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 × 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.     

Superparamagnetic Iron Oxide Hepatic MR Imaging: Efficacy and Safety Using Conventional and Fast Spin-Echo Pulse Sequences

The purpose of this study was to evaluate the technical efficacy and safety of iv ferumozldes (Feridex^a), a superparamagnetic iron oxide contrast agent for detection of hepatic lesions using conventional spin-echo and fast spin-echo MR images. Precontract and postcontrast MR studies were performed on 25 patients with suspected focal hepatic lesions. Conventional Tl-and T2-weighted MR images, as well as fast spin-echo and fat suppressed fast spin-echo MR images, were evaluated. Quantitative assessment of the contrast agent was performed obtaining region of interest measurements of the liver, spleen, and selected hepatic lesions. The pulse sequences were also evaluated subjectively for overall image quality and a subjective assessment of lesion detection. The use of a superparamagnetic iron oxide contrast agent led to a decrease in hepatic signal intensity on all pulse sequences. Lesion-to-liver contrast increased 41.1%, 36.5%, and 32.0% on the conventional T2, fast spin-echo, and fat suppressed fast spin echo pulse sequences, respectively. Lesion-to-liver contrast decreased on the T1-weighted postcontrast pulse sequence by 23.8%. Despite Improvement in lesion-to-liver contrast, radiologists subjectively preferred the precontract sequences because of overall better image quality. At a dose of 10 μmol/kg, fenunoxides favorably impacts lesion-to-liver contrast, and may be useful in hepatic imaging, more with conventional T2-weighted spin-echo pulse sequences than with T2-weighted fast spin-echo pulse sequences.     

Focal nodular hyperplasia of the liver on ferumoxides-enhanced MR imaging: features on conventional spin-echo, fast spin-echo and gradient-echo pulse sequences

The aim of this study was to assess the efficacy of a superparamagnetic iron oxide, ferumoxides, in the detection and characterization of focal nodular hyperplasia (FNH) on MR conventional spin-echo (SE), fast spin-echo (FSE) and gradient-echo (GRE) images. Fourteen adults with 27 FNHs were evaluated at 1.5 T before and after injection of ferumoxides. T1-weighted and T2-weighted SE, T2-weighted FSE and T2^*-weighted GRE sequences were used and analysed qualitatively and quantitatively. One hundred percent of FNHs showed a significant postcontrast decrease in signal intensity on T2- and T2*-weighted images. Heavily T2-weighted SE images showed the maximum decrease in FNH signal-to-noise ratio (S/N). Postcontrast GRE T2^*-weighted images improved the detection of the central scar and the delineation of FNHs and demonstrated the best lesion-to-liver contrast-to-noise ratio (C/N). Postcontrast T1-weighted SE images showed the least lesion-to-liver C/N. Ferumoxides-enhanced MR imaging can help detect and characterize FNH. Conventional pre- and postcontrast T2-weighted SE images and postcontrast GRE T2*-weighted images should be used preferentially. Received: 30 November 1998; Revised: 5 April 1999; Accepted: 6 April 1999     

First clinical trial of a new superparamagnetic iron oxide for use as an oral gastrointestinal contrast agent in MR imaging

The authors report the results of preclinical testing and initial clinical application of a superparamagnetic iron oxide specifically prepared as a contrast agent for magnetic resonance (MR) imaging of the gastrointestinal tract. MR imaging was performed at 0.6 and 1.5 T in 15 volunteers. Images of the upper abdomen and pelvis were obtained before and after ingestion of the contrast material at doses of 22.5-225.0 mg of iron in 600-900 L. Two readers scored the images. Delivery of contrast material into the proximal and distal small bowel, with obvious loss of signal intensity (T2 enhancement), was achieved in all subjects. Enhanced images showed improved delineation of the head and tail of the pancreas, anterior margins of the kidneys, and paraaortic region. The contrast agent did not generate artifacts, an improvement over prototype formulations evaluated previously in animals. Except for a brief episode of diarrhea in five subjects, the agent was well tolerated. Use of this contrast agent improved the diagnostic quality of abdominal MR images by enabling the distinction of the bowel from nonbowel structures at concentrations that did not produce image distortion.     

