Search

Comprehensive bowel examination results from the combined use of T2-weighted single-shot and breath hold T1-weighted gradient echo, minus/plus fat suppression, and gadolinium-enhanced 3D gradient echo (3D VIBE, T1 FAME, 3D THRIVE). Gadolinium-enhanced imaging should be performed dynamically, but the venous 60- to 90-second delayed phase images with fat suppression are generally the most valuable. Removal of fat signal for detection of enhancing normal and abnormal structures is critical. Newly available True-FISP (FIESTA, BFFE) sequences obtained in the 2D form can be very helpful in delineation of bowel wall pathology and overall bowel anatomy, particularly when combined with a water-based intraluminal distending agent. Advantages include rapid acquisition, high signal-to-noise, and motion insensitivity. Generalized protocol for comprehensive evaluation of the entire abdomen and pelvis can be used for the following bowel indications: type and severity of inflammatory bowel disease (IBD); identifying enteric abscesses and fistulae; preoperative staging of malignant neoplasms, including rectal carcinoma; differentiating postoperative and radiation therapy changes from recurrent carcinoma; follow-up evaluation of metastases response to localized ablative or systemic chemotherapy. For improved visualization of bowel wall in dedicated examinations, bowel distension should be achieved using either orally or rectally delivered contrast agents to produce either bright or dark lumen. We have found 2D True-FISP without fat suppression superior to 3D True-FISP and to single-shot echo-train sequences to provide a T2-weighted image of bowel morphology. Strengths include: performed without fat suppression results in the very dark bowel wall being sandwiched between intermediate high signal fat adjacent to bowel serosa, and very high lumen signal from water-distending agent; 2D True-FISP provides motion insensitivity that is lost if 3D is used; True-FISP produces better edge sharpness than single-shot echo-train, higher contrast, and resists flow void artifacts commonly seen with single-shot echo-train imaging combined with a water distending agent. Drawbacks of this technique include: artifacts related to extreme sensitivity to field inhomogeneity, including air-soft tissue interfaces at the patient skin surface, and from retained bowel gas; retained bowel gas is dark against dark bowel wall, impairing bowel wall assessment; and True-FISP does not provide sensitivity for edema, which is superior on single-shot echo-train imaging. Small/large bowel indications for MRI include: inflammatory bowel disease, infectious disease including abscess evaluation or for appendicitis, inflammatory conditions including ischemia, and partial obstruction, malnutrition, and neoplasm search. [ABSTRACT FROM AUTHOR]

Background: Mucosal healing predicts clinical remission and improved outcomes in patients with Crohn disease (CD). Magnetic resonance enterography (MRE) is a noninvasive imaging modality that can assess small and large bowel wall inflammation. Evidence suggests that MRE may be an acceptable alternative to evaluate mucosal healing over endoscopy. Our objective is to determine whether MRE remission predicts clinical remission at follow-up in children with CD., Methods: We performed an institutional review board-approved retrospecitve chart review using our prospectively maintained MRE CD database. Inclusion criteria were all children who underwent an MRE more than 6 months after diagnosis with CD who had follow-up of at least 1 year from imaging., Results: A total of 101 children with CD underwent MRE, a median of 1.3 years from diagnosis with a median follow-up of 2.8 years after MRE. Active inflammation was detected in 65 MRE studies, whereas 36 MRE studies demonstrated MRE remission. A total of 88.9% of children demonstrating MRE remission were in clinical remission at follow-up, whereas only 44.6% of those demonstrating MRE active inflammation achieved clinical remission. Children demonstrating MRE-active inflammation were more likely to have a change in medication (44.6% vs 8.3%) and more likely to undergo surgery (18.5% vs 2.8%)., Conclusions: MRE remission is associated with clinical remission at follow-up at least 1 year after MRE. MRE remission was associated with fewer medication changes and fewer surgeries suggesting that, similar to endoscopic remission, MRE remission demonstrates improved outcome. Additional research is needed to confirm that MRE can be used as a surrogate for mucosal healing.

Background and Objective: Children with Crohn disease (CD) often undergo cross-sectional imaging during clinical evaluation. Magnetic resonance enterography (MRE) is becoming the preferred radiologic assessment due to the lack of radiation exposure; however, there are few data in children with CD comparing MRE with objective disease measures. The aim of the present study was to compare MRE with endoscopy, histopathology, and laboratory evaluation in children with CD., Methods: We performed an institutional review board-approved query of our prospective CD MRE database, which includes data in children with CD undergoing MRE since 2008., Results: A total of 147 MRE studies were performed in 119 different children with symptomatic CD. Of those, 53 (39.6%) MRE studies were performed at diagnosis to evaluate small bowel disease burden. A total of 117 (79.6%) MRE studies displayed active and/or chronic disease, whereas 30 (20.4%) MRE studies were normal. When compared with normal MRE studies, active inflammation on MRE was associated with a higher mean C-reactive protein (3.6 vs 1.1, P < 0.001), higher erythrocyte sedimentation rate (36 vs 22, P = 0.0.31), higher platelet value (439 vs 352, P = 0.033), and lower albumin (3.4 vs 3.7, P = 0.049). Comparison between MRE and endoscopy demonstrated excellent agreement when ulcers were present, and moderate agreement with histopathology., Conclusions: Active inflammation on MRE is associated with higher C-reactive protein, erythrocyte sedimentation rate, platelets, and lower albumin in children with CD. MRE displays excellent agreement with endoscopic disease described by ulcers but poor agreement with mild mucosal disease described by erythema and friability. The present study adds to a growing body of evidence that MRE provides excellent assessment of inflammation and measures disease activity in CD.

