Attenuation of bremsstrahlung generated at constant medium potentials

Soole, B W; Jager, Wolter F.

doi:10.1088/0031-9155/15/1/006

Cited by 7 publications

(14 citation statements)

References 13 publications

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“…However, although agreement with published experimental data was reasonably good (Soole and Jager 1970), it was found subsequently (Soole 1971) that this was somewhat fortuitous, the measurements considered having been normalized to a total filtration of only 2.273 m air + 0.2 mm AI (273.9 mgcm-2 air+ 54 mg cm12 Al) a thickness which allowed the penetration of some softening tungsten L-radiation originating in the target. Removal of this by normalization of the data to the greater thickness of 2.273 m air + 0.5 mm Al (subsequently increased to 2.273 m air + 1.0 mm A1 (Soole 1976)), showed the radiation to be distinctly and consistently more penetrating than the computations predicted.…”

Section: Theoretical and Computational Methodssupporting

confidence: 62%

“…It was originally assumed (Soole and Jager 1970) that the spectral distribution of the radiation leaving an X-ray target surface could be taken to be as given by the Kramers (1923) expression and a computer program was developed whereby the modification of this spectrum by the passage of the radiation through the tube window, air and any added filtration could be determined using the attenuation coefficients of Hubbell (1969).…”

Section: Theoretical and Computational Methodsmentioning

confidence: 99%

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A determination by an analysis of X-ray attenuation in aluminium of the intensity distribution at its point of origin in a thick tungsten target of bremsstrahlung excited by constant potentials of 60-140 kV

Soole¹

1977

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A recently described, computer aided method of attenuation analysis has been applied to free-air chamber measurements of the attenuation by up to 30mm A1 of the exposure rate of a narrow beam of X-radiation excited at a thick W target in a Be window tube by constant potentials of 60, 80, 100, 120 and 140 kV. It has been shown that the general characteristics of the intensity distributions of the bremsstahlung at its point of origin within the target found by an earlier analysis are fully confirmed but that, for radiation excited at potentials appreciably above the K-absorption edge of the tungsten target, the attenuation measurements must first be corrected for the pressure of target characteristic K-fluorescence radiation. A method for doing this from published estimates of the relative amounts of W K-fluorescence at various filtrations in radiation excited by the same potentials is described, and it is shown that these amounts come into reasonable agreement when translated to the target surface. Curves of the intensity distribution of the bremsstrahlung at its point of origin within the target are presented which are consistent with attenuation data corrected according to these estimates. They show a good general agreement with theoretical expectation.

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Section: Theoretical and Computational Methodssupporting

confidence: 62%

Section: Theoretical and Computational Methodsmentioning

confidence: 99%

A determination by an analysis of X-ray attenuation in aluminium of the intensity distribution at its point of origin in a thick tungsten target of bremsstrahlung excited by constant potentials of 60-140 kV

Soole¹

1977

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“…Tungsten L-radiation, with a weighted mean energy of 9.17 keV (Storm and Israel 1967), will, however, be generated a t all exciting potentials above 12.1 kV (Fine and Hendee 1955). It was considered (Soole and Jager 1970) on the basis of observations by Wang, Raridon and Tidwell (1957), using a NaI(T1) scintillation spectrometer, that 0.25 mm A1 was sufficient to render this radiation relatively negligible, but evidence from transmission curves obtained with a free-air chamber suggests that, for such observations, the greater thickness of 0.5 mm A1 is necessary (Soole 1971).…”

Section: For Target Characteristic Radiationmentioning

confidence: 99%

“…where If the elementary composition of all the material, including the X-ray tube window, through which the radiation passes after leaving the target is known, then ( 5 ) may be multiplied by an appropriate attenuation factor to give a quantity proportional to the resultant differential intensity, and by another air-absorption factor to give a quantity proportional to the corresponding differential exposure rate; a numerical integration with respect to the photon energy hv from zero to hv,, where hv, = To, then provides a figure proportional to the total exposure rate after a known degree of filtration (Soole and Jager 1970). When such calculations were carried out for conditions appropriate to those for which complete experimental data are available (Thoraeus 1940) it was found (Soole 1972) that beyond a filtration (0.5 mm Al) sufficient to remove the tungsten fluorescent L-radiation o significantly greater penetration was predicted than had been observed.…”

