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PubMed1988

Magnetic resonance imaging evaluation: preliminary utilization and application report. Magnetic Resonance Imaging Technical Committee, National Health Technical Committee, National Health Technology Advisory Panel.

Preliminary results from 2723 examinations to June 30, 1987, at the first two installations that are participating in a broadly-based prospective trial of the utilization and diagnostic value of magnetic resonance imaging are presented. Compliance by the investigators with the trial protocol was excellent. The head (60% of cases) and spine (31% of cases) were the most common regions that were examined, and such examinations were completed mostly in one hour. Active, mobile outpatients were predominant among those who were examined. Further reports will be directed to particular disease groups, cost studies and patient outcomes.

Australia↗
PubMed1989

Magnetic resonance diagnostic device; panel recommendation and report on petitions for magnetic resonance reclassification and codification of reclassification--FDA. Final rule.

The Food and Drug Administration (FDA) is announcing that it has issued an order in the form of a letter to a petitioner reclassifying the magnetic resonance diagnostic device, from class III (premarket approval) into class II (performance standards). The order is being codified in the Code of Federal Regulations as specified herein.

Classification↗
PubMed2000

Ethanol in human brain by magnetic resonance spectroscopy: correlation with blood and breath levels, relaxation, and magnetization transfer.

BACKGROUND: Proton magnetic resonance spectroscopy (1H MRS) allows measurement of alcohol in the human brain after alcohol consumption. However, the quantity of alcohol that can be detected in the brain by 1H MRS pulse sequences has been controversial, with values ranging from about 24% to 94% of the temporally concordant blood alcohol concentrations. The quantitation of brain alcohol is critically affected by the kinetics of alcohol uptake and elimination, by the relaxation times of the protons that give rise to the brain alcohol signal, and by the specifics of both pulse sequence timing and radio frequency pulse applications. METHODS: We investigated these factors in 20 light-drinking subjects after oral administration of approximately 0.85 g/kg body weight of alcohol by localized 1H MRS and measurements of blood and breath alcohol concentrations obtained at the same time. Specifically, we measured transverse and longitudinal relaxation times of brain alcohol and its signal saturation on application of on- or off-resonance radio frequency pulses. All 1H MRS measurements were performed at a time after brain and blood alcohol concentrations had equilibrated. RESULTS: 1H MRS measures of brain alcohol were correlated highly with both breath and blood alcohol concentrations after equilibration in brain tissue. The measured 1H MRS relaxation times of brain alcohol were shorter than given in previous reports that were limited by smaller subject numbers, improper use of 1H MRS methods, and estimates rather than measurements. The brain alcohol signal decreased by about 30% on application of on- or off-resonance saturation pulses. CONCLUSIONS: 1H MRS allows direct measurement of brain alcohol, formerly only possible indirectly through inferences from breath alcohol levels. Quantitation of brain alcohol levels need to take into account measured relaxation times and alcohol signal attenuation due to presence and timing of standard radio frequency MRS pulses. Saturation experiments give evidence for the existence of more than one compartment of brain alcohol characterized by different molecular environments. They suggest that a fraction of brain alcohol is invisible to 1H MRS.

Adult↗
PubMed2001

Scan-rescan variation of measures derived from brain magnetization transfer ratio histograms obtained in healthy volunteers by use of a semi-interleaved magnetization transfer sequence.

SUMMARY: A novel semiinterleaved gradient-echo (GE) sequence for quantitative measurement of magnetization transfer ratio (MTR) is described. With this sequence, several lines of k-space are collected for the non-MT image then several lines are collected for the MT image, thus building up the entire k-space in distinct acquisition blocks, with a good trade-off between motion-induced misregistration and degree of MT effect. The scan-rescan coefficients of variation for several MTR histogram-derived measures from 10 healthy volunteers scanned serially with this semiinterleaved sequence proved to be lower than those achieved using a conventional GE sequence. This sequence may be useful in a clinical environment to measure MTR changes over time more reliably than when acquiring the non-MT and MT images sequentially, which inevitably are affected by patient motion.

Adult↗
PubMed2001

Dynamic micro-magnetic resonance imaging of liver micrometastasis in mice with a novel liver macromolecular magnetic resonance contrast agent DAB-Am64-(1B4M-Gd)(64).

