Improving soft tissue imaging with volume-of-interest cone-beam CT

Current cone-beam CT systems acquire full field-of-view projections in which x-ray scatter degrades the contrast of soft-tissue in the reconstructed images. The objective of this work was to simulate volume-of-interest (VOI) imaging, which reduces scatter and dose to the patient through beam collimation, to investigate the improvements in soft-tissue visibility on the Gamma Knife Icon. The results indicated that as field size decreased, contrast and noise increased, leading to only modest improvements in the contrast-to-noise ratio when using the same initial photon fluence. A reconstruction framework called the interior virtual method was adapted to suppress truncation-induced artifacts and noise in the VOI image. In this framework the projection data were extrapolated using a cosine function, an intermediate image was reconstructed analytically, and virtual projections of the intermediate image were created for iterative reconstruction. The framework supports high quality VOI reconstruction and can allow clinicians to optimize dose for soft-tissue visualization.

Improving soft tissue imaging with volume-of-interest cone-beam CT

Current cone-beam CT systems acquire full field-of-view projections in which x-ray scatter degrades the contrast of soft-tissue in the reconstructed images. The objective of this work was to simulate volume-of-interest (VOI) imaging, which reduces scatter and dose to the patient through beam collimation, to investigate the improvements in soft-tissue visibility on the Gamma Knife Icon. The results indicated that as field size decreased, contrast and noise increased, leading to only modest improvements in the contrast-to-noise ratio when using the same initial photon fluence. A reconstruction framework called the interior virtual method was adapted to suppress truncation-induced artifacts and noise in the VOI image. In this framework the projection data were extrapolated using a cosine function, an intermediate image was reconstructed analytically, and virtual projections of the intermediate image were created for iterative reconstruction. The framework supports high quality VOI reconstruction and can allow clinicians to optimize dose for soft-tissue visualization.

Time Resolved Photon Fluencies for Different Input Angle Sources

The variation of photon fluence distributions [photon/cm2.s] for different input angle laser sources was shown by researchers experimentally [1]. According to this philosophy, different input angle source and detector photon entrance from tissue surface into imaging media have different photon fluence distributions for a specific tissue type. In this study, different input angle simulations were used for pulsed laser photons which uses time resolved (TR) Monte Carlo (MC) photon-tissue interaction simulation program to prove the philosophy in TR run mode. TR run mode MC simulation program trmc.c [2] was modified and used to generate TR photon counts inside the homogenous simulation environment. It has homogeneous tissue optical properties, absorption μa = 0.1 cm-1, scattering μs = 100 cm-1, and anisotropy g = 0.90 coefficients. Multi-input angle philosophy was first demonstrated by the researchers [1]. It was defined and experimentally proven. Photon fluencies which are forward model weight matrix coefficients differences were successfully shown for TR laser as a general procedure. In this study, differences were drawn for seven different input angle sources with pulsed laser photons. The proof-of-concept philosophy was shown successfully. The purpose of the use of pulsed laser is to show the righteousness of the philosophy in TR run mode, since the TR diffuse optical tomography (TRDOT) device would be made as a biomedical optic imaging (BOI) device. Cylindrical radial coordinate system which was defined in trmc.c [2] in earlier was used, the code was modified, and photon fluencies were generated based on the different input angle laser photons. Cylindrical coordinate system has 1 cm and 36-element radial r, and depth z grids. 100.000 photons were sent from pencil beam tissue surface point. Photons would be thought as group of ultra-narrow band pulsed laser photons. The main purpose of showing photon fluencies for different laser source input angles were succeeded and image reconstruction procedure was also applied. Ten time series were used which are [4, 8, 12, 16, 22, 26, 30, 38, 46, 52] picoseconds (ps). Different input angle photon fluence distribution figures were drawn. These are 0º, 15º, 30º, 45º, 60º, 75º, 90º. Photon fluence differences were also drawn and observed for different input angle laser sources. Forward model problem different input angle laser source and detector transfer functions were also drawn. Finally inlusion was embedded inside the homogenous simulation environment and images were reconstructed for both scenarios and localization error (LE), and concentration error (CE) was calculated for both scenarions and compared with each other.

Proposed Innovative Correlations for some Nuclear and Radiological Fields using Theorem of S. El-Mongy

Thinking and thought are divine urge in the Great Quran. The published S. El-Mongy theorem (L= eπrsA) correlates eπ with radius r of circular and spherical geometries by a factor sA (θ/10ϕ) to be used for calculations of arc length and astronomical distance. In this article, Sayed’s formula was used to produce correlations with the well-established laws and formulas of different nuclear and radiological fields. The formula was directed to be correlated with half-life time, activity, flux, reaction rate, reactor power, mean free path, photon fluence rate, radiation dose rate and half value thickness equations. It was also oriented to calculate fuel rods circumstances of different reactor types; PWR, BWR, VVER1200 and Candu-6. The produced correlations of eπ and sA with the above mentioned topics are given with simplified reduced forms, limitation and some comparative calculations between old and the proposed innovative formulas. New formulas for sphere volume and surface area and cylinder are also given based on eπ term.

Multiple Sequential Ionization of Valence n = 4 Shell of Krypton by Intense Femtosecond XUV Pulses

Sequential photoionization of krypton by intense extreme ultraviolet femtosecond pulses is studied theoretically for the photon energies below the 3d excitation threshold. This regime with energetically forbidden Auger decay is characterized by special features, such as time scaling of the level population. The model is based on the solution of rate equations with photoionization cross sections of krypton in different charge and multiplet states determined using R-matrix calculations. Predictions of the ion yields and photoelectron spectra for various photon fluence are presented and discussed.

Monte Carlo-based analysis of the photon beam fluence with air gap thickness between Linac head exit window and patient’s skin in radiotherapy treatments

Linear accelerators (Linac) are used in radiation therapy treatment and its technology improvement ensures high dosimetry quality that should be conserved for high radiotherapy efficiency. However, does the air gap between the exit window of Linac head and patient’s skin alters the physical properties of the photon beam? The objective of this study is to assess the physical properties changes of photon beam fluence according to air gap thickness under the Linac head. The air gap under the Linac head is the last material in the photon beam path; it induces alterations in the beam quality before reaching the patient’s skin. The Varian Clinac 2100 head and the air gap up to the phantom surface are modelled using Monte Carlo BEAMnrc code; the nominal beam energy is 6 MV. The BEAMDP code is used to extract the photon fluence. The photon beam fluence is affected by the air gap under Linac head and decreases by six times due to the photon beam attenuation with air gap thickness; in addition to increasing of beam contamination by scattered photons and electrons. Thus, the air gap induces the beam quality deterioration which is evaluated in terms of photon fluence with air gap thickness. To remove the particles contaminations and conserve integrally the photon beam quality, the number of the photon interactions with air atoms should be as low as possible under Linac head up to patient’s skin and ensure a higher quality of the radiotherapy treatment of deep tumour.