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PubMed1999

Magnetic resonance imaging of ischemic heart disease: why cardiac magnetic resonance imaging will play a significant role in the management of patients with coronary artery disease.

The role of magnetic resonance imaging in the diagnosis of ischemic heart disease has great potential impact on patient management, because a number of aspects of ischemic heart disease can be evaluated in one imaging session. High resolution coronary magnetic resonance angiography is currently available, although several technical improvements are awaited to make the technique routinely applicable. A major advance will probably include the availability of magnetic resonance blood pool contrast agents to improve vessel visualization. Contrast media, in combination with either first pass or delayed myocardial scanning, will also play an important role in myocardial perfusion imaging. Functional magnetic resonance assessment of regional and global ventricular function is currently a well-established technique and is considered a new gold standard, which may impact on routine cardiology practice. This review summarizes some of the recent magnetic resonance developments for evaluating various aspects of ischemic heart disease, including magnetic resonance coronary angiography, flow imaging, and imaging of myocardial perfusion and function.

Blood Flow Velocity↗
PubMed2005

Optimal arrangement of magnetic coils for functional magnetic stimulation of the inspiratory muscles in dogs.

In an attempt to maximize inspiratory pressure and volume, the optimal position of a single or of dual magnetic coils during functional magnetic stimulation (FMS) of the inspiratory muscles was evaluated in twenty-three dogs. Unilateral phrenic magnetic stimulation (UPMS) or bilateral phrenic magnetic stimulation (BPMS), posterior cervical magnetic stimulation (PCMS), anterior cervical magnetic stimulation (ACMS) as well as a combination of PCMS and ACMS were performed. Trans-diaphragmatic pressure (Pdi), flow, and lung volume changes with an open airway were measured. Transdiaphragmatic pressure was also measured with an occluded airway. Changes in inspiratory parameters during FMS were compared with 1) electrical stimulation of surgically exposed bilateral phrenic nerves (BPES) and 2) ventral root electrical stimulation at C5-C7 (VRES C5-C7). Relative to the Pdi generated by BPES of 36.3 +/- 4.5 cm H2O (Mean +/- SEM), occluded Pdi(s) produced by UPMS, BPMS, PCMS, ACMS, and a combined PCMS + ACMS were 51.7%, 61.5%, 22.4%, 100.3%, and 104.5% of the maximal Pdi, respectively. Pdi(s) produced by UPMS, BPMS, PCMS, ACMS, and combined ACMS + PCMS were 38.0%, 45.2%, 16.5%, 73.8%, and 76.8%, respectively, of the Pdi induced by VRES (C5-C7) (48.0 +/- 3.9 cm H2O). The maximal Pdi(s) generated during ACMS and combined PCMS + ACMS were higher than the maximal Pdi(s) generated during UPMS, BPMS, or PCMS (p < 0.05). ACMS alone induced 129.8% of the inspiratory flow (73.0 +/- 9.4 L/ min) and 77.5% of the volume (626 +/- 556 ml) induced by BPES. ACMS and combined PCMS + ACMS produce a greater inspiratory pressure than UPMS, BPMS or PCMS. ACMS can be used to generate sufficient inspiratory pressure, flow, and volume for activation of the inspiratory muscles.

Animals↗
PubMedDate not supplied

Quantification of magnetic nanoparticles by magnetorelaxometry and comparison to histology after magnetic drug targeting.