DAB-Am64-(1B4M-Gd)(64) is a newly synthesized macromolecular liver magnetic resonance imaging (MRI) contrast agent with a polypropylenimine diaminobutane (DAB) dendrimer conjugated with a bifunctional diethylenetriaminepentaacetic acid (DTPA) derivative for complexing Gd(III) atoms. The characteristics of DAB-Am64-(1B4M-Gd)(64), which quickly accumulated in the liver, have been reported recently. In the present study, the dynamic micro-MRI with DAB-Am64-(1B4M-Gd)(64) was obtained in the mouse liver metastasis model using colon carcinoma cells to evaluate the ability to visualize the micrometastatic tumors compared with that using Gd-DTPA. The dynamic micro-MRI with DAB-Am64-(1B4M-Gd)(64) was able to homogeneously enhance the normal liver parenchyma and visualize micrometastatic tumors of 0.3-mm diameter in the liver of the mice with better contrast than that with Gd-DTPA. In conclusion, DAB-Am64-(1B4M-Gd)(64) is a new liver MRI contrast agent potentially useful for diagnosis of micrometastasis in the liver.

Animals↗
PubMed2002

Three-dimensional phase-contrast magnetic resonance angiography: a useful clinical adjunct to gadolinium-enhanced three-dimensional renal magnetic resonance angiography?

OBJECTIVE: To assess the value of three-dimensional (3D) phase-contrast (PC) magnetic resonance angiography (MRA) after gadolinium (Gd)-enhanced 3D MRA for renal artery imaging. METHODS: Twenty-one patients with suspected renal artery hypertension were reviewed. All studies included Gd-enhanced 3D MRA and 3D PC MRA. Blinded interpretation of the images was performed for each technique independently and in combination. Conventional X-ray angiography was used for diagnostic correlation when available. RESULTS: Renal artery stenosis was present in 7 (16.3%) of 43 renal arteries, confirmed by X-ray angiography. MRA images demonstrated 100% sensitivity and 74% specificity for Gd-enhanced 3D MRA and 100% sensitivity and 94% specificity for 3D PC MRA. All vessels were diagnosed correctly when both image sets were viewed. CONCLUSION: 3D PC MRA can improve the specificity of renal MRA by decreasing the number of false-positive Gd-enhanced 3D MRA interpretations.

Female↗
PubMed2003

[Studies on the toxic effects of magnetic targeting adriamycin-carboxymethyldextran magnetic nanoparticles].

In this paper, adriamycin-carboxymethyldextran magnetic nanoparticles (ADR-CMD MNPs) were prepared. After i.v. administration in mice, acute toxicity, cumulative toxicity and the distribution profiles of heart were studied both for free adriamycin(ADR) and ADR-CMD MNPs. The results showed conjugation with CMD MNPs, the acute toxicity of ADR was decreased significantly, the LD50 value of ADR-CMD MNPs was 5.06 times as high as that of the free ADR. Altogether, the cumulative toxicity of conjugate MNPs is significantly decreased as expressed by the mortality, the loss for both weight and leucocyte after repeated injection. Tissue distribution studies show the reduced cardiac uptake of ADR after i.v. which possibly contributes to minimizing the cardiotoxic effect of ADR.

Animals↗
PubMed2005

[Combined bolus magnetic resonance angiography and two-dimensional time-of-flight magnetic resonance angiography in patients with occlusive diseases of lower limb arteries].

AIM: The purpose of the work was to assess the diagnostic significance of combined bolus magnetic resonance angiography (MRA) and two-dimensional time-of-flight MRA of lower limb arteries as compared to radioangiography in patients with occlusive diseases of lower limb arteries. MATERIAL AND METHODS: Twenty-six patients with the symptoms of lower limb ischemia of varying severity were provided bolus MRA with prolonged manual injection of contrast substance and transposition of the MR-tomograph table. Additionally, all the patients underwent two-dimensional time-of-flight (2D TOF) MRA of the leg arteries. RESULTS: The statistic processing of bolus MSA for visualization of the pelvic segment has demonstrated its high sensitivity and specificity (97.74% and 92.31% respectively). On visualization of the femoral artery segment the sensitivity of this modality accounted for 97.57%, the specificity for 94.57%. In patients with severe ischemia, visualization of the leg arteries was difficult. Consequently, the specificity of the modality accounted for 44.58%. However, when this technique was combined with two-dimensional time-of-flight MRA of the leg arteries, the sensitivity and specificity of the modality reached 96.38% and 91.92% respectively. CONCLUSION: Bolus MRA of lower limb arteries is marked by the high sensitivity and specificity for visualization of the arteries of the iliac and femoral segments. To visualize the leg arteries in patients with severe forms of lower limb ischemia, this modality should be supplemented by two-dimensional time-of-flight MRA.

