the diagnostic accuracy of single photon emission computed tomography (spect) is profoundly influenced by attenuation phenomenon. soft tissue attenuation degrades cardiac spect image quality, thereby decreasing the possibility of the detection of the lesions. a variety of correction techniques based on different assumptions have been used to reduce the impact of attenuation. several types of sy...

Underground rocks usually have complex pore system with a variety of pore types and a wide range of pore size. The effects of pore structure on elastic wave attenuation cannot be neglected. We investigated the pore structure effects on P-wave scattering attenuation in dry rocks by pore-scale modeling based on the wave theory and the similarity principle. Our modeling results indicate that pore ...

background: in megavoltage radiotherapy rooms, ordinary concrete is usually used due to its low construction costs, although higher density concrete are sometimes used, as well. the use of high-density concrete decreases the required thickness of the concrete barrier hence, its disadvantage is its high cost. in a nuclear reactor, neutron radiation is the most difficult to shield. a method for p...

Introduction: The role of radiotherapy as a part of cancer management increases every year around the world. Thus, Radiation protection in the design of radiotherapy rooms are of great importance.   Materials and Methods: In present study using Monte Carlo method, MCNPX code, fourteen types of developed high density concretes with densities ranging from 2.45 ...

A simple method which does not require calibration with a reference liquid for the determination of attenuation and density of a fluid contained within a thin-walled cell is demonstrated. The method relies on temporally filtering the impulse response of the system to partially deconvolve the transfer function associated with the wall. Experiments are conducted on cells of differing material con...

Density is an important parameter to determine the strength of road, and it will ensure the safety of the use as well as maintaining the quality of road pavement. In this paper, the validation of GPR mixture model based on the microwave nondestructive free space method to determine the density of road pavement typed Hot Mix Asphalt (HMA) will be presented. The frequency range of operation used ...

development of ultrasound technique has not been progressing for evaluating the internal quality of fruits as fast as that of processed foods. in this research for quality assessment of pear fruit (shah miveh variety) an ultrasonic measurement system was constructed to transmit and receive the ultrasonic waves. the apparatus included a pulser-receiver, a pair of 75 khz ultrasonic transducers wi...

spect detects γ-rays from administered radiopharmaceutical within the patient body. γ-rays pass through different tissues before reaching detectors and are attenuated. attenuation can cause artifacts; therefore different methods are used to minimize attenuation effects. in our study efficacy of chang method was evaluated for attenuation purpose, using a custom made heart phantom. due to differe...