Ultrasmall superparamagnetic iron oxide particles (AMI 227) as a blood pool contrast agent for MR angiography: experimental study in rabbits

We report a case of successful surgical management of a potentially life-threatening complication of aortoiliac stent placement. A 59-year-old man who had Leriche syndrome underwent bilateral iliac artery and infrarenal aortic stent placement at another institution. His history was significant for retroperitoneal lymph node dissection at 19 years of age for testicular cancer. One week after stent placement, the patient was readmitted with abdominal pain, poor oral intake, and diffuse intermittent tenderness. Evaluation with computed tomographic scanning and endoscopy was unremarkable, and the patient was discharged. He was admitted to our institution 1 week later with persistent abdominal pain. A computed tomographic scan of the abdomen revealed a large pseudoaneurysm of the abdominal aorta. The patient underwent urgent exploration, and exclusion of his infrarenal aorta was achieved with aortobifemoral bypass grafting. After the operation, the patient's course was complicated by a large paraduodenal hematoma, which resulted in a gastric outlet obstruction, which was managed without operation. This case illustrates a potential life-threatening complication of extensive stent placement for aortoiliac occlusive disease. Injury to the abdominal aorta must be considered in a symptomatic patient after the placement of stents in the aortoiliac region, beyond the immediate periprocedural period.     

Superparamagnetic iron oxide particles (SH U 555 A): evaluation of efficacy in three doses for hepatic MR imaging

The rotational spectrum of vinylarsine in the ground state has been studied in the range 7-320 GHz. The spectra of a syn conformer and a gauche conformer have been unambiguously assigned on the basis of the existence of a b-type or a c-type spectrum. Rotational constants, quartic, and some sextic centrifugal distortion constants were derived. For the syn form, measurements of low J aR0,1 transitions in a pulsed-nozzle Fourier transform microwave spectrometer (FTMWS) enabled the determination of the diagonal elements of the quadrupole tensor, as well as two spin-rotation constants. Ab initio calculations performed at the MP2 level using the 6-311++G(3df, 3pd) basis set reproduced experimental rotational constants within 0.2%. Copyright 1998 Academic Press.     

Fast gradient echo MR imaging of the liver enhanced with superparamagnetic iron oxide

Urinary proteins of patients with diabetes mellitus (DM) were analyzed using cellulose acetate membrane electrophoresis, to determine the clinical usefulness of fraction patterns of the proteins in detecting the group at high risk for diabetic nephropathy. We divided the protein patterns into 5 groups. Four groups (I, II, III, IV) were found in the healthy group and a newly classified group was termed group 0 and was characterized by a prominent albumin peak with a negligible or small globulin peak. The incidence of groups 0, I, II, III, and IV, was 36.6%, 13.3%, 18.7%, 10.7% and 22.7%, respectively. This distribution was clearly different from that of healthy subjects and the most characteristic feature of diabetics was that group 0 accounted for 36.6% of the total cases. Characteristic features of each group were examined from the aspect of laboratory and clinical findings. Urinary protein patterns were concluded to be useful not only to predict the high risk group for diabetic nephropathy in the preclinical stage but also to discriminate nephropathic types of glomerular or tubular origin. It is useful for clinicians to know the risk stage and prognosis for diabetic nephropathy.     

Characterization of reactive versus tumor-bearing lymph nodes with interstitial magnetic resonance lymphography in an animal model