Aged↗
PubMed1991

[Cerebrovascular pathology. Comparison of magnetic resonance and magnetic resonance angiography].

After making the visualization of the intracranial circulation possible without contrast media, the radiologist is now evaluating the diagnostic role of the different techniques of MRA. Attempts are also being made to characterize the main patterns of intracranial vascular diseases. The authors examined, with 3D TOF MRA, 40 patients presenting with 50 vascular lesions on MRI scans. Twenty of 40 patients were also studied with angiography. Seventeen aneurysms were detected, together with 3 stenoses of the cerebral arteries, 13 arteriovenous malformations, 12 dolichobasilar arteries, 3 postoperative and 2 post-embolization controls. MRI was performed with a superconductive magnet (1.5 T), a dedicated coil and gradient-echo 3D TOF FT sequences. The refocused sequence for flux, FISP 3DFT, required the following parameters: TR = 0.04 s, TE = 10 ms, flip angle = 15 degrees, 256 x 256 matrix, 1 acquisition. The 64-80 mm volume along the axial plane was divided so that an actual 1-mm thickness was excited. In post-processing, the maximum-intensity projection was employed on the axial plane 0 degrees-90 degrees (15 degrees interval). In the various conditions, the results obtained with MRA were correlated and compared with MRI findings. MRA provided useful additional information in 27.4% of cases in the study of aneurysms, arteriovenous malformations, vascular occlusion and dolichobasilar arteries, as well as in the follow-up of these lesions. MRA is currently suggested in the evaluation of cerebral circulation and is considered a complementary technique to MRI. MRA is also to be used preliminary to angiography.

Arteriovenous Malformations↗
PubMed1989

[Magnetic resonance in hepatic lesions. Experience with a 1.5-T magnetic field].

Forty-one patients with histologically proven hepatic lesions (6 cysts, 6 hemangiomas, 8 hepatomas, 19 metastases and 2 negative cases) were studied with Magnetic Resonance (MR) imaging at 1.5 T, and with US and CT. This prospective study was aimed at evaluating: the comparative accuracy of MR, US and CT; the sensitivity and specificity of spin-echo (SE) vs FISP pulse sequences; the efficacy of T1 and T2 relaxation time values in differentiating hemangiomas from hepatomas and metastases. MR diagnostic accuracy was 94.7% vs 89.4% of CT and 84.2% of US. FISP sequences provided 60% sensitivity and 66% specificity. T2 relaxation time values were statistically significant (p less than 0.05) in differentiating hemangiomas (T2 range: 80.9-218.9 ms) from hepatomas (T2 range: 59.4-83.2 ms). The differences in mean T2 values between hemangiomas and metastases (T2 range 54.3-177.3 ms) were not statistically significant (p greater than 0.25).

Carcinoma, Hepatocellular↗
PubMedDate not supplied

Coil selection for magnetic resonance imaging of the cervical and thoracic spine using a vertical magnetic field.

In order to optimize the coil selection for cervical and thoracic spine imaging the signal characteristics of two different solenoidal surface coils (15 cm and 30 cm diameter, respectively) as well as the head coil and body coil were determined using a 0.3 T MR scanner with a vertical magnetic field. Signal-to-noise ratio curves were obtained for each coil using tube phantoms and a human-like phantom. The findings were compared with images obtained in two healthy volunteers. The head coil was found to be superior for imaging of the cranio-cervical junction while the 15 cm surface coil gave better results in the remaining part of the cervical spine and the upper thoracic spine. The body coil was superior for imaging of the thoracic region at the level of the shoulders (T4-T6) but the 30 cm surface coil was better for the more caudal part of the thoracic spine. Combined phantom and in vivo studies are also recommended for evaluation of future, improved coils.

Cervical Vertebrae↗
PubMed1988

Magnetic resonance imaging of the head and neck region. Present status and future potential. Council on Scientific Affairs. Report of the Panel on Magnetic Resonance Imaging.

