Compton spectrometry applied to clinical CT axial beams from tubes stopped and in revolution

Terini, Ricardo Andrade; Nerssissian, Denise; Campelo, Maria Carolina S.; Morice, Vincent; Yoshimura, Elisabeth Mateus

doi:10.1016/j.radphyschem.2020.108734

Cited by 4 publications

(2 citation statements)

References 24 publications

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“…The x‐ray spectra used in the present work 49–51 were validated by comparison with those measured by Terini et al. employing a Compton spectrometer, 57 to TASMICS 58 and SpekPy 59 x‐ray spectra generator models and by comparing the corresponding measured HVL values. The average differences between the experimental and semi‐empirical spectra were less than 16% in the energy range from 20 to 140 keV.…”

Section: Resultsmentioning

confidence: 91%

“…Additionally, the x-ray spectra generated with the semi-empirical TBC model [49][50][51] were validated by comparison to those measured by Terini et al employing a Compton spectrometer 57 and also to other x-ray spectra generator models. 58,59 Another cross-check was done comparing the HVLs resulting from the TBC model and measurements made with an ionization chamber in the GE Discovery CT750HD system at the same voltages.…”

Section: Validation Using Analytical Equationsmentioning

confidence: 99%

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A comprehensive Monte Carlo study of CT dose metrics proposed by the AAPM Reports 111 and 200

et al. 2021

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Purpose: A Monte Carlo (MC) modeling of single axial and helical CT scan modes has been developed to compute single and accumulated dose distributions. The radiation emission characteristics of an MDCT scanner has been modeled and used to evaluate the dose deposition in infinitely long head and body PMMA phantoms. The simulated accumulated dose distributions determined the approach to equilibrium function, H(L). From these H(L) curves, doserelated information was calculated for different head and body clinical protocols. Methods: The PENELOPE/penEasy package has been used to model the single axial and helical procedures and the radiation transport of photons and electrons in the phantoms. The bowtie filters, heel effect, focal-spot angle, and fan-beam geometry were incorporated. Head and body protocols with different pitch values were modeled for x-ray spectra corresponding to 80, 100, 120, and 140 kV. The analytical formulation for the single dose distributions and experimental measurements of single and accumulated dose distributions were employed to validate the MC results. The experimental dose distributions were measured with OSLDs and a thimble ion chamber inserted into PMMA phantoms. Also, the experimental values of the CTDI 100 along the center and peripheral axes of the CTDI phantom served to calibrate the simulated single and accumulated dose distributions. Results: The match of the simulated dose distributions with the reference data supports the correct modeling of the heel effect and the radiation transport in the phantom material reflected in the tails of the dose distributions. The validation of the x-ray source model was done comparing the CTDI ratios between simulated, measured and CTDosimetry data. The average difference of these ratios for head and body protocols between the simulated and measured data was in the range of 13-17% and between simulated and CTDosimetry data varied 10-13%. The distributions of simulated doses and those measured with the thimble ion chamber are compatible within 3%. In this study, it was demonstrated that the efficiencies of the CTDI 100 measurements in head phantoms with nT = 20 mm and 120 kV are 80.6% and 87.8% at central and peripheral axes, respectively. In the body phantoms with nT = 40 mm and 120 kV, the efficiencies are 56.5% and 86.2% at central and peripheral axes, respectively. In general terms, the clinical parameters such as pitch, beam intensity, and voltage affect the D eq values with the increase of the pitch decreasing the D eq and the beam intensity and the voltage increasing its value. The H(L) function does not change with the pitch values, but depends on the phantom axis (central or peripheral). Conclusions: The computation of the pitch-equilibrium dose product, Deq , evidenced the limitations of the CTDI 100 method to determine the dose delivered

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Section: Resultsmentioning

confidence: 91%

Section: Validation Using Analytical Equationsmentioning

confidence: 99%

A comprehensive Monte Carlo study of CT dose metrics proposed by the AAPM Reports 111 and 200

et al. 2021

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A dosimetric study of occupational exposure during computed tomography procedures

Silva,

Caixeta,

Souza

et al. 2024

Radiation Physics and Chemistry

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On the relativistic impulse approximation for the calculation of Compton scattering cross sections and photon interaction coefficients used in kV dosimetry

Wang

Miguel²,

Seuntjens³

et al. 2020

Phys. Med. Biol.

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We calculate differential and integrated cross sections for the Compton interaction as well as mass attenuation (), mass energy-transfer (), and mass energy-absorption () coefficients, within the relativistic impulse approximation (RIA) using Compton profiles (CPs) obtained from unrestricted Hartree–Fock electron densities. We investigate the impact of using molecular as opposed to atomic CPs on dosimetric photon interaction coefficients for air, water and graphite, and compare our cross sections to the simpler Waller–Hartree (WH) and Klein–Nishina (KN) formalisms. We find that differences in and resulting from the choice of CPs within the RIA are small relative to the differences between the RIA, WH, and KN calculations. Surprisingly, although the WH binding corrections seem accurate when considering , there are significant discrepancies between the WH and RIA results when we look at . The WH theory can differ substantially from the predictions of KN and the RIA in the tens of keV range (e.g. 6%–10% at 20 keV), when Compton scattering becomes the dominant interaction mechanism. For lower energies, the disagreement further grows to about one order of magnitude at 1 keV. However, since the photoelectric effect transfers more energy than the Compton interaction in the tens of keV range and below, the differences in the total values resulting from the choice of Compton models (KN, WH, or RIA) are not larger than 0.4%, and the differences between WH and the other two theories are no longer prominent.

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Compton spectrometry applied to clinical CT axial beams from tubes stopped and in revolution

Cited by 4 publications

References 24 publications

A comprehensive Monte Carlo study of CT dose metrics proposed by the AAPM Reports 111 and 200

A comprehensive Monte Carlo study of CT dose metrics proposed by the AAPM Reports 111 and 200

A dosimetric study of occupational exposure during computed tomography procedures

On the relativistic impulse approximation for the calculation of Compton scattering cross sections and photon interaction coefficients used in kV dosimetry

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