RATIONALE AND OBJECTIVES: To determine if magnetic resonance lymphography performed with subcutaneously administered AMI-227, a nanoparticulate iron oxide contrast agent, can distinguish reactive from tumor-bearing lymph nodes. MATERIALS AND METHODS: Mature male Copenhagen rats were inoculated with cell suspensions of R3327-MAT-LyLu rat prostate carcinoma (n = 21) or Freund's complete adjuvant (n = 15) in the left footpad to generate ipsilateral popliteal lymph node metastases or lymphadenitis. At 12 to 14 days after inoculation, T1-and T2-weighted magnetic resonance images of bilateral popliteal areas were obtained before and 24 hours after subcutaneous administration of AMI-227. Contrast-to-noise ratios were calculated in precontrast and postcontrast images. Bilateral popliteal nodes were excised for pathologic assessment. RESULTS: AMI-227 resulted in decreased contrast-to-noise ratios in reactive (T1-W = -7.01 +/- 1.13, T2- W = -31.64 +/- 5.35) and normal (T1 - W = -13.56 +/- 1.97, T2 - W = -21.62 +/- 2.51) nodes. Contrast-to-noise ratios were unchanged (T1 - W = -0.22 +/- 1.71, T2 - W = -2.20 +/- 4.19) in tumor-containing nodes. These differences in contrast-to-noise ratio changes between tumor-bearing versus nontumor-bearing nodes were statistically significant (P < 0.05). Histologic analysis showed similar distribution of AMI-227 within normal and reactive nodes, but not in tumor-bearing nodes. CONCLUSIONS: Differences in AMI-227-uptake between tumor- and nontumor-bearing nodes detected with magnetic resonance imaging are helpful for distinguishing the two entities.     

Macromolecular intravenous contrast agent for MR lymphography: characterization and efficacy studies

PURPOSE: To determine the pharmacokinetic and magnetic resonance (MR) imaging properties of diethylenetriaminepentaacetic acid (DTPA) conjugated with a polyglucose-associated macrocomplex (PGM), which accumulates in lymph nodes. MATERIALS AND METHODS: In 124 normal and 20 tumor-bearing rats, Gd-DTPA PGM was administered intravenously in doses of 2, 10, 20 mumol gadolinium per kilogram of tissue. RESULTS: Mean blood half-life was 2 hours. Maximum accumulation in peripheral (33.0% injected dose [ID]/g +/- 16.2 [standard deviation]) and central lymph nodes (63.2% ID/g +/- 16.5) was observed within 24 hours after administration. The optimum dose range was 10-20 mumol Gd/kg in rats. At 24 hours after administration of 20 mumol Gd/kg, the signal-to-noise ratio increased from 30.9 +/- 0.4 to 83.2 +/- 5.2 in normal lymph nodes (P < .001). Differentiation between normal and metastatic lymph nodes was improved. CONCLUSION: When labeled with Gd-DTPA, the PGM-based graft copolymer significantly increases signal intensity at MR imaging of normal but not metastatic lymph nodes without causing distortion artifacts.     

MR imaging of pelvic lymph nodes in primary pelvic carcinoma with ultrasmall superparamagnetic iron oxide (Combidex): preliminary observations

The potential of ultrasmall superparamagnetic iron oxide (Combidex)-enhanced MRI of pelvic lymph nodes in patients with primary pelvic carcinoma is evaluated. Fifteen histologically classified lymph nodes in six patients with known primary pelvic cancer (four prostate; one rectum; one uterus) were evaluated with T2-weighted fast spin-echo (FSE) and T2*-weighted gradient-echo (GRE) MRI at 1.5T 12 to 48 hours after intravenous administration of Combidex at a dose of 1.7 mg Fe/kg. Quantitative image evaluation was performed by comparing signal intensity of individual nodes on pre- and postcontrast images. All patients proceeded to pelvic lymph-node biopsy or surgical dissection, where six were found to be benign and nine were malignant. Of the 15 lymph nodes, four nodes showed a decrease in signal intensity. Of these, three, in which signal loss was homogenous were benign, and one, in which the signal-intensity decrease was heterogeneous, was malignant (micrometastases). No signal change was noted in 11 of 15 lymph nodes of which three were benign (inflammatory) and eight were malignant. Combidex is a promising MR contrast agent for evaluating pelvic lymph nodes. Our preliminary observations suggest that the agent is most useful for classifying normal lymph nodes.     

The influence of MR field strength on the detection of focal liver lesions with superparamagnetic iron oxide

Isolated nerve segments may inherently contain all of the necessary factors required to support regeneration within a silicone tube conduit placed across a nerve gap. Thirty-six adult Lewis rats each weighing approximately 250 g were randomized into three groups. A sciatic nerve gap (13-15 mm in length) was bridged by an empty silicone tube (Group I), a silicone tube containing a short 2-mm interposed nerve segment (Group II), or a nerve autograft (Group III). At 16 weeks postoperatively, no regeneration was observed through the empty silicone tube. In contrast, regeneration across the silicone tube containing the isolated nerve segment was equivalent to that noted through nerve autografts as assessed by histological, electrophysiological, and functional criteria. Thus, an interposed nerve segment will extend the length of successful nerve regeneration through a silicone tube conduit.     

