bluuebunny/crossref_metadata_2025 huggingface dataset:
Close relationships and placemaking: Do objects in a couple's home reflect couplehood?
Authors: Lohmann Andrew , Arriaga Ximena B. , Goodfriend Wind
Published: August 2003

The domain of couple closeness extends well beyond the individual couple members themselves. Current research suggests that there are also indicators of couple closeness, functioning, and commitment that reside in the couple's physical environment. Two community samples of adults in marital or cohabitating romantic relationships (N = 110) completed a questionnaire that tapped several relationship qualities and that asked them to indicate (a) the objects in their home that they most wanted visitors to notice and (b) their favorite objects. We examined couple displays (the percentage of objects they wanted a visitor to notice that were jointly acquired, as opposed to individually acquired), and couple markers (the percentage of favorite objects that were jointly acquired). Consistent with hypotheses, relationship qualities (closeness, dyadic adjustment, and commitment) were positively associated with reporting a relatively high proportion of (a) jointly acquired objects among those they wanted visitors to notice and (b) jointly acquired favorite objects. We discuss these results in the context of couple placemaking—the physical and symbolic creation of a home as represented operationally in the acquisition and placement of relationship–relevant objects.
Adolescents' Characteristics and Parents' Beliefs as Predictors of Parentsapos; Peer Management Behaviors
Authors: Tilton‐Weaver Lauree C. , Galambos Nancy L.
Published: August 2003

This study examined parents' reported use of peer management behaviors (i.e., communicating preferences, communicating disapproval, supporting friendships, and information seeking) and linked these behaviors to (a) adolescentsapos; self‐reported psychosocial adjustment and friendships and (b) parents' beliefs about adolescents' peer relationships (i.e., perceived efficacy in managing adolescents' friendships and concerns about adolescents' friendships). The participants were 269 parents (161 mothers, 108 fathers) and their predominantly White adolescents in Grades 6 and 9 (N=177). Results suggest that parents may be more apt to use some behaviors (e.g., communicating disapproval and information seeking) when there are indications that their adolescents are engaged in problem behaviors and have friends who are deviant. In addition, parents' concerns about their adolescents' friends mediate the relationship between adolescent problem behaviors and parents' communications of disapproval. Parents' peer management is promising as a route to understand further the nature of parent–peer linkages.
The Role of Assertiveness and Decision Making in Early Adolescent Substance Initiation: Mediating Processes
Authors: Trudeau Linda , Lillehoj Catherine , Spoth Richard , Redmond Cleve
Published: August 2003

This study examined the mediating processes linking assertiveness and decision making to early adolescent substance initiation, along with the moderating effect of gender on those processes. Models specifying negative expectancies and refusal intentions as mediators of individual rights assertiveness and decision‐making effects on substance initiation were evaluated across 18 months on a nontreatment cohort of young adolescents participating in a prevention trial (average age 12.3 years at baseline; N=357). Results indicated that individual rights assertiveness and decision making had indirect effects on substance initiation through effects on negative outcome expectancies and refusal intentions. Gender differences were found in both the average level and the pattern of relationships among the variables. For girls, refusal intentions were negatively associated with later substance initiation. For boys, early levels of substance initiation were negatively associated with later levels of negative expectancies and refusal intentions. Implications for prevention programming are discussed.
Ecological Theology: Roots in Tradition, Liturgical and Ethical Practice for Today
Authors: Ruether Rosemary Radford
Published: August 2003

Often it is claimed that themes occasionally present in Christianity such as anthropocentrism, ecological alienation, and redemption as a world‐escaping disembodied immortality, translated directly into large‐scale abuse of nature and subsequent ecological crisis. Such a view is too simplistic, however. Instead the present environmental and ecological crisis may be primarily traced to cultural, economic, and technological developments of the last 500 years. Indeed, within Christian monasticism, ecofeminism, covenantal ethics, and cosmic christology, one finds ample resources for the transformation of human attitudes towards nature and a brighter ecological future.
Ecology Needs Theology
Authors: Siegenthaler David
Published: August 2003

A primary purpose of theology is the explication of the relationship of Creation to the transcendent for the sake of responsible action in the world. Environmental policy arenas need a perspective that can take them beyond a more limited utilitarianism. Ecology needs theology. We can appreciate to a much greater extent today than we could a generation ago that all theologies are products of particular people within particular social, cultural, historical, geographical situations. To do theology adequately, it is clearer now that many perspectives must be considered—both within and outside one's own tradition. Theology must be conversational. One's assertions of values and proposed actions must be weighed against the assertions of others. Only through such engagement will theology be meaningful to lives that must be lived with integrity in a world of manifold ambiguities. That world is the whole world in which human community is sustained and to which human beings are responsible. The practical effects of theological engagement will be to help us all find a better “common good” than may be obtained otherwise.
Globalization in Light of Luther's Eucharistic Economic Ethics
Authors: Moe‐Lobeda Cynthia
Published: August 2003

This article suggests that Christ “filling all things,” and abiding in a special way in the assembly of believers, offers moral agency for faithful response to economic structures that gravely threaten Earth's regenerative capacities. That claim is explored through Luther's theology of Christ indwelling creation held together with his eucharistic economic ethics, his call to certain practices, his refusal to minimize the pervasiveness of human sin, and his insistence that in brokenness and defeat the saving God is present and calls forth power. The trends designated by the term “globalization,” as used in this essay, are clarified. Dangers posed to the Earth community by that constellation of trends are illustrated.
Ecclesial DNA
Authors: Murphy George L.
Published: August 2003

