Mass attenuation coefficient of the Earth, Moon and Mars samples over 1 keV-100 GeV energy range.
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Biomedical subjects
Eduardo Galiano
Publications and source records attributed to Eduardo Galiano.
Experimental determination of the extrinsic sensitivity and counting efficiency of a nuclear gamma camera using a homogeneous circular planar source.
Two important operational parameters of medical gamma cameras are the extrinsic counting efficiency and sensitivity. Historically, for practical reasons these two parameters have been defined using a point source of radiation at a certain distance from the detector. This definition has the disadvantage of producing measurements of limited clinical relevance since real patients are not point sources of radiation. In this work, we propose a more clinically relevant method of determining efficiency and sensitivity, using a planar, circular, homogeneous source. For this purpose, a gamma camera of 39 cm diameter, and a circular, homogeneous, 36.5 cm diameter Co-57 source with an activity of 5.5+/-0.7%mCi were employed. The source was placed coaxially with the detector at distances of 50, 100, and 150 cm. Data were acquired using a medium and a high-resolution collimator. The efficiency was found to depend directly on the solid angle subtended by the detector. Computed values for the sensitivity are in the range of 5-6 kcts/sec-mCi, and values for the efficiency were found to range between 0.2% and 2%. The results show an approximate 2:1 ratio in sensitivity and efficiency between the medium and high-resolution collimators regardless of source-detector distances.
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Peak efficiency calibration for attenuation corrected cylindrical sources in gamma ray spectrometry by the use of a point source.
A theoretical method of determining the gamma-ray peak efficiency for a cylindrical source, based on a modified expression for point sources is derived. A term for the photon self-attenuation is included in the calculation. The method is valid for any source material as long as the source activity concentration is considered to be homogeneous. Results of this expression are checked against experimental data obtained with (241)Am, (57)Co, (137)Cs, and (60)Co sources.
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An analytical solution for the solid angle subtended by a circular detector for a symmetrically positioned linear source.
The analytical determination of the solid angle subtended by a circular detector for a line source in a parallel plane, whose midpoint is co-axial with the detector's center, is of some relevance to the medical and nuclear power fields. No report has been found in the literature of a closed-form solution to this problem. We present a first principles solution to the problem along with a graph, which gives some indication of the behavior of the derived expression.
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A comparison of different analytical methods of determining the solid angle of a circular coaxial source-detector system.
In this work, seven different analytical expressions for the solid angle subtended by a circular detector for a coaxial circular source are compared. These expressions -- which have been published by different investigators over the course of the last half century -- are compared for previously published geometries, and for geometries planned in future experimental work. As compared to benchmark Monte Carlo calculations, the expressions published by Segre, Knoll, and Ruby, were the most accurate and exhibited the highest degree of self-correlation.
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A statistical analysis of the initial biodistribution of 153Sm-EDTMP in a canine.
(153)Sm (t(1/2)=46 h) emits a 103 keV gamma photon and two medium-energy beta particles. Five mCi of Samarium-153 ethylenediaminetetramethylenephosphonic acid ((153)Sm-EDTMP) were administered to a clinically normal dog and whole body scans were obtained at 15min, 2h, and 24h post-injection (PI). Regions of interest (ROIs) were drawn representing abdomen, knee, rib, vertebral bodies, bladder, kidney, and liver, in each image. For each ROI, the mean intensity and standard deviation were computed, and a histogram was created. Clinically significant increased uptakes were found in liver and kidney.
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Determination of the activity concentration of a 238 Pu solution by the defined solid angle method utilizing a novel dual diaphragm-detector assembly.
The activity concentration of a (238)Pu solution was measured by the determined solid angle method employing a novel dual diaphragm-detector assembly, which has been previously described. Due to the special requirements of the detector, a new type of source holder was developed, which consisted of sandwiching the radioisotope between two organic films called VYNS. It was experimentally demonstrated that the VYNS films do not absorb alpha particles, but reduce their energy by an average of 22 keV.A mean activity concentration for (238)Pu of 359.10+/-0.8 kBq/g was measured.
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Theoretical estimates of the solid angle subtended by a dual diaphragm-detector assembly for alpha sources.
Knowledge of the solid angle subtended by a detector is essential for the determination of the activity of a radioactive source. This work investigates the influence of diaphragm and source diameter, and source to diaphragm distance, on the solid angle subtended by a dual opposed alpha diaphragm-detector assembly. Expressions published by Segre, Ruby, and others, and the Monte Carlo method are used. The analytical expressions consistently produced higher estimates than the Monte Carlo method for the solid angle.
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Proposed definitions for isodose flatness and symmetry in clinical radiotherapy beams.
In clinical radiotherapy it is important that beam intensity be as homogeneous as possible to reduce the probability of treatment failure. As an extension of the well established concepts of beam flatness and symmetry for characterizing radiotherapy beams, the concepts of isodose flatness and symmetry are introduced. The definitions are tested with actual data obtained from a Co-60 unit and a linear accelerator and results are presented. The concepts as defined appear to provide a useful quantitative indication of beam homogeneity.
Cobalt Radioisotopes↗