Showing papers on "Imaging phantom published in 1973"
TL;DR: The presence of a phantom arm that resembles the descriptions of phantom limbs by amputees and paraplegics is reported by human subjects who receive an anesthetic block of the sensory and motor nerves of the arm.
148 citations
TL;DR: Heterogeneity in the composition and density of tissue is most marked in bone and lung, and although without them diagnostic radiology would be impossible, they create difficulties in radiotherapy where field planning is usually based on calculation for a homogeneous phantom.
Abstract: Heterogeneity in the composition and density of tissue is most marked in bone and lung. Although without them diagnostic radiology would be impossible, they create difficulties in radiotherapy where field planning is usually based on calculation for a homogeneous phantom. For the radiation qualities currently used in radiotherapy the shadowing effect of bone on deeper tissue is usually negligible and the main problem is the enhanced energy absorption in bone itself due to photo-electrons with a fairly short range. Even this effect is small at high energies where the photo-electric absorption coefficients account for only a small fraction of the total energy transfer. However, at all energies the reduced density of lung causes dose distributions in the thorax to be significantly different from those estimated for a homogeneous phantom. Greene and Stewart reviewed the sparse literature in 1965. Where data for homogeneous phantoms is corrected for clinical use the corrections are usually made by semi-empiric...
9 citations
TL;DR: A complete analogue Monte Carlo program is described for the detailed computation of neutron-photon interactions with matter to at least 15 MeV, with versions for the CDC 3600 and IBM 360/75 systems.
Abstract: For pt. I see abstr. A13171 of 1973. A complete analogue Monte Carlo program is described for the detailed computation of neutron-photon interactions with matter to at least 15 MeV, with versions for the CDC 3600 and IBM 360/75 systems. Forty-five regions, of any composition chosen from fifteen elements, may be specified, of any size, interrelation and shape expressible as algebraic functions. Similarly, a variety of sources may be included. Two geometric descriptions of Standard Man are proposed, closely matching ICRP specifications. One is an eleven region phantom which is homogeneous in composition excepting the lung regions and the second a heterogeneous phantom of 29 regions. The fraction of gamma -ray energy absorbed by, and the fraction of first collisions within these phantoms were obtained as a function of point source location along the phantom midline at gamma -ray source energies of 0.34, 2.75 and 8.00 MeV. The results obtained differ markedly, in many regions, from those previously obtained with the simple, symmetric, homogeneous solids used as human phantoms.
7 citations
5 citations
TL;DR: Durable solid anatomic phantoms are often needed when roentgen diagnostic methods are evaluated experimentally and should, as closely as possible, agree with those of human tissue as regards attenuation of photons of diagnostically important energies.
Abstract: Durable solid anatomic phantoms are often needed when roentgen diagnostic methods are evaluated experimentally. The radiophysical properties of the phantom should, as closely as possible, agree with those of human tissue as regards attenuation of photons of diagnostically important energies. In a material consisting of light elements, simulating human soft tissue, photons within the energy interval 10 keV to 1.5 MeV interact by coherent scattering, photoelectric effect and Compton scattering. The relative importance of the three processes depends on the photon energy (d. e.g. ATTIX & ROESCH 1968) . The linear attenuation coefficient for the Compton process is determined by the electron density of the material. The coefficients for the photoelectric effect and for coherent scattering depend on the electron density but also on the atomic numbers of the elements in the material. The radiophysical properties of a phantom material can therefore be described by its chemical composition and electron density or mass density (SPIERS 1943, 1946, MARKUS 1956, W,EBER & VAN DEN BERGE 1969, HEMMINGSSON 1971, JAYACHANDRAN 1971, among others) .
5 citations
TL;DR: Results showed that hypocycloidal motion degrades the input to the imaging system considerably, implying that an imaging system of high resolution may not be necessary to obtain tomograms of diagnostic quality.
Abstract: A method of measuring the one-dimensional input x-ray pattern of a bone phantom exposed with tomographic motion was used to study image quality in laminagraphy. Results showed that hypocycloidal motion degrades the input to the imaging system considerably, implying that an imaging system of high resolution may not be necessary to obtain tomograms of diagnostic quality.
4 citations
TL;DR: This application of computer simulation of area scans from digital phantoms suggests the use of similar procedures first to analyze and then to aid in the modification and improvement of digital computer techniques of scan analysis.
3 citations
TL;DR: It is indicated that photoroentgenographic pantomography could be made available and put to practical use if certain problems were overcome and not totally satisfactory with regard to sharpness of the images.
2 citations
TL;DR: The application of 4096 channel memory unit to the radioisotope imaging is described, and digital data storage has proved to be useful for diagnosis of scintigrams.
Abstract: The application of 4096 channel memory unit to the radioisotope imaging is described. At the time of scanning, the radioactive distribution in the organ is stored in digital form. The content of the memory unit is displayed on the oscilloscope during or after examination. The digital scan can be trans-ferred to magnetic tape or paper tape for further processing. Since data are digital, image smoothing or scan mixing are possible. With this system, total counts of scintiscan matrix can be summed up. The uptake of radionuclide in the organ is calculated with a proper phantom. We have applied this method to thyroid uptake. As a result of this method, digital data storage has proved to be useful for diagnosis of scintigrams.
1 citations
TL;DR: A test phantom that is useful for evaluation of procedures in chest roentgenography has been made and its use to evaluate a technique or facility is not complicated.
Abstract: A test phantom that is useful for evaluation of procedures in chest roentgenography has been made. It is not expensive, the materials are generally available and its use to evaluate a technique or a facility is not complicated.
1 citations
TL;DR: The method has been verified experimentally to an accuracy of ±3 per cent and is expected to be useful in radiotherapy for measuring transmission through tissue inhomogeneities to help establish tumour dose more accurately.
Abstract: This method describes the measurement of the transmission of mono-energetic γ rays between any point on the surface of a phantom and any point inside. It utilizes the Compton-scattered radiation generated by narrow beams of primary radiation which are directed at the phantom. Radiation scattered at 90 deg. to the incident beam from a small internal volume is measured for two opposing directions of the incident beam, i.e., 0 deg. and 180 deg. The ratio of these two measurements is a measure of the relative transmission between the scattering volume and each of the two opposite surfaces. Multiplication of this ratio, or its inverse by the measured total transmission along the beam path gives the square of the partial transmission from one surface to the internal volume. The method has been verified experimentally to an accuracy of ±3 per cent and is expected to be useful in radiotherapy for measuring transmission through tissue inhomogeneities to help establish tumour dose more accurately. Equipmen...
TL;DR: Comparing the effects of changes in density, geometry and composition are compared with effects predicted on the basis of simplified models and applications of Monte Carlo computations to a number of depth-dose situations are illustrated.
Abstract: For pt. II see ibid., vol. 18, no. 1, 53 (1973). Applications of Monte Carlo computations to a number of depth-dose situations are illustrated by comparisons of program output with a number of simple and complex experiments. Comparisons are also made with the computations of other workers, using their simplified geometries and abbreviated compositions for man-like phantoms. Absorbed fractions, dose distributions and photon spectra are presented for a 70 kg heterogeneous Standard Man, using the ICRP composition for the eleven most prevalent elements in each of twenty-nine body regions, and air composition in the two lungs. The effects of changes in density, geometry and composition are compared with effects predicted on the basis of simplified models.