Experimental verification of reverse order of diagnostic X-ray beam quality in voltage-ripple dependence

Matsumoto, Masao; Kubota, Hideaki; Ozaki, Yoshiharu; Kanamori, Hitoshi

doi:10.1007/bf02522945

Cited by 7 publications

(3 citation statements)

References 17 publications

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“…Storm et al, 6 Israel et al, 7 Seelentag and Panzer, 8 and Birch and Marshall 9 introduced another experimental method for direct measurement of x-ray spectra using nuclear detectors such as NaI and Ge, References 6-9͒ worked under the real operating conditions of an x-ray machine, but required unsuitable geometries for pile up due to the high counting rates; they needed sourcedetector distances of up to several meters and very narrow collimation of the beam. A collection of spectra from 10 to 300 kVp have been published by Seelentag et al 10 and from 30 to 150 kVp by Birch et al 11 We [12][13][14][15][16] are experimentally investigating the spectra emitted from x-ray tubes by using Ge detector systems.…”

Section: Introductionmentioning

confidence: 99%

Direct measurement of mammographic x‐ray spectra using a CdZnTe detector

et al. 2000

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Our purpose is to directly measure mammographic x-ray spectra with collimators and a low-efficiency CdZnTe detector developed recently and to find out the best fit response function of CdZnTe detector to correct the measured spectra. Photon spectra (target Mo or Rh) produced by a mammographic x-ray unit at 25-32 kV and 240 mAs (= 3 times of 80 mAs) and transmitted through 0.03 mm Mo or 0.025 mm Rh filter and object (0.1 mm Al to 0.8 mm Al phantoms) have been analyzed. Since detected spectra were distorted by the response of CdZnTe detector and did not present the true photon spectra, the correction was applied by the stripping procedure. The response function of detector used in this procedure has been determined by the evaluation of interactions (K-escape, coherent scattering, and Compton scattering processes) and incomplete charge collection calculated using the Monte Carlo method. We have used Kalpha1, Kalpha2, Kbeta1, Kbeta2 radiations of Cd, Zn, and Te, respectively and have used the weight function for the incomplete charge collection and have considered Compton scattering. The Monte Carlo simulations were continued by changing the important factors (mean path length of hole lambda(h), dead layer of the CZT crystal and weight factor Wq) of incomplete charge collection until the best fit response function was found out. Corrected photon spectra were compared with the mammographic x-ray spectral data of Bureau of Radiological Health (BRH) measured using a Ge detector. Attenuation curves of aluminum for 25-32 kV were calculated from the corrected photon spectra and compared with the attenuation curves measured using an ionization chamber. These results obtained using the CdZnTe detector agreed with the mammographic x-ray spectral data of BRH and attenuation curves obtained by the ionization chamber.

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Section: Introductionmentioning

confidence: 99%

Direct measurement of mammographic x‐ray spectra using a CdZnTe detector

et al. 2000

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“…We obtained the x-ray photon spectra incident on the front screen per mAs mm 2 for a tube voltage of 80 kV by using a method similar to our previous work (Arimura et al 1994). The x-ray photon spectra per mAs mm 2 were measured by means of our x-ray spectrum measuring system (Ozaki et al 1993, Matsumoto et al 1995, and were corrected by using the stripping method (Seelentag and Panzer 1979). We consider that the measured x-ray spectra are the spectra averaged over a wide area of the screen.…”

Section: Number Of X-ray Photons Incident On the Screensmentioning

confidence: 99%

Proportionality between Wiener spectra of quantum mottle and the squares of modulation transfer functions

