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Photon-counting Computed Tomography
Photon-counting computed tomography (PCCT) is a form of X-ray computed tomography (CT) in which X-rays are detected using a photon-counting detector (PCD) which registers the interactions of individual photons. By keeping track of the deposited energy in each interaction, the detector pixels of a PCD each record an approximate energy spectrum, making it a spectral or energy-resolved CT technique. In contrast, more conventional CT scanners use energy-integrating detectors (EIDs), where the total energy (generally from a large number of photons as well as electronic noise) deposited in a pixel during a fixed period of time is registered. These EIDs thus register only photon intensity, comparable to black-and-white photography, whereas PCDs register also spectral information, similar to color photography. The first clinically-approved PCCT system was cleared by the Food and Drug Administration (FDA) in September 2021. General advantages Often EIDs are used as a baseline for com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CT Scan
A computed tomography scan (CT scan; formerly called computed axial tomography scan or CAT scan) is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers or radiology technologists. