Plastic scintillating fibers have been shown to be very effective for high spatial and time resolution of gamma rays. They may be expected to significantly improve the resolution of current medical imaging systems such as PET and SPECT. Monte Carlo simulation of imaging systems using these detectors, provides a means to optimize their performance in this application, as well as demonstrate their resolution and efficiency. Monte Carlo results will be presented for PET and SPECT systems constructed using these detectors. I. INTRODUCIION The recently developed high photon conversion efficiency scintillating fibers will greatly enhance the spatial and time resolution for gamma ray detectors which use optical methods[l]. The combined system of these fibers, coupled with position sensitive photomultipliers or solid state photomultipliers, will have a great impact on many fields which rely on these detectors. Monte Carlo modeling provides the insight into optimizing design parameters for systems using these detectors and gives an indication of their performance. In a previous paper we discussed Monte Carlo simulation for scintillating fiber systems in Positron Emission Tomography (PET) and Single Photon Emission Tomography (SPECT)[2]. In this paper, we show reconstructed images which give the spatial resolution and efficiency for systems using these detectors. 11. MODELING PARAMETERS
Fluorinated macromolecular probes (6-fluoropyridoxal−polymer conjugates) have been synthesized and characterized as potential pH indicators for magnetic resonance spectroscopy and imaging applications. The 19F pH sensor 2-fluoro-5-hydroxy-3-(hydroxymethyl)-6-methyl-4-pyridinecarboxaldehyde (6-fluoropyridoxal; 2) has been conjugated to carrier molecules (polyamino dextran, polylysine, and albumin) by reductive alkylation for enhanced vascular retention and tissue targeting. The pH indicator polymer conjugates were purified by exhaustive dialysis and isolated in good yields (66−84%). The 6-fluoropyridoxal−polymer conjugates exhibit excellent 19F pH sensitivity and pKa suitable for in vivo studies. The potential application of these polymeric indicators has been demonstrated in whole blood. These novel macromolecular pH probes offer a new approach for studying tissue physiology.
This paper discusses the measurement of velocity in a solid based on the analysis of the amplitude and phase of ultrasound waves reflected by a solid, a technique called ultrasound critical-angle reflectometry (UCR). To this end, the complete formulation of ultrasound wave reflection and refraction from a liquid - solid interface is described. Differences between this formulation and previously published ones are briefly discussed. Based on this analysis it is in particular possible to measure by this technique not only pressure but also, for the first time in such studies, shear wave velocities, an experimentally confirmed result. The measurement of the complete stiffness matrix of a transversely isotropic solid, specifically cortical bone, by applying UCR elastometry to any point on the solid's surface is demonstrated. Finally this method is extended to functional elastometric imaging. The techniques presented in this paper offer new opportunities for applications of UCR imaging to the assessment of bone metabolism, formation and disease and also to the analysis of composite materials in general.
Double quantum selective coherence transfer proton NMR spectroscopy has been used to observe glutathione in whole blood. The efficient water suppression of this technique avoids the need to resuspend the cells in D 2 O, hence avoiding equilibrium and kinetic isotope effects. Using this method we estimate the concentration of glutathione in fresh whole rabbit blood at ~1.7 mM.
Abstract The intrinsic (material) quality of cancellous and cortical bone was evaluated in vivo from the measurement of reflection ultrasound velocities in the ulna. In cancellous bone, the reflection ultrasound velocity was inversely correlated with age in normal women (r = −0.48, p = 0.001), with a significantly lower mean value in 32 normal postmenopausal women than in 14 premenopausal women (3124 versus 3341 m/s, p < 0.0001). In 32 untreated osteoporotic women the cancellous bone velocity was lower than in normal postmenopausal subjects (2906 versus 3124 m/s, p = 0.0001). Following treatment with slow-release sodium fluoride plus calcium citrate (mean 2.4 years in 33 osteoporotic patients with no fracture during treatment), the cancellous bone velocity was significantly higher than in untreated osteoporotic women (3082 versus 2906 m/s, p = 0.0002) and was not significantly different from that in normal postmenopausal women. The cortical bone velocity displayed similar trends, but the changes did not attain statistical significance. The measurements were repeated approximately 9 months later in 9 untreated and in 20 treated patients; in 5 additional patients, the measurements were made both before and after 9 months of treatment with slow-release sodium fluoride and calcium citrate. The cancellous bone velocity increased significantly (p = 0.046) in these patients, from 3008 m/s before treatment to 3112 m/s after the first 9 months of treatment. The velocity rose significantly from 3037 to 3167 m/s (p = 0.017) in patients treated for a short time (12–30 months at first measurement), but it did not change in untreated patients or those treated for more than 30 months. Thus, the material quality of cancellous bone decreases with normal aging and is reduced further with the osteoporotic process. This impaired quality may be corrected by treatment with slow-release sodium fluoride plus calcium citrate.
Obstructive sleep apnea/hypopnea Syndrome (OSAHS) is the most common form of Sleep Disordered Breathing (SDB) and it is estimated to affect approximately 15% of US adult population. In this paper, we report on the results of in vivo experiments of an ultrasonic device for the non-invasive detection of obstructive sleep apnea/hypopnea (OSAH). A description of the ultrasonic system used is presented, followed by the results of a full night sleep study. The findings show a significant difference in the spectral features extracted from the received ultrasonic waveform during apneic breathing, compared to the hyperventilation that follows. Therefore, the findings indicate the feasibility of developing an ultrasonic detection device for low cost diagnosis of SDB.
