Biomedical subjects

F Boada

Publications and source records attributed to F Boada.

5 recordsLinked to original sources

PubMed2001

Brain lithium concentrations in bipolar disorder patients: preliminary (7)Li magnetic resonance studies at 3 T.

BACKGROUND: This study was conducted to investigate the feasibility of human brain (7)Li MRS investigations at a high magnetic field (3 T), and to further explore the relationship between brain and serum lithium measures in lithium-treated bipolar patients. METHODS: Eight bipolar disorder type I patients (5 males, 3 females; mean age +/- SD = 33 +/- 9 years) were studied. A 3-T scanner, using a dual-tuned ((1)H and (7)Li) echoplanar imaging (EPI) compatible radiofrequency (RF) birdcage coil was used. (7)Li magnetic resonance spectroscopy (MRS) signal was acquired at the frequency of 49.64 MHz using an imaging selective in vivo spectroscopy (ISIS) sequence (TR = 15 sec, 128 averages), and quantitation was obtained in reference to an external standard. RESULTS: The mean +/- SD oral lithium dose was 1265 +/- 442 mg/day, and the mean +/- SD 12-hour serum level was 0.69 +/- 0.19 mEq/L. The measured brain lithium concentrations varied from 0.23 to 0.55 mEq/L (mean +/- SD = 0.35 +/- 0.11 mEq/L). The brain-serum ratios varied from 0.30 to 0.80 (mean +/- SD = 0.52 +/- 0.16). Subjects on single daily doses of lithium at bedtime (n = 5) had higher brain-serum lithium ratios compared with those on twice-a-day schedules (n = 3) (0.61 +/- 0.12 and 0.37 +/- 0.07, respectively; Mann--Whitney U test, Z = -2.24, p =.03). CONCLUSIONS: This study demonstrated for the first time the feasibility of (7)Li MRS human studies at 3 T. Future studies should examine a possible role for this methodology in investigations of lithium refractoriness and prediction of treatment outcome in bipolar patients.

Adult↗

PubMed2000

Brain lithium measurements with (7)Li magnetic resonance spectroscopy (MRS): a literature review.

7Li magnetic resonance spectroscopy (MRS) has been successfully used in recent years as a new tool to measure brain tissue lithium concentrations in vivo. After demonstration of its feasibility in animal studies over a decade ago, human investigations have characterized the brain pharmacokinetics of lithium. Preliminary studies have investigated brain pharmacokinetic correlates of clinical response in the treatment of bipolar disorder patients, with indication of possible clinical relevance of 7Li MRS measures. In this paper we reviewed the accumulated literature in this area, and discuss possible directions for this research in the context of preliminary studies conducted by our group that demonstrated the feasibility of 7Li MRS at 3 T.

Animals↗

PubMed2000

Magnetic resonance imaging in human body composition research. From quantitative to qualitative tissue measurement.

Incremental improvements in our knowledge of human body composition are abetted by advances in research technology. Indeed, magnetic resonance imaging (MRI) represents a technological advance that has profoundly influenced body composition research. Routine applications of MRI include the measurement of whole-body and regional adipose tissue distribution, quantification of lean tissue and its principal constituent skeletal muscle, and the measurement of visceral adipose tissue. MRI is now the method of choice for calibration of field methods designed to measure body fat and skeletal muscle in vivo. Common to these applications is the measurement of tissue quantity. More recently proton (1H) and sodium (23Na) MRI protocols have been developed that measure the quality (lipid and sodium concentration) of skeletal muscle tissue. These unique applications of MRI represent a major advance in the study of altered muscle composition in vivo, with numerous applications in both applied and clinical medicine. In this review we provide a brief overview of routine applications of MRI in body composition research, followed by a focus on more recent applications of MRI that employ fast-imaging sequences for qualitative measurement of human skeletal muscle.

Adipose Tissue↗

PubMed1990

In vivo biomicroscopy with ultrasound 2.

In the first article of this series it was shown that the use of inverse scattering theory to analyse ultrasound reflections could provide high resolution images of the acoustic impedance profile of the retina. Unlike the retina, most tissue structures of interest, like small tumours and arterial plaque deposits, are shielded from view by intervening layers of tissue of appreciable acoustic impedance and attenuation. By analysing a one-dimensional model for a plaque deposit on the wall of a carotid artery embedded in a 5 cm thick layer of tissue, we demonstrate that a relatively high quality image can be recovered when compensation for the attenuation of the intervening tissue is made. We observe that because of the dearth of low frequency power in the recovered signal of ultrasound transducers, it is important that the field of view imaged is not taken to be too large. We compare the exact iterative distorted wave Born approximation inverse scattering method with the approximate but computationally faster plane wave Born approximation method and find that they give images of comparable quality for this model.

Acoustics↗

PubMedDate not supplied

Phase-constrained data extrapolation method for reduction of truncation artifacts.

The authors present an improvement to a sigma-filter extrapolation method for the reconstruction of magnetic resonance (MR) images from symmetric discrete Fourier data. By making use of the phase information in the image data, the proposed method can overcome the data inconsistency problem of the original method for handling MR image data with large phase variations, such as those obtained in gradient-echo pulse sequences. Reconstruction results show that its performance is comparable with that of the modified complex sigma-filter method proposed previously to handle the inconsistency problem. However, the new approach has the advantage of reducing computation time by a factor of two with use of a sigma filter applied to real instead of complex images. It is expected that this method will be more practical for use in clinical MR imaging systems.

Algorithms↗