Magnetic resonance imaging using hyperpolarized He-gas

Rationale and Objectives. Current imaging procedures of the lung concentrate on visualization of morphology. Computed tomography is the imaging method of choice for the majority of pulmonary diseases. Functional data are commonly obtained from arterial blood gas analysis, spirometry, and body plethysmography, which all suffer from lack of regional information.Materials and Methods. Magnetic resonance imaging (MRI) of the lung has been advanced recently by the use of hyperpolarized ³He as a new contrast mechanism. Four different image acquisition modes are performed during a typical patient study.Results. ³He-MRI yields functional information about the lung with a high spatial and temporal resolution, avoiding the risks of ionizing radiation. The method is currently limited by high costs and restricted availability of the gas.Conclusion. In this article, the experience obtained at the University of Mainz, being Europe’s most experienced center performing ³He-MRI in humans, is reviewed against the international background.     

Magnetic resonance imaging of themusculoskeletal system

The accuracy of magnetic resonance imaging (MRI) in evaluating disorders of the musculoskeletal system is wellestablished. MRI is especially valuable in evaluating pathology of the major joints and soft tissues of the body. Importantly, MRI is a noninvasive technology. As with any new technology in medicine, time is required to establish the place of the technology in the armamentarium of clinicians. This is the unsettled situation MRI finds itself in today.     

Magnetic resonance imaging fundamentals and system performance

The underlying physical principles of magnetic resonance (MR) imaging are discussed. MR imaging system components are described, and system performance criteria are discussed and demonstrated. Examples of image quality variables are shown, and measurement techniques and apparatus are given.     

Magnetic resonance imaging of the musculoskeletal system

During the last few years, the interest and experience in magnetic resonance imaging (MRI) of the musculoskeletal system has increased rapidly. Modern equipment with good spatial resolution and multislice, multiecho technique provides detailed information on the joints, soft tissue and spine within a reasonable examination time, both with superconductive and resistive systems. Today, MRI is an established technique for examination of musculoskeletal tumors and aseptic bone necrosis and it has proven to be of great value for evaluation of diseases of the spine and spinal canal. The definite place of MRI within musculoskeletal diagnostic imaging is not yet settled, but its potential is great, and it will have an important role in the future.     

Magnetic resonance imaging of suspected scaphoid fractures using a low field dedicated extremity MR system

AIM: To determine whether magnetic resonance imaging (MRI) using a dedicated extremity system could be utilized for the routine assessment of patients with a clinically suspected scaphoid fracture, and to determine the most cost-effective timing of MRI for these patients. MATERIALS AND METHODS: MRI of the wrist using a 0.2T extremity MR system was performed in two groups of patients. Fifty-six patients were examined within 4 days of injury and 53 with persistent symptoms at 10 days to 6 weeks following injury. A scaphoid series of radiographs was negative in both groups. RESULTS: The early MR group had seven scaphoid, six radial and four other fractures. Management was altered in 89%. The late MR group had 14 scaphoid, nine radial and three other fractures. Management was altered in 69%. A cost model showed that overall costs are less with early rather than late scanning. CONCLUSION: MRI of the wrist when scaphoid fracture is suspected can be undertaken in all patients with negative radiographs and could be performed in most departments with an MRI machine. There are significant patient benefits and overall costs would change little from conventional practice.     

Magnetic resonance imaging using gadolinium labeled monoclonal antibody

Gadolinium was attached to antibodies and tested in vitro and in vivo for its effect on proton relaxation enhancement. Using the cyclic anhydride method, diethylenetriaminepentaacetic acid (DTPA) was attached to albumin, IgG and anti-CEA monoclonal antibody. Gadolinium (Gd) was then chelated to the protein complexes forming protein-DTPA-Gd complex. With this technique approximately 9 atoms of Gd could be attached to each albumin molecule, 4 to each IgG molecule and 1.5 to each monoclonal antibody molecule. The minimal in vitro concentration of Gd in the form of IgG-DTPA-Gd necessary to produce proton relaxation enhancement at 0.35 tesla was 10(-1) mM. An in vivo experiment using anticarcinoembryonic antigen (CEA) monoclonal antibody-DTPA-Gd in hamsters implanted with human colon carcinoma resulted in a tumor concentration of Gd of less than 10(-4) mM. No enhancement of the tumors was detected at that concentration. For monoclonal antibodies to function as selective MR contrast agents, substantial advances in technology must occur.     

Magnetic resonance velocity imaging using a fast spiral phase contrast sequence

Time-resolved velocity imaging using the magnetic resonance phase contrast technique can provide clinically important quantitative flow measurements in vivo but suffers from long scan times when based on conventional spin-warp sequences. This can be particularly problematic when imaging regions of the abdomen and thorax because of respiratory motion. We present a rapid phase contrast sequence based on an interleaved spiral k-space data acquisition that permits time-resolved, three-direction velocity imaging within a breath-hold. Results of steady and pulsatile flow phantom experiments are presented, which indicate excellent agreement between our technique and through plane flow measurements made with an in-line ultrasound probe. Also shown are results of normal volunteer studies of the carotids, renal arteries, and heart.     

Magnetic resonance imaging of the orbits using a binocular surface coil

Sixty subjects, including 12 normal volunteers, have been studied using the Aberdeen 0.08 T magnetic resonance imager. A wide range of pathological conditions, including both ocular and and orbital disease, have been examined using a specialized binocular surface coil. The images produced using this coil are superior to those made with a head coil and have the advantage of demonstrating both eyes simultaneously. Each patient has been studied using a pulse sequence combining alternate saturation-recovery and inversion-recovery pulses. The resultant short time-to-inversion inversion-recovery and saturation-recovery images have been shown to be accurate in demonstrating the normal anatomy of the globe and orbit and for the demonstration of a wide range of disease states.     

