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PubMed2004

A blood-oxygenation-dependent increase in blood viscosity due to a static magnetic field.

As the magnetic field of widely used MR scanners is one of the strongest magnetic fields to which people are exposed, the biological influence of the static magnetic field of MR scanners is of great concern. One magnetic interaction in biological subjects is the magnetic torque on the magnetic moment induced by biomagnetic substances. The red blood cell is a major biomagnetic substance, and the blood flow may be influenced by the magnetic field. However, the underlying mechanisms have been poorly understood. To examine the mechanisms of the magnetic influence on blood viscosity, we measured the time for blood to fall through a glass capillary inside and outside a 1.5 T MR scanner. Our in vitro results showed that the blood viscosity significantly increased in a 1.5 T MR scanner, and also clarified the mechanism of the interaction between red blood cells and the external magnetic field. Notably, the blood viscosity increased depending on blood oxygenation and the shear rate of the blood flow. Thus, our findings suggest that even a 1.5 T magnetic field may modulate blood flow.

Adult↗
PubMed1994

Magnetization transfer: a potential method to determine the age of multiple sclerosis lesions.

PURPOSE: To determine whether magnetization transfer contrast can differentiate acute from chronic lesions in multiple sclerosis. METHODS: Thirteen patients with multiple sclerosis and eight healthy patients were studied with MR using a 0.1-T system. Relatively T2-weighted spin-echo images were obtained without and with magnetization transfer contrast. The magnetization transfer effect of multiple sclerosis lesions was calculated and compared with the ages of the lesions. The magnetization transfer effect of normal-appearing white matter in patients with multiple sclerosis was calculated and compared with the magnetization transfer effect of white matter in healthy volunteers. Statistical analysis was performed. RESULTS: White matter in the healthy volunteers had values from 0.40 to 0.45. Normal-appearing white matter in the patients with multiple sclerosis had magnetization transfer effect values ranging from 0.41 to 0.45. Multiple sclerosis plaques of less than 1 year's duration had magnetization transfer effect values ranging from 0.05 to 0.26; older plaques had values from 0.25 to 0.41. The difference in the distributions of these values for acute and chronic multiple sclerosis plaques is statistically significant. CONCLUSION: Current imaging modalities do not differentiate acute multiple sclerosis lesions from chronic ones. Our data on magnetization transfer show a statistically significant difference in magnetization transfer effect values between lesions of less than 1 year's duration and older lesions. The different values may correspond to the histologic changes of multiple sclerosis plaques over time. Magnetization transfer may be a reliable method for determining the age of multiple sclerosis lesions.

Acute Disease↗
PubMed2002

Magnetic anisotropy of the radula of chiton Acanthochiton rubrolinestus LISCHKE.

The magnetic anisotropy of the whole radula, the major lateral radula teeth, and magnetic material in the major lateral radula teeth of the chiton Acanthochiton rubrolinestus LISCHKE have been studied by a magnetic torque meter and superconducting quantum interference device (SQUID) magnetometer. The length and width axes of the teeth are the easily magnetized axes, while the thickness axis is difficult to magnetize. The width and thickness axes of the radula are the easily magnetized axes, and the length axis is difficult to magnetize. The measurement results of the whole radula and the major lateral radula teeth agree well with each other. The magnetic anisotropy of the magnetic material is given as well as a possible distribution of the magnetic material in the major lateral radula teeth.

Animals↗
PubMed1999

Asymmetric MRI magnet design using a hybrid numerical method.

This paper describes a hybrid numerical method for the design of asymmetric magnetic resonance imaging magnet systems. The problem is formulated as a field synthesis and the desired current density on the surface of a cylinder is first calculated by solving a Fredholm equation of the first kind. Nonlinear optimization methods are then invoked to fit practical magnet coils to the desired current density. The field calculations are performed using a semi-analytical method. A new type of asymmetric magnet is proposed in this work. The asymmetric MRI magnet allows the diameter spherical imaging volume to be positioned close to one end of the magnet. The main advantages of making the magnet asymmetric include the potential to reduce the perception of claustrophobia for the patient, better access to the patient by attending physicians, and the potential for reduced peripheral nerve stimulation due to the gradient coil configuration. The results highlight that the method can be used to obtain an asymmetric MRI magnet structure and a very homogeneous magnetic field over the central imaging volume in clinical systems of approximately 1.2 m in length. Unshielded designs are the focus of this work. This method is flexible and may be applied to magnets of other geometries.