Magnetic nanoparticles can be used in medicine in vivo as contrast agents and as a drug carrier system for chemotherapeutics. Thus local cancer therapy is performed with Magnetic Drug Targeting (MDT) and allows a specific delivery of therapeutic agents to desired targets, i.e., tumors, by using a chemotherapeutic substance bound to magnetic nanoparticles and focused with an external magnetic field to the tumor after intraarterial application. Important for this therapeutic principle is the distribution of the particles in the whole organism and especially in the tumor. Therefore we used magnetorelaxometry to quantify ferrofluids delivered after MDT. Tissue samples of some mm3 volume of a VX2 squamous cell carcinoma were measured by magnetic relaxation and the amount of iron was determined using the original ferrofluid suspension as a reference. From this the distribution of the magnetic particles within the slice of tumor was reconstructed. Histological cross-sections of the respective tumor offer the opportunity to map quantitatively the particle distribution and the vascularisation in the targeted tumor on a microscopic scale. Our data show that the integral method magnetorelaxometry and microscopic histological methods can complete each other efficiently.

Animals↗
PubMedDate not supplied

Diagnostic accuracy of clinical assessment, magnetic resonance imaging, magnetic resonance arthrography, and intra-articular injection in hip arthroscopy patients.

BACKGROUND: Hip arthroscopy has defined elusive causes of hip pain. HYPOTHESIS/PURPOSE: It is postulated that the reliability of various investigative methods is inconsistent. The purpose of this study is to evaluate the diagnostic accuracy of these methods. STUDY DESIGN: Retrospective review of prospectively collected data. METHODS: Five parameters were assessed in 40 patients: clinical assessment, high-resolution magnetic resonance imaging, magnetic resonance imaging with gadolinium arthrography, intra-articular bupivacaine injection, and arthroscopy. Using arthroscopy as the definitive diagnosis, the other parameters were evaluated for reliability. RESULTS: Hip abnormality was clinically suspected in all cases with 98% accuracy (1 false positive). However, the nature of the abnormality was identified in only 13 cases with 92% accuracy. Magnetic resonance imaging variously demonstrated direct or indirect evidence of abnormality but overall demonstrated a 42% false-negative and a 10% false-positive interpretation. Magnetic resonance arthrography demonstrated an 8% false-negative and 20% false-positive interpretation. Response to the intra-articular injection of anesthetic was 90% accurate (3 false-negative and 1 false-positive responses) for detecting the presence of intra-articular abnormality. CONCLUSIONS: In this series, clinical assessment accurately determined the existence of intra-articular abnormality but was poor at defining its nature. Magnetic resonance arthrography was much more sensitive than magnetic resonance imaging at detecting various lesions but had twice as many false-positive interpretations. Response to an intra-articular injection of anesthetic was a 90% reliable indicator of intra-articular abnormality.

Arthrography↗
PubMed1992

Children with cerebral venous thrombosis diagnosed with magnetic resonance imaging and magnetic resonance angiography.

From 1985 to 1991, 13 children were diagnosed at the University of Illinois College of Medicine at Peoria, Saint Francis Medical Center, with cerebral venous thrombosis (CVT) by magnetic resonance imaging scan. Ages ranged from newborn to 5 years. Six children were premature neonates, five were term neonates and two were 5 years old. In the premature neonates, thrombosis was usually associated with other problems. All the term neonates had seizures. In all neonates, thrombosis resolved without any specific treatment. In the two older children, one presented with pseudotumor cerebri and one with coma. These children required neurosurgical intervention. Follow-up magnetic resonance imaging scans were obtained in 9 of 13 children and showed thrombus resolution in each case. Three children were studied in the acute and convalescent stages by magnetic resonance angiography using time-of-flight techniques. Each follow-up magnetic resonance angiogram showed improvement in venous flow consistent with their clinical course and other imaging studies. We conclude that 1) CVT in children encompasses a range of clinical conditions which may or may not require neurosurgical intervention; 2) magnetic resonance imaging is superior to other modalities for the diagnosis of CVT; and 3) magnetic resonance angiography is an alternative means to monitor the evolution of CVT and efficacy of therapeutic intervention.

Cerebral Angiography↗
PubMed1996

Effects of magnetic flux density and direction of the magnetic field on growth and CO2 exchange rate of potato plantlets in vitro.

