A comparative study between Gd-DTPA and oral magnetic particles (OMP) as gastrointestinal (GI) contrast agents for MRI of the abdomen

Magnetic resonance enterography in Crohn’s disease: Standard and advanced techniques

Crohn’s disease (CD) is a chronic autoimmune disorder that affects mainly young people. The clinical management is based on the Crohn’s Disease Activity Index and especially on biologic parameters with or without additional endoscopic and imaging procedures, such as barium and computed tomography examinations. Recently, magnetic resonance (MR) imaging has been a promising diagnostic radiologic technique with lack of ionizing radiation, enabling superior tissue contrast resolution due to new pulse-sequence developments. Therefore, MR enterography has the potential to become the modality of choice for imaging the small bowel in CD patients.

Value of MRCP using oral Gd-DTPA as negative contrast materials in diagnosis of atypical juxtapapillary duodenal diverticulum

OBJECTIVE

To investigate value of magnetic resonance cholangiopancreatography (MRCP) using oral diluted gadolinium (Gd)-diethylenetriamine penta-acetic acid (DTPA) as negative contrast materials in diagnosis of juxtapapillary duodenal diverticulum with atypical imaging features.

METHODS

Nineteen patients with juxtapapillary duodenal diverticula of which imaging findings were atypical underwent MRCP using oral diluted Gd-DTPA as negative contrast materials after conventional MRCP without any oral contrast materials.

RESULTS

Twenty diverticula were revealed in the 19 patients. At conventional MRCP, the diverticula appeared as rounded lesion with high signal intensity. After oral administration of diluted Gd-DTPA, they disappeared at MRCP. These entities were diagnosed as duodenal diverticula for they communicate with duodenal lumen.

CONCLUSION

MRCP using oral Gd-DTPA as negative contrast materials can be helpful in obtaining definitive diagnosis of those juxtapapillary duodenal diverticula without typical imaging features.

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.

MR imaging of the small bowel with increasing concentrations of an oral osmotic agent

The aim of this study was to assess the quality of MR imaging and level of adverse effects with increasing concentrations of gastrografin. This is a prospective study with 24 healthy volunteers which were randomised into four groups receiving 50%, 25%, 10% and 0% gastrografin. The endpoint was bowel image quality based on distension, signal homogeneity and wall delineation evaluated by three independent radiologists, and the maximum bowel diameter at three different levels. The subjects also scored any adverse events on a 1-5 scale. The interradiologist agreement was relatively good, with kappa values varying between 0.81 and 0.41. Improved bowel distension and image quality were achieved with increasing concentrations. But significant dose-response effects were found between increasing osmolalities and the bowel diameters and also versus the score of adverse events. The most frequent adverse reactions were diarrhea, nausea and lack of palatability. There is a gradient relationship between increasing osmolality of gastrografin and improved image quality and the score of adverse effects. The optimum concentration of gastrografin is dependent of the tolerance of the adverse events.

Regional lung functional impairment in acute airway obstruction and pulmonary embolic dog models assessed with gadolinium-based aerosol ventilation and perfusion magnetic resonance imaging

RATIONALE AND OBJECTIVES

Gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA)-based aerosol ventilation and perfusion magnetic resonance (MR) images were used to define regional functional impairment in acute airway obstruction (AO) and pulmonary embolic (PE) dog models.

METHODS

The aerosol study was performed in 10 anesthetized normal dogs in a supine position during 20-minute spontaneous inhalation of an aerosol of 100- or 200-mmol-Gd/L Gd-DTPA solute produced by an ultrasonic nebulizer in an open-circuit delivery system, combined with a dynamic perfusion study after a 3-second intravenous bolus injection of a 0.1 mmol/kg dose of Gd-DTPA. These MR studies were also performed in the same 10 dogs approximately 30 minutes after obstructing the segmental (n = 6) or lobar (n = 4) bronchus with a balloon catheter, and in another six dogs after segmental (n = 6) and lobar (n = 4) pulmonary arterial embolization with enbucrilate. Regional lung enhancement was assessed on time-signal intensity (SI)-curves and ventilation- and perfusion-weighted images produced by a subtraction technique.

RESULTS

The normal lungs were gradually and gravity-dependently enhanced with time after Gd-DTPA aerosol inhalation regardless of the respiratory SI changes, except for three animals with the fastest breathing rate. The averaged maximal relative lung SI increase against the baseline in the successful animals was significantly greater in the slowly and deeply breathing animals than in the fast and shallow breathing animals, regardless of the difference in Gd-concentration (100 mmol Gd/L: 153.3% +/- 69.7% vs. 54.2% +/- 23%; P < 0.001; and 200 mmol Gd/L: 189.7% +/- 68.0% vs. 75.6% +/- 42.2%; P < 0.0001, respectively). There was an additional enhancement of 382% +/- 101 in the ventral lung and 722% +/- 160 in the dorsal lung on the pulmonary arterial phase perfusion image even in the slowly and deeply breathing animals who inhaled 200-mmol-Gd/L aerosol, and the enhancement effect was significantly greater compared with that with the aerosol (P < 0.0001). The ventilation- and perfusion-weighted images clearly defined the regionally matched perfusion-ventilation deficits in all the AO models, and the regionally mismatched perfusion-ventilation in all the PE models.