Algorithms↗
PubMed1993

Wavelength-dependent effects of light on magnetic compass orientation in Drosophila melanogaster.

1. Wildtype Oregon-R Drosophila melanogaster were trained in the ambient magnetic field to a horizontal gradient of 365 nm light emanating from one of the 4 cardinal compass directions and were subsequently tested in a visually-symmetrical, radial 8-arm maze in which the magnetic field alignment could be varied. When tested under 365 nm light, flies exhibited consistent magnetic compass orientation in the direction from which light had emanated in training. 2. When the data were analyzed by sex, males exhibited a strong and consistent magnetic compass response while females were randomly oriented with respect to the magnetic field. 3. When tested under 500 nm light of the same quantal flux, females were again randomly oriented with respect to the magnetic field, while males exhibited a 90 degree clockwise shift in magnetic compass orientation relative to the trained direction. 4. This wavelength-dependent shift in the direction of magnetic compass orientation suggests that Drosophila may utilize a light-dependent magnetic compass similar to that demonstrated previously in an amphibian. However, the data do not exclude the alternative hypothesis that a change in the wavelength of light has a non-specific effect on the flies' behavior, i.e., causing the flies to exhibit a different form of magnetic orientation behavior.

Animals↗
PubMed2001

A comparison between dynamic pelvic magnetic resonance imaging and videoproctography in patients with constipation.

PURPOSE: This study attempts to compare the diagnostic efficacy of dynamic pelvic magnetic resonance imaging with that of videoproctography for the presence of rectocele, sigmoidocele, and intussusception as well as the measurement of anorectal angle and perineal descent in constipated patients. METHODS: Patients volunteering for the study and fulfilling the criteria for videoproctography to evaluate constipation were also scheduled for dynamic pelvic magnetic resonance imaging. Patients undergoing videoproctography were placed in the left lateral decubitus position, after which 50 ml of liquid barium paste was introduced into the rectum. After this, approximately 100 ml of thick barium paste similar to stool in consistency was injected into the rectum, and the patient was instructed to defecate while video images were taken. For dynamic pelvic magnetic resonance imaging, air, to be used as contrast, was allowed to accumulate in the rectum via examination with the patient in the prone position. A capsule was taped to the perineal skin immediately posterior to the anal orifice for marking. Sagittal and axial T1 images were obtained through the pelvis at 8-mm intervals with dynamic breathhold sagittal images of the anorectal region obtained at rest and during strain and squeeze maneuvers. Total acquisition time per maneuver was approximately 19 seconds. The tests were performed by different examiners blinded to the result of the other evaluation. The investigations were independently interpreted, findings compared, and patients questioned regarding their impression of dynamic pelvic magnetic resonance imaging and videoproctography. RESULTS: From June 1996 to April 1997, 22 patients (15 females) with a mean age of 68 (range, 21-85) years underwent both videoproctography and dynamic pelvic magnetic resonance imaging. Dynamic pelvic magnetic resonance imaging was only able to detect 1 of 12 (8.3 percent) anterior rectoceles and one of two (50 percent) posterior rectoceles identified by videoproctography. It failed to recognize any of the rectoanal intussusception (zero of four) but did show 9 of 12 (75 percent) sigmoidoceles. Significant discrepancy of measurement of the anorectal angle and perineal descent exists between the two studies, and dynamic pelvic magnetic resonance imaging was not able to detect any (0 of 11) of the patients with increased fixed perineal descent and only half (one of two) of the patients with increased dynamic perineal descent noted on videoproctography. All 22 patients preferred dynamic pelvic magnetic resonance imaging over videoproctography because of greater comfort. CONCLUSION: Occasionally, the increased cost of new technology can be justified by the enhanced diagnostic yield. The ability to avoid unnecessary surgery or, conversely, to continue to search for otherwise occult pathology that can be surgically corrected justifies routine application of these new tools. However, this study has shown that, despite a cost of approximately ten times more for dynamic pelvic magnetic resonance imaging than for videoproctography, no clinical changes were made. Thus, on the basis of this study, we cannot endorse the routine application of dynamic pelvic magnetic resonance imaging for the evaluation of constipated patients. In certain selected individuals, it may play a role, but further study is necessary to clarify its exact role.

