introduction: attenuation correction is a useful process for improving myocardial perfusion spect and is dependent on activity and distribution of attenuation coefficients in the body (attenuation map). attenuation artifacts are a common problem in myocardial perfusion spect. the aim of this study was to compare the effect of attenuation correction using different attenuation maps and different...

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...

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 d...

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...

ultrasonic testing (ut), a nondestructive testing (ndt) method, is under development for quality determination of agricultural products, although it has long been used in the food industry. determination and measurement of product quality are important in modern agricultural research. noninvasive/nondestructive quality determination is a novel aspect of the postharvest process in which paramete...

introduction: nowadays, imaging of the myocardial perfusion (mpi) using the single photon emission tomography (spet) in the diagnosis of coronary artery disease, especially myocardial ischemia, is of great importance. in contrast to the coronary artery angiography, mpi is non-invasive, less expensive and more physiological. unfortunately, this image is affected by the some artifacts. these arti...

In the measurement of acoustic attenuation that obeys a power-low alpha = beta f, the traditional through-transmission method uses only the amplitude information of the recorded pulses to determine the two parameters, beta and n. In this paper, we propose a new method that utilizes both the amplitude and phase information of the pulses to determine the two parameters. According to this method, ...

natural hazards such as earthquakes have threatened the life of human beings during the history.as a consequence, the vibration mitigation of structures has caught great importance. activecontrol of structures is one of the rapidly emerging areas in the concept of structural control. thispaper presents a control method to deal with this subject when the dynamics of the structure ishysteretic an...