Liquid oral magnetic particles as a gastrointestinal contrast agent for MR imaging: efficacy in vivo

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.

MRI in staging advanced gastric cancer: is it useful compared with spiral CT?

PURPOSE

During the last decade, rapid progress has been made in MR technology. Our objective was to evaluate the role of MRI in staging advanced gastric cancer (AGC; gastric cancer invading the muscularis propria) and to compare it with that of spiral CT.

METHOD

We prospectively performed both MR and CT examinations on 26 patients with AGC proven by endoscopic biopsy. Contrast-enhanced CT and nonenhanced MRI with a 1.0 T scanner using FLASH, HASTE, and true-FISP sequences were obtained in each patient after injection of antiperistaltic drug and ingestion of 1 L of tap water. Fifty-two sets of CT and MR images were analyzed by two radiologists in consensus without any information from other images. T and N staging of AGC was determined according to the TNM classification. All patients underwent surgery within 1 week after both examinations. Diagnostic accuracy of each staging of AGC on CT or MRI was evaluated by comparison with the pathologic results.

RESULTS

MRI was slightly superior to CT in T staging (81 vs. 73%, respectively; p < 0.05). Although MRI had a tendency to overstage the pathologic T2 cancer, positive predictability of T2 stage and sensitivity of T3 stage were high (100%, respectively). Regarding the N staging, CT was slightly superior to MRI (73 vs. 65%; p > 0.05). However, both CT and MRI demonstrated the tendency of understaging in N staging.

CONCLUSION

Although MRI was superior to spiral CT in T staging, MRI cannot completely replace spiral CT in staging AGC because of its limitation in N staging.

A multisite phase III study of the safety and efficacy of a new manganese chloride-based gastrointestinal contrast agent for MRI of the abdomen and pelvis

The purpose of this study was to evaluate the safety and efficacy of a manganese chloride-based oral magnetic resonance (MR) contrast agent during a Phase III multisite clinical trial. Two hundred seventeen patients were enrolled who were already scheduled for MRI of the abdomen and/or pelvis. In this group of patients, it was postulated that the use of an oral agent would better allow discrimination of pathology from bowel. Patients with known gastrointestinal pathology including peptic ulcer disease, inflammatory bowel disease, obstruction, or perforation were excluded to minimize confounding variables that could affect the safety assessment. Of these 217 patients, 18 received up to 900 mL of placebo, and 199 patients were given up to 900 mL of a manganese chloride-based oral contrast agent, LumenHance (Bracco Diagnostics, Inc.). Safety was determined by comparing pre- and post-dose physical examinations, vital signs, and laboratory examinations and by documenting adverse events. Efficacy was assessed by unblinded site investigators and two blinded reviewers who compared pre- and post-dose T1- and T2-weighted MRI scans of the abdomen and/or pelvis. In 111 (57%) of the 195 cases evaluated for efficacy by site investigators (unblinded readers), MRI after LumenHance provided additional diagnostic information. Increased information was found by two blinded readers in 52% and 51% of patients, respectively. In 44/195 cases (23%) unblinded readers felt the additional information would have changed patient diagnosis and in 50 patients (26%), it would have changed management and/or therapy. Potential changes in patient diagnosis or management/therapy were seen by the two blinded readers in 8-20% of patients. No clinically significant post-dose laboratory changes were seen. Forty-eight patients (24%) receiving LumenHance and four patients (22%) receiving placebo experienced one or more adverse events. Gastrointestinal tract side effects were most common, seen in 29 (15%) of LumenHance patients and in 3 (17%) of the placebo patients. LumenHance is a safe and efficacious oral gastrointestinal contrast agent for MRI of the abdomen and pelvis.

MRI of pelvic masses: efficacy of the rectal superparamagnetic contrast agent Ferumoxsil