Adult↗
PubMed1992

[The effect of static magnetic fields on osteoblast activity: an in-vitro study].

The aim of the present study was to investigate whether the influence of static magnetic fields can be demonstrated in an osteoblast cell culture. For this in-vitro study we used osteoblasts originating from the embryonal calvariae of rats. The total material (n = 41) was divided in four groups: a) cell cultures submitted to the fields of attracting magnets (n = 11), b) cell cultures in the fields of repelling magnets (n = 10), c) cell cultures under the influence of demagnetized magnets (sham group, n = 11), d) control cultures (n = 9). The cell cultures were subjected for 21 days to magnetic fields (intensity 178 ml) using Neodynium magnets. Osteoblast activity was histo-chemically determined by staining the alkaline phosphatase produced. The quantitative evaluation was performed by measuring the optical density of the cell cultures and the results were statistically analysed. The results of these in-vitro study are: 1. The optical density of the cell cultures was nearly the same in samples with or without the influence of magnetic fields. 2. No divergent reaction could be found between the application of homogeneous and heterogeneous magnetic fields. 3. The different orientation of homogeneous magnetic fields in vertical or horizontal direction did not effect the osteoblast cell culture. 4. The cellular distribution in the osteoblast cultures does not follow the orientation of the magnetic field lines. 5. The form of the osteoblasts was nearly the same among all four groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Sinusoidal 50-Hz magnetic fields depress rat pineal NAT activity and serum melatonin. Role of duration and intensity of exposure.

The purpose of this study was to determine whether the exposure to a 50-Hz sinusoidal magnetic field could influence serum melatonin concentration and pineal enzymes activities in rats. The effects of both duration and intensity of exposure were also looked at. Two groups of Wistar male rats were exposed to 50-Hz magnetic fields of either 1, 10 or 100 microT. The first group was exposed for 12 hours and the second for 30 days (18 hours per day). During this time the animals were kept under a standard 12:12 light: dark cycle with a temperature of 25 degrees C and a relative humidity of 45 to 50%. Control (Sham-exposed) animals were kept in a similar environment but without exposure to a magnetic field. The animals were sacrificed under red dim light. Serum melatonin concentration and pineal N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT) activities were studied. Long-term exposure to a magnetic field (10 and 100 microT) significantly depressed the nocturne peak of serum melatonin concentration and pineal NAT activity whereas no effect was observed on HIOMT activity. Short-term exposure depressed both pineal NAT activity and nocturnal serum melatonin concentration but only with the highest intensity used (100 microT). Our results suggest that sinusoidal magnetic fields alter the production of melatonin through an inhibition of pineal NAT activity. Both duration and intensity of exposure play an important role in this effect. This work shows that, 1) sinusoidal magnetic field depresses NAT activity as static magnetic field does whereas HIOMT activity remains unaltered whatever the type of experiment and the intensity used, 2) the effect observed is related to both the duration of exposure and the intensity of magnetic fields, 3) the sensitivity threshold to magnetic fields vary with the duration of exposure which strongly suggests a cumulative effect of sinusoidal magnetic fields on pineal function.

Acetylserotonin O-Methyltransferase↗
PubMed2004

Strong static magnetic field effects on yeast proliferation and distribution.