Magnetite albumin suspension: a superparamagnetic oral MR contrast agent

Suspensions of magnetite albumin microspheres (MAM), a new biodegradable particulate iron superparamagnetic MR contrast material, were evaluated in vitro and in vivo as an oral contrast agent. MAM is stable over a broad range of pH and tolerates proteolytic enzyme exposure over 24 hr in vitro. MAM possesses a much larger magnetic moment than do paramagnetic contrast agents. The transverse relaxation rate (R2) of MAM can be as much as 40 times the longitudinal relaxation rate (R1). In vitro spectroscopy studies confirm the potency of MAM in promoting T2 relaxation at concentrations of 10-1000 mg/l. Preliminary studies in rabbits and dogs show that in contrast to oral gadolinium-DTPA, which causes increased signal in bowel, MAM causes marked signal loss in the stomach and small bowel on both T1- and T2-weighted pulse sequences. Radionuclide labeling studies of MAM suspension with 99mTc show no evidence of absorption of MAM suspension from the gastrointestinal tract in small animals. Superparamagnetic suspensions such as MAM that reduce bowel signal on T1- and T2-weighted pulse sequences offer the unique benefit of reducing motion artifacts throughout the gastrointestinal tract, which should allow for improved evaluation of intra- and retroperitoneal diseases, particularly with high-field strength and gradient-echo "fast-scan techniques." Unlike paramagnetic material, MAM appears effective as a small-bowel contrast material.     

Iron oxide-enhanced MR lymphography: initial experience

The detection of nodal metastases is of utmost importance in oncologic imaging. Ultrasmall superparamagnetic iron oxide particles (USPIO) are novel contrast agents specifically developed for MR lymphography. After intravenous administration, they are taken up by the macrophages of the lymph nodes, where they accumulate. They reduce the signal intensity (SI) of normally functioning nodes on postcontrast T2-and T2*-weighted images through the magnetic susceptibility effects on iron oxide. Metastatic nodes, in which macrophages are replaced by tumor cells, show no significant change in SI on postcontrast T2-and T2*-weighted images. Early clinical experience suggests that USPIO-enhanced MR lymphography improves the sensitivity and specificity for the detection of nodal metastases. It also suggests that micrometastases could be detected in normal-sized nodes. This article reviews the physiochemical properties of USPIO contrast agents, their enhancement patterns, and early clinical experience.     

Oral superparamagnetic contrast agent (ferumoxsil): Tolerance and efficacy in MR imaging of gynecologic diseases

The purpose of this study was to determine the tolerance and the efficacy of the oral contrast agent ferumoxsil in the assessment of gynecologic diseases. Twenty patients underwent MR imaging at 1.5 T. T1-weighted spin-echo (SE) and T2-weighted fast SE images were obtained before and after ingestion of 600900 mL of the Superparamagnetic negative contrast agent ferumoxsil. No side effects were observed. No statistically significant increase in artifact generation was present in the postcontrast images. The efficacy in bowel marking was significant for the small bowel (P = 0.0001) and the cecum (P < 0.01), but not significant in all sequences for the sigmoid. In the postcontrast images, delineation of the uterus, the right-sided adnexa, the lymph nodes, and the pathologic lesions was significantly better (P < .01), but not all sequences showed an improvement in delineation of the other pelvic organs. After administration of ferumoxsil, the level of confidence in diagnosis was significantly higher (P = .0001), but no change in diagnosis was made from the preto the postcontrast images. We found the oral contrast agent ferumoxsil to be well tolerated and effective in marking the bowel and in delineating the normal organs as well as the pathologic lesions on pelvic MR images.     

