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...

Purpose: Fiber carbon is the most common material used in treating couch as it causes less beam attenuation than other materials. Beam attenuation replaces build-up region, reduces skin-sparing effect and causes target volume under dosage. In this study, we aimed to evaluate beam attenuation and variation of build-up region in 550 TxT radiotherapy couch.Materials and Methods: In this study, we ...

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 combined PET/MR, the high soft tissue contrast of Magnetic Resonance Imaging (MRI) and the functional information of Positron Emission Tomography (PET) are combined in one machine. Although this combination still poses many technological challenges, recent progress [1] indicates that it is only a matter of time before PET/MR machines enter the market. On the software side, attenuation correc...

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. Thes...

We have performed measurements of third sound attenuation in thick films of superfluid He in the presence of small amounts of He. The attenuation due to He appears to depend linearly on the number density of He atoms in the film. We discuss the results in context of a recently proposed mechanism where the attenuation is caused by the interaction of the excitations in helium with the trapped vor...

OBJECTIVE To refine the CT prediction of emphysema by comparing histology and CT for specific regions of lung. To incorporate both regional lung density measured by CT and cluster analysis of low attenuation areas for comparison with histological measurement of surface area per unit lung volume. METHODS The histological surface area per unit lung volume was estimated for 140 samples taken fro...

Introduction: The main goal of SPECT imaging is to determine activity distribution inside the organs of the body. However, due to photon attenuation, it is almost impossible to do a quantitative study. In this paper, we suggest a mathematical relationship between activity distribution and its corresponding projections using a transfer matrix. Monte Carlo simulation was used to find a precise tr...

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...