Sharif Digital Repository

Millimeter waves provide an effective opportunity to improve vision and imaging in addition to systems based on visible light, X-rays, and infrared, and researchers have paid special attention to the field of millimeter waves to develop imaging. The spectrum of millimeter waves is in the frequency between 30GHz and 300GHz, which is equivalent to the wavelength in free space, between 1 and 10mm. The advantage of millimeter waves is that it works well in different weather conditions. Also, these millimeter waves have the ability to pass through clothing and provide a suitable level of resolution in reconstructed images and provide a suitable ability to separate different materials from each... 

Nowadays, electromagnetic waves with millimeter wavelengths have various usages including medical,non destructive testings, structure inspection and imaging usages. Millimeter waves go through most of common clothings, but unlike x-ray waves, these waves have no ionizing effects.Therefore, they have low health risks for humans. This characteristic makes the imaging systems based on millimeter wave suitable for security purposes, such as airport security. The inclined usage of these systems requires an increase in precision, speed, reduction of error and automatic object detection algorithms. An important way to increase precision is to change the imaging system structure, resulting in... 

Nowadays active Millimeter Wave Imaging Systems are used in verity of medical and security applications. This widespread application re- sults from the intrinsic characteristic of electromagnetic waves in this rang of frequency that can penetrate through interior body structures and clothing with- out bringing harmful ionizing efects to the body. Millimeterwave systems can be very high resolution due to the relatively short wavelength. The current state-of-the-art in active millimeter-wave imaging systems use a set of transmit/receive antennae. The transmitter antennae illuminated the intended person with millimeter waves while the back scattered signal is recorded by the receiver antennae.... 

Small animal SPECT imaging systems have a broad application in developing new diagnostic or therapeutic radiopharmaceutical and biomedical researches. The main goal of this imaging method is to determine distribution tendency and amount of radio pharmaceutics in body. In this study we have developed a reconstruction technique along with photon attenuation correction so as to obtain a high quality image and the finding a relationship between image matrix and absorbed radioisotope in tissues in order to quantify SPECT images with acceptable error range. In this research we have used MLEM method for image reconstruction and the obtained images were evaluated from quantitative and qualitative... 

The aim of this thesis is to investigate recent methods for Image Processing(Any signal process which it’s input is an image and it’s ouput is an image or a set of Image parameters) using Calculus of variation tools. Methods which are to be investigated has been divided into two well known parts of Image Processing : Image Restoration and Image Segmentation.Image Processing Chapter includes two sections: one calculus of variations methods(energy method), other methods based on PDEs(heat equation and Malik-Perona equation). In studing each of this methods, It has been tried to include experimental results and negative and positive points of them.In Image Segmentation Chapter, first... 

In this thesis, we study image restoration problems, which can be modeled as inverse problems. Our main focus is on inverse problems with Poisson noise; which are useful in many problems like positron emission tomography, fluorescence microscopy, and astronomy imaging. As a popular method in the literature, we use statistic modeling of inverse problem with Poisson noise, in the MAP-estimation framework. Then we introduce a semi-implicit minimization method, FB-EM-TV, that involves two alternate steps, including an EM step and a weighted ROF problem. Then we study well-posedness, existence and stability of the solution. This method can be interpreted as a forward-backward splitting strategy,... 

Recently, there has been an increasing trend towards the use of millimeter-wave (MMW) imaging in various detection applications. This is mainly due to two factors: first, the radiation in the MMW band (30–300 GHz) is nonionizing and safe to use and second, it is able to penetrate through most dielectric materials as well as poor weather conditions, such as smoke and fog. With these potentials, MMW imaging has been used in a variety of applications, including target surveillance and precision target imaging, safe aircraft landing, highway traffic monitoring in fog, remote sensing for civil applications and concealed threat object detection for security concerns. Moreover, it can also find... 

Conventional imaging systems composed of two linear arrays of antennas as a transmitter and receiver. These arrays of antennas electronically scan along their antenna elements and are mechanically moved along a second orthogonal direction for scanning large two-dimensional areas quickly. In this thesis, the transmitter antenna elements are Tapered slot-line Antenna operating at 20-30GHz. A multiplexer circuit is used to transmit wideband signals to each antenna in the array. The receiver is composed of Schottky diode and pick up antenna that they are printed onto the radiating end of the antennas on the edge of the transmitter circuit board.In the available imaging systems, for achieving the... 

Frequency-scan millimeter-wave imaging systems are of high interest due to their low cost and acceptable performance in many applications such as concealed-weapon-detection. In recent years, the performance of this system in view of imaging time, image quality and cost has been improved via its implementation based on metamaterial apertures. These structures take advantage from the famous theory of single pixel imaging in optics. Through using the compressive sensing principle, the number of required imaging modes for obtaining diffraction limited resolution is reduced which in turn lessens the imaging time and more importantly the required bandwidth. Still, the image quality and resolution... 

Positron Emmision Tomography is one of the most important methods in molecular imaging field. One of the challenges over PET imaging is the resolution of reconstructed images. To overcome this problem, one can use more exact image reconstruction methods called, iterative methods. It has been showed that Iterative methods like MLEM have advantages over Analytical ones. Main drawback of iterative methods is time consuming computation. Then you should reduce the image reconstruction’s time for clinical time constraints. Using Graphic Proccessing Unit for accelerating computational works, raised in recent years. In this work, we used GPU for accelerating pet image reconstruction and simulation... 