Iron oxide-enhanced MR lymphography: The evaluation of cervical lymph node metastases in head and neck cancer

Accurate diagnosis of cervical lymph node metastasis is challenging, even with the latest computed tomography or MR equipment and technique. The lack of definitive criteria for distinguishing metastatic from benign nodes is a serious shortcoming of current imaging options. Dextran-coated, ultrasmall superparamagnetic iron oxide is a new MR contrast agent, which accumulates in the reticuloendothelial system of lymph nodes. Small iron oxide particles are taken up by macrophages within normal functioning nodes, reducing their signal on postcontrast MR because of the magnetic susceptibility effects of iron oxide. Metastatic nodes, on the other hand, remain high in signal on postcontrast T2*-weighted gradient echo images. Early clinical experience in cancer patients suggests that iron oxide-enhanced MR lymphography is a valuable imaging technique that may improve diagnostic accuracy for nodal metastases. This article reviews development of superparamagnetic iron oxide compounds, their imaging characteristics, and clinical experience for evaluating head and neck cancer metastases.     

OMR, a positive bowel contrast agent for abdominal and pelvic MR imaging: safety and imaging characteristics.

To determine the safety and imaging characteristics of OMR--an effervescent solution of ferric ammonium citrate--as a bowel contrast agent, magnetic resonance (MR) imaging at 1.5 T was performed in 29 volunteers. T1- and T2-weighted images of the upper abdomen and pelvis were obtained before and after oral administration of OMR at doses of 100-400 mg of iron in 300-600 mL of water. Respiratory-ordered phase encoding and presaturation pulses were used routinely for artifact suppression. All dose levels of OMR provided marking of the bowel by increasing intraluminal signal intensity; however, the degree and percentage of small bowel opacification appeared more prominent at higher dose levels of iron. Semisolid or watery bowel movements were noted in 31% of subjects, but no clinically important laboratory abnormalities were seen. OMR improved delineation of the head of the pancreas on T1-weighted images in 72% of subjects but was less useful in defining the body and tail. OMR is a safe and effective bowel contrast agent for MR imaging. Because artifacts due to movement of hyperintense bowel may degrade the images, OMR may be most useful on short TR/TE or fast imaging pulse sequences or when combined with antiperistaltic agents.     

Detection of liver metastases with superparamagnetic iron oxide in 15 patients: results of MR imaging at 1.5 T

The first clinical results of using superparamagnetic ferrite particles as a tissue-specific contrast agent for MR of the liver are reported at high fields (1.5 T). Fifteen patients with proved secondary liver malignancies were studied with plain and contrast-enhanced MR. Superparamagnetic iron oxide was administrated IV in a dose of 20 mumol/kg. Intermediate TR, 820/30, 60 (TR/TE), and long TR, 2200/22, 70, spin-echo sequences were used before and 1 hr after injection of contrast material. Before injection, the largest number of lesions (437) was detected with the T2-weighted sequence. Lesion-to-liver contrast, expressed as the difference between the tumor and liver signal-to-noise, improved after ferrite administration in both sequences from -1 to 20 and from 7 to 15 for the 820/30, 60 sequence and from 9 to 34 and 15 to 21 for the 2200/22, 70 sequence. Despite this significant improvement in terms of the number of lesions detected, contrast-enhanced images did not show significantly more metastases than the unenhanced T2-weighted images did (383, 421, 407, and 407 vs as many as 437, respectively). In this limited study at 1.5 T, the benefit of ferrite enhancement was only marginal when postcontrast images were compared with heavily T2-weighted precontrast scans.     