Potato plantlets (Solanum tuberosum L. cv. Benimaru) were cultured in vitro for 20 days on a 10 ml MS agar medium under a magnetic flux density of 0 (control: Cont), 2, 4 or 6 mT (T=Wb m-2) in both upward and downward directions of magnetic field. Air temperature in the head space of the test tubes and photosynthetic flux density on the culture shelf were 25 +/- 1 degrees C and 38 micromoles m-2 s-1 respectively. The results showed that a magnetic flux density of around 4 mT had beneficial effects, regardless of the direction of magnetic field, on the growth promotion and enhancement of CO2 uptake of potato plantlets in vitro The direction of magnetic field at the magnetic flux densities tested had no effects on the growth and CO2 exchange rate.

Biomass↗
PubMed2005

Effect of magnetic vs sham-magnetic insoles on nonspecific foot pain in the workplace: a randomized, double-blind, placebo-controlled trial.

OBJECTIVE: To determine whether magnetic insoles are effective for relieving nonspecific subjective foot pain in the workplace, resulting in improved job satisfaction. SUBJECTS AND METHODS: A prospective, randomized, double-blind, placebo-controlled study of health care employees who experienced nonspecific foot pain for at least 30 days, which occurred more days than not, was conducted between February 2001 and January 2002 at the Mayo Clinic in Rochester, Minn. Participants were asked to wear either magnetic or sham-magnetic cushioned insoles for at least 4 hours daily, 4 days per week for 8 weeks. The primary outcome variable was reported foot pain (by categorical response of change from baseline and by visual analog scale) at 4 and 8 weeks. Secondary outcome variables included graded intensity of pain experienced during various daily activities and the effect of insoles on job performance and enjoyment. RESULTS: Among 89 enrolled participants, 6 either withdrew before wearing insoles or were noncompliant with follow-up questionnaires; 83 participants remained for full statistical analysis. Participants in both treatment groups reported improvements in foot pain during the study period. No significant differences in categorical response to pain or pain intensity were seen with use of magnetic vs sham-magnetic insoles. CONCLUSIONS: The magnetic insoles used in this study by a heterogeneous population with chronic nonspecific foot pain were not clinically effective. Findings confirmed that nonspecific foot pain significantly interferes with some employees' ability to enjoy their jobs and that treatment of that pain improves job satisfaction.

Adult↗
PubMed1999

[Biologic effects of the static magnetic field generated by a 0.5 T magnetic resonance tomograph on the enzyme activity of catalase and creatine kinase in the rat].

PURPOSE: We investigated possible alterations in the enzyme activity of catalase and isozyme MB-creatine kinase induced by prolonged exposure of laboratory rodents to a static magnetic field generated by a .5 T Magnetic Resonance unit. MATERIAL AND METHODS: Thirty Wistar albino mice were divided into two groups of 15 mice, one to be exposed to the static magnetic field for 12 hours and the other to be kept in the same environmental conditions as a control group. Immediately after the exposure a peripheral venous blood sample was collected, the cardiac muscle was removed from the mice and the enzyme activity of catalase and MB-creatine kinase were assayed using the spectrophotometric analysis. RESULTS: No statistically significant variation was detected between the enzyme activity of catalase and MB-creatine kinase in the serum and cardiac muscle of the exposed versus the control mice. In the mice exposed to the static magnetic field the enzyme activity of serum and cardiac muscle catalase were respectively .2154 U/L and .0707 U/L after 10 minutes; they were; .2699 U/L and .0946 U/L after 160 minutes. In the control mice the enzyme activity of serum and cardiac muscle catalase were respectively .1941 U/L and .0707 U/L after 10 minutes; they were .2061 U/L and .1068 U/L after 160 minutes. The enzyme activity of MB-creatine kinase in mice was measured in the exposed (80.8 U/L) versus the control (79.6 U/L) group: the difference does not exceed standard deviation. DISCUSSION AND CONCLUSION: Our results seem to exclude any alteration in the activity of catalase and MB-CK after 12 hours' exposure to the static magnetic field. However some homeostatic mechanisms peculiar to pluricellular organisms might act in vivo to adapt to the effects of the static magnetic field during exposure.