Each year, large quantities of low/intermediate operational radioactive wastes are produced in different matrices. Usually, these wastes are temporarily stored within the plants and after a certain period, they have to be transferred to landfill sites for final disposal. According to international regulations recommended by IAEA as well as, requirements imposed by national regulatory bodies, waste packages must clear certain requirments called Waste Acceptance Criteria. As such, all waste packages are subject to certain inspections in plant or at disposal facilities. Computerized Tomography (CT) is proven to be one of the most efficient inspection tools for waste packages that can reveal... 

Millimeter wave imaging systems have unique features and have been used extensively in a variety of applications including medical imaging, construction operations, places with high security such as airports, Nondestructive testing and etc. These systems provide high resolution, due to the order of wavelength which is several millimeter or centimeter in this band. Also in places with high security and for detecting the concealed objects under people’s clothing, these waves can easily pass through the materials and investigate the person’s body without causing health problems. A wide variety of these imaging systems , each with different design parameters and resolutions, have been proposed.... 

Magnetic Resonance Imaging is one of the most advanced medical imaging procedure that noninvasively played in most applications. However, this imaging method is a good resolution, but not in the conventional high speed imaging method, in fact, the main problem is slow. In recent years many studies have been done to accelerate MRI that compressed sensing can be mentioned among them. Such methods, however, have had very good results but MRI systems are very complex. This project investigates the reconstruction of MR images using data from partial non-Cartesian samples aimed at reducing sampling time and also speed up the process of reconstruction of MR images have been studied. In this regard,... 

Computerized tomography (CT) is a powerful tool among existing bioimaging techniques for capturing bio-images. In fact, CT imaging systems have attracted great attention in the last decades, because of their fast and high-quality reconstruction, low complexity and low-cost hardware solutions. In a CT scan procedure, linear sensors receive x-ray radiations, passed through the patient’s body and The quality of the reconstructed image is essentially influenced by the number of captured line projections. Nevertheless, gathering the adequate amount of data requires the patient to being exposed to X-ray radiations for a long time. However, the intensification of x-ray radiations could lead to... 

Tomography offers a unique opportunity to unravel the complexities of the internal structure of an object without the need to invade it. There are various methods for this reason, in which all of them occupy wave or energy,ffiduction for imaging inside an object. Since the tomography plays a vital role in medicine and industry and present methods have limitation and difficulties to operate, the necessity for developing it has been inevitable. In this thesis a new tomography method has been presented in which uses inverse heat conduction for estimating unknown object with heat conductivity k2 inside a known domain with heat conductivity k 1 • For this purpose temperature is measured at... 

X-ray Computed Tomography (CT) is a widely used medical imaging technique that provides cross-sectional images by measuring the attenuation of X-rays in the body. However, the increasing use of CT has raised concerns about the potential long-term risks associated with radiation exposure. Various approaches have been proposed to reduce radiation dose, and one of the latest methods is sparse-view CT, which has gained popularity due to its lower challenges compared to other techniques. In sparse-view CT, data acquisition is restricted to specific angles, resulting in a significant reduction in radiation dose. However, this approach can introduce streak artifacts in the reconstructed images due... 

Magnetic Resonance Imaging ,MRI, although as one of the most advanced medical imaging equipment is well known but compared to other medical imaging systems needs more time to imaging, so it has caused the patient dissatisfaction. According to the recently researches, filling the image data in a space of information that called ‘k-space’, in the process of image reconstruction, is the main reason of slow MRI. Image reconstruction methods for accelerating like half scan based on image reconstruction by using only a part of k-space is used in MRI systems today, but this method is associated with lower SNR image. Recent research on the theory of compressed sensing has been opened a new approach... 

The conventional cameras and displays do not have the ability to record and display the full brightness of the world around us. These deficiencies have led to the development of methods known as High Dynamic Range Imaging. Most of the work done in this field falls into two groups: compression of the light range and its expansion. In compression, the brightness range is intended to display content with a high dynamic range in simple displays. But the goal of expanding the brightness range is to reconstruct HDR content from a low dynamic range one. In addition to the above classification, this field is also categorized based on the type of content (image or video). In this study, the... 

Today digital imaging systems have been widely used due to their ease of use and proper costs, but still they suffer from low contrast and resolution. Because of technical limits and expensiveness of hardware, software techniques like super resolution have been used. By super resolution we mean increasing the density of an image’s pixels. Super resolution can be categorized as “single image super resolution” and “multi-image super resolution”. Single image super resolution is applied on a low quality image which has blur and/or noise of environment and imaging system and increases its quality and density to an acceptable level. In multi-image super resolution some auxiliary images captured... 

Increasing advances in millimeter-wave imaging have given the new technology a special place in military and civilian activities. A very important advantage of this imaging system, which has led to its rapid development and growth, is that unlike methods such as X-ray imaging, the millimeter-wave signal is completely harmless to the human body. Because millimeter-wave imaging is non-ionizing, allowing for non- invasive imaging. Also, the millimeter-wave easily passes through human clothing and is reflected when it hits the human body, metal and ceramic objects, and some other objects. As a result, it can be used to photograph underwear, insensitive and safe places such as airports. In this...