The present study focuses on the effects of gradient magnetic fields on the behavior of yeast, such as its proliferation and mass distribution, and evaluates the effects of magnetism on materials in the yeast culture system. Yeast, Saccharomyces cerevisiae, was incubated in a liquid medium under magnetic fields (flux density B = 14 T). When yeast in a tube was exposed to 9-14 T magnetic fields with a maximum flux density gradient of dB/dx = 94 T/m, where x is the space coordinate, the rate of yeast proliferation under the magnetic fields decreased after 16 h of incubation compared to that of the control group. The physical properties of the yeast culture system were investigated to discover the mechanism responsible for the observed deceleration in yeast proliferation under magnetic fields. Gas pressure inside the yeast culture flask was compared with and without exposure to a magnetic field. The results suggested that the gas pressure inside a flask with 6 T, 60 T/m slowly increased in comparison to the pressure inside a control tube. Due to the diamagnetism of water (medium solution) and yeast, the liquid surface distinctly inclined under gradient magnetic fields, and the hydrostatic force in suspension was strengthened by the diamagnetic forces. In addition, magnetophoresis of the yeast cells in the medium solution exhibited localization of the yeast sedimentation pattern. The roles of magnetically changed gas-transport processes, hydrostatic pressures acting on the yeast, and changes in the distribution of the yeast sedimentation, as well as the possible effects of magnetic fields on yeast respiratory systems in the observed disturbance of the proliferation are discussed.

Cell Proliferation↗
PubMed2005

Central nervous system findings by magnetic resonance in children with profound sensorineural hearing loss.

INTRODUCTION: High-resolution magnetic resonance studies are an important tool in the investigation of the etiology of childhood sensorineural hearing loss. An added benefit with magnetic resonance is the ability to screen the central nervous system for findings which may adversely affect the neurodevelopmental outcome of these children. OBJECTIVE: To determine the proportion of cases and significance of associated intracranial abnormalities as detected by central nervous system high-resolution magnetic resonance imaging in children with profound sensorineural hearing loss. METHODS: Retrospective chart review of children undergoing evaluation for cochlear implantation in a tertiary care academic children's hospital with high-resolution magnetic resonance of the temporal bone and brain during a 21 month period. Magnetic resonance studies were interpreted by an experienced senior neuroradiologist blinded to the identity and clinical data of the patients. RESULTS: Forty patients were identified. All had the same magnetic resonance study consisting of a 3D high-resolution sequence through the temporal bone as well as a T1 sagittal and T2 axial screening sequence of the brain. Eight patients (20%) showed significant brain abnormalities by magnetic resonance imaging ranging from myelination delays to migrational anomalies. Temporal bone abnormalities were not seen. Three patients with Connexin-26 mutations had no associated brain abnormalities by magnetic resonance. CONCLUSIONS: A significant proportion of our patients being investigated by magnetic resonance imaging for profound sensorineural hearing loss show migrational abnormalities of the central nervous system, suggesting a central origin to their hearing loss. Some of these findings may result in neurodevelopmental delay and hence, negatively impact the success of cochlear implantation. We propose that magnetic resonance imaging of the temporal bone as part of the evaluation protocol for cochlear implantation in children should include central nervous system screening.

Brain↗
PubMed2004

Application of a magnetic extraction technique to assess radionuclide-mineral association in Cumbrian shoreline sediments.

An assessment has been made of the association of (239+240)Pu, 241Am and 210Po (in secular equilibrium with 210Pb) with iron minerals using a magnetic extraction technique. Grab samples of beach sand from the Cumbrian (UK) coastline were subjected to successive extractions with an approximately 0.1 T ferrite magnet and an approximately 0.3 T rare-earth magnet procedure to separate magnetic iron oxide minerals. Radionuclide concentrations in the magnetic extracts were enhanced (by approximately 4-6-fold) relative to the residue. Those in the approximately 0.1 T magnet extracts were broadly similar to those in the antiferromagnetic material extracted by the approximately 0.3 T magnet, despite the very large differences in magnetic property values between the two fractions (one to two orders of magnitude). The percentage of magnetic material in terms of mass was small and therefore, the majority of these radionuclides (on average 88%) were associated with the residue. Removal of stable Fe was incomplete. Given that the radionuclides may also bind to paramagnetic (nonmagnetic) Fe minerals, the data were extrapolated by normalising the results to quantitative Fe removal. This yielded average values of 37%, 45% and 46% for (239+240)Pu, 241Am and 210Po(210Pb), respectively, as upper limits for the fraction associated with magnetic + nonmagnetic Fe minerals. There are significant uncertainties inherent in quantifying data from this extraction technique. Nevertheless, it seems reasonable to conclude that radionuclide association with Fe minerals is unlikely to have a significant impact upon the physical dispersion of sediment contaminated by Sellafield discharges in the Irish Sea. However, it may be an important factor in governing Pu redox and redissolution behaviour.