et al. 1999

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Rossmann proposed that the Wiener spectra of the quantum mottle of radiographs made using screen-film systems were proportional to the squares of the modulation transfer functions (MTFs) of the screen-film systems. On the other hand, Lubberts theoretically pointed out that the shape of the Wiener spectrum of the quantum mottle depended on the sum of the squares of the MTFs for different depths in the screen phosphor layer, rather than the square of the sum of the MTFs for the different depths, i.e. the square of the MTF of the screen-film systems. The purpose of this study is to experimentally investigate the proportionality between the Wiener spectra of the quantum mottle and the squares of the MTFs of screen-film systems using two screen-film systems having different screen thicknesses. For this purpose, we determined correction factors for the square of the MTF of the screen-film system in the Wiener spectrum of the quantum mottle at each spatial frequency when the Wiener spectral values of the screen mottle were separated into those of the quantum mottle and structure mottle. The correction factor is the ratio of the normalized Wiener spectrum of the quantum mottle to the square of the MTF of the screen-film system. As a result, for a thin screen, the correction factors were unity for all spatial frequencies; on the contrary, for a thick screen, the factor increased with spatial frequency. By calculating the theoretical correction factors using the models for the MTF and Wiener spectrum of the quantum mottle of Nishikawa and Yaffe based on Lubberts' theory, we verified that our experimental results agreed with Lubberts' theory. Furthermore, by obtaining the screen thickness dependence of the theoretical correction factors for the two screens, we showed that, for screens thinner than 0.02 mm, Rossmann's theory can be applied to the relationship between the Wiener spectrum of the quantum mottle and the MTF of the screen-film system, whereas for screens thicker than 0.02 mm, Lubberts' theory should be applied.

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“…However, the method introduced above has a drawback in that it does not take the voltage fluctuation ( 12 , 13 ) into consideration. It only utilizes the model spectra at a preset voltage, and we therefore refer to it as the single-voltage method.…”

Section: Introductionmentioning

confidence: 99%

A transmission measurement-based spectrum estimation method incorporating X-ray tube voltage fluctuation

Pan¹,

Li²,

Lin³

et al. 2023

Quant Imaging Med Surg

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Background The energy spectrum is the property of the X-ray tube that describes the energy fluence per unit interval of photon energy. The existing indirect methods for estimating the spectrum ignore the influence caused by the voltage fluctuation of the X-ray tube. Methods In this work, we propose a method for estimating the X-ray energy spectrum more accurately by including the voltage fluctuation of the X-ray tube. It expresses the spectrum as the weighted summation of a set of model spectra within a certain voltage fluctuation range. The difference between the raw projection and the estimated projection is considered as the objective function for obtaining the corresponding weight of each model spectrum. The equilibrium optimizer (EO) algorithm is used to find the weight combination that minimizes the objective function. Finally, the estimated spectrum is obtained. We refer to the proposed method as the poly-voltage method. The method is mainly aimed at the cone-beam computed tomography (CBCT) system. Results The model spectra mixture evaluation and projection evaluation showed that the reference spectrum can be combined by multiple model spectra. They also showed that it is appropriate to choose about 10% of the preset voltage as the voltage range of the model spectra, which can match the reference spectrum and projection quite well. The phantom evaluation showed that the beam-hardening artifact can be corrected using the estimated spectrum via the poly-voltage method, and the poly-voltage method provides not only the accurate reprojection but also an accurate spectrum. The normalized root mean square error (NRMSE) index between the spectrum generated via the poly-voltage method and the reference spectrum could be kept within 3% according to above evaluations. There existed a 1.77% percentage error between the estimated scatter of polymethyl methacrylate (PMMA) phantom using the two spectra generated via the poly-voltage method and the single-voltage method, and it could be considered for scatter simulation. Conclusions Our proposed poly-voltage method could estimate the spectrum more accurately for both ideal and more realistic voltage spectra, and it is robust to the different modes of voltage pulse.

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Experimental verification of reverse order of diagnostic X-ray beam quality in voltage-ripple dependence

Cited by 7 publications

References 17 publications

Direct measurement of mammographic x‐ray spectra using a CdZnTe detector

Direct measurement of mammographic x‐ray spectra using a CdZnTe detector

Proportionality between Wiener spectra of quantum mottle and the squares of modulation transfer functions

A transmission measurement-based spectrum estimation method incorporating X-ray tube voltage fluctuation

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