstruction.

Multidetector CT enteroclysis: comparison of the reading performance for axial and coronal views

The purpose of this study was to compare the diagnostic performance of axial and coronal views in multidetector CT enteroclysis (MDCTE). We retrospectively evaluated 48 patients with pathological correlation investigated by MDCTE for small bowel disorders. After nasojejunal administration of 2 l of 5% methylcellulose axial arterial and venous acquisition of MDCTE was followed by coronal reconstructions using equal slice thicknesses of 2.5 mm with 2 mm increments. Spatial resolution of both planes was evaluated by phantom. Three radiologists independently read axial and coronal images concerning 12 pathological features. The interobserver agreement and time of reading was calculated. Sensitivity and specificity resulted from comparison with histopathology (n=39) or follow-up (n=9). Phantom study revealed higher spatial resolution for axial than coronal views, whatever reconstruction interval was used. However, spatial frequency always remained high. Most pathological signs, such as bowel wall thickening (BWT), bowel wall enhancement (BWE) and intraperitoneal fluid (IPF), showed better interobserver agreement on axial than coronal views (BWT: 0.61 vs. 0.44; BWE: 0.56 vs. 0.5; IPF:0.53 vs. 0.43). The Wilcoxon signed-rank test revealed significantly higher sensitivity for axial than coronal views (P=0.0453); the time of reading was significantly shorter for the latter (P=0.0146). The diagnostic value of axial slices is superior to coronal reconstructions despite the reduced data volume and display of the physiological course of bowel loops on the coronal plane.

Mr enteroclysis using iron oxide particles (ferristene) as an endoluminal contrast agent: An open phase III trial

To evaluate efficacy and safety of a superparamagnetic iron oxide contrast agent (ferristene) as an endoluminal contrast medium for magnetic resonance (MR) enteroclysis in a phase III trial. Twenty-three patients with history of known or suspected small bowel Crohn's disease underwent MR imaging of the abdomen at 0.5 T unit. The imaging protocol included two phases: the first one without administration of any contrast agent and the second one, where the small bowel was filled by enteroclysis with 800 ml of the luminal iron oxide contrast medium and Gd-DTPA (0.1 mmol/Kg) was administered intravenously. Axial Spin-Echo (SE) T1-weighted (T1w), proton-density and T2w images, sagittal and coronal SE T1w and Short TI Inversion Recovery (STIR) sequences were subsequently obtained. Three investigators blindly evaluated images to determine small bowel distribution of ferristene, presence of artifacts, delineation of bowel lesion/wall and the diagnostic value of ferristene combined with gadolinium. Pre- and postcontrast signal intensity measurements of bowel lesion/wall, bowel lumen and background noise were also calculated. Three patients withdrew before the procedure, therefore 20 patients were effectively included in the study. No significant difference between the three investigators' evaluations of the improvement of the diagnostic information was found (percentage of improvement of 90% with 95% confidence limits of 68% and 99%). A statistically significant difference between the first and third investigators was found for grading of quality of delineation of bowel lesion/wall. Signal intensity measures showed a significant increase of the bowel lesion/wall and background noise/lesion for the SE T1w images. No serious adverse event was reported in our series. MR enteroclysis using ferristene as an endoluminal contrast agent appears to be a safe and efficient procedure for the study of the small bowel.

Abdominal MRI after enteroclysis or with oral contrast in patients with suspected or proven Crohn's disease

BACKGROUND & AIMS

Diagnostic results of magnetic resonance (MR) enteroclysis correlate highly with those from conventional enteroclysis; nevertheless, intubation of the patient and positioning of an intestinal tube is still necessary for the examination, which is often remembered as the most embarrassing part of the examination by the patient. A more comfortable and highly sensitive examination of the small bowel therefore would increase patient acceptance for recurring examinations, which are often necessary, for example, in patients with Crohn's disease. This study evaluates the diagnostic efficacy of abdominal MR imaging (MRI) of the small bowel after drinking contrast agent only compared with conventional enteroclysis and abdominal MRI performed after enteroclysis in patients with suspected or proven Crohn's disease.

METHODS

Twenty-one patients with Crohn's disease referred for conventional enteroclysis underwent abdominal MRI after enteroclysis. Additionally, 1 to 3 days before or after these examinations, abdominal MRI was performed using only orally administered contrast. All MRI examinations were performed using a 1.5T scanner.