Arterioportal shunts in cirrhotic patients: evaluation of the difference between tumorous and nontumorous arterioportal shunts on MR imaging with superparamagnetic iron oxide

OBJECTIVE: The study objective was to distinguish between the features of tumorous and nontumorous arterioportal shunts on superparamagnetic iron oxide-enhanced MR imaging in patients with cirrhosis. SUBJECTS AND METHODS: Ten arterioportal shunts in eight patients, including four tumorous and six nontumorous arterioportal shunts, were evaluated on T2-weighted turbo spin-echo and T2(*)-weighted gradient-echo sequences before and after administration of superparamagnetic iron oxide. Qualitatively, the relative signal intensity of the arterioportal shunt compared with that of the surrounding liver parenchyma was categorized into three grades: high, slightly high, and not detected. Quantitatively, signal-to-noise ratio, contrast-to-noise ratio, lesion-to-liver contrast, and percentage enhancement were calculated and compared between tumorous and nontumorous arterioportal shunts by a nonparametric statistical test (Mann-Whitney test). RESULTS: Qualitatively, all four tumorous arterioportal shunts appeared as areas of slightly high or high intensity without and with superparamagnetic iron oxide on T2-weighted turbo spin-echo images and changed from isointensity to high intensity after the administration of superparamagnetic iron oxide on T2(*)-weighted gradient-echo images. All nontumorous arterioportal shunts except one could not be recognized without or with superparamagnetic iron oxide on either sequence. Quantitatively, with superparamagnetic iron oxide the contrast-to-noise ratio and the lesion-to-liver contrast of the tumorous arterioportal shunts were significantly higher than those of the nontumorous arterioportal shunts. CONCLUSION: Tumorous arterioportal shunts are seen as areas of reduced signal loss, whereas most nontumorous arterioportal shunts are seen as areas of normal signal loss, like the normal liver parenchyma. The difference is more marked on T2(*)-weighted gradient-echo images than on T2-weighted turbo spin-echo images.     

Splenic imaging with ultrasmall superparamagnetic iron oxide ferumoxtran-10 (AMI-7227): preliminary observations

PURPOSE: Ferumoxtran-10 (ultrasmall superparamagnetic iron oxide; Combidex, AMI-7227) is a long-circulating MR contrast agent with reticuloendothelial uptake known to enhance tissue T1 and T2 relaxation rates. The purpose of this study was to assess the effect of ferumoxtran-10-enhanced MRI in evaluating focal splenic lesions. METHOD: Eighteen patients underwent MR evaluation of the spleen. Two of these patients with exophytic normal splenic tissue (splenules) and 13 of these patients with 24 focal splenic lesions (7 cysts, 2 hemangiomas, 7 metastases, 1 infarct, 7 lymphoma) were assessed by T1-weighted gradient echo and T2-weighted fast SE MRI following intravenous administration of ferumoxtran-10 (1.1 mg of Fe/kg). Qualitative analysis involving improved lesion detection and/or characterization, additional information from postcontrast images affecting staging, and patient management was performed. Quantitative measurements of lesion-to-spleen contrast-to-noise ratio were also performed. RESULTS: Additional information was provided by ferumoxtran-10-enhanced images in 15 of 18 patients. In 8 of 15 (53%) patients, improved lesion detection (i.e., number of lesions) was obtained on contrast-enhanced images. Improved lesion visualization (i.e., conspicuity) was noted in 11 of 15 (73%) of patients. In 10 of 15 (67%) patients, postcontrast imaging provided additional information leading to lesion characterization. Staging of disease and patient management were affected in 5 of 15 (33%) and 6 of 15 (40%) patients, respectively. CONCLUSION: Ferumoxtran-10 is a promising contrast agent for the evaluation of focal splenic lesions.     