We discuss here the metaphor of church DNA which has been used in arguments against Called to Common Mission. Consideration of the role of the genetic material in biological organisms enables us to suggest what it might mean to say that the DNAs of different Christian traditions are or are not compatible. As plants or animals belong to the same species if they can propagate their kind, church bodies can be said to be compatible if their inter‐communion furthers the church's mission to make disciples. Some ways in which ecumenical agreements might make this possible are considered.
Laser modification to an x‐ray collimator: An aid in positioning patients for neurosurgical and radiographic procedures
Authors: Galkin Benjamin M. , Vogel Harold B. , McArdle George H. , Baust George F. , Boon Raymond , O'Donnell Valerie
Published: August 2003

In high‐ambient‐light levels such as are found in operating rooms, and at long target‐to‐patient distances, the cross lines and light field projected from conventional x‐ray collimators are not easily visible and proper patient positioning is difficult. The collimators on two mutually perpendicular x‐ray units have been modified by replacing the incandescent bulbs with lasers and adjusting the lasers to be coaxial with the x‐ray beams. These modifications have been coupled with a third wall‐mounted laser to facilitate patient positioning for stereotaxic thermal hypophysectomy. The use of the laser‐modified collimators has resulted in considerable saving of time for the operating team and has markedly reduced patient anesthesia time. The laser‐modified collimator has also been found useful in positioning patients for other radiographic procedures in the operating room and has virtually eliminated retakes due to malpositioning.
Current status of DT targets for cancer therapy
Authors: Kelsey C. A.
Published: August 2003

The current status of DT targets for cancer therapy is reviewed with regard to beam composition and energy as well as target configuration, lifetime, and neutron output. The advantages and shortcomings of the various target designs are discussed. It is concluded that several approaches can provide the necessary dose rate and target lifetime for clinical therapy purposes.
Early history (1936–1946) of nuclear medicine in thyroid studies at Massachusetts General Hospital
Authors: Evans Robley D.
Published: August 2003

A recounting of the beginnings of nuclear medicine is given with a review of thyroid studies at Massachusetts General Hospital using radioactive iodine. (AIP)
Dosimetry intercomparisons between fast‐neutron radiotherapy facilities
Authors: Smith Alfred R. , Almond Peter R. , Smathers James B. , Otte Victor A. , Attix Frank H. , Theus Richard B. , Wootton Peter , Bichsel Hans , Eenmaa J. , Williams D. , Bewley David K. , Parnell C. J.
Published: August 2003

Neutron dosimetry intercomparison visits have been made by physicists from the M. D. Anderson Hospital–Texas A&M University Project to the Naval Research Laboratory, the University of Washington, and the MRC Cyclotron at Hammersmith Hospital. The Naval Research Laboratory and University of Washington physicists have made dosimetry intercomparisons at the Texas A&M Variable‐Energy Cyclotron (TAMVEC). The parameters that are usually measured during these visits are tissue kerma in air, tissue dose at depth of dose maximum, relative central‐axis depth dose, neutron/gamma ratios in air and in phantom, and photon calibrations of ionization chambers. In addition, beam profiles and dose buildup curves are sometimes measured. Other parameters that are compared are values of W, stopping power ratios, kerma corrections, and calculations that lead to the statement of tumor doses for patients. This paper presents some of the results of the intercomparisons and discusses the implications of the findings.
Experimental test of a new method for kVp measurements
Authors: Joseph Peter M.
Published: August 2003

We present the results of an experimental test of a new method for measuring the kVp of a diagnostic x‐ray beam. The method involves measuring x‐ray attenuation in copper or tin absorbers and plotting the attenuation curve in a new way. Our measurements were done at 60, 90, 100, and 120 kVp on a 3‐phase, 12‐pulse diagnostic generator. The kVp was measured with a calibrated voltage divider‐oscilloscope system. Except at 90 kVp, excellent agreement was found, with precisions on the order of ±1%. The 90‐kVp point appeared to be somewhat affected by characteristic tungsten radiation and gave agreement with a lower value of precision.
Series of high‐sensitivity TL phosphors made from divalent‐metal sulfates
Authors: Ekstrand Kenneth E. , Dixon Robert L.
Published: August 2003

A systematic survey of the thermoluminescence (TL) of rare earth activated sulfates of the form MeSO4:RE was made, where Me denotes a divalent metal and RE the rare earth. SrSO4:Tb3+ and BaSO4:Eu2+ exhibit very high TL efficiency following gamma irradiation, comparable to that of the most sensitive phosphors currently available for TL dosimetry. Due to their relatively high Z, these phosphors could prove useful as quality indicators for personnel dosimetry or for detecting very small exposures of low‐energy x rays of a known quality.
Mechanism to facilitate the fine adjustment of sidelights
Authors: Goitein Michael
Published: August 2003

A simple optical mechanism is presented for the fine adjustment of sidelights. The characteristics of the device are that large angular displacements are required to achieve small lateral motions of a light beam. For this reason, the mounting mechanism may be made to quite coarse tolerances.
X‐ray scatter background signals in transmission radiography
Authors: Motz J. W. , Dick C. E.
Published: August 2003

