PubMed Health⌕ Search

Biomedical subjects

L D Spicer

Publications and source records attributed to L D Spicer.

25 records · Page 2Linked to original sources
PubMed1990

Use of gel filtration in the preparation of biological fluids for magnetic resonance spectroscopy.

Analysis of biological fluids by proton magnetic resonance spectroscopy is often complicated by dynamic range problems created from the large water resonance. Gel filtration chromatography is found to be a simple and nondestructive method for exchanging D2O for H2O and for removing low molecular weight molecules from both plasma and urine, significantly improving subsequent one- and two-dimensional MRS spectra.

Body Water↗
PubMed1989

Synthesis of 11C-labeled chlorpromazine directly from [11C]carbon dioxide.

Radiolabeled chlorpromazine was prepared by carboxylation of the N-trimethylsilyl derivative of norchlorpromazine with [11C]carbon dioxide, followed by in situ lithium aluminum hydride reduction. Radiochemical yields of 22-24% and radiochemical purities in the range of 93-98% were achieved.

Carbon Dioxide↗
PubMed1989

Synthesis of the labeled D1 receptor antagonist SCH 23390 using [11C]carbon dioxide.

A new synthesis is described for the production of the positron emitting radiopharmaceutical R-(+)-7-chloro-8-hydroxy-2,3,4,5-tetrahydro-3-N-[11C]methyl-1-phenyl-1H- 3-benzazepine (SCH 23390, 2a). This novel method involves reductive carboxylation, in which [11C]CO2 is reacted with the trimethylsilyl derivative of the desmethyl compound (SCH 24518, 1a) followed by treatment with lithium aluminum hydride, to afford no carrier added 11C-labeled SCH 23390. The procedure gave chemically and radiochemically pure 11C-labeled SCH 23390 in 53-72% radiochemical yield with an unoptimized specific activity of 40 Ci/mmol within 45-50 min from the end of bombardment.

Benzazepines↗
PubMed1987

Magnetic field effects on surgical ligation clips.

Magnetic forces exerted on surgical clips and the magnetic resonance imaging distortion they create in phantoms and rabbits at magnetic field strengths of 1.5 Tesla were investigated. Results are reported for both ligation and aneurysm clips manufactured from three types of stainless steel as well as titanium, tantalum and niobium metals. Paramagnetism and eddy currents were measured in a customized moving Gouy balance. Direct measurements of other magnetic forces were carried out in a 1.5T MRI system. The titanium and tantalum clips showed the least interaction with the magnetic field, both in terms of forces exerted and the observed image distortion with the larger clips generating the larger interactions. The strongest field distortions and attractive forces occurred with 17-7PH stainless steel clips. These interactions were ferromagnetic in origin and of sufficient strength to present significant risk to patients having this type of clip present during an MRI scan.

Animals↗
PubMed1986

NMR studies of combined lanthanide shift and relaxation agents for differential characterization of 23Na in a two-compartment model system.

Spin relaxation and chemical shifts by lanthanide chelate complexes are used to distinguish 23Na signals in a simulated two-compartment model. Both effects are significant in EDTA, DTPA, and TPP complexes of Gd and in the TPP complex of Dy. The simultaneous measurement of these properties is illustrated and represents a promising method for monitoring sodium concentrations and fluxes including fast transport components.

Animals↗
PubMedDate not supplied

Computed tomographic evaluation of surgical clip artifact: tissue phantom and experimental animal assessment.

Surgical clips in postoperative patients create streak artifact on computed tomographic (CT) studies which often significantly degrade image quality. We have evaluated three types of surgical clips: tantalum, stainless steel, and titanium in a phantom and animal model to assess their relative CT artifact. Tantalum clips showed the greatest artifact, stainless steel intermediate, and titanium the least artifact. Artifact could be reduced with the use of faster scan times. The type of clip used may enter into surgical decision making depending upon the need for high resolution scanning to detect small pathological processes in the area of surgical clips.

Animals↗