Americium↗
PubMed2006

Dynamic contrast enhanced, pelvic phased array magnetic resonance imaging of localized prostate cancer for predicting tumor volume: correlation with radical prostatectomy findings.

PURPOSE: We assessed the value of pelvic phased array dynamic contrast enhanced magnetic resonance imaging for predicting the intraprostatic location and volume of clinically localized prostate cancers. MATERIALS AND METHODS: Suspicious areas on prospective pre-biopsy magnetic resonance imaging in 24 patients were assigned a magnetic resonance imaging malignancy score and located with respect to anatomical features, gland side, and transition and peripheral zone boundaries. The largest surface area and volume were measured. These magnetic resonance imaging findings were compared with radical prostatectomy specimen histopathology findings. RESULTS: Histopathology maps detected 56 separate cancer foci. The largest tumor focus was located in the peripheral zone in 14 patients and in the transition zone in 10. T1-weighted dynamic contrast enhanced magnetic resonance imaging identified 30 of the 39 tumor foci greater than 0.2 cc and 27 of the 30 greater than 0.5 cc. T2-weighted sequences were suspicious in 22 of 30 foci greater than 0.2 cc that were identified by T1-weighted dynamic contrast enhanced magnetic resonance imaging sequences. Sensitivity, specificity, and positive and negative predictive values for cancer detection by magnetic resonance imaging were 77%, 91%, 86% and 85% for foci greater than 0.2 cc, and 90%, 88%, 77% and 95% for foci greater than 0.5 cc, respectively. Median focus volume was 1.37 cc (range 0.338 to 6.32) for foci greater than 0.2 cc detected by magnetic resonance imaging in the peripheral zone and 0.503 cc (range 0.337 to 1.345) for those not detected by magnetic resonance imaging (p <0.05). Corresponding median values for transition zone foci were 2.54 (range 0.75 to 16.87) and 0.435 (range 0.26 to 0.58). CONCLUSIONS: Pre-biopsy pelvic phased array dynamic contrast enhanced magnetic resonance imaging is an accurate technique for detecting and quantifying intracapsular transition or peripheral zone tumor foci greater than 0.2 cc. It has promising implications for cancer detection, prognosis and treatment.

Aged↗
PubMed2005

Cochlear implant magnet displacement with minor head trauma.

OBJECTIVES: Manufacturers have introduced cochlear implants (CIs) with removable magnets to allow for magnetic resonance imaging after placement. The purpose of this study was to describe magnet displacement as a new CI complication and to suggest a possible treatment option to prevent its recurrence. STUDY DESIGN: Retrospective case series. METHODS: The records of 3 young males who experienced CI magnet dislodgement were reviewed and compared against records from the institutional implant database. RESULTS: Magnet displacement was observed only in young males (14% of male children) who received CI with removable magnets. This occurred 13-14 months after CI placement. Magnets were replaced under general anesthesia, and the scalp was bolstered with a dermal allograft. Recurrent magnet dislodgement was encountered in 1 patient, 6 months later. CONCLUSIONS: Magnet displacement may be a relatively common complication after minor head trauma in pediatric patients with certain CIs that have removable magnets.

Child, Preschool↗
PubMed2005

Use of mineral magnetic concentration data as a particle size proxy: a case study using marine, estuarine and fluvial sediments in the Carmarthen Bay area, South Wales, U.K.