Doxycycline pleurodesis in rabbits: comparison of results with and without chest tube

We have reported previously that there is a high incidence of hemothorax and substantial mortality in rabbits that are given tetracycline derivatives intrapleurally. However, such complications have not been reported in humans when pleurodesis is attempted with tetracycline derivatives. One primary difference in the two situations is that a chest tube is placed only in humans. The objective of this study was to evaluate the hypothesis that chest tube placement would prevent the development of hemothoraces and lead to better pleurodesis in rabbits given doxycycline intrapleurally. Eighty New Zealand White male rabbits received doxycycline, 20 mg/kg, in a total volume of 2 mL. One half of the rabbits were randomized to receive a chest tube at the time of the injection and were subjected to pleural fluid aspiration twice daily. The remaining rabbits (control group) received no chest tube and no aspiration. Ten rabbits from each group were killed on days 4, 7, 14, and 28. The intrapleural injection of doxycycline induced the production of large exudative effusions. The insertion of chest tubes prevented the development of hemothorax (0/20 in chest tube group, 15/20 in control group, p<0.001). The insertion of chest tubes was also associated with a significant reduction in mortality and a significant improvement in pleurodesis. When pleurodesis is attempted in rabbits with intrapleural doxycycline, the insertion of a chest tube will prevent hemothorax and lead to a better pleurodesis.     

MR of carcinoma-specific monoclonal antibody conjugated to monocrystalline iron oxide nanoparticles: the potential for noninvasive diagnosis

PURPOSE: To determine if tumor-specific monoclonal antibodies conjugated to superparamagnetic monocrystalline iron oxide nanoparticles can be used to yield specific diagnoses with the use of MR imaging. METHODS: Monoclonal antibodies conjugated to monocrystalline iron oxide nanoparticles were given to nude rats with intracranial tumors either by intravenous injection, intraarterial injection with osmotic blood-brain barrier disruption, or direct intratumoral inoculation. Either L6, a tumor-specific antibody, or P-1.17, a control isotype-matched antibody, was used. Coronal T1-weighted, T2-weighted, and spoiled gradient-recalled acquisition in the steady state images were obtained before, 30 minutes after, 6 hours after, and 24 hours after injection. RESULTS: Intravenous injection of greater than 2 mg of the tumor-specific antibody showed a specific pattern of enhancement of the tumors with the largest concentration of antibody in the area with the greatest density of tumor cells. The control antibody showed nonspecific changes. After intraarterial injection with barrier disruption to increase delivery globally or direct inoculation to increase delivery focally, no specific enhancement pattern was seen. CONCLUSION: Monoclonal antibodies conjugated with monocrystalline iron oxide particles may provide a method to obtain specific diagnoses with the use of MR imaging.     

Nitric oxide reduces nontransferrin-bound iron transport in HepG2 cells

Nitric oxide (NO) donors S-nitroso-N-acetylpenicillamine (SNAP) and sodium nitroprusside (SNP) modulate iron regulatory protein (IRP) activity and may, therefore, affect iron uptake through transferrin receptor expression. However, iron also enters the cell as nontransferrin-bound iron (NTBI), and the aim of this study was to evaluate the effects of NO donors on NTBI transport in HepG2 cells, a model of liver physiology. Incubation with SNP and SNAP led to a time- and concentration-dependent reduction in Fe3+ and Fe2+ uptake, thus indicating an effect on the transporter rather than on the reductase. In terms of Fe2+ uptake, no variations in the Michaelis-Menten constant (Km) and a reduction in maximum uptake (Vmax) (50, 33, and 16.6 fmol/microgram protein/min in control, SNP-, and SNAP-treated cells, respectively) were detected, which suggested a decrease in the number of putative NTBI transport protein(s). Gel shift assays showed that IRP activity was reduced by SNP and slightly increased by SNAP. Northern blot analysis of transferrin receptor messenger RNA (mRNA) levels showed variations similar to those observed for IRPs, but both NO donors increased L-ferritin mRNA levels and had no effect on the stimulator of Fe transport (SFT) mRNA. In conclusion, NO donors significantly reduce NTBI transport in HepG2 cells, an effect that seems to be IRP and SFT independent. Moreover, the reduction in NTBI uptake after NO treatment suggests that this form of iron may play a minor role in the increased hepatic iron stores observed in inflammation or that other liver cells are more involved in this pathological condition.     