Animals↗
PubMed1997

[Comparison between magnetic resonance imaging and CT in detection and localization of non-magnetic intraocular foreign bodies].

OBJECTIVE: To approach the characteristics of magnetic resonance imaging (MRI) and CT in detection and localization of intraocular foreign bodies. METHODS: Detection and localization of 28 cases (42 foreign bodies) of non-magnetic intraocular foreign body were compared in MRI and CT with criteria of operative results. RESULTS: The positive rates of MRI and CT in detection of 42 non-magnetic intraocular foreign bodies were respectively 90.5% and 95.2% (chi 2 test: P > 0.5). The positive rates of MRI and CT in localization were respectively 89.5% and 60.0% (chi 2 test: P < 0.05). CONCLUSION: MRI could be used in detection and localization of non-magnetic intraocular foreign bodies with high positive rates in detection and superior to CT in demonstrating non-magnetic intraocular foreign bodies with low density and the relationship between foreign bodies and intraocular tissues. MRI was not as believable as CT in detection of foreign bodies in eye wall and not an appropriate modality in examinations of magnetic intraocular foreign body.

Eye Foreign Bodies↗
PubMedDate not supplied

[Magnetic resonance spectroscopy and functional magnetic resonance images: non-invasive alternatives for identifying epileptogenic foci].

Magnetic resonance spectroscopy and functional magnetic resonance images are new non-invasive techniques which have the potential for localization of the epileptogenic focus in patients with refractory focal epilepsy, who are candidates for surgery. Determination of patterns of asymmetry of the N-acetyl-aspartic acid (NAA) between homologous regions of the temporal lobes, using magnetic resonance spectroscopy contributes to preoperative lateralization in patients with temporal lobe epilepsy. This technique may become a method for localization if its usefulness in the differentiation of mesial temporal lobe epilepsy from neocortical epilepsy is validated. Functional magnetic resonance images triggered by epileptiform discharges on the EEG, when combined with methods for localizing the source, permit the site of the epileptogenic focus to be found. This would particularly benefit patients with non-lesional extra-temporal epilepsy who are potential candidates for invasive recordings. The use of magnetic resonance spectroscopy and functional magnetic resonance images in the preoperative evaluation of patients with refractory focal epilepsy, especially if it is used together with the relevant clinical data and that from other structural and functional imaging techniques, will reduce invasive monitoring and increase the accessibility to surgical treatment for this condition.

Animals↗
PubMed2001

[The cytotoxic effects of the adriamycin magnetic albumin microspheres combined with external magnetic fields on the malignant tumor cells].

This study sought to assess the inhibitory effects of the adriamycin magnetic albumin microspheres (ADM-MAMs) on Walker-256 malignant tumor cells in vitro induced by the permanent magnetic fields. The cultured Walker-256 cells were divided into three groups; the group of ADM-MAMs combined with magnetic fields, the group of AMD-MAMs without magnetic fields, and ADM group. The growth states of the cells were observed and photographed under the inverted microscope. The inhibitory rates(IR) were assayed by the modified MTT colorimetric method. The results showed that the IR of the ADM-MAMs group were similar to those of the ADM group (P > 0.05), but the group of ADM-MAMs combined with magnetic fields had obviously higher IR and significant changes of the cells' shapes. These findings indicate that the anticancer effect of ADM-MAMs on malignant tumor cells is similar to that of ADM, and such effect can be increased by the combined use of ADM-MAMs and external magnetic fields.

Albumins↗
PubMed1996

Magnetization transfer magnetic resonance imaging: a clinical review.