Compositional (non-magnetic) data can correlate strongly with particle size, which deems it appropriate as a particle size proxy and, therefore, a reliable means of normalising analytical data for particle size effects. Previous studies suggest magnetic concentration parameters represent an alternative means of normalising for these effects and, given the speed, low-cost and sensitivity of the measurements may, therefore, offer some advantages over other compositional signals. In this work, contemporary sediments from a range of depositional environments have been analysed with regard to their mineral magnetic concentration and textural characteristics, to observe if the strength and nature of the relationship identified in previous studies is universal. Our data shows magnetic parameters (chi(LF), chi(ARM) and SIRM) possess contrasting relationships with standard textural parameters for sediment samples collected from marine (Carmarthen Bay), estuarine (Gwendraeth Estuary) and fluvial (Rivers Gwendraeth Fach and Gwendraeth Fawr) settings. Magnetic concentrations of sediments from both the marine and estuarine environments are highly influenced by the magnetic contribution of finer particle sizes; Gwendraeth Fawr River sediments are influenced by the magnetic contribution of coarser particle sizes, while sediments from the Gwendraeth Fach River are not influenced significantly by any variations in textural properties. These results indicate mineral magnetic measurements have considerable potential as a particle size proxy for particular sedimentary environments, which in certain instances could be useful for geochemical, sediment transport, and sediment provenance studies. However, the data also highlight the importance of fully determining the nature of the relationship between sediment particle size and magnetic properties before applying mineral magnetic data as a particle size proxy.

Aluminum Silicates↗
PubMed2000

Analytical magnetapheresis of magnetically susceptible particles.

Analytical magnetapheresis is a newly developed technique for analyzing magnetic particles. The magnetically susceptible particles form deposition patterns after flowing through a separation channel in a magnetic field. The separation channel requirements for analytical magnetapheresis are an excellent seal for the carrier flow and ease of disassembly after magnetapheresis. Previously used separation channels often exhibit variable channel leakage and unstable flow velocities. We improved the separation channel assembly to ensure stable, high flow velocities and characterized the system with various magnetically susceptible and labeled particles. Our new separation channel featured silicone sealant with embedded nylon wires and met analytical magnetapheresis requirements. Characterization of this system was performed using several magnetically susceptible particles, and we studied a variety of diamagnetic sample labels with paramagnetic ions and magnetically susceptible particles at different flow-rates and solution pH values. The minimal labeling concentration for complete deposition was determined to be approximately 2.50 x 10(10) ions per particle for test samples at a flow velocity of 0.67 mm s(-1) and a magnetic field gradient of 2.8 T mm(-1). Silicas, yeasts and blood cells were used for these studies. We determined that the minimal difference in magnetic susceptibility (delta(chi)) for successful separation was approximately 2.00 x 10(-6) [SI]. The magnetic susceptibilities of Dynabeads M-450 at several separation distances and flow-rates were determined to be 0.25 [SI], within 2% of values published by other workers. The magnetic susceptibilities of various ion-labeled yeasts and cells were determined and most varied by less than 5% at different flow-rates. The results of this study provide very important references for analytical magnetapheresis applications.

Chemistry Techniques, Analytical↗
PubMed1998

Ultra high resolution nonenhanced fast spin echo magnetic resonance imaging: cost-effective screening for acoustic neuroma in patients with sudden sensorineural hearing loss.

The financial burden for the evaluation of patients for acoustic neuroma in an otolaryngology practice is substantial. Patients with sudden sensorineural hearing loss represent a portion of that population seen with unilateral, asymmetric auditory symptoms who require investigation for acoustic neuroma. For these patients, gadolinium-enhanced magnetic resonance imaging is the diagnostic gold standard. Auditory brain stem response testing has been used in the past as a screening test for acoustic neuroma, but its apparent sensitivity has fallen as the ability to image smaller acoustic neuromas has improved. Fast spin echo magnetic resonance imaging techniques without gadolinium have been shown to be as effective in the detection of acoustic neuroma as contrast-enhanced magnetic resonance imaging. Limited nonenhanced fast spin echo magnetic resonance imaging now provides an inexpensive alternative for high-resolution imaging of the internal auditory canal and cerebellopontine angle. Fast spin echo magnetic resonance imaging can now be done at a cost approximating auditory brain stem response testing while providing the anatomic information of contrast-enhanced magnetic resonance imaging. Cost analysis was done in the cases of 58 patients with sudden sensorineural hearing loss by comparing the costs for routine workup and screening of acoustic neuroma with the cost of fast spin echo magnetic resonance imaging with the use of screening protocols based on literature review. The potential cost savings of evaluating patients with sudden sensorineural hearing loss with fast spin echo magnetic resonance imaging for acoustic neuroma was substantial, with a 54% reduction in screening costs. In an era of medical economic scrutiny, fast spin echo magnetic resonance imaging has become the most cost-effective method to screen suspected cases of acoustic tumors at our institution by improving existing technology while reducing the cost of providing that technology and eliminating charges for impedance audiometry, auditory brain stem response testing, and contrast-enhanced magnetic resonance imaging.

