Evaluation of Compton attenuation and photoelectric absorption coefficients by convolution of scattering and primary functions and counts ratio on energy spectra

Quantitative assessment of full-width at half-maximum and detector energy threshold in X-ray imaging systems

BACKGROUND

The response function of imaging systems is regularly considered to improve the qualified maps in various fields. More the accuracy of this function, the higher the quality of the images.

METHODS

In this study, a distinct analytical relationship between full-width at half-maximum (FWHM) value and detector energy thresholds at distinct tube peak voltage of 100 kV has been addressed in X-ray imaging. The outcomes indicate that the behavior of the function is exponential. The relevant cut-off frequency and summation of point spread function S(PSF) were assessed at large and detailed energy ranges.

RESULTS

A compromise must be made between cut-off frequency and FWHM to determine the optimal model. By detailed energy range, the minimum and maximum of S(PSF) values were revealed at 20 keV and 48 keV, respectively, by 2979 and 3073. Although the maximum value of FWHM occurred at the energy of 48 keV by 224 mm, its minimum value was revealed at 62 keV by 217 mm. Generally, FWHM value converged to 220 mm and S(PSF) to 3026 with small fluctuations. Consequently, there is no need to increase the voltage of the X-ray tube after the energy threshold of 20 keV.

CONCLUSION

The proposed FWHM function may be used in designing the setup of the imaging parameters in order to reduce the absorbed dose and obtain the final accurate maps using the related mathematical suggestions.

Dual energy window imaging for optimisation of P/V ratios in VP SPECT

Purpose

Ventilation–perfusion single-photon emission computed tomography (VP SPECT) plays an important role in pulmonary embolism diagnosis. Rapid results may be obtained using same-day ventilation followed by perfusion imaging, but generally requires careful attention to achieving an optimal count rate ratio (P/V ratio) of ≥ 3:1. This study investigated whether the ratio of counts simultaneously acquired in adjacent primary and Compton scatter energy windows (E_ratio) on V SPECT was predictive of final normalised perfusion count rate (PCR_norm) on P SPECT using [^99mTc]Tc-macroaggregated albumin (MAA), thus allowing for optimisation of P/V ratios.

Methods

Same-day VP SPECT studies acquired using standard protocols in adult patients during a 2-year period (training dataset) were assessed. Studies were included provided they were acquired with correct imaging parameters, and injection site imaging and laboratory records were available for quality control and normalised count rate corrections. Extraction of DICOM information, and linear regression were performed using custom Python and R scripts. A predictive tool was developed in Microsoft Excel. This tool was then validated using a second (validation) dataset of same-day studies acquired over a subsequent 7-month period. Accuracy of the prediction tool was assessed by calculating the mean absolute percentage error (MAPE).

Results

Of 643 studies performed, the scans of 342 participants (median age 30.4 years, 318 female) were included in the training dataset, the analysis of which yielded a significant regression equation (F(1,340) = 1057.3, p < 0.0001), with an adjusted R² of 0.756 and MSE of 0.001089. A prediction tool designed for routine clinical use was developed for predicting final P/V ratio. Of an additional 285 studies, 198 were included in the second (validation) dataset (median age 29.7 years, 188 female). The Excel-based tool was shown to be 91% accurate (MAPE: 9%) in predicting P/V ratio.

Conclusion

The relationship between the ratio of simultaneously acquired counts in adjacent energy windows on V SPECT and perfusion count rate after administration of a known activity of [^99mTc]Tc-MAA can be linearly approximated. A predictive tool based on this work may assist in optimising the dose and timing of [^99mTc]Tc-MAA administration in same-day studies to the benefit of patients and workflows.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40658-021-00417-z.

Appraisal of new density coefficient on integrated-nanoparticles concrete in nuclear protection

The most important material for shielding is concrete in nuclear facilities which performance can be improved by addition some Nanoparticles (NP) at the various concentrations. Nanoparticles, which have a distinctive potential for bio-radiation and shielding of nuclear reactors, are used in many areas due to their special characteristics, which lead to an improvement in the mechanical properties and the pore structure of the concrete shield. The aim of this research was to initiate a novel coefficient (n), experiment to theory density ratio for integrated NP at different nanoparticle concentrations (xnano), established upon purely mathematical viewpoints and some appropriate physical objectives.