With monoenergetic x‐ray beams incident on polystyrene phantoms, the spectra of the transmitted x rays were measured with a scintillation spectrometer. The scattered and unscattered components of the transmitted x‐ray fluence at a point on the beam axis were determined as a function of (i) the incident x‐ray energy (18, 22, 32, 49, 58, 69, and 660 keV), (ii) the phantom thickness (5.3, 10, and 21 cm), (iii) the scatter solid angle determined by the exposed area of the phantom and the separation distance of the image plane (0.090, 0.31, 0.66, 1.8, 3.5, 4.3, 4.8, and 5.1 sr), and (iv) the beam diameter at the image plane (25, 17, and 10 cm). The results indicate that, as the incident x‐ray energy decreases from 660 to 30 keV, the contribution of the scattered component to the transmitted fluence increases from approximately 50% to 90% for the 21‐cm phantom and from 21% to 50% for the 5.3‐cm phantom. For typical cases, the data show the effect of the scatter component on the ratio of the image to the background signals. In addition, the examples show that optimum conditions for maximizing this signal ratio may be obtained by a careful selection of the incident x‐ray energy for low‐, medium‐, and high‐contrast objects.
Effect of microdensitometer scan slit misalignment in MTF determinations
Authors: Villafana Theodore
Published: August 2003

To determine the modulation transfer function (MTF) of a radiographic film or film‐screen system, it is common to expose the system to a line source and scan the result with a microdensitometer. The question arises as to how the MTF determination is affected by such factors as microdensitometer slit width and possible misalignment of the slit with the line pattern being scanned. In any experiment, some degree of misalignment can be expected. This paper analyzes the resulting problem and derives an expression for the MTF of slit misalignment and slit width: MTF={sin[2πf (L/2)]/2πf (L/2) } (sin{2πf [H sin(θ/2)]}/2πf [H sin(θ/2)]}), whereL is the slit width, H the slit height, θ the angle of misalignment, and f the spatial frequency variable. The left‐hand factor of this product is the MTF of a finite slit width, while the right‐hand factor is the MTF of misalignment. It is shown that, for radiographic film‐screen combinations, small‐angle misalignment up to 0.25° is not serious with 1.5‐cm‐long slits, while such a misalignment may become serious in high‐bandwidth systems such as nonscreen films.
New device for accurate measurement of the x‐ray intensity distribution of x‐ray tube focal spots
Authors: Doi Kunio , Fromes Bernard , Rossmann Kurt
Published: August 2003

A new device has been developed with which the focal spot distribution can be measured accurately. The alignment and localization of the focal spot relative to the device are accomplished by adjustment of three micrometer screws in three orthogonal directions and by comparison of red reference light spots with green fluorescent pinhole images at five locations. The standard deviations for evaluating the reproducibility of the adjustments in the horizontal and vertical directions were 0.2 and 0.5 mm, respectively. Measurements were made of the pinhole images as well as of the line‐spread functions (LSFs) and modulation transfer functions (MTFs) for an x‐ray tube with focal spots of 1‐mm and 50‐μm nominal size. The standard deviations for the LSF and MTF of the 1‐mm focal spot were 0.017 and 0.010, respectively.
Displacement correction factor for fast‐neutron dosimetry in a tissue‐equivalent phantom
Authors: Shapiro P. , Attix F. H. , August L. S. , Theus R. B. , Rogers C. C.
Published: August 2003

The displacement correction factor to be used for analysis of fast‐neutron dosimetric measurements using air‐filled EG and G tissue‐equivalent ion chambers in a tissue‐equivalent phantom has been investigated using the MANTA neutron radiotherapy beam generated by 35‐MeV deuterons on a thick Be target. The displacement correction factor inferred from these measurements is 0.970 for the EG and G IC‐17 (1.0‐cm3) ion chamber, and is 0.989 for the EG and G IC‐18 (0.1‐cm3) ion chamber. This multiplicative displacement correction factor has no significant dependence on depth in the phantom or on neutron beam size.
Reduced output of orthovoltage radiotherapy units
Authors: Bomford C. K.
Published: August 2003

Three causes of reduced output of orthovoltage radiotherapy units have recently been reported in this journal, each being due to faults external to the tube insert. A further incident is now reported where the output was reduced by 30% due to the tungsten target foil becoming partially detached from the anode, while the unit continued to operate normally. The possible cause and the prevention of a repeat occurrence are discussed.
Simultaneous determinations of Fe, Cu, Zn, and Br concentrations in human tissue sections
Authors: Kubo Hideo , Hashimoto Shozo , Ishibashi Akira , Chiba Ren , Yokota Hitoshi
Published: August 2003

Proton‐induced x‐ray fluorescence has been used to determine the concentration of trace elements in human prostate and liver tissue samples. Ca, Fe, Cu, and Zn were observed in all specimens. Small amounts of Br were detected in most of the prostates, and in nearly half of the livers. The data indicate that the Fe content decreases in malignant liver tissues and the quantities of Cu and Zn are also decreased, but to a lesser extent.
Method for calculating dose when lung tissue lies in the treatment field
Authors: McDonald Stanley C. , Keller Bowen E. , Rubin Philip
Published: August 2003