Section: Introductory Theorymentioning

confidence: 99%

A method of X-ray attenuation analysis for approximating the intensity distribution at its point of origin of bremsstrahlung excited in a thick target by incident electrons of constant medium energy

Soole¹

1976

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A computer-aided method of analysis of the attenuation by known materials of the exposure rate of a narrow beam of X-radiation generated by a constant medium potential at a thick smooth plane target is described. On the assumption that the average loss of energy of initially monoenergetic electrons is given by the Thomson-Whiddington relation, expressions are derived for the differential intensity of radiation leaving the surface of a solid plane target for a number of analytical approximations to the intensity distribution of the bremsstrahlung at its point of origin within the target. Particular forms of these approximations have been determined which yield attenuation curves closely matching those experimentally determined by Thoraeus for constant exciting potentials of 50, 60, 80 and 100 kV. They are found to be generally consistent with theoretical expectation and the few direct measurements available.

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“…Kramers' early theory describing the bremsstrahlung spectrum generated by an x-ray tube neglected target attenuation and assumed a constant value for the differential cross-section coefficient used to calculate the intensity of emitted photons at the point of production. 19 One of the earliest models for spectrum calculation [20][21][22] was based on data from Kramers' theory adjusted for absorption within the target. Calculated data were compared to attenuation measurements to determine the differential energy intensity of bremsstrahlung production.…”

Section: B Methods To Calculate Energy Spectramentioning

confidence: 99%

Deblurring of x‐ray spectra acquired with a Nal‐photomultiplier detector by constrained least‐squares deconvolution

Skipper

Hangartner

2002

Medical Physics

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A constrained least-squares technique to correct diagnostic x-ray tube energy spectra for inherent blurring by scintillation detectors was developed. The measured detector response function to monoenergetic sources was used to construct a matrix that modeled the energy broadening in the crystal. This blurring operator, along with an estimate of statistical noise in the count data, comprised the a priori system knowledge required for application of the method. Tungsten anode spectra up to 90 kVp were acquired with a Nal-photomultiplier detector system at a source-to-detector distance of 30 cm. X-ray tube output was collimated at the detector by a 0.5 mm diameter pinhole collimator. Measured Nal spectra were compared to both published reference data and to spectra acquired in our laboratory with a Ge detector system. Application of the constrained least-squares technique involved first defining a criterion function that combined an assessment of the goodness of fit with a weighted measure of the smoothness of the solution. Minimization of this function resulted in the corrected spectrum. While it is not possible to recover the characteristic tungsten peaks, the success of our method in deconvolving the measured spectra was demonstrated by a significant improvement in agreement with reference data. To provide a measure of this agreement, a histogram of the differences between the two curves was generated. The full width at half maximum (FWHM) of the Gaussian distribution fit to the histogram was used to quantify the similarity between the spectra and the reference data, both before and after correction. As spectral agreement improves, the FWHM becomes smaller. We show that application of the constrained least-squares technique improved spectral matching by 20%-60%.

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Attenuation of bremsstrahlung generated at constant medium potentials

Cited by 7 publications

References 13 publications

A determination by an analysis of X-ray attenuation in aluminium of the intensity distribution at its point of origin in a thick tungsten target of bremsstrahlung excited by constant potentials of 60-140 kV

A determination by an analysis of X-ray attenuation in aluminium of the intensity distribution at its point of origin in a thick tungsten target of bremsstrahlung excited by constant potentials of 60-140 kV

A method of X-ray attenuation analysis for approximating the intensity distribution at its point of origin of bremsstrahlung excited in a thick target by incident electrons of constant medium energy

Deblurring of x‐ray spectra acquired with a Nal‐photomultiplier detector by constrained least‐squares deconvolution

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