Introducing a novel coefficient on mixed-nanoparticles material: relationship between the theoretical and experimental densities

Nanoparticles (NPs) indicating a unique potential in bioradiation and nuclear reactor shielding are employed in many fields due to their particular specifications leading improving the mechanical properties as well as pore structure of the concrete-shield. The aim was to introduce a novel coefficient ( ξ ), namely the experimental to theoretical density ratio for mixed-NPs material at various nanoparticles percent concentrations (ω n a n o ) based on pure mathematical aspects along with the some suitable physical purposes by Monte Carlo method. The change in the mixture density to the change inω n a n o is always proportional to theω n a n o value. The density will become maximum at theω n a n o ∗ in which the physical, morphological and chemical features of NPs along with the amounts of voids in the material have a key role over estimating porosity percentage. The NPs' separation probability as born-cascaded-pairs towards very small radii may be formulated as ξ - ξ - 1 + ω n a n o ∗ + k ' ' | ω n a n o - ω n a n o ∗ | = k ' wherek ' andk ' ' are constant values. In conclusion, the theoretical results may be experimentally used in future work for different applications such as designing shield at a nuclear facility.

Determination of Gamma Camera's Calibration Factors for Quantitation of Diagnostic Radionuclides in Simultaneous Scattering and Attenuation Correction

OBJECTIVE

The characterization of cancerous tissue and bone metastasis can be distinguished by accurate assessment of accumulated uptake and activity from different radioisotopes. The various parameters and phenomena such as calibration factor, Compton scattering, attenuation and penetration intrinsicallyinfluence calibration equation, and the qualification of images as well.

METHODS

The camera calibration factor (CF) translates reconstructed count map into absolute activity map, which is determined by both planar and tomographic scans using different phantom geometries. In this study, the CF for radionuclides of Tc-99m and Sm-153 in soft tissue and bone was simulated by the Monte Carlo method, and experimental results were obtained in equivalent tissue and bone phantoms. It may be employed for the simultaneous correction of the scattering and attenuation rays interacted with the camera, leading to corrected counts. Also, the target depth (d) may be estimated by a combination of scattering and photoelectric functions, which we have published before.

RESULTS

The calibrated equations for soft tissue phantom for the radionuclides were obtained by RTc = - 10d+ 300 and RSm = -8d + 100, and the relative errors between the simulated and experimental results were 4.5% and 3.1%, respectively. The equations for bone phantom were RTc = -30d + 300 and RSm = - 10d + 100, and the relative errors were 5.4% and 5.6%. The R and d are in terms of cpm/mCi and cm. Besides, the collimators' impact was evaluated on the camera response, and the relevant equations were obtained by the Monte Carlo method. The calibrated equations as a function of various radiation angles on the center of camera's cells without using collimator indicated that both sources have the same quadratic coefficient by -2E-08 and same vertical width from the origin by 8E-05.

CONCLUSION

The presented procedure may help determine the absorbed dose in the target and likewise optimize treatment planning.

Spectroscopy and Optimizing Semiconductor Detector Data Under X and γ Photons Using Image Processing Technique

BACKGROUND

Spectroscopy is the study of the absorption and emission of light or other radiation by material. It is used to measure intensity of radiation by a function of wavelength.

METHODS

The spectra of semiconductor detector cadmium tungstate from water, iron, lead, aluminum, and soft tissue targets were experimentally obtained through incident 1E-3 GeV X-ray and ⁶⁰Co γ-ray and then optimized. The amounts of transmitting radiation attenuation were calculated in 0.2-2 cm thicknesses of the materials using reduction coefficient in theory. Data obtained from FLUKA's simulations were then compared with theoretical values by dividing per theoretical parameter, and mean values were obtained for the attenuation coefficients. Finally, by using the MATLAB software, these corrected coefficients were applied to the simulated data, and the spectra were replotted to optimize the detected values.

RESULTS

These obtained parameters increased while the material density increased, except for water and soft tissue materials under γ-ray of ⁶⁰Co. The multiple Compton scattering inside the low-density material affected the γ-photon deviation to reach the crystal. Also, iron had the lowest values of mass attenuation coefficient for both incident radiations, causing a great corrected coefficient and then a greater count in redrawing.

DISCUSSION

Although the lead material had the greatest density and X-attenuation coefficient, it revealed large amounts for both corrected coefficients, X and γ rays, of 100.90848 and 1.90900, respectively. In count estimation, results showed that the simulated spectra after optimization are more similar to practical spectra.

CONCLUSION

The policy on reducing radiation damage from ionizing particles necessitates evaluation of various material behaviors to determine which one will be instrumental for imaging or radiotherapy concerns.