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At least 865 records · Page 48Linked to original sources
PubMed1983

Single-photon emission computed tomography of the normal liver.

Single-photon emission computed tomography (SPECT) is a new imaging method that offers the advantage of cross-sectional imaging and improved contrast resolution as compared with conventional planar imaging. Preliminary SPECT studies of the liver for detection of metastatic disease are very promising. However, these studies indicate some potential pitfalls in the interpretation of the normal liver SPECT images. Experience with 58 tomographic studies obtained with a General Electric 400T rotating gamma camera is presented, with special emphasis on the areas of potential misinterpretation and on recognition of the normal anatomy as seen by this technique.

Elementary Particles↗
PubMed1977

Diminution of bone mass in childhood diabetes.

Photon absorption measurements of forearm bone density in 196 insulin-dependent patients, age 6--26 years, were compared with findings in 124 controls. Expected density, gm. Ca/cm.2 bone width (M/W), was calculated from regressions of M/W on ulnar length for white and black male and female controls. There were no significant correlations between M/W differences from expected and serum Ca, Mg, P, or alkaline phosphatase levels, estimated physical activity level, insulin dosage, or the presence of joint contracture. White females averaged 8.2 per cent (+/- 1 S.E.M.) loss of M/W, as against white male average loss of 4.7 per cent +/- 1 and black female loss of 2 per cent +/- 2 (p less than 0.001); the black male population was too small for separate analysis. M/W loss greater than 10 per cent was seen in 29 per cent of white males, 19 per cent of blacks, and 48 per cent of white females (p less than 0.02). When the groups were further divided into those with duration of diabetes less than or equal to five years and those with duration greater than five years, significant reduction in M/W average loss over time was seen with white females (10.6 per cent +/- 1.2 to 3.7 per cent+/- 1.5, p less than 0.0001). Expression of this defect in bone mineralization is controlled by race and sex acting independently of each other.

Adolescent↗
PubMed1980

Electron and photon beams from a 50 MeV racetrack microtron.

The quality of broad high energy photon and electron beams can be improved considerably by the scanning of elementary narrow beams. Dose distributions produced in this way have advantages with respect to improved dose gradients and therapeutic ranges for electrons and lower surface doses, increased depth doses and half value depths for photons. The possibility of giving the whole therapeutic dose in a single local pulse of short duration is discussed as a new method to protect superficial tissues.

Electrons↗
PubMed1983

Elastooptic photon signal modulation in collagenic fiber optics of tendon.

In a test of a hypothesis of cell-to-cell communication via their endogeneous photon emissions, the nearly pure collagen fibers in tendon were found to exhibit the fiber optic property of axially conducting light, providing a mechanism for photon exchange between nonadjacent cells. Further, it was found that light penetrates farther along the tendon fibers when tension is applied to an end-illuminated tendon, establishing that an elastooptic mechanism exists for the modulation of photon signals in transit between cells, in the hypothesized system of cell-to-cell photon communication.

Animals↗
PubMed1979

[Microdosimetry of in-flight pi-beams (author's transl)].

Microdosimetry of in-flight pi-beams was performed at the T1 channel of National Laboratory for High Energy Physics (KEK), Tsukuba, Japan. Distributions of lineal energy (y) in-flight pi-beams having six momentum values from 120 MeV/c to 1000 MeV/c were measured with an LET counter which simulates 2 micron sphere of soft tissue filled with the methane base tissue equivalent gas. Frequency spectra were obtained in the range of 1.6 less than y less than 430 keV/micron. Fractional dose y . d(y), cumulative dose D(y), and mean lineal energy were calculated from these spectra; then momentum dependences were investigated. These absolute values have little physical application because of the lack of data for y less than 1.6 keV/micron. However, the general trends of y distribution in momentum dependence were found, qualitatively. As the momentum becomes smaller, the rate of high y component in the dose increased.

Elementary Particles↗
PubMed1980

[Dependence of scattered Mn K alpha / K beta X-ray intensity ratio on the scatterer materials].

The K alpha / K beta ratio of Mn KX-rays scattered by metallic samples changed remarkably with the geometry between the sample and the (55)Fe source-Si(Li) detector system. On the contrary, this intensity ratio changed little in the cases of non-metallic scatterer samples such as lucite or mylar. This difference is interpreted as due to the occurrence of strong or weak interference in the coherent scattering photons.

Elementary Particles↗
PubMed1984

Modelling of cosmic-ray muon exposure in building's interior.

Physical parameters on the exposure indoors from cosmic ray muons were determined in order to undertake computer simulations. The hitherto known information was compiled, and the unknowns were newly calculated. Assumptions and approximations required in making a practical model were also described. The stopping power and the range of muons in a normal concrete as well as the air were calculated for the energy up to hundreds GeV. The consistency of those results with ready-made tables was found satisfactory although the comparisons were available only in the low energy tail. The scattering effect of cosmic ray muons in building's interior was examined numerically through very simple model calculations. It was revealed that the overall scattering effect would be ignored unless very small variations are wanted. The iron fraction in a reinforced concrete as well as the density of the concrete was also shown to be an ineffective factor.

Computers↗
PubMed1984

Calculation on cosmic-ray muon exposure rate in non-walled concrete buildings.

Computer simulations on the exposure indoors from cosmic ray muons were practiced in the framework of non-scattering and non-cascade assumptions. The model buildings were two-dimensional, rectangular, and were made of a normal concrete. A stratified structure was assumed in each building, where no mezzanine was considered. Walls were not taken into account yet. The distributions of the exposure rates in 26-story buildings were illustrated in contour maps for various sets of parameters. All of them gave basically archlike patterns. Analyses of the results showed that the exposure rate is affected most largely by the floor board thickness. The ceiling height would be an insignificant factor for short buildings. The min/max ratio of the muon exposure rate in a moderate size building was estimated to be more than 0.7.

Computers↗
PubMed1983

[The applicability of pions to cancer radiotherapy. I. Experimental measurements of the capture and absorption of pions in polymer].

A future application of negative pions to radiotherapy has arrived at a promising stage. Negative pions, in addition to their good localization characteristics, offer an advantage of favorably influencing biological factors because of differences in the quality of radiation given to a) the treatment volume and b) the intervening normal tissue. By utilizing dose fractionation, the low dose to intervening normal tissue with its low LET allows these tissues to recover better than cells in the treatment volume. In this study the lucite phantom was bombarded with 150 MeV/c and 173 MeV/c negative pions and 173 MeV/c positive pions, respectively, by using the 12 GeV proton synchrotron of the National Laboratory for High Energy Physics (KEK). Range-energy relations in the lucite and the remaining curves of pions were observed. The observed range of pions in lucite agreed well with the theoretical prediction. The remaining curves show the different structures for pi+ and pi- mesons. Peak to plateau ratio is ten times.

Elementary Particles↗
PubMed1984

In flight negative pion assessments using time-of-flight technique.

Time-of-flight measurement was applied to obtain the energy spectra of the neutron emitted from tissue-equivalent plastic (TEP) exposed by pi- mesons. The separation of electrons and muons in beams was attempted. Neutrons from TEP exposed by pi- mesons at P pi = 500 MeV/c were separated from gamma-rays by the NE 213 liquid scintillator and the pulse-height analyzer. The double differential cross sections for neutron energy are obtained. The cross sections of the neutron energy distributions show a preponderance of low energy neutrons and a high energy tail extending to approximately 100 MeV.

Electrons↗