The purpose of this study was to determine the potential value of rectally administered Ferumoxsil for pelvic MRI. Twenty patients with suspected rectosigmoid and ovarian tumors were prospectively examined before and after rectal administration of 300 to 600 ml of the superparamagnetic contrast agent Ferumoxsil. Imaging parameters (1.5-T system, phased-array coil, transverse T1-weighted spin echo (SE) and T2-weighted turbo-SE sequences, 6-mm slice thickness, 350-mm field of view [FOV], 512 x 512 matrix) were kept constant. Images were evaluated for tumor presence, lymphadenopathy, bowel involvement, and peritoneal implants. Precontrast and postcontrast studies were rated for bowel delineation, lesion/organ-to-bowel differentiation, presence of artifacts, and confidence of diagnosis. Delineation of rectum and sigmoid colon (P < .001) as well as separation of bowel and vagina, uterus/adnexa, dome of the urinary bladder, lymph nodes, and vessels improved significantly (P < .01) on both T1-weighted and T2-weighted postcontrast sequences. The rectal contrast agent did not increase the level of artifacts. Changes in diagnosis in 7 of 20 patients were mainly due to identification of colorectal tumors or bowel involvement on postcontrast images. The readers' diagnostic confidence was significantly higher on contrast-enhanced than on unenhanced studies (93 +/- 6.4% vs 68 +/- 25.2%). Rectal application of Ferumoxsil improves lesion/organ-to-bowel delineation and overall diagnostic confidence in pelvic MRI.

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.

Oral administration of a low-cost negative contrast agent: a three-year experience in routine practice

A low cost, well tolerated, and effective gastrointestinal contrast agent is needed for abdominal MRI. The authors tested, in vitro and in routine practice, a mixture of 192 g of barium sulfate (Micropaque HD oral, Guerbet, France) diluted in 500 ml of gastric antacid (Maalox, Rohrer, Fort Washington, PA). Its T1 and T2 relaxation times were 324 and 14 msec, respectively (.2 T). This contrast agent was used in routine practice in 789 patients (.5 T). It had a low signal intensity in 86% and 82% of the cases on T1- and T2-weighted sequences, respectively. No side effect due to magnetic susceptibility was seen, even with gradient-echo sequences. The dilution of barium sulfate in gastric antacid, instead of water, causes a low signal intensity on all sequences for a low barium sulfate concentration (38% w/v). This product is an effective and low cost contrast agent in routine practice.

Gadolinium zeolite as an oral contrast agent for magnetic resonance imaging

The purpose of this study was to evaluate efficacy and safety of a gadolinium (Gd) zeolite suspension as an oral MRI contrast agent. Serial dilutions of GADO-LITE Oral Suspension 1,2-300 micrograms of Gd(III)/mL) were prepared. MRI (T1 and T2 weighted) of standards and dogs (precontrast and postcontrast) were performed. Toxicity and Gd absorption were also assessed. Subsequently, 30 normal male adult volunteers were divided into six groups of five subjects each. Gd zeolite po suspension was administered before and after MRI in volumes and concentrations ranging from 250 to 1500 mL; 6 to 60 micrograms of Gd+3/mL. The images were rated (efficacy score) by a blinded reader. Vital signs, blood chemistries and urinalysis were recorded. Gadolite Oral Suspension produced excellent enhancement of the dog gastrointestinal (GI) tract. No toxicity or absorption of Gd was observed in dogs receiving doses up to 4 times the anticipated human dose daily for 14 consecutive days. In clinical trials, Gd zeolite significantly improved the efficacy scores for all groups and all pulsing sequences (all P values < .05). Efficacy scores and signal intensities generally increased with concentration and volume. No Gd was detected in blood or urine specimens. No significant adverse events were reported. Gd zeolite is a promising contrast medium for enhancement of the GI tract in MRI.

Intraluminal contrast agents for MR imaging of the abdomen and pelvis

Magnetic resonance (MR) imaging of the abdomen and pelvis with use of gastrointestinal (GI) contrast agents is slowly emerging as a valuable diagnostic tool. In the past few years, considerable effort has been expended on developing an oral contrast agent to serve as a bowel marker during abdominal and pelvic imaging. Four major categories of agents have been studied: compounds with positive contrast-enhancing characteristics (ie, which increase signal intensity), which may be either miscible or immiscible with bowel contents, and compounds with negative contrast-enhancing characteristics (ie, which decrease signal intensity), which also may be miscible or immiscible. Compared with precontrast images, MR images acquired after administration of GI contrast agents have shown increased anatomic delineation of the bowel lumen, pancreas, and paraaortic nodes, allowing increased detection of pancreatic lesions, improved assessment of bowel wall lesions, and distinction between intrahepatic and extrahepatic lesions. This review focuses on the general physics and requirements for intraluminal GI contrast media for MR imaging, the currently used intraluminal agents and their regulatory status, current and near-future availability, and cost considerations.