The interaction of hydrogen with the interface of AI2O3 particles in iron

A mathematical model to calculate the trap binding energy and trap density is suggested considering the theories of hydrogen trapping and hydrogen retrapping. When iron containing 2.0 wt pct Al₂O₃ is heated with a uniform heating rate of 3 K-min^-1, a hydrogen peak is observed at 853 K in the evolution ratevs temperature plot. This is due to hydrogen evolution from the Al₂O₃/lattice interface. The trap activation energy and trap binding energy of hydrogen at the Al₂O₃/lattice interface are estimated as 79 kJ ⋅ mol^-1 and 71.4 kJ ⋅ mol^-1, respectively, fitting experimental data to the model. This indicates that the Al₂O₃/lattice interface acts as an irreversible trapping site for hydrogen. By combining the trap binding energy and trap activation energy, the energy level of hydrogen around the Al₂O₃/lattice interface is suggested. The saddle point energy of hydrogen at Al₂O₃/lattice interface, 7.56 kJ ⋅ mol^-1 is nearly equivalent to the activation energy for hydrogen diffusion through a normal lattice, 6.9 kJ ⋅ mol^-1. Formerly Graduate Student, Korea Advanced Institute of Science and Technology.     

Kinetics of iron oxide reduction from CaO-MgO-FeOn-SiO2 slags by silicon dissolved in liquid iron

At steelmaking temperatures, the kinetics of slag-metal reactions is usually determined by mass transfer. This occurs in two ways: normal mass transfer which is induced by stirring, and mass transfer by interfacial convection induced by interfacially active elements like oxygen and sulphur. In the present work, mass transfer during the reduction of iron oxide from a basic slag by silicon dissolved in liquid iron was studied under defined conditions of gas stirring by argon in MgO crucibles with 1500 g iron and 250 g slag. The variations of the FeO content in the slag and the silicon content in the iron during the reaction were measured by sampling. Trials were carried out with stirring gas flow rates between 1 and 20.4 l/h(STP). The experimental data were evaluated with the multi-component transport model in order to determine the mass transfer coefficients of the reaction components. Simultaneously, the coefficients of normal mass transfer were calculated with the boundary layer theory of liquid-liquid mass transfer for non-turbulent flow conditions. The measured mass transfer coefficients were by a factor 2.5 larger than the theoretically calculated. The difference indicates the presence of mass transfer by interfacial convection. Mass transfer by interfacial convection is superimposed to normal mass transfer.     