Acoustic Impedance Tests↗
PubMed1997

Magnetically-enhanced radionuclide therapy (MERiT): in vitro evaluation.

PURPOSE: Radionuclide therapy is a promising method for delivering radiation dose selectively to tumors. In situations where electron -emitters are used and the tumor is small relative to the maximum range of therapeutic electrons, these particles exit the tumor before delivering the maximum amounts of radiation dose. In this study, the method of magnetically constraining electrons to small tumors, known as magnetically -enhanced radionuclide therapy (MERiT), is explored using in vitro experiments. METHODS AND MATERIALS: The potential utility of MERiT was investigated by first measuring the reduction of number of electrons exiting a small sphere containing 90Y embedded in a block of plastic scintillator. Measurements of total energy deposited in the plastic scintillator made inside and outside a 7 Tesla magnetic field were compared. Furthermore, an experiment utilizing lymphoma cells of human origin was performed. Groups of cells were added to wells containing 90Y-labeled bovine serum albumin (and control groups containing no radioactivity) were placed either inside a 7 Tesla magnet or at a position where the magnetic field was minimal (essentially zero) for 18 hr. RESULTS: The presence of a 7 Tesla magnetic field reduced the amount of energy deposited in the scintillator by 16.63 +/- 1.05%. This demonstrates that the magnetic field constrains a large fraction of the emissions to the sphere and implies that normal tissues adjacent to radiotracer-avid tumors can be protected from radiation dose. Results from the cell culture experiment showed that the presence of a 7 Tesla magnetic field significantly (p < 0.005) reduced the number of viable cells remaining after treatment with non-specific 90Y-labeled bovine serum albumin by 11.7% compared to the appropriate control group (90Y treated, not exposed to magnetic field). CONCLUSIONS: These initial physical and biological studies indicate that magnetically-enhanced radionuclide therapy can be effective in increasing radiation absorbed dose to small tumors, consequently reducing radiation dose to surrounding normal structures.

Cell Survival↗
PubMed2003

MR imaging at high magnetic fields.

Recently, more investigators have been applying higher magnetic field strengths (3-4 Tesla) in research and clinical settings. Higher magnetic field strength is expected to afford higher spatial resolution and/or a decrease in the length of total scan time due to its higher signal intensity. Besides MR signal intensity, however, there are several factors which are magnetic field dependent, thus the same set of imaging parameters at lower magnetic field strengths would provide differences in signal or contrast to noise ratios at 3 T or higher. Therefore, an outcome of the combined effect of all these factors should be considered to estimate the change in usefulness at different magnetic fields. The objective of this article is to illustrate the practical scientific applications, focusing on MR imaging, of higher magnetic field strength. First, we will discuss previous literature and our experiments to demonstrate several changes that lead to a number of practical applications in MR imaging, e.g. in relaxation times, effects of contrast agent, design of RF coils, maintaining a safety profile and in switching magnetic field strength. Second, we discuss what will be required to gain the maximum benefit of high magnetic field when the current magnetic field (< or = 1.5 T) is switched to 3 or 4 T. In addition, we discuss MR microscopy, which is one of the anticipated applications of high magnetic field strength to understand the quantitative estimation of the gain benefit and other considerations to help establish a practically available imaging protocol.

Animals↗