Background: Noninvasive diagnosis of giant cell arteritis (GCA) remains challenging, particularly with regard to evaluation of extracranial arterial disease., Objectives: The objective of the study was to retrospectively review extracranial involvement in patients with GCA and/or polymyalgia rheumatica (PMR), evaluated with magnetic resonance imaging (MRI), especially 3-dimensional contrast-enhanced magnetic resonance angiography images of the aortic arch and its branches., Methods: Clinical information, biopsy status, and MRI examinations of 28 patients with GCA/PMR were reviewed. Patient images were mixed randomly with 20 normal control images and were independently reviewed by 2 radiologists. Interobserver agreement for detection of arterial stenosis was determined by the k coefficient., Results: Both readers described vascular alterations in keeping with extracranial GCA in 19 of 28 patients (67%) with good interobserver agreement (k = 0.73) and with even higher agreement on diagnosing nonocclusive versus occlusive disease (k = 1.00). The most common lesions were bilateral axillary stenosis or obstructions, observed by both readers in 8 patients (28%). Among the 19 patients with magnetic resonance angiography lesions in the subclavian/axillary arteries, 12 (75%) had biopsy-proven GCA, but only 5 (41%) of these patients had clinical features of large artery disease., Conclusions: In our series review, MRI could provide accurate information on involvement of the aortic arch and its branches in extracranial GCA, depicting different degrees of stenosis. Our analysis also illustrates that occult large artery vasculitis should be considered in patients without biopsy-proven GCA, patients with classic GCA but without clinical signs of large artery disease, and in patients initially diagnosed as having PMR.

The ability for contrast-enhanced magnetic resonance imaging to provide significant diagnostic impact to focal and diffuse liver diseases requires knowledge, analysis, and technical optimization of the imaging techniques. Our review outlines the technical requirements needed to perform reproducible contrast-enhanced liver imaging and describes the important imaging features for assessing liver disease with conventional and alternate gadolinium-based contrast media. We present an experimental review of timing and quantification methods in dynamic contrast-enhanced liver imaging, with results of analysis showing perfusion and uptake curves in a series of patients and healthy subjects. An evidence-based methodology for reproducible arterial-phase imaging is detailed for performing a real-time bolus-tracking method. Additional diagnostic imaging features manifest at later imaging phases, in which the kinetic behavior of the contrast media serves to further specify focal lesions, while revealing detailed information of diffuse liver disease, particularly hepatic fibrosis. We review the utility of alternate gadolinium-based contrast media that undergo hepatocyte uptake, for applications related to liver tumor imaging. We also introduce results showing the potential for using alternate hepatocyte uptake agents to detect and quantify liver changes related to acute and chronic hepatitides.

Chronic kidney disease is a significant public health problem, and a comprehensive evaluation of renal disease often requires accurate evaluation of both kidney structure and function. Magnetic resonance (MR) nephrourography refers to newly developed imaging techniques that have the ability to provide a quantitative assessment of renal function, especially glomerular filtration rate and renal blood flow. Our review outlines several different methodologies that are present in the literature and also details the specifics of our own methods for renal imaging. Though varied, all MR imaging methods use the common steps of image acquisition, image postprocessing, and tracer kinetics modeling of the processed image data. The optimal methodology should be practical and based primarily on simplicity, speed, and reproducibility. The combination of anatomic and quantitative functional information of the kidneys provided by MR imaging allows for a safe, comprehensive evaluation of renal disease, with particular utility in the settings of urinary tract obstruction and renal transplantation.

The development of transmit-receive body coils and local and phased-array radiofrequency receive coils for 3.0-T magnetic resonance imaging (MRI) systems, and their recent approval in Europe and North America has promoted a move toward higher field, whole-body MRI. With approximately double the signal-noise ratio of a 1.5-T system, 3.0-T MR systems can substantially improve image quality and image acquisition speed; 3.0 T can potentially deliver square root(2) improvement in resolution in the same acquisition time of a comparable study at 1.5 T or one-half slice thickness with identical coverage or 4-fold speedup in scanning time for identical resolution settings. Parallel imaging, multiple coil elements, specific absorption rate, and altered MR physical properties at 3.0 T (T1 relaxation times, susceptibility, T2*) are important issues during optimization of sequences at high field. Possible future applications in the abdomen include high-resolution, contrast-enhanced imaging of the liver and pancreas; MR angiography; and MR spectroscopy. In this article, we will present our initial experience with optimization of sequences for abdominal MRI at 3.0 T and will include a short description of parallel imaging because of its importance for imaging at 3.0 T, general remarks comparing some of the physical properties of 1.5 T and 3.0 T, and some of the challenges during sequence optimization for the abdomen at 3.0 T with examples of abdominal MRI at 3.0 T with 4- and 8-channel coils.

Antenatal diagnosis of fetal goiter should be appropriately managed to avoid perinatal complications. Here, we present the MR imaging features of a fetal goiter caused by maternal Graves disease. Diffusely enlarged fetal thyroid gland was seen showing homogeneously elevated signal on T1-weighted images and intermediate signal on T2-weighted images. To our knowledge, this is the first MR imaging documentation of fetal goiter.