RESULTS

All pathological findings on conventional enteroclysis were shown correctly with MRI after enteroclysis and MRI after oral contrast only. Additional information by MRI was obtained in 6 of 21 patients. No statistically significant differences were found in assessing the diagnostic efficacy of the 3 examinations.

CONCLUSIONS

Abdominal MRI with oral contrast only can be used as a diagnostic tool for evaluation of the small bowel in patients with Crohn's disease and has the potential to replace conventional enteroclysis as follow-up.

Modern imaging using computer tomography and magnetic resonance imaging for inflammatory bowel disease (IBD) AU1

Radiologic imaging--especially of the small bowel--plays an important role in the diagnosis and management of patients with inflammatory bowel disease. The radiographic examination of the small intestine with barium either as enteroclysis or as small bowel follow through are still the mainstays in small bowel imaging. However, abdominal CT or MRI, which has the advantage of not utilizing ionizing radiation, or the techniques of CT- or MR-enteroclysis, are overall comparable with regard to the sensitivity and specificity in detecting intestinal pathologies and have already replaced the conventional techniques in centers dedicated to the management of inflammatory bowel disease. Additionally, these cross-sectional imaging techniques provide, in a sense, a "one stop abdominal imaging workup," the diagnosis of extraluminal disease manifestations or complications. Future developments of CT- or MR-based virtual colonography and endoscopy in patients with inflammatory bowel disease are currently being investigated, but should momentarily be considered as purely experimental approaches.

Dark lumen magnetic resonance colonography: comparison with conventional colonoscopy for the detection of colorectal pathology

BACKGROUND

The purpose of this study was to assess the feasibility and usefulness of a new magnetic resonance (MR) colonography technique for the detection of colorectal pathology in comparison with conventional colonoscopy as the standard of reference.

PATIENTS AND METHODS

A total of 122 subjects with suspected colorectal disease underwent "dark lumen" MR colonography. A contrast enhanced T1w three dimensional VIBE sequence was collected after rectal administration of water. The presence of colorectal masses and inflammatory lesions were documented. Results were compared with those of a subsequently performed colonoscopy.

RESULTS

MR colonography was found to be accurate regarding detection of clinically relevant colonic lesions exceeding 5 mm in size, with sensitivity and specificity values of 93%/100%.

CONCLUSION

Dark lumen MR colonography can be considered as a promising alternative method for the detection of colorectal disease. In addition, it allows assessment of extraluminal organs.

MR enteroclysis

MR enteroclysis provides adequate image quality and sufficient distention of the entire small bowel. The functional information provided by MR enteroclysis equals that provided by conventional enteroclysis, which implies the ability reliably to depict even low-grade SBO. The inherent advantages of enteroclysis over conventional enteroclysis are the potential to detect extraluminal pathologic conditions and the ability to provide detailed information about the wall of the small bowel and the entire abdomen. Unlike conventional enteroclysis, MR enteroclysis does not have problems with overlapping bowel loops. MR enteroclysis has the potential to be an excellent diagnostic method for examinations of small bowel disease because of the functional information, the soft tissue contrast, and multiplanar imaging capabilities.

Technical challenges and clinical applications of magnetic resonance enteroclysis

With the advent of gradient systems the image quality of ultrafast pulse sequences, i.e., half Fourier acquisition single shot turbo spin echo (HASTE), true fast imaging with steady-state processing and fast low angle shot (FLASH), improved substantially and clinical applications including small bowel imaging became feasible. Within this context, magnetic resonance enteroclysis was developed as a comprehensive examination of the small bowel, providing luminal, transmural, and exoenteric diagnostic information of small bowel abnormalities. Clinical applications of magnetic resonance enteroclysis include diagnostic evaluation and follow-up of patients with inflammatory or neoplastic diseases and small bowel obstruction.

