Sharif Digital Repository

At almost all frequencies, we have good methods to generate and detect electromagnetic radiations. One crucial exception is the low terahertz range,where despite intensive research there is a severe lack of proper devices for many applications in this frequency range such as oscillators and detectors that is so-called THz gap and includes 0.3 to 10 THz spectrum. There are different types of THz detectors but bandwidth of dection of most of them is narrow. Among these detectors, superconducting transition edge balometer detector has detectivity in wide frequency range. But generally, detectivity of these detectors strongly depends on their ability to absorb radiations of electromagnetic waves... 

Positron Emission Tomography (PET) imaging is a modern sectional imaging technique widely used due to its advantages in visualizing the physiological functions of body tissues. In this method, a radiotracer is injected into the body, concentrating in the area of interest. As the positron-emitting radionuclide decays, positron annihilation occurs, resulting in the emission of two gamma rays in opposite directions. The PET scanner detects these gamma rays; however, scattering may occur during their journey from the patient’s body to the detector, which can introduce errors in tumor localization. To reconstruct images and correct for these scatter effects, various techniques such as iterative...