Single photon emission computed tomography (SPECT) is based on the measurement of radiation emitted by a radiotracer injected into the patient. Because of photoelectric absorption and Compton scatter, the gamma photons are attenuated inside the body before arriving at the detector. A quantitative reconstruction must consider the attenuation, which is usually nonuniform. Novikov has derived an e...

In this paper, we propose an iterative beam hardening correction method that is applicable for the case with multiple materials. By assuming that the materials composing scanned object are known and that they are distinguishable by their linear attenuation coefficients at some given energy, the beam hardening correction problem is converted into a nonlinear system problem, which is then solved ...

In CT, the nonlinear attenuation characteristics of polychromatic X-rays cause beam hardening artifacts in the reconstructed images. When datasets contain multiple materials in the field of scan, the performance of state-of-the-art beam hardening correction approaches is limited by high computational load and reduced correction efficiency. An image based multi-material beam hardening correction...

This paper presents a mathematical characterization and analysis of beam-hardening artefacts in X-ray computed tomography (CT). In the field of dental and medical radiography, metal artefact reduction in CT is becoming increasingly important as artificial prostheses and metallic implants become more widespread in ageing populations. Metal artefacts are mainly caused by the beam-hardening of pol...

Single-photon emission computed tomography (SPECT) is based on the measurement of radiation emitted by a radiotracer injected into the patient. Because of photoelectric absorption and Compton scatter, the γ photons are attenuated inside the body before arriving at the detector. A quantitative reconstruction must consider the attenuation, which is usually non-uniform. Novikov and Natterer had de...

A large set (100 data points at each wavelength) of multispectral beam attenuation, c(X), data at nine wavelengths (440, 450, 490, 520, 535, 550, 565, 630, and 670 nm) is used to develop a spectral model of the beam attenuation coefficient. The relationship c(X) cW(X) = [c(490 nm) cW(490 nm)](1.563 1.149 x 1O-3 X) describes the spectral variation of c(X) where cW(X) is the pure water beam atten...

Introduction: Globally, the need for radiotherapy as a part of cancer management increases every year. Thus, the shielding for megavoltage radiotherapy rooms is of great importance. Materials and Methods: In the present study, 14 types of developed high-density concrete with densities ranging from 2.45 to 5.11 were simulated by using Monte Carlo method. The linear attenuation coefficient and t...

Using QCD-inspired time dependent cross sections for pre-hadrons we provide a combined analysis of available experimental data on hadron attenuation in DIS off nuclei as measured by HERMES with 12 and 27GeV and by EMC with 100 and 280GeV lepton beam energies. We extract the complete four-dimensional evolution of the pre-hadrons using the Jetset-part of Pythia. We find a remarkable sensitivity o...

This paper investigates the use of capacitive proximity sensors as sources of contact-free feedback signal measurement for active vibration attenuation applications. An experimental laboratory device is introduced, which consists of a clamped cantilever beam and actuated by bonded piezoelectric actuators. A measurement model is created and experimentally verified for the assessment of beam tip ...

This work is focused on the atmospheric turbulence effect and a new method for determining optical signal attenuation caused by turbulence is presented here. A new method of power budget of optical links comes from optical intensity distribution in a laser beam after the beam passed through turbulent atmosphere. Results given by this method are compared with Rytov approximation which is nowaday...