The absorbed dose in lung and beyond lung as a result of increased lung transmission of x and γ irradiation is described. The correction factor used to calculate the absorbed dose is a function of beam energy, field area, lung density, and lung and soft tissue depth. Agreement between measurements and calculations in the Alderson phantom is within 3%. An example of how this technique can be used is described.
Intensity distribution, modulation transfer function, and the effective dimension of a line‐focus x‐ray focal spot
Authors: Prasad Satish C. , Hendee William R. , Carson Paul L.
Published: August 2003

The radiant intensity along the anode–cathode dimension of a line‐focus x‐ray focal spot tends to peak at the center and decrease gradually to zero at the edges. In recognition of this varying intensity, the ICRU has recommended that the anode–cathode dimension of the focal spot be reported as 0.7 times the dimension measured with a pinhole camera. In this paper more objective correction factors are developed. These correction factors are based upon comparison of calculated MTFs of focal spots with Gaussian and cosine intensity distributions with the MTF for focal spots with a uniform intensity distribution.
Statistical limitations in x‐ray reconstructive tomography
Authors: Brooks Rodney A. , Di Chiro Giovanni
Published: August 2003

Statistical fluctuations, or noise, in reconstructed tomograms are analyzed as a function of x‐ray energy. The result is essentially constant for energies above 50 keV, assuming constant dose and spatial resolution, and is in close agreement with the actual performance of the EMI‐Scanner (water‐bag model). The noise is inversely proportional to the square of cell dimensions. For scanners without a water bag, the theoretical noise is approximately 30% less.
Polynomial and power law of central axis backscatter factors for external and γ‐ray sources
Authors: Tsung Pei‐nan
Published: August 2003

A third‐degree polynomial and power‐law analysis with the method of least‐squares fit are computed for backscatter factor with a continuous variation of field size and different beam quality of radiation from 1.0‐mm Al external x ray to 60Co γ ray. Three coefficients are required for a third‐degree polynomial and two coefficients for power law method of each beam quality.
Modified transit dosemeter system for 60Co rotational therapy
Authors: Battista Jerry J. , Leung Philip M. K. , Taylor William B.
Published: August 2003

The transit dosemeter has been used in obtaining inhomogeneity corrections for 60Co rotational therapy. A modified approach is presented which features a rapid electronic system for determining the average tissue–air ratio (T̄ĀR̄) for a 360° rotation. Experimental results and early clinical experience show that this system is capable of providing a T̄ĀR̄ value directly, and more rapidly. It can be readily incorporated in a therapy system which already includes a transit dosemeter.
Closed‐system ionography for diagnostic radiology
Authors: Fenster A. , Johns H. E.
Published: August 2003

Three methods are described whereby radiographic electrostatic images are transferred from inside of a liquid ionography chamber to the outside. One of these methods is implemented showing that multiple‐charge images can be transferred from a single original without significant degradation of image quality and each copy may be developed with a different amount of edge contrast. This new method of imaging was applied to a radiograph of a test pattern and a hand phanton. An exposure of about 6 mR to the imaging chamber is needed to produce a useful image with a resolution of about 8 1p/mm.
Frequency of occurrence of various nuclear reactions when fast neutrons (≲50 MeV) pass through tissue‐equivalent material
Authors: Alsmiller R. G. , Barish J.
Published: August 2003

Calculated results are presented for the frequency with which various partial nuclear reaction cross sections are utilized when fast neutrons (≲50 MeV) are transported through a tissue‐equivalent phantom to obtain an indication of which cross sections are of most importance for radiotherapy applications and are therefore in need of experimental verification.
Nuclide parameters and S factors for 201Tl dosimetry estimates
Authors: Feller Paul A. , Scholz Kenneth L.
Published: August 2003

The mean numbers per disintegration, n, and equilibrium‐dose constants Δ for the various emissions of 201Tl were computed. The sums of the penetrating and nonpenetrating equilibrium‐dose constants are 0.1931 and 0.0874 g rad/μCi h, respectively. The S factor, the value of that portion of the MIRD dose equation which is independent of biological distribution, was calculated for various combinations of target and source organs.
Saturation curve in gases of high atomic number at pressures up to 8 atm. Part II: Freon 13‐B1, and mixtures of Freon with xenon and krypton
Authors: Seelentag W. W. , Boag J. W. , Barish R. J.
Published: August 2003

The saturation curve has been studied in Freon 13‐B1 (CF3Br) and in mixtures of Freon with xenon and krypton up to a pressure of 8 atm. The enhanced initial recombination due to the electron affinity of Freon has been evaluated and an empirical formulas constructed that describes the fraction of current which escapes initial recombination over a wide range of voltages, pressures, and electrode spacings. After correction for this initial recombination, the general saturation curve for Freon and for mixtures of this gas with krypton and xenon has been derived and, again, convenient empirical formulae established which allow the current collection efficiency to be calculated for any given parameters within the range investigated. These formulae are of practical value in the design of image‐forming ionization chambers.
Heuristic model for understanding x‐ray film characteristics
Authors: Dixon Robert L. , Ekstrand Kenneth E.
Published: August 2003

