Present and future clinical position of magnetic resonance imaging

Nuclear magnetic resonance in clinical pharmacology and measurement of therapeutic response

Images

Magnetic resonance image degradation from prosthetic magnet keepers

Eight types of prosthetic magnet keepers were imaged in a water phantom and a living human subject by a 1.5 T magnetic resonance device. Image artifacts were present for all eight samples and ranged from 160 mm to greater than 280 mm in diameter. These artifacts obliterate vital craniocervical areas making their examination by magnetic resonance impossible. Patients with magnetic keepers requiring comprehensive magnetic resonance imaging of the head and neck region must have them removed.

The relevance of socioeconomic and health policy issues to clinical research. The case of MRI and neuroradiology

Magnetic resonance imaging (MRI) is a high-cost, new technology with great potential for improving patient care. The lack of a coherent public policy for MRI, or its predecessor computed tomography (CT), has caused considerable problems. Lack of an enunciated public policy has led to inconsistent reimbursement and reimbursement levels that develop in haphazard ways. Furthermore, diffusion has been unpredictable and has led to geographical excesses and deficiencies. Technology assessments of MRI, although numerous, have used inconsistent criteria to rate MRI's clinical efficacy. The lack of methodologically sound studies of MRI severely hampered early evaluation. This article examines these problems and suggests that the medical profession take a stronger leadership role in developing policies for expensive, promising new diagnostic technologies. The profession should promote, demand, and perform rigorous clinical evaluations of new technologies, and help develop a consensus regarding the criteria for what constitutes a clinically valuable advance in diagnostic technology.

Is the magnetic resonance imaging proton spin-lattice relaxation time a reliable noninvasive parameter of developing liver fibrosis?

During the development of liver fibrosis in rats by an individual dose-titrated CCl4 administration, hepatic proton spin-lattice relaxation time (T1) has been measured in vivo every 2 weeks for 8 weeks. Liver content of collagen, triglycerides and water has been measured biochemically in biopsy material. After 4 weeks of CCl4 treatment, T1 increased significantly and remained at the same level, whereas liver collagen reached its maximum at 8 weeks. It is concluded that, under our experimental conditions, increased hepatic T1 represents drug-induced edema and that hepatic T1 is not a reliable noninvasive parameter for developing liver fibrosis in vivo.

NMR imaging in dentistry: relaxation and diffusion studies

Magnetic resonance imaging has been widely used for medical diagnosis in recent years. The knowledge of the proton spin-lattice relaxation time, T1, represents the basis for NMR imaging. In the present study, we measured T1 in saliva, gingival fluid, gingival blood, and inflamed gingiva by means of a pulsed NMR Fourier-transform spectrometer. From several measurements, we found the following average T1 values: in saliva, T1 = 2550 msec; in gingival fluid, T1 = 2085 msec; in gingival blood, T1 = 1515 msec; and in inflamed gingiva samples, T1 = 840 msec.

In addition, electron paramagnetic resonance imaging was used to demonstrate the in vitro diffusion processes of spin-labeled molecules into tooth enamel by application of the linear magnetic field gradient to a conventional EPR spectrometer. The diffusion coefficient for the nitroxide spin-labeled molecules into tooth enamel was evaluated as D = 10-7 cm2 sec-1.