MR cholangiopancreatography: technique, indications and clinical results

INTRODUCTION: MR cholangiopancreatography (MRCP) is a new noninvasive imaging technique for the study of biliopancreatic disorders, providing projectional images of the biliary tree and pancreatic duct without any contrast agent. MATERIAL AND METHODS: We used different sequences, with both breath-hold and nonbreath-hold techniques, to acquire MRCP images, first based on GE and then on FSE sequences. FSE images provide higher SNR and are less susceptible to artifacts (metal objects, motion and blood flow artifacts). At the Department of Radiology of the University of Rome La Sapienza, we acquired MRCP images with non breath-hold, 3D fat-suppressed TSE sequences (TR = 3000-2000, TE 700, turbo factor 128) optimized on a .5T magnet with 15 mT/m gradients. No patient preparation or sedation was required, although antiperistaltic drugs and oral administration of tap water were preferred. Four hundred and thirty patients were examined, all of them with an indication to conventional cholangiography. RESULTS: MRCP depicted the whole common bile duct and the first-order intrahepatic branches in all the normal cases. Its accuracy in identifying biliary obstruction level and site was 100%, versus 94.6% in characterizing its cause. MRCP had 96.3% diagnostic accuracy in choledocholithiasis, with some false positives and false negatives caused by: 1) small stones missed on MIP reconstructions; 2) signal loss due to complete CBD obstruction by stones; 3) pneumobilia; 4) differential diagnosis between small stones and air bubbles. The main role of MRCP in benign strictures is to provide a detailed map of the biliary tract for better treatment planning. In particular, MRCP is extremely useful in hepaticojejunostomy patients, where ERC is not indicated because of postoperative anatomical changes. Both conventional MRI and MRCP are important in malignant strictures to identify the lesion and to characterize and stage it. Finally, MR pancreatography is very useful to follow up chronic pancreatitis patients because it shows Wirsung duct strictures and dilatations, intraductal filling defects and, in some cases, the communication between the pseudocyst and the pancreatic duct. CONCLUSIONS: MRCP combined with conventional MRI can completely replace CT and ERCP in bilio-pancreatic disorders.     

Metallic iron whisker formation and growth during iron oxide reduction: basicity effect

Abstract

The effect of basicity on the metallic iron whisker growth during wüstite reduction was studied in the present investigation. Compacts of pure and CaO/SiO₂ doped wüstite were synthesised. The annealed compacts were isothermally reduced in thermogravimetric apparatus with CO gas at 800–1100°C. The course of reduction was followed by measuring the weight loss as a function of time. X-ray diffraction (XRD), scanning electron microscope (SEM), optical microscope and porosity measurements were used to characterise the annealed and reduced samples. The influence of temperature and basicity (CaO/SiO₂) on the reduction behaviour and the morphology of the annealed samples were investigated. The reduction rate increased with temperature but decreased by increasing basicity value. Metallic iron whisker shape structure was detected in the pure wüstite samples after reduction at high temperatures while in basic wüstite samples, whiskers were formed at the surface of the compacts. From the activation energy values, the reduction of pure wüstite is most likely controlled by a combined effect of gaseous diffusion and interfacial chemical reaction mechanisms. The reduction of basic wüstite compacts with 0·2 and 0·5 basicity ratios are most likely controlled by chemical reaction mechanism while for 0·8 basicity ratio, the reduction rate is most likely controlled by solid state reaction mechanism.     

Rate of interfacial reaction between liquid iron oxide and CO-CO2

The interfacial reaction rate between liquid iron oxide and CO-CO₂ was determined using a thermogravimetric technique. The measured rates were controlled by the chemical reactions at the gas-slag interface. The apparent first-order rate constant, for the oxidation of liquid iron oxide by CO₂, decreased sharply with the equilibrium CO₂/CO ratio. The rate of reduction of liquid iron oxide by CO showed a slight increase with the oxidation state of the melt. At 1773 K, the apparent first-order rate constants are given by k=4.0×10⁻⁵(CO₂/CO)^−0.8 and k=4.0 × 10⁻⁵(CO₂/CO)^0.18 mol cm⁻² s⁻¹ atm⁻¹ for the oxidation and reduction, respectively. The addition of basic oxides, such as BaO and CaO, resulted in an increased reaction rate, while the addition of acidic oxide, such as SiO₂, decreased the rate. The results are consistent with the dissociation or formation of the CO₂ molecule, involving the transfer of two charges, being the rate controlling mechanism of the reactions. This article is based on a presentation made in the “Geoffrey Belton Memorial Symposium,” held in January 2000, in Sydney, Australia, under the joint sponsorship of ISS and TMS.     

