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.

Comparison of magnetic resonance enterography and video capsule endoscopy in evaluating small bowel disease.

PURPOSE: The goal of this study was to compare magnetic resonance enterography (MRE) and video capsule endoscopy (VCE) in suspected small bowel disease. MATERIALS AND METHODS: Nineteen patients with suspected small bowel disease participated in a prospective clinical comparison of MRE versus VCE. Both methods were evaluated separately and in conjunction with respect to a combined diagnostic endpoint based on clinical, laboratory, surgical, and histopathological findings. The Fisher's exact and j tests were used in comparing MRE and VCE. RESULTS: Small bowel pathologies were found in 15 out of 19 patients: Crohn's disease (n= 5), lymphoma (n= 4), lymphangioma (n= 1), adenocarcinoma (n= 1), postradiation enteropathy (n= 1), NSAID-induced enteropathy (n =1), angiodysplasia (n= 1), and small bowel adhesions (n= 1). VCE and MRE separately and in conjunction showed sensitivities of 92.9, 71.4, and 100% and specificities of 80, 60, and 80% (kappa= 0.73 vs. kappa = 0.29; P= 0.31/kappa = 0.85), respectively. In four patients, VCE depicted mucosal pathologies missed by MRE. MRE revealed 19 extraenteric findings in 11 patients as well as small bowel adhesions not detected on VCE (n= 1). CONCLUSION: VCE can readily depict and characterize subtle mucosal lesions missed at MRE, whereas MRE yields additional mural, perienteric, and extraenteric information. Thus, VCE and MRE appear to be complementary methods which, when used in conjunction, may better characterize suspected small bowel disease.

MR arthrography of the hip: diagnostic performance of a dedicated water-excitation 3D double-echo steady-state sequence to detect cartilage lesions.

OBJECTIVE: The objective of our study was to compare the diagnostic performance of a dedicated cartilage MR sequence (water-excitation 3D double-echo steady-state) with a standard MR sequence (T1-weighted spin-echo) in detecting articular cartilage lesions of the hip after intraarticular injection of gadopentetate dimeglumine. MATERIALS AND METHODS: In 50 MR arthrograms of the hip joint obtained in 47 consecutive patients, a sagittal 3D double-echo steady-state sequence (TR/TE, 24/6.5; flip angle, 25 degrees ) was compared with a sagittal T1-weighted spin-echo sequence (350/14). Two musculoskeletal radiologists independently evaluated articular cartilage. Sensitivity and specificity for detecting cartilage defects were calculated for those hips that underwent open surgery (n = 21). Lesion conspicuity was retrospectively reviewed and graded between 1 (not visible) and 5 (well defined). RESULTS: At surgery, a total of 26 lesions of the acetabular (n = 20) and femoral (n = 6) cartilage were found. For the 3D double-echo steady-state and T1-weighted spin-echo sequences, sensitivities and specificities for cartilage lesion detection were 58% and 88% and 81% and 81% for reviewer 1 and 62% and 94% and 62% and 100% for reviewer 2, respectively. Lesion conspicuity was significantly superior (p = 0.036) for the 3D double-echo steady-state sequence (mean grade, 3.4) compared with the T1-weighted spin-echo sequence (mean grade, 3.0). The kappa value was fair for the 3D double-echo steady-state sequence (kappa = 0.40) and moderate for the T1-weighted spin-echo sequence (kappa = 0.55). CONCLUSION: The 3D double-echo steady-state sequence optimized for cartilage imaging improves lesion conspicuity but does not improve diagnostic performance.

Characterization of dysfunctional myocardium by positron emission tomography and magnetic resonance: relation to functional outcome after revascularization.

BACKGROUND: Metabolic assessment of dysfunctional myocardium by PET allows prediction of functional recovery after revascularization. Contrast-enhanced MR (ce-MR) discriminates transmural distribution of viable and scar tissue with excellent spatial resolution. Both techniques were applied in ischemic chronic left ventricular dysfunction to relate metabolism and tissue composition to changes of contractile function after revascularization. METHODS AND RESULTS: Nineteen patients with myocardial infarctions (>3 months) were studied by MR and PET, and 10 patients were followed by MR 11+/-2 months after revascularization. In 56 to 64 segments/heart, systolic wall thickening, viable mass, and thickness of viable rim tissue were determined by MR (inversion-recovery MR with 0.25 mmol/kg Gd-chelate). [18F]Fluorodeoxyglucose (FDG) uptake and resting perfusion (13N-ammonia) were determined by PET. Viable tissue per segment on ce-MR correlated with FDG uptake per segment (r=0.62 and 0.82 for segments with and without flow metabolism mismatch, P<0.0001). FDG uptake > or =50% (a predictor of functional recovery) corresponded to a viable rim thickness of 4.5 mm on ce-MR. Thick (>4.5 mm) and metabolically viable segments (> or =50% FDG uptake) showed functional recovery in 85%, whereas thin metabolically nonviable segments improved function in 13% (P<0.0005). Metabolically viable segments with a thin viable rim and thick segments with reduced FDG uptake improved function in only 36% and 23% of segments, respectively (NS versus thin metabolically nonviable). In these 2 classes of segments, scar per segment was higher than in thick viable segments (P<0.0001). CONCLUSIONS: Metabolism and tissue composition discriminate various classes of dysfunctional myocardium. Most metabolically viable segments with a thick viable rim on ce-MR recover function after revascularization, whereas all other classes showed low recovery rates of contractile function.

Multislice breath-hold spiral magnetic resonance coronary angiography in patients with coronary artery disease: effect of intravascular contrast medium.

PURPOSE: First, to apply a breath-hold multislice 2D spiral magnetic resonance (MR) approach in patients acquiring within 16 heartbeats (acquisition window, 116 msec) a 10-mm-thick stack of four slices (resolution, 1.3 x 1.3 mm(2)); and second, to evaluate the effect of an intravascular Fe-based contrast medium (CM) on a signal-to-noise ratio (SNR) and a contrast-to-noise ratio (CNR). MATERIALS AND METHODS: In each patient one or two coronary arteries were imaged prior to and following cumulative doses of 0.25, 0.5, and 0.75 mg of Fe/kg of body weight (bw) of an intravascular CM (CLARISCAN trade mark, Nycomed-Amersham, Princeton, NJ, USA) containing ultrasmall superparamagnetic iron oxide (USPIO) particles. RESULTS: On precontrast maximum intensity projection (MIP) images generated from the stack of slices, 10 and 11 stenoses of 12 stenoses confirmed by coronary angiography were detected by readers 1 and 2, respectively. SNR and CNR in the coronary arteries peaked at 0.50 mg of Fe/kg of bw, yielding a slight increase of 15.5% and 18.4%, respectively (P < 0.05 vs. precontrast), which did not improve detection of coronary artery stenoses. CONCLUSION: The presented multislice spiral approach allows display of coronary anatomy in MIP formats for convenient display of coronary stenoses. The pulse sequence did not benefit from an intravascular USPIO-based CM, since little improvement in SNR and CNR was achieved.