A simple, heuristic model of a photographic emulsion is described for the purpose of illustrating the fundamental physical processes and emulsion properties which determine the characteristics of an x‐ray film (viz., the shape of the H−D curve, film gamma, and film speed). By means of this model, it is shown that the contrast multiplication afforded by an x‐ray film (i.e., a film gamma greater than unity) is a direct result of the exponential attenuation of the viewing light by the developed film, and that film gamma is proportional to grain size, grain density, and emulsion thickness. The difference in the H−D curve that is observed when the same film is exposed to light from an intensifying screen or directly to x rays is also predicted by the model.
Equation for scatter–air ratios for megavoltage radiotherapy calculations
Authors: Tatcher M. , Wolberg J. R.
Published: August 2003

Scatter–air ratios are tabulated quantities which are based on measurement and which are used to calculate the dose to points in the body of a patient exposed to radiation fields of arbitrary shape. For computing purposes it is convenient to represent these quantities by an equation. We have found a nine‐parameter empirical function which expresses scatter–air ratio data for 60Co γ rays and for 4‐ and 6‐MV x rays. To test the equation it was used to calculate tissue–air ratios for a range of rectangular fields. The results are in good agreement with published values.
Portable tissue equivalent calorimeter
Authors: McDonald Joseph C. , Laughlin John S. , Freeman Richard E.
Published: August 2003

A portable tissue equivalent calorimeter has been constructed and employed to measure absorbed dose in a mixed fast‐neutron and γ‐ray field. Design details and measurement techniques are described along with the limits of precision and absolute accuracy. Experiments have been carried out with a cyclotron produced neutron beam using the 9Be(d,n)10B reaction at dose rates ranging from 3 to 25 rad/min. A series of ten measurements at a dose rate of approximately 10 rad/min were performed with a precision of ±2% (standard deviation about the mean). The compact design of this calorimetric dosimeter system facilitates transport to other laboratories for the measurement of absorbed dose in several complex radiation fields.
In vivo activation analysis following neutron therapy in cancer patients
Authors: Bond C. D. , Theus R. B. , August L. S. , Shapiro P. , Rogers C. C.
Published: August 2003

A new mode of local in vivo activation analysis following neutron therapy in cancer patients has been explored at the Naval Research Laboratory Cyclotron Facility. The level of the therapeutic neutron dose administered to a patient presents a unique opportunity to use a Ge(Li) detector to obtain rapidly a high‐resolution γ‐ray spectrum of the activity induced in and around the tumor mass. Methods of analysis and local geometrical effects are discussed.
Comparisons of calorimetric and ionometric measurements in graphite irradiated with electrons from 15 to 50 MeV
Authors: Domen S. R. , Lamperti P. J.
Published: August 2003

Extensive experimental comparisons of calorimetric and ionometric measurements have been made that cover a broader range of electrons energies and depths in graphite than previously reported. Electron beams of 15, 20, 25, 30, 40, and 50 MeV were used. Calorimetric absorbed‐dose measurements and ionometric specific‐charge measurements in air were compared in graphite at depths from 1 to 51 g/cm2. The medium was irradiated with uncollimated electron beams produced by scattering after passing through a 0.1‐g/cm2 aluminium vacuum window, various thicknesses of lead foils, and air. The variation in the quotient of the two measurements was studied as a function of lead‐foil thickness, depth in the medium, beam energy, foil‐to‐detector distance, and off‐axis distance. These studies permitted the measurements to be corrected and compared with theoretical calculations that assume a broad medium irradiated with broad, parallel, monoenergetic electron beams. The overall experimental uncertainty is estimated to be 1%. The results are generally in good agreement with theoretical and experimental results of other investigators. The calorimeter received close to 1 Mrad during preliminary measurements and from 1 to 2 Mrad during the measurements reported. The results showed no detectable heat defect in graphite after prolonged periods of exposing the calorimeter to air at atmospheric pressure.
Relationship between tissue–phantom ratio and percentage depth dose
Authors: Purdy James A.
Published: August 2003

The relationship between the tissue–phantom ratio and central‐axis percentage depth‐dose data is derived. Relationships between the tissue–phantom ratio, tissue‐maximum ratio, and tissue–air ratio are given. A simple model is developed which suggests that the degree to which the TPR and TMR are independent of distance from the source depends largely on the collimator/flattening‐filter scatter.
Dosimetry measurements and analyses of 10‐MV x rays for Clinac‐18
Authors: Wu Andrew , Leavitt Dennis D. , Campbell Dale W.
Published: August 2003

Radiation parameters for two Varian Clinac‐18 10‐MV x‐ray units were measured and compared with the same parameters for the Toshiba LMR‐13 and the Arco Mevatron XII. Comparison of the percentage depth dose, surface dose, and depth of maximum ionization as a function of field size are presented.
Use of 48Ca as a stable isotope tracer analyzed by proton activation
Authors: Edwards F. M. , Kraushaar J. J. , Ristinen R. A. , Rudolph H.
Published: August 2003

The use of the stable isotope 48Ca as a tracer in biological systems has been studied. Determination of 48Ca concentrations in samples was accomplished by proton activation via the (p,n) reaction with subsequent measurement of γ‐ray spectra from 44‐h 48Sc and 4‐h 44Sc. With protons of about 5.5 MeV and a Ge(Li) γ‐ray detector, and with no chemical processing of the samples, ratios of these two radioisotopes can be determined with sufficient precision to allow 48Ca tracer studies to be performed with sensitivity at least equivalent to that possible with the common 45Ca radioactive tracer.
Dysprosium‐159 for transmission imaging and bone mineral analysis
Authors: Rao Dandamudi V. , Govelitz George F. , Sastry Kandula S. R.
Published: August 2003

