X‐ray scatter background signals in transmission radiography

Abstract

With monoenergetic x-ray beams incident on polystyrene phantoms, the spectra of the tramsmitted 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.

Tissue‐equivalent materials for construction of tomographic dosimetry phantoms in pediatric radiology

“…Polystyrene ͑soft tissue equiva-lent͒ was not considered as it is seldom used in diagnostic radiology except in scatter measurements. 13,14 Our calculations also show that it does not match the ORNL reference soft tissues as closely as does acrylic across the energy range of interest ͑20 to 80 keV͒. Copper, a bone-tissue equivalent material, was excluded from the comparisons as it never matches ORNL reference bone tissue as closely as does aluminum ͑20 to 80 keV͒.…”

A new volumetric CT machine for dental imaging based on the cone-beam technique: preliminary results

“…Moreover, it permits intrinsically the manufacture of less expensive CT machines. Potential disadvantages are, however, the scattered radiation [12] and the limited dynamic range of the X-ray area detectors, based on the presently employed image intensifier tube and TV chain. Image intensifiers have also low diameters as regards CT applications; thus, ªtrun-cated-viewº artifacts are also present [13].…”

Near Infrared Light Amplification in Dye-Doped Polymer Waveguide

“…The category of experimental studies contains the work of Motz and Dick (1975) and Dick et a1 (1978). These authors determined the sum of the scattered and the primary x-ray fluence I, + Ip transmitted through a polystyrene phantom, using a NaI(T1) scintillation spectrometer.…”

“…This seems a plausible explanation, because they used the same phantom for all measurements instead of using a phantom of small cross-section for the narrow beam measurements. Motz and Dick (1975) determined the primary component by measuring the unattenuated x-ray fluence and calculating the attenuation of the phantom. A drawback of this method is that the attenuation of the phantom must be accurately known.…”