Small bowel magnetic resonance imaging for inflammatory bowel disease

The presented concept of hydro-magnetic resonance imaging (MRI) using a 2.5% mannitol solution as an orally applicable intraluminal contrast agent is a meaningful, reproducible, and reliable imaging method for the depiction of the small bowel. Especially in patients with Crohn's disease, hydro-MRI is the imaging method of first choice because hydro-MRI offers the advantage of a superior depiction of the inflamed bowel wall and the extramural complications of this disease without radiation exposure. In addition, hydro-MRI allows for a reliable assessment of the inflammatory activity, especially for the differentiation between an active and an inactive (scarred) stenosis. In particular, the mural enhancement, the length as well as the wall thickness of inflamed bowel segments, are considered to be significant MR parameters for the determination of the activity of Crohn's disease. Hydro-MRI of the colon is suitable for the depiction of pathologic changes in ulcerative colitis, but in contrast to Crohn's disease, the assessment of disease activity by hydro-MRI is unreliable in ulcerative colitis, probably because of the low spatial resolution (mucositis in ulcerative colitis vs. transmural inflammation in Crohn's disease). Hydro-MRI does not allow a reliable classification of inflammatory bowel diseases, but in ambiguous cases, hydro-MRI may provide helpful information for the differentiation of Crohn's disease and ulcerative colitis. There are no data of larger patient groups published regarding MR findings in inflammatory bowel diseases besides Crohn's disease and ulcerative colitis, but hydro-MRI is a promising imaging tool for these entities, which should be assessed in additional studies.

Ultrasound and magnetic resonance imaging assessmentof active bowel segments in Crohn's disease

AIM

Determining bowel disease activity in Crohn's patients can be difficult on clinical and laboratory assessment. Endoscopy is invasive and barium studies use ionising radiation. The aim of this study was to compare ultrasound and magnetic resonance imaging (MRI) in detecting Crohn's disease activity in the small or large bowel.

MATERIALS AND METHODS

Thirty patients, previously diagnosed with Crohn's disease, had bowel ultrasound and MR imaging, and were deemed active or inactive on each test. The 'gold standard' was based on clinical assessment and one or more of the following: endoscopy, barium studies or surgery.

RESULTS

For determining Crohn's disease activity, the sensitivities and specificities of bowel ultrasound and MRI were 87 percent and 100 percent, and 87 percent and 71 percent, respectively. Significant parameters that defined disease activity were bowel wall thickening on ultrasound and MRI, and contrast enhancement of the bowel wall and mesenteric vascularity/stranding on MRI.

CONCLUSION

Ultrasound and MRI were both sensitive for determining Crohn's disease activity in the bowel, but MRI with gadolinium enhancement was less specific.

3D modeling and virtual endoscopy of the small bowel based on magnetic resonance imaging in patients with inflammatory bowel disease

RATIONALE AND OBJECTIVES

Small bowel MRI (MR imaging) is a new imaging modality that excellently depicts small intestine pathology in patients with inflammatory bowel disease. Virtual endoscopy based on sectional imaging is a recently introduced technique to create endoscopy like views. The aim of this study was to evaluate the feasibility of virtual small bowel endoscopy based on MR imaging in patients with Crohn disease.

MATERIALS AND METHODS

Thirty consecutive patients with Crohn disease were scanned after oral application of pineapple juice for contrasting the small bowel. Dedicated high resolution T1 weighted 3D-FLASH sequences with fat suppression were used for volume scanning. Volume-rendered 3D models of the small bowel were created and virtual endoscopy was performed. The feasibility and quality of this new visualization method was assessed.

RESULTS

In nine of 30 patients virtual endoscopy was considered as good quality (flight through the entire small bowel was possible, typical folds were revealed). In 18 patients fair quality (at least 4/5 of the small bowel were depicted adequately) was assessed. In three of 30 patients virtual endoscopy was not sufficiently possible because of inadequate bowel filling or breathing artifacts. Three fistulae diagnosed on 2D MRI were visualized on the virtual endoscopic view.

CONCLUSION

Virtual endoscopy of the small bowel is feasible based on high resolution MR imaging. Vivid insight views and 3D models provide an interesting addition to sectional MR findings.

Dynamic studies of gadolinium uptake in brain tumors using inversion-recovery echo-planar imaging

Echo-planar imaging has been used to observe the dynamics of Gd-DTPA uptake in brain tumors. It has been possible to examine both vascular uptake and diffusion across the blood-brain barrier in a single experiment, by using the IR-MBEST echo-planar sequence which combines a high temporal resolution (approximately 3 s) with strong T1 weighting. To model the uptake it is necessary to know the arterial concentration of Gd-DTPA; in this study the signal in the sagittal sinus was measured to avoid the need to take repeated blood samples. The time constant for transfer across the blood-brain barrier was measured to be between 20 and 1050 s for different tumors. The results of the modeling correlated with the results of other assessments of tumor vascularity.