SiO_2-CaO-MgO-Al_2O_3熔渣中铁氧化物的分解电压

电解含有铁氧化物的熔融电解质提铁是一种钢铁冶炼短流程新工艺,该工艺可以减少甚至消除CO2排放。为测定熔渣中铁氧化物的分解电压,采用一端封闭的氧离子传导的氧化锆基固体电解质管内装熔渣,并以烧结在固体电解质管封闭端外侧表面的多孔铂金作为阳极,构建一种阴、阳极相互隔离的新型管状电解池。将该电解池的多孔铂金阳极置于恒定氧分压的气氛下,在熔渣中分别插入铱丝、铁棒作为阴极,利用线性扫描伏安法测定了1 723K下SiO2-CaO-MgO-Al2O3熔渣中FeO的分解电压,研究了熔渣碱度、阴极材料以及阳极气氛氧分压等因素对FeO分解电压的影响。结果表明,增大熔渣碱度、阴极还原合金化以及降低电解产物气体O2的分压,均可降低FeO的分解电压,有利于FeO的电解。测定结果与采用FactSage 6.1热力学软件理论计算的结果一致。证实采用氧离子传导的固体电解质管构建新型管状电解池,测定固体电解质管内熔渣中氧化物的分解电压是可行的。     

Interaction of iron particles with a solid-liquid interface in lead and lead alloys

The interaction of iron particles with an advancing solid-liquid interface has been examined in lead and lead alloys. In the case of pure lead solidified with a planar interface, the particle distribution in the solid and quenched liquid was uniform, indicating particles werenot rejected at the interface. For interfaces with a cellular and dendritic structure the particles were concentrated in the cell walls and interdendritic regions. This concentration is accounted for on the basis of the particle velocity and convective flow in the melt during the particle interface interaction. A water model was examined which simulated the metal system, using nylon spheres for particles and a lucite cellular surface for the interface. The results confirmed that particles are concentrated at intercellular regions as a result of the particle velocity and fluid flow. On leave from Universidad Nacional de Misiones, Argentina.     

Functional MR of frontal lobe activation: comparison with Wada language results

PURPOSE: Our purpose was to determine the utility of functional MR imaging in conjunction with a word-generation paradigm in the assessment of language lateralization. METHODS: Functional MR imaging and Wada testing for language lateralization was performed in patients with complex partial seizures during the performance of word-generation tasks. A language lateralization quotient was calculated from the number of activated pixels in the right and left hemispheres. A language laterality score was derived from the Wada results as the percentage of correct responses during right internal carotid artery injection minus the percentage of correct responses during left internal carotid injection. A correlation coefficient between the functional MR imaging results and the Wada language laterality scores was calculated. RESULTS: In 13 patients, hemispheric dominance based on Wada testing was confirmed by functional MR imaging during silent word generation. The Wada laterality scores varied from 100 to -100 and the functional MR imaging scores varied from 100 to -10. The language lateralization scores determined by functional MR imaging correlated significantly with the language lateralization scores derived from Wada testing. CONCLUSION: Functional MR imaging performed during word generation is an accurate method for lateralizing language function in patients with complex partial epilepsy.     

Bithalamic hyperintensity on T2-weighted MR: vascular causes and evaluation with MR angiography

PURPOSE: To determine whether MR angiography can be used to differentiate between the two vascular causes of bithalamic hyperintensity on T2-weighted MR images: "top of the basilar" artery occlusion and deep cerebral vein thrombosis. METHODS: A retrospective review identified six patients with bithalamic T2 hyperintensity of vascular causes. MR angiography was performed in four patients, MR angiography and conventional angiography in one patient, and conventional angiography in one patient. Data pertaining to clinical presentation and hospital course were collected. MR angiographic techniques were multislab overlapping three-dimensional time-of-flight, 2-D time-of-flight, and 2-D phase-contrast. RESULTS: Three cases of top of the basilar artery occlusion and three cases of deep cerebral vein thrombosis were recognized. In all cases, T2 hyperintensity in a vascular distribution suggested cerebral occlusive disease. Infarction involving the thalami and basal ganglia was present in two cases of deep cerebral vein thrombosis. Infarction of the thalami, mesodiencephalic region, and cerebellar hemispheres was present in two cases of basilar artery occlusion. Bithalamic infarction alone was seen in one case of deep cerebral vein thrombosis and one case of basilar artery occlusion. In the five cases in which MR angiography was used, this technique accurately distinguished the vessels involved (arterial or venous). CONCLUSION: MR angiography is a useful adjunct to MR imaging in the evaluation of bithalamic T2 hyperintensity. It does help distinguish between the two vascular causes: top of basilar artery occlusion and deep cerebral vein thrombosis.