Magnetic resonance imaging of the normal pituitary gland and pituitary adenoma: preliminary experience with a resistive magnet

Magnetic resonance (MR) imaging was performed in fifty normal pituitary glands, ten pituitary microadenomas, and twelve adenomas with extrasellar extension using a 0.15 Tesla resistive magnet. The average height of normal glands was 5.6 +/- 1.2 mm, whereas that of microadenomas was 6.8 +/- 1.0 mm. The superior surface and internal texture of these conditions were well delineated. Adenomas that showed extrasellar extension together with surrounding structures were well demonstrated on sagittal and coronal scans. It can be expected that with further technical developments MR imaging will play an important role in the clinical management of pituitary adenomas.     

A description of a low field resistive magnetic resonance imaging system and its application in imaging midline central nervous system pathology

A commercial low field magnetic resonance imaging (MRI) system installed in the Royal Infirmary, Edinburgh at the end of 1983 has since been used for the clinical investigation of over 1000 patients. This system uses an interlaced saturation recovery and inversion recovery pulse sequence which yields four types of clinical image. AT1 weighted image has been found to be the most sensitive for the detection of pathology. Several examples of pathology with negative X-ray computed tomography examinations including three examples of a syrinx and two cases of tonsillar herniation have been demonstrated using this system. It is suggested that the system could provide a routine clinical service for imaging the central nervous system.     

磁共振pH成像的研究

1概述 磁共振成像（MRI）技术的重要优势在于其无放射损伤及组织结构的高分辨力,可无创实时地检测组织结构及代谢物。众所周知,人体正常机能活动有赖于正常的细胞内外环境,     

磁共振pH成像的研究

<正>1概述磁共振成像(MRI)技术的重要优势在于其无放射损伤及组织结构的高分辨力,可无创实时地检测组织结构及代谢物。众所周知,人体正常机能活动有赖于正常的细胞内外环境,包括正常的酸碱度     

Magnetic resonance imaging methodology

Introduction  

Magnetic resonance (MR) methods are non-invasive techniques to provide detailed, multi-parametric information on human anatomy, function and metabolism. Sensitivity, specificity, spatial and temporal resolution may, however, vary depending on hardware (e.g., field strength, gradient strength and speed) and software (optimised measurement protocols and parameters for the various techniques). Furthermore, multi-modality imaging may enhance specificity to better characterise complex disease patterns.     

Magnetic resonance: a new imaging modality

Magnetic resonance utilizes the magnetic properties of atoms within the tissues of the body to produce images. This paper is intended to provide the reader with the most basic information concerning magnetic resonance. The principles, fundamental parameters, equipment, and site planning considerations are presented to familiarize the radiologic technologist with this new imaging modality.     

Magnetic resonance imaging of local soft tissue inflammation using gadolinium-DTPA

Chemical inflammation was induced subcutaneously in 10 rats using carrageenan mucopolysaccharide. Dual spin echo (SE) imaging of inflammatory loci was performed employing a 0.35 tesla resistive magnet. In addition, gadolinium-DTPA was administrated intravenously into 5 rats to evaluate the potential benefits of paramagnetic contrast medium for the detection and characterization of inflammatory loci. T2 weighted SE images demonstrated the edematous lesions as zones of high intensity. This was attributed to the increased relaxation times of lesions when compared to the adjacent soft tissue. The inflammation was also delineated on T1 weighted SE images, but only after injection of paramagnetic Gd-DTPA. Carrageenan mucopolysaccharide-induced lesions provide a useful experimental model for in vivo evaluation of soft tissue inflammation using magnetic resonance imaging. No special benefit of paramagnetic contrast enhancement was demonstrated in this model of local edema.     

Magnetic resonance imaging of acute myocardial ischemia using a manganese chelate, Mn-DPDP

Nine adult rats underwent occlusion of the left coronary artery (LCA) to assess the ability of a manganese chelate of N, N'-Bis (pyridoxal-5-phosphate) ethylenediamine-N, N'-diacetic acid (Mn-DPDP), to delineate acute myocardial ischemia. Hemodynamic effects of the contrast medium were tested in the isolated rat heart. Gated transaxial images of the heart at the mid-ventricular level were obtained using a 2 Tesla magnet. A TE of 20 msec and a TR of 1 R-R interval (approximately 250 msec) were used. Images were taken prior to injection of 400 mumol/kg of Mn-DPDP, 2 minutes after injection, and then at 15 minute intervals for one hour. The time between LCA occlusion and injection of contrast averaged 95 minutes. The signal intensity (SI) of normal myocardium was increased by 125 +/- 9% immediately after injection, and did not significantly vary over one hour. SI of ischemic myocardium increased by only 16 +/- 14% immediately after injection, gradually rising to 44 +/- 13% after one hour. Visual discrimination between normal and ischemic myocardium was obtained throughout the study. The percent contrast between normal and ischemic myocardium was 47.2 +/- 6% at 2 minutes after injection, gradually decreasing to a final value of 31.3 +/- 4%. No hemodynamic effects were produced in the isolated heart using concentrations in the perfusate several-fold higher than those expected to be produced by the intravenous injection of 400 mumol/kg Mn-DPDP. Mn-DPDP shows the potential for delineation of the jeopardy area resulting from coronary occlusion for at least one hour after injection of the agent.