CONCLUSION

Gd-based aerosol can provide efficient lung enhancement in spontaneously and adequately breathing animals, using a relatively noninvasive aerosol delivery system. The combined use of Gd-based perfusion MR imaging may be acceptable for defining regionally impaired function associated with acute AO and PE.

Bile-tagged 3d magnetic resonance colonography after exclusive intravenous administration of gadobenate dimeglumine, a contrast agent with partial hepatobiliary excretion

RATIONALE AND OBJECTIVES

Imaging of the colon is an important diagnostic procedure. Endoscopic colonoscopy and x-ray barium enemas are currently the standard diagnostic procedures. Magnetic resonance (MR) and computed tomographic colonography have been recently introduced with true three-dimensional (3D) cross-sectional imaging. Up to now, all imaging techniques have required the use of oral and/or aboral contrast agents for luminal enhancement and commonly, a relaxation medication (glucagon or N-butylscopolamine). While performing several phase I, II, and III studies with a new partially hepatobiliary excreted gadolinium-based MR contrast agent, we noted substantial intraluminal enhancement within the colon and investigated its potential for imaging.

METHODS

Three-dimensional MR angiographic techniques enable imaging of large volumes. We have used these sequences to detect contrast enhancement within the hepatobiliary and gastrointestinal systems. A 3D volume of 40 x 32 x 12 cm with 42 images was acquired under breath-hold. Six volunteers were studied according to the protocol. No bowel preparation was performed and no medication given. Subsequent follow-ups of the abdomen were performed at 1, 12, 24, 36, 48, 70, and 105 hours postinjection. Gadobenate dimeglumine at 0.1 mmol/kg body weight was given intravenously. Images were assessed quantitatively and by blinded reader analysis.

RESULTS

Intense intraluminal contrast enhancement within the colon was seen within 24 hours in all subjects. The homogeneous enhancement was of sufficient intensity to enable 3D visualization and virtual endoscopy. The optimal time window for imaging was determined to be 16 to 50 hours postinjection.

CONCLUSIONS

We report for the first time the feasibility of exclusively bile-tagged MR colonography with the use of only an intravenous MR contrast that exhibits partial hepatobiliary excretion. This new diagnostic procedure will enable not only morphological assessment of the colon but also functional and pathophysiological studies on the transport kinetics of bile and stool without any preparation of the patient.

Superparamagnetic agents in magnetic resonance imaging: physicochemical characteristics and clinical applications. A review

Superparamagnetic agents in magnetic resonance imaging: physico-chemical characteristics and clinical applications. Superparamagnetic agents have been the subject of extensive research over the last decade. They consist of iron oxide nanoparticles which are highly effective in Magnetic Resonance Imaging (MRI). The particle size varies widely and influences their physicochemical and pharmacokinetic properties. Their main present and future applications by the parenteral route are: imaging of gastrointestinal tract, liver and spleen, lymph nodes. Ultrasmall superparamagnetic iron oxide particles (USPIO) are also blood pool agents which could be used for perfusion imaging (i.e. brain or myocardial ischemic diseases) as well as for imaging of vessels in Magnetic Resonance Angiography. These agents open up an important field of research into more specific agents adapted to clinicians' needs in diagnostic imaging.

Appearance of canine abdominal tumors with magnetic resonance imaging using a low field permanent magnet

The study was carried out to evaluate the applicability of magnetic resonance imaging (MRI) in detecting tumors in the abdomen of the dog. Abdominal ultrasound and MRI were performed on 8 dogs having a mass lesion on abdominal radiography. MR images were obtained in the transverse, sagittal and dorsal planes using T1- and T2-weighted spin echo pulse sequences. There was good visual correlation of the lesion site by MRI and ultrasonography (US).

A multicenter clinical trial of Gadolite Oral Suspension as a contrast agent for MRI

The purpose of this study was to assess the effectiveness and safety of Gadolite Oral Suspension as a gastrointestinal (GI) contrast agent for MRI in a phase II and two phase III multicenter clinical trials. Gadolite was administered to 306 patients with known or suspected abdominal and/or pelvic disease. MRI with T1- and T2-weighted sequences was performed before and after ingestion. Efficacy was evaluated by having two masked readers rate the certainty of their MR diagnosis (0 = uncertain, 1 = probable, 2 = definite) on randomly presented pre- and post-Gadolite Oral Suspension enhanced images. Principal investigators also evaluated the images and established the final diagnosis. Vital signs, clinical chemistries, and adverse events were documented. Blood and urine samples were analyzed for gadolinium content to determine whether Gadolite Oral Suspension was absorbed systemically. Certainty in MR diagnosis increased significantly (P < .001) for both blinded readers between pre- and post-Gadolite images (.49-1.18 for reader 1: .46-1.53 for reader 2). Sensitivity, specificity, and accuracy also increased for both masked readers. No gadolinium was detected in blood or urine samples. There were no serious adverse events and no apparent drug-related trends in mean vital signs or laboratory values. Gadolite is a highly effective, safe, and well tolerated contrast agent for clinical use with MRI.

MR imaging contrast agents--what's in a name?

The purpose of this brief review is to reduce the confusion surrounding the nomenclature of MRI contrast agents. There are several different categories of contrast agents for potential use in human diagnosis and several alternative names for each contrast agent, an array of choices that actually changes over time. This review describes the general process by which these various agents are named, presents one general categorization by which these agents can be considered, and provides a concise table to which readers can refer to identify the proper name to use for each of the agents that has thus far been administered to humans.