Magnetic resonance imaging (MRI) has many bona fide applications in the head and neck region. The major strengths of its current conventional use include excellent soft-tissue contrast, multiplanar capabilities, noninvasiveness, and lack of ionizing radiation. Newer advances, including gradient-echo techniques, three-dimensional fourier transformation, paramagnetic contrast, and more efficient receiver coils, will improve images and expand indications for MRI. The technology, however, remains relatively expensive, and the additional information compared with that of other techniques might not always justify the difference in cost. Moreover, MRI's insensitivity to calcifications, lack of depiction of fine bone detail, and, in some areas, degradation caused by motion and other artifacts make computed tomography and other noninvasive studies more appropriate as a primary imaging tool in many circumstances. Continued careful clinical research should clarify the relative role of MRI and other imaging tools during the next several years.

Fourier Analysis↗
PubMed1988

Magnetic resonance imaging of the cardiovascular system. Present state of the art and future potential. Council on Scientific Affairs. Report of the Magnetic Resonance Imaging Panel.

State-of-the-art magnetic resonance imaging (MRI) generates high-resolution images of the cardiovascular system. Conventional MRI techniques provide images in six to ten minutes per tomographic slice. New strategies have substantially improved the speed of imaging. The technology is relatively expensive, and its cost-effectiveness remains to be defined in relation to other effective, less expensive, and noninvasive technologies, such as echocardiography and nuclear medicine. The ultimate role of MRI will depend on several factors, including the development of specific applications such as (1) noninvasive angiography, especially of the coronary arteries; (2) noninvasive, high-resolution assessment of regional myocardial blood flow distribution (eg, using paramagnetic contrast agents); (3) characterization of myocardial diseases using proton-relaxation property changes; and (4) evaluation of in vivo myocardial biochemistry. The three-dimensional imaging capability and the ability to image cardiovascular structures without contrast material give MRI a potential advantage over existing noninvasive diagnostic imaging techniques. This report analyzes current applications of MRI to the cardiovascular system and speculates on their future.

Angina Pectoris↗
PubMed1986

[Effects of the magnetic field in magnetic resonance imaging on 15 tested cardiac valve prostheses].

The effects of static magnetic fields used in MR imaging at 0.5 Tesla have been studied on 15 different types of cardiac valves. The displacement of the valves was insignificant at 0.5 Tesla. No significant heating effects was observed with the standard sequences used in cardiac imaging. The image artefacts remain confined to the area immediately surrounding these different valves. It seems possible to perform MRI examinations on patient with the prosthetic heart valves without any risk.

Electromagnetic Fields↗
PubMedDate not supplied

[Use of paramagnetic ions in the study of intercellular water transport by nuclear magnetic resonance with pulsed gradient ofthe magnetic field].

A methodical approach to the studies of water transport in biological cells by NMR method with impulse gradient of the magnetic field is proposed. It allows to exclude experimentally water transport through the plasmalemma, without touching upon transport along intercellular contacts. The effect is achieved by preliminary introduction of paramagnetic ions into intercellular space.

Biological Transport↗
PubMed1994

[Measurement of the magnetic field dispersed in places with installed magnetic resonance equipment. Characteristics of the control instrumentation].

Among the various controls prescribed by the standards for NMR equipment installations, the measurement of dispersed magnetic field values is of utmost technical importance. The paper deals with scope, strategy and practical execution of the measurements. It also analyzes the question of measurement errors and their effect on the strategy to be adopted and on the final accuracy of isomagnetic tracings.

Electromagnetic Fields↗
PubMed1996

Development of a target-directed magnetic resonance contrast agent using monoclonal antibody-conjugated magnetic particles.

We developed a novel magnetic resonance (MR) imaging contrast agent, MAb-magnetite, that was prepared by covalently linking polyethylene glycol-coated magnetite to a monoclonal antibody specific for a human glioma cell-surface antigen. When MAb-magnetite was injected intravenously into tumor-bearing nude mice at a dose of 100 mumol Fe/kg body weight, a 50% decrease in the T2 signal intensity of the tumor was observed, immediately following administration and continued for 48 h. Microscopic observation of the tumor tissue demonstrated localization of MAb-magnetite in cancer cells. These results suggest that MAb-magnetite is a promising agent for MR imaging of neoplasms.

Animals↗