The suitability of the intense Kα x rays of terbium emitted in the electron‐capture decay of 159Dy for use in transmission imaging and bone mineral analysis is investigated. It is found that this radionuclide offers all the advantages of radiations from 210 Pb and none of the disadvantages inherent in the use of the latter. Yields of the Kα and Kβ x rays of terbium and the 58‐keV γ rays emitted in 159Dy decay are determined using a high‐resolution Si(Li) photon spectrometer. Attenuation coefficients for these photons in gadolinium (critical) absorber are measured in a narrow‐beam geometry. For Tb Kβ x rays, whose average energy is only about 0.4 keV above the K edge of Gd, our experimental attenuation coefficient is about 10% less than the theoretical value given by Storm and Israel. Transmission images of regular and irregular bones obtained using 159Dy are presented.
Corrections to megavoltage depth‐dose values due to reduced backscatter thickness
Authors: Goede Myron R. , Anderson David W. , McCray Ken L.
Published: August 2003

Multiplicative corrections for percent depth‐dose values were measured for situations with nonmaximal backscatter because of reduced thickness of the irradiated phantom. Data were obtained for common clinical field sizes for a 60Co beam as well as beams from a 2.5‐MV and a 4.0‐MV generator. Functional forms, which summarize the results and include field size effects, depth, and the thickness of the backscatter medium as variables, were obtained by regression analysis.
Magnetic enhancement of electron dose distribution in a phantom
Authors: Whitmire Daniel P. , Bernard Davy L. , Peterson Mary D. , Purdy James A.
Published: August 2003

We have measured the effect of a 10‐kG magnetic field on the dose distribution of electrons in a polystyrene phantom. Isodensity plots and depth‐dose curves are presented for 22‐ and 28‐MeV electron beams with and without the magnetic field applied. The measurements show that magnetic fields as low as 10 kG can produce a substantial modification of the absorbed dose distribution. When compared with the zero‐magnetic‐field distribution of the same energy, the magnetic field significantly improves the Dmax‐surface dose ratio and increases the fall off in dose past the Dmax region.
A new type of grid
Authors: Brezovich Ivan A. , Barnes Gary T.
Published: August 2003

A new type of grid is discussed. It is anticipated that it will have the same primary transmission as and will eliminate scatter more efficiently than a conventional linear grid of equal thickness and lead content. The construction of the new type of grid is similar to a conventional one except that the lead strips are arranged in zigzag rather than linear pattern. Geometrically ideal “zigzag” and linear grids were constructed and their performance tested. The scatter transmitted by the ideal zigzag grid was one‐half that of the comparable ideal linear grid. The implications regarding the improved scatter‐eliminating capabilities of a practical zigzag grid are discussed.
Neutron spectra at 0° from 83.7‐MeV deuterons and 100.2‐MeV protons on beryllium
Authors: Madey R. , Waterman F. M. , Baldwin A. R.
Published: August 2003

Neutron energy spectra were measured at 0° from 83.7‐MeV deuteron bombardment of a 2.0‐cm‐thick beryllium target and 100.2‐MeV proton bombardment of a 60‐MeV‐thick beryllium target backed with aluminum.
Imaging soft tissue through bone with ultrasound transmission tomography by reconstruction
Authors: Carson Paul L. , Oughton Thomas V. , Hendee William R. , Ahuja Avtar S.
Published: August 2003

A phantom consisting of a 2.5‐cm‐diameter aluminum rod, a balloon filled with castor oil, and a balloon filled with a phenylated silicone fluid was imaged in water with ultrasound transmission tomography by reconstruction (UTTR). This phantom was chosen for investigation of the feasibility of detecting small changes in the ultrasound velocity and ultrasound attenuation coefficient of soft tissues in planes containing bones. Attenuation images of a transverse section of a leg of lamb were obtained as well. Opposed transmitting and receiving transducers were scannned on either side of the imaged object, just as an x‐ray tube and detector are scanned in the pencil beam geometry employed with the first x‐ray computerized axial tomographic system. More than adequate signal was transmitted through the aluminum rod and the bone to obtain reconstructions; but, in these crude images, there were numerous artifacts which maintain the uncertainty regarding the future utility of this promising technique. Although velocity imaging should not be as sensitive to reflection and refraction as attenuation imaging, a very narrow ultrasound beam must be employed to obtain reasonable resolution in velocity imaging.
Scattered photons as the cause for the observed dmax shift with field size in high‐energy photon beams
Authors: Marbach James R. , Almond Peter R.
Published: August 2003

Measurements on the Sagittaire linear accelerator and Allis–Chalmers betatron at M. D. Anderson Hospital indicate that the observed dmax shift with field size is due to the presence of Compton‐scattered photons in the therapy beam, and not electrons as proposed by others. Separating the primary from other radiation components indicates that the secondary fraction represents a percentage contribution to the overall beam that increases as the collimators are opened. This is consistent with what would be expected from Compton scattering and explains the effective softening of the beam as field size increases.
Dosimetric measurements in the neutron field produced by a deuterium gas target with a compact medical cyclotron
Authors: McDonald Joseph C. , Kuo Thomas Y. T. , Freed Barry R. , Laughlin John S.
Published: August 2003