Magnetic resonance imaging has traditionally used the T1 and T2 relaxation times and proton density (PD) of tissue water (hydrogen protons) to manipulate contrast. Magnetization transfer (MT) is a new form of tissue contrast based on the physical concept that tissues contain two or more separate populations of hydrogen protons: a highly mobile (free) hydrogen (water) pool, Hr, and an immobile (restricted) hydrogen pool, Hr, the latter being those protons bound to large macromolecular proteins and lipids, such as those found in such cellular membranes as myelin. Direct observation of the Hr magnetization pool is normally not possible because of its extremely short T2 time (< 200 microseconds). But saturation of the restricted pool will have a detectable effect on the mobile (free) proton pool. Saturation of the restricted pool decreases the signal of the free pool by transferring the restricted pool's saturation. Exchange of magnetization between the free and restricted hydrogen protons is a substantial mechanism for spin-lattice (T1) relaxation in tissues and the physical basis of MT. Through an appropriately designed pulse sequence, magnetization transfer contrast (MTC) can be produced. MT contrast is different from T1, T2, and PD, and it likely reflects the structural integrity of the tissue being imaged. A variety of clinically important uses of MT have emerged. In this clinical review of the neuroradiological applications of MT, we briefly review the physics of MT, the appearance of normal brain with MT, and the use of MT as a method of contrast enhancement/background suppression and in tissue characterization, such as evaluation of multiple sclerosis and other white-matter lesions and tumors. The role of MT in small-vessel visualization on three-dimensional time-of-flight magnetic resonance angiography and in head and neck disease and newer applications of MT are also elaborated.

Brain↗
PubMed1995

[Extraction of intraocular magnetic foreign body using intraocular earth magnet].

PURPOSE: To determine the effects of extraction of intraocular magnetic foreign body with intraocular earth magnet (IOEM). METHOD: From 1992 to 1994, 22 cases with intraocular foreign body were treated with self-made intraocular earth magnet (IOEM): 2 patients with foreign body remained on lens, 7 on posterior segment of global wall, 12 lodged in the post pole of retina and 1 on the surface of optic disk. These patients were operated under microscope. The foreign bodies on the posterior segment were removed by using IOEM combined with pars plana vitrectomy. RESULT: The foreign bodies of these 22 patients were successfully removed with one operation respectively. The minimum volume of the foreign bodies was 0.5 x 0.5 x 0.5 mm3. The maximum volume of the foreign bodies was 5 x 2 x 1.5 mm3. The average maximum diameter of the foreign bodies was 2.47 +/- 1.2 mm. CONCLUSION: Intraocular earth magnet (IOEM) is a permanent magnetic instrument with moderate magnetic power. Direct observation and detachment of the foreign body with ocular tissue are necessary during the remowal of the forreign body. This instrument is suitable for intraocular microsurgery, can be handled easily, used for extraction of foreign bodies in anterior chamber, on turbid lens and in vitreous body, in removing foreign bodies in vitreous chamber with obvious injured retina and on posterior segment, the surface of retina, and can also be applied toextract foreign bodies on optic disk as well asforeign bodies partly oldged on global wall.

Adolescent↗
PubMed2005

Comparison of magnetic properties of MRI contrast media solutions at different magnetic field strengths.

RATIONALE AND OBJECTIVES: To characterize and compare commercially available contrast media (CM) for magnetic resonance imaging (MRI) in terms of their relaxivity at magnetic field strengths ranging from 0.47 T to 4.7 T at physiological temperatures in water and in plasma. Relaxivities also were quantified in whole blood at 1.5 T. METHODS: Relaxivities of MRI-CM were determined by nuclear magnetic resonance (NMR) spectroscopy at 0.47 T and MRI phantom measurements at 1.5 T, 3 T, and 4.7 T, respectively. Both longitudinal (T1) and transverse relaxation times (T2) were measured by appropriate spin-echo sequences. Nuclear magnetic resonance dispersion (NMRD) profiles were also determined for all agents in water and in plasma. RESULTS: Significant dependencies of relaxivities on the field strength and solvents were quantified. Protein binding leads to both increased field strength and solvent dependencies and hence to significantly altered T1 relaxivity values at higher magnetic field strengths. CONCLUSIONS: Awareness of the field strength and solvent associated with relaxivity data is crucial for the comparison and evaluation of relaxivity values. Data observed at 0.47 T can thus be misleading and should be replaced by relaxivities measured at 1.5 T and at 3 T in plasma at physiological temperature.