Intra- and paraorbital lesions: value of fat-suppression MR imaging with paramagnetic contrast enhancement

The orbital area of 18 individuals was examined by using a combination of fat-suppression contrast-enhanced MR imaging to determine whether contrast between fat and surrounding tissues could be improved over that obtained with conventional fat-suppression techniques alone. We used a hybrid technique combining two independent methods of fat suppression. Subjects consisted of 16 patients and two normal volunteers. Fifteen individuals received gadopentetate dimeglumine, and conventional T1-weighted, T2-weighted, and fat-suppression T1-weighted images were obtained. The fat-suppressed T1-weighted images obtained after contrast administration provided more information than did the conventional MR images. Intraorbital and paraorbital lesions could be distinguished easily from intraorbital fat that had been suppressed. Cases of chorioretinitis and optic neuritis could be confidently diagnosed only by this technique. Cases of optic nerve meningioma and mixed conal lesions also were better appreciated. Because of sharp contrast between tissue planes, this technique was helpful for detecting any intraorbital invasion from paraorbital lesions. Fat-suppression MR imaging with paramagnetic contrast enhancement can significantly improve the delineation of both normal and abnormal structures and better define lesional margins in the orbit, where large amounts of fat are present. Our results support earlier findings, and we suggest that postcontrast fat-suppressed T1-weighted imaging be used instead of conventional T1-weighted postcontrast imaging in evaluating orbital and paraorbital lesions.     

Multicentre dose-ranging study on the efficacy of USPIO ferumoxtran-10 for liver MR imaging

AIM: A dose ranging multicentre phase-II clinical trial was conducted to evaluate the efficacy of ultrasmall superparamagnetic iron oxide (USPIO) ferumoxtran-10 for magnetic resonance (MR) imaging of focal hepatic lesions. MATERIAL AND METHODS: Ninety-nine patients with focal liver lesions received USPIO at a dose of 0.8 (n = 35), 1.1 (n = 32), or 1.7 (n = 32) mg Fe/kg. Liver MR imaging was performed before and after USPIO with T1-weighted and T2-weighted pulse sequences. Images were analysed by two independent readers for additional information (lesion detection, exclusion, characterization and patient management). Signal intensity (SI) based quantitative measurements were also taken. RESULTS: Post-contrast medium MR imaging showed additional information in 71/97 patients (73%) for reader one and 83/96 patients (86%) for reader two. The results with all three doses were statistically significant (P < 0.05). Signal intensity analysis revealed that all three doses increased liver SI on T1-weighted images and decreased liver SI on T2-weighted images. On T2-weighted images metastases increased in contrast relative to normal hepatic parenchyma whereas haemangiomas decreased in contrast. On T2-weighted images there was statistically improved efficacy at the intermediate dose, which did not improve at the highest dose. CONCLUSION: Ultrasmall superparamagnetic iron oxide was an effective contrast agent for liver MR imaging at all doses and a dose of 1.1 mg Fe/kg was recommended for future clinical trials.     

Oral magnetic particles in MR imaging of the abdomen and pelvis

Two phase 2 clinical trials of an oral superparamagnetic contrast agent for enhancement on magnetic resonance images of the intestine were performed. In trial 1, 31 male patients with cancer of the testis underwent follow-up examinations of the abdomen at 0.5 and 1.5 T after oral administration of magnetic particles. In trial 2, 31 female patients with pelvic and lower abdominal disease were examined at 1.5 T after administration of the contrast material. The patients each ingested 800 mL of contrast material over approximately 2 hours. Concentrations of 0.25 and 0.5 g/L did not induce blurring or metallic artifacts. Distribution was homogeneous through the gastrointestinal tract. In all patients, a loss of signal intensity was observed on proton density-, T1-, and T2-weighted images. The diagnostic information from postcontrast images in trial 2 was greater in 16 patients (52%). Contrast enhancement was independent of field strength; no major side effects were observed. Artifacts from moving bowels were less troublesome, and delineation of intraabdominal and pelvic organs was better with the use of oral magnetic particles.     