Several dosimetric measurements have been carried out in the neutron field produced by accelerated deuterons incident upon a pressurized deuterium gas target. A significant improvement has been achieved in central‐axis depth dose when compared to the 9Be(3He,n)11C interaction previously studied. Designs for a target with a high‐power dissipation capability are currently underway.
Measurement of photon dose fraction in a neutron radiotherapy beam
Authors: Weaver Keith , Bichsel Hans , Eenmaa Juri , Wootton Peter
Published: August 2003

Photon dose fractions (PDFs) have been measured in and around a neutron radiotherapy beam with a tissue‐equivalent proportional counter (TEPC) and with paired ion chambers. The PDFs were found to increase linearly with increasing field size and width depth in phantom. PDFs were shown to decrease with decreasing phantom size and to be larger in the shielded region of the phantom than in the direct beam. Uncertainties in the PDF values were estimated to be 10%–15% for the TEPC measurements but about 50% for the measurement made with ion chambers.
Dosimetry of pion therapy beams
Authors: Smith Alfred R. , Rosen Isaac I. , Hogstrom Kenneth R. , Lane Richard G. , Kelsey Charles A. , Amols Howard I. , Richman Chaim , Berardo Peter A. , Helland Jerome A. , Kittell Richard S. , Paciotti Michael A. , Bradbury James N.
Published: August 2003

Cellular, animal, and human radiobiology studies are in progress at the Los Alamos Meson Physics Facility as part of a joint University of New Mexico and Los Alamos Scientific Laboratory pion therapy project. To support these activities, dosimetry has been performed on many different pion beam configurations. The effect of both static and dynamic momentum spreaders and of collimators on beam profiles, depth‐dose distributions, and peak‐to‐plateau ratios have been studied. The absorbed dose is obtained by the application of Bragg–Gray cavity theory to ionization chamber measurements. Calculations have been made for the effective W values and average mass‐stopping‐power ratios needed for the Bragg–Gray equation. Kerma corrections are applied to transform the dose from the chamber wall to dose in muscle.
High‐energy‐photon dose measurements using exposure‐calibrated ionization chambers
Authors: Kutcher G. , Strubler K. , Suntharalingam N.
Published: August 2003

The current method for determining absorbed dose from high‐energy photons is to use in water a Cobalt‐60 exposure‐calibrated ionization chamber and Cλ. Recently questions have arisen about the correctness of currently recommended Cλ values and whether or not the Cobalt‐60 buildup cap should be used for in‐water dose measurements. The effect of the buildup cap on Cλ was obtained by measuring Farmer chamber response in water with and without the buildup cap. Results show no measurable change at Cobalt‐60 or 4 MV but an increase of 1%–2% above 20 MV. The effects of the wall materials and the displacement factors on Cλ are also considered. It is shown that at high energies errors of 3%–5% can be made in determining dose in water using commercially available Farmer or Farmer‐like chambers and currently recommended Cλ. The exact size of the error depends upon the materials and thicknesses of the wall and cap, the chamber cavity volume, and whether or not the buildup cap is used.
Tissue‐maximum ratios for high‐energy x rays
Authors: Dawson Donald J.
Published: August 2003

The tissue‐maximum ratios for high‐energy betatron x rays, measured at target‐axis distances of 90, 110, and 130 cm, exhibit a strong dependence on the target‐axis distance in the buildup region as well as a significant dependence in the exponential region. This dependence and the field‐size dependence of the tissue‐maximum ratios at a fixed target‐axis distance are studied with the use of phantom and collimator scatter factors. The depth and field‐size dependence of these scatter factors are determined experimentally. The measurements indicate that the collimator scatter factor is dependent on both the collimator opening and the target‐axis distance. These components are quantitated separately and are associated primarily with high‐energy electron scatter from the collimating system. An equation involving these components of the collimator scatter factor is derived for the conversion of tissue‐maximum ratios from one target‐axis distance to another. With the use of this equation, the tissue‐maximum ratios measured for one target‐axis distance can be used to calculate within 1% those at other target‐axis distances.
Electrical constancy check for remote‐reading op–amp radiation dosimeters
Authors: Stanton Robert
Published: August 2003

A constancy check is described for dosimeters using fast op–amp electrometers with remote ionization chambers. The check's usefulness is reported, as are capacitance values for some commercial ion chambers.
Effects of red cell shape and orientation on propagation of sound in blood
Authors: Ahuja Avtar S. , Hendee William R.
Published: August 2003

In this paper, the red blood cell (RBC) is assumed to have an oblate spheroidal shape and the same volume (87 μm3) and about the same sphericity index (0.7) as a typical human RBC. The acoustic field is assumed to be either parallel or perpendicular to the axis of symmetry of the spheroid, and a wave equation is formulated for a dilute RBC suspension. Because of the small density difference between the RBC and plasma (about 5%), the assumption of spherical shape of the RBC suffices for computation of the velocity and the scattering of sound in blood. For all practical purposes, scattering of sound in blood follows Rayleigh's law of scattering. However, the viscous absorption coefficient at 1 MHz for a spheroidally shaped RBC oscillating broadside and edgewise to an acoustic field is about 40% and 136%, respectively, of that for a spherically shaped RBC. These results illustrate the significant effects of RBC shape and orientation on the viscous loss of sound energy in blood.
Radiation from the uranium collimators of the Varian 4‐MeV accelerator
Authors: Nibhanupudy J. Rao , Henschke Ulrich K.
Published: August 2003