Contrast Media↗
PubMed2001

Synthesis, structure, and magnetic properties of three new one-dimensional nickel(II) complexes: new magnetic model for the first one-dimensional S = 1 complex with alternating ferro-ferromagnetic coupling.

Three new one-dimensional nickel(II) complexes with the formulas trans-[Ni(N-Eten)2(mu1.3-N3)]n(ClO4)n (1), trans-[Ni(N-Eten)2(mu1.3-N3)]n(PF6)n (2), and cis-[Ni(N-Eten)(mu1.1-N3)2]n (3) (N-Eten = N-Ethylethylenediamine) were synthesized and characterized. Complex 1 has the P2(1)/c space group and consists of a structurally and magnetically alternating one-dimensional antiferromagnetic system with end-to-end azido bridges. Compound 2 has the P1 space group and has alternate units in its structure but consists of a magnetically uniform one-dimensional antiferromagnetic system with end-to-end azido bridges. Complex 3 has the I2/a space group and may be described as a structurally and magnetically alternating one-dimensional ferromagnetic system with double azido bridged ligands in an end-on coordination mode. The chi(M)T versus T plots for compound 3 suggest an intramolecular ferromagnetic interaction between adjacent NiII ions and metamagnetism at low temperature (below 10 K). The magnetization measurements versus applied field confirm this metamagnetic ordering. In order to describe the magnetic data of this compound we developed a general formula for the magnetic susceptibility of the isotropic ferro-ferromagnetic S = 1 Heisenberg chain in terms of the alternation parameter alpha (= J2/J1); this assumed a variation of chi(M)T versus the length N.

Journal Article↗
PubMed2006

Chiral molecular magnets: synthesis, structure, and magnetic behavior of the series [M(L-tart)] (M = Mn(II), Fe(II), Co(II), Ni(II); L-tart = (2R,3R)-(+)-tartrate).

A new series of layered magnets with the formula [M(L-tartrate)] (M = Mn(II), Co(II), Fe(II), Ni(II); L-tartrate = (2R,3R)-(+)-tartrate) has been prepared. All of these compounds are isostructural and crystallize in the chiral orthorhombic space group I222, as found by X-ray structure analysis. Their structure consists of a three-dimensional polymeric network in which each metal shows distorted octahedral coordination bound to four L-tartrate ligands, two of which chelate through an alcohol and a carboxylate group and the other two bind terminally through a monodentate carboxylate group. The chirality of the ligand imposes a Delta conformation on all metal centers. Magnetically, the paramagnetic metal centers form pseudotetragonal layers in which each metal is surrounded by four other metals, with syn,anti carboxylate bridges. These salts show intralayer antiferromagnetic or ferromagnetic interactions, depending on the electronic configuration of the metal, and weak interlayer antiferromagnetic interaction. In all cases the magnetic properties are strongly affected by the anisotropy of the system, and the presence of magnetic canting has been found. The Mn derivative behaves as a weak ferromagnet with a critical temperature of 3.3 K. The Ni derivative shows very unusual magnetic behavior in that it exhibits antiferromagnetic ordering below 6 K, the onset of spontaneous magnetization arising from spin reorientation into a canted phase below 4.5 K, and a field-induced ferromagnetic state above 0.3 T at 2 K, behavior typical of metamagnets. The Fe and Co derivatives show antiferromagnetic interactions between spin carriers, but do not order above 2 K.

Journal Article↗