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R P Gardner

Publications and source records attributed to R P Gardner.

7 recordsLinked to original sources
PubMed2001

Preliminary studies on combining the K and L XRF methods for in vivo bone lead measurement.

Lead is a toxic material that invokes irreversible neurological problems. Once ingested, lead accumulates in the bones. To study detailed lead poisoning effects it is essential to have an in vivo bone lead measurement tool with a small minimum detectable concentration (MDC). Both K- and L-based XRF methods for the tibia bone have been suggested and developed in the past and are presently in use. In this work a combined K and L XRF method for the tibia bone is proposed. The proposed system consists of a 109Cd point source and Ge and Si(Li) detectors for optimum detection of the K and L X-rays, respectively. Experimental and Monte Carlo simulated results are given here for a prototype combined K and L XRF system. This system promises to yield a better MDC and the possibility of obtaining information on the near-surface bone lead content as well as the average lead content throughout the bone.

Bone and Bones↗
PubMed1989

Symptomatic hypercalcemia pulmonary tuberculosis.

We describe a case of active pulmonary tuberculosis whose care was complicated by the onset of severe hypercalcemia that manifested after the institution of standard antituberculous therapy. We review the knowledge regarding the association of hypercalcemia with active pulmonary tuberculosis and present the proposed mechanisms for the pathogenesis of the disorder.

Aged↗
PubMedDate not supplied

Monte Carlo simulation for IRRMA.

Monte Carlo simulation is fast becoming a standard approach for many radiation applications that were previously treated almost entirely by experimental techniques. This is certainly true for Industrial Radiation and Radioisotope Measurement Applications--IRRMA. The reasons for this include: (1) the increased cost and inadequacy of experimentation for design and interpretation purposes; (2) the availability of low cost, large memory, and fast personal computers; and (3) the general availability of general purpose Monte Carlo codes that are increasingly user-friendly, efficient, and accurate. This paper discusses the history and present status of Monte Carlo simulation for IRRMA including the general purpose (GP) and specific purpose (SP) Monte Carlo codes and future needs--primarily from the experience of the authors.

Computer Simulation↗
PubMedDate not supplied

Black box radiation gauges and analyzers: dream or reality?

This paper describes our attempts to make radiation gauges and analyzers operate in more of a 'black box' manner-being more independent of or at least more insensitive to changes in such things as sample composition and position. Our overall approach relies heavily on Monte Carlo simulation and that is discussed first in relation to radiation gauge and analyzer design and usage. Then the principles and applications of radiation gauges and analyzers including the Measurement Chi-Square and Monte Carlo Library Least-Squares, respectively, are treated. Finally, future work in this area is discussed.

Monte Carlo Method↗
PubMedDate not supplied

Development of the specific purpose Monte Carlo code CEARXRF for the design and use of in vivo X-ray fluorescence analysis systems for lead in bone.

X-ray fluorescence (XRF) systems have been increasingly used for in vivo toxic trace-element analysis in the human body, such as lead in the tibia. Monte Carlo simulation can provide an efficient and flexible method for designing and using in vivo XRF systems. The Monte Carlo code CEARXRF has been developed specifically to simulate the complete pulse height spectrum of energy-dispersive XRF systems. This code is capable of tracking photons in a general geometry and modelling all of the physics of photon interactions in the energy range 1-150 keV for elements Z = 1-94, including primary and higher degree excitations of K and L XRF, the Doppler broadening of Compton-scattered photon energies, and the polarization effects in low-energy photon scatterings. The scattering background for minimum detectable concentration (MDC) analysis may be simulated more accurately by taking into account Doppler broadening in the distribution of the Compton-scattered photon energy due to electron-binding effects. The use of polarized excitation photons has been shown to be important in producing a low scattering background and good measurement sensitivity. The code has two very unique and important features: (1) complete composition and density correlated sampling that is extremely useful for studying measurement sensitivity to small changes in sample composition and density; and (2) Monte Carlo library spectra calculation for the determination of elemental amounts by the Monte Carlo-Library Least-Squares (MCLLS) method. The capability of CEARXRF to aid the design and optimization of in vivo XRF analysis has been verified by modelling hypothesized lead K and L XRF measurement systems.

Bone and Bones↗
PubMedDate not supplied

Optimization of in vivo X-ray fluorescence analysis methods for bone lead by simulation with the Monte Carlo code CEARXRF.

In the design of X-ray fluorescence (XRF) systems for in vivo measurements of lead in human bone, the most important considerations are the minimum detectable concentration (MDC), and accuracy and precision. Possible design optimizations can be investigated much more easily and economically by Monte Carlo simulation than by experiment. The specific purpose Monte Carlo code CEARXRF has been used in the present study for: (1) improving the MDC of a hypothesized in vivo 109Cd source-based KXRF system and a 109Cd source or X-ray tube source-based LXRF system by investigating the effects of source polarization and source-bone-detector geometry modification on reducing the scattering background, and (2) investigating the effects of sample variables, such as overlying skin thickness on the MDC and the lead XRF intensity precision. In addition, the feasibility of the Monte Carlo-Library Least-Squares (MCLLS) approach has been investigated in a preliminary fashion for 109Cd-based KXRF spectroscopy analysis.

Bone and Bones↗