The uranium collimator of the Varian 4‐MeV accelerator produces a dose rate of 100 mR/h near the collimator opening. It can be decreased to 4% by a 6‐mm Lucite shield at the level of the collimator opening. A better solution is a leadglass–mylar (LM) shield which decreases the uranium radiation to less than 3% and also provides better skin sparing during treatment than the open collimator.
Silicon diode detectors used in radiological physics measurements. Part I: Development of an energy compensating shield
Authors: Gager L. David , Wright Ann E. , Almond Peter R.
Published: August 2003

Silicon diode detectors have the advantages of high resolution, large signal, and fast response, but lack the flat energy response of the Farmer ion chamber. A study was undertaken to develop a compensating shield for a diode which would make it suitable for use in the spectrum of energies produced by a high‐energy radiation beam at depth in a phantom. The energy response of the unshielded diode was quantitated over a range of energies from 18.5 keV to 8 MeV. Shields of different thicknesses, density, and design were tested experimentally. A partial shield of high‐Z material over a diode with miniaturized contacts produced a probe which duplicated the relative dose measurements of the Farmer chamber with less than 1% variation. Typical central axis depth‐dose curves and a beam profile, measured with the chamber and the shielded and unshielded probe, are illustrated.
Energy dependence of correction factors for some low‐energy direct‐reading pocket dosimeters
Authors: Morgan Tommie J. , Brateman Libby , Dirkse John
Published: August 2003

The energy dependence for each of five models of low‐energy direct‐reading pocket dosimeters was characterized through an examination of the exposure correction factors determined over the diagnostic x‐ray range (0.4–4.1‐mm Al HVL) for many samples of each model. The results of an analysis of variance performed by model on the correction factors are reported as mean correction factors for the x‐ray beams evaluated, the relative standard error being less than 0.8% in all cases. Energy‐dependence curves for the dosimeter models are given, and their use is described.
Toward a unified view of radiological imaging systems. Part II: Noisy images
Authors: Wagner Robert F.
Published: August 2003

“The imaging process is fundamentally a sampling process.” This philosophy of Otto Schade, utilizing the concepts of sample number and sampling aperture, is applied to a systems analysis of radiographic imaging, including some aspects of vision. It leads to a simple modification of the Rose statistical model; this results in excellent fits to the Blackwell data on the detectability of disks as a function of contrast and size. It gives a straightforward prescription for calculating a signal‐to‐noise ratio, which is applicable to the detection of low‐contrast detail in screen–film imaging, including the effects of magnification. The model lies between the optimistic extreme of the Rose model and the pessimistic extreme of the Morgan model. For high‐contrast detail, the rules for the evaluation of noiseless images are recovered.
Radiations emitted in the decay of 165Er: A promising medical radionuclide
Authors: Rao Dandamudi V. , Hallee Gary J. , Ottlinger Michael E. , Sastry Kandula S. R.
Published: August 2003

The 10.3‐h 165Er, decaying by electron capture to stable 165Ho, offers an excellent promise for use in diagnostic nuclear medicine, especially in conjuction with multiwire proportional‐counter cameras. Using an ultra‐high‐resolution Si(Li) photon spectrometer, L and K x‐ray photon yields in 165Er decay have been measured. The ratio PL/PK of electron‐capture probabilities in L and K shells is determined to be 0.196±0.030, in good agreement with theory. Estimates of Auger electron yields and yields of very‐low‐energy electrons from Coster–Kronig transitions are presented. Levels of 169Er and 171Er radioactive impurities in the reactor‐produced 165Er sample are experimentally determined. Whole‐body dose estimates for 165Er are given. These compare favorably with 99mTc dose.
Proton penetration and control in nonhomogeneous phantoms
Authors: Wingate Catharine L. , Archambeau John O. , Koehler Andreas M. , Bennett Gerald W.
Published: August 2003

Accurate bolus is needed for extension of Bragg‐peak therapy. Proton beam‐stopping profiles in a lucite–styrofoam–tissue phantom and in a Rando phantom were recorded photographically. Air volumes caused the largest distortions. Lucite bolus was cut to achieve desired beam‐stopping profiles. Verification of bolus effect in situ will be important to control beam penetration within 5 mm.
Iterative method for elimination of the Kβ filter in dual‐beam differential tissue absorptiometry
Authors: Bolin Frank P. , Preuss Luther E.
Published: August 2003

The application of a dual photon beam to the measurement of tissue and tissue‐like substances has generally required the use of a filter to attain the required monochromaticity of the lower‐energy x‐ray photons. In many cases this has the undesirable effect of also severely attenuating the desired low‐energy beam. A method for circumventing the use of the filter is described. The technique relies on a knowledge of the initial intensities of the components of the x‐ray portion of the dual beam and involves an iterative mathematical procedure. Experimental verification of the method using both tissue and nontissue substances has been carried out. R values obtained with the iterative system show good correlation with filtered values.