Imaging of macrophages in soft-tissue infection in rats: relationship between ultrasmall superparamagnetic iron oxide dose and MR signal characteristics

PURPOSE: To describe dose-dependent signal intensity (SI) characteristics of experimentally induced soft-tissue abscesses on 1.5-T T1- and T2*-weighted magnetic resonance (MR) images obtained 24 hours after administration of ultrasmall superparamagnetic iron oxide (USPIO) and to describe the relationship between SI and amount of USPIO uptake and macrophage iron content. MATERIALS AND METHODS: Local institutional review committee on animal care approved the experiments, which were performed according to the guidelines of the National Institutes of Health and the committee on animal research at our institution. Unilateral calf muscle abscesses were induced in 21 rats with an injection of a Staphylococcus aureus suspension. The rats were divided into three groups of seven animals each: low USPIO dose (50 micromol of iron per kilogram of body weight), high USPIO dose (150 micromol Fe/kg), and control (saline solution). All rats were imaged before and 24 hours after USPIO administration at 1.5 T (transverse T1-weighted spin-echo, T2*-weighted fast gradient-echo, and short inversion time inversion-recovery sequences). Images were analyzed quantitatively and qualitatively with regard to SI and signal pattern. Temporal variation of calculated contrast-to-noise ratios was analyzed with the Wilcoxon signed rank test. MR findings were correlated with histopathologic findings, including those of electron microscopy. RESULTS: Twenty-four hours after USPIO administration in the high-dose group, susceptibility effects were present in abscess periphery on postcontrast T2*-weighted images (P=.04), and SI enhancement was noted on postcontrast T1-weighted images within both abscess wall and abscess center (P=.04 for both). In the low-dose group, SI enhancement was noted in entire abscess on T1-weighted postcontrast images (P=.03). Neither significant SI loss (P=.09) nor susceptibility effects were detected in periphery or center of any abscess on postcontrast T2*-weighted images. There was no obvious difference in total amount of macrophages among the groups, but there was a clear difference with regard to individual iron content of iron-positive macrophages between the USPIO dose groups. CONCLUSION: At 1.5 T, SI characteristics of abscesses on T1- and T2*-weighted images obtained 24 hours after USPIO injection strongly depend on administered dose of the contrast agent. At low doses, T1 effects were stronger than T2* effects.     

Comparative efficacy of and sequence choice for two oral contrast agents used during MR imaging.

OBJECTIVE: Our objective was to compare the efficacy of a positive and a negative oral contrast agent and to determine the optimal sequence choice for use in pelvic MR imaging. SUBJECTS AND METHODS: We undertook a prospective randomized trial of 57 patients with pelvic cancer who were examined with MR imaging after oral administration of a positive contrast agent (27 patients) or a negative contrast agent (30 patients). T1- and T2-weighted breath-hold and non-breath-hold gradient-recalled echo and turbo spin-echo sequences were obtained. Using the hard-copy images, we graded filling and distention of the small bowel, bowel wall conspicuity, delineation of normal and pathologic structures, and artifacts. RESULTS: Good or excellent small-bowel filling and distention was obtained in 17 patients (63%) receiving the positive agent and in 26 patients (87%) receiving the negative agent, and bowel wall conspicuity was graded good or excellent in 19 patients (70%) and 20 patients (67%), respectively. Normal and pathologic structures were better delineated with the negative agent (20 patients [74%] and 27 patients [90%], respectively; p = .02). Breath-hold gradient-recalled echo T1-weighted images were preferred for the positive agent (78%), and breath-hold T2-weighted images were preferred for the negative agent (93%). Contrast artifacts were more frequently seen with the negative agent (11% and 93%, respectively; p = .0001), and such artifacts were eliminated using T2-weighted sequences. CONCLUSION: Both contrast agents were effective in pelvic MR imaging, but delineation of normal and pathologic structures was better with the negative agent. Gradient-recalled echo T1-weighted sequences are recommended for positive contrast agents, and breath-hold T2-weighted sequences are recommended for negative contrast agents.     

Comparison of two superparamagnetic viral-sized iron oxide particles ferumoxides and ferumoxtran-10 with a gadolinium chelate in imaging intracranial tumors

BACKGROUND AND PURPOSE: Ultrasmall superparamagnetic iron oxide particles result in shortening of T1 and T2 relaxation time constants and can be used as MR contrast agents. We tested four hypotheses by evaluating MR images of intracranial tumors after infusion of two iron oxide agents in comparison with a gadolinium chelate: 1) Ferumoxtran in contrast to ferumoxides can be used as an intravenous MR contrast agent in intracranial tumors; 2) ferumoxtran enhancement, albeit delayed, is similar to gadolinium enhancement; 3) ferumoxtran-enhanced MR images in contrast to gadolinium-enhanced MR images may be compared with histologic specimens showing the cellular location of iron oxide particles; 4) ferumoxtran can serve as a model for viral vector delivery. METHODS: In 20 patients, ferumoxides and ferumoxtran were intravenously administered at recommended clinical doses. MR imaging was performed 30 minutes and 4 hours after ferumoxides infusion (n = 3), whereas ferumoxtran-enhanced MR imaging (n = 17) was performed 6 and 24 hours after infusion in the first five patients and 24 hours after infusion in the remaining 12. MR sequences were spin-echo (SE) T1-weighted, fast SE T2- and proton density-weighted, gradient-recalled-echo T2*-weighted, and, in four cases, echo-planar T2-weighted sequences. Representative regions of interest were chosen on pre- and postcontrast images to compare each sequence and signal intensity. RESULTS: Despite some degree of gadolinium enhancement in all tumors, no significant T1 or T2 signal intensity changes were seen after ferumoxides administration at either examination time. Fifteen of 17 patients given ferumoxtrans had T1 and/or T2 shortening consistent with iron penetration into tumor. Histologic examination revealed minimal iron staining of the tumor with strong staining at the periphery of the tumors. CONCLUSION: 1) Ferumoxtran can be used as an intravenous MR contrast agent in intracranial tumors, mostly malignant tumors. 2) Enhancement with ferumoxtran is comparable to but more variable than that with the gadolinium chelate. 3) Histologic examination showed a distribution of ferumoxtran particles similar to that on MR images, but at histology the cellular uptake was primarily by parenchymal cells at the tumor margin. 4) Ferumoxtran may be used as a model for viral vector delivery in malignant brain tumors.     

Brain: gadolinium-enhanced fast fluid-attenuated inversion-recovery MR imaging

PURPOSE: To determine the clinical utility of gadolinium-enhanced fluid-attenuated inversion-recovery (FLAIR) magnetic resonance (MR) imaging of the brain by comparing results with those at gadolinium-enhanced T1-weighted MR imaging with magnetization transfer (MT) saturation. MATERIALS AND METHODS: In 105 consecutive patients referred for gadolinium-enhanced brain imaging, FLAIR and T1-weighted MR imaging with MT saturation were performed before and after administration of gadopentetate dimeglumine (0.1 mmol per kilogram of body weight). Pre- and postcontrast images were evaluated to determine the presence of abnormal contrast enhancement and whether enhancement was more conspicuous with the FLAIR or T1-weighted sequences. RESULTS: Thirty-nine studies showed intracranial contrast enhancement. Postcontrast T1-weighted images with MT saturation showed superior enhancement in 14 studies, whereas postcontrast fast FLAIR images showed superior enhancement in 15 studies. Four cases demonstrated approximately equal contrast enhancement with both sequences. Six cases showed some areas of enhancement better with T1-weighted imaging with MT saturation and other areas better with postcontrast fast FLAIR imaging. Superficial enhancement was typically better seen with postcontrast fast FLAIR imaging. CONCLUSION: Fast FLAIR images have noticeable T1 contrast making gadolinium-induced enhancement visible. Gadolinium enhancement in lesions that are hyperintense on precontrast FLAIR images, such as intraparenchymal tumors, may be better seen on T1-weighted images than on postcontrast fast FLAIR images. However, postcontrast fast FLAIR images may be useful for detecting superficial abnormalities, such as meningeal disease, because they do not demonstrate contrast enhancement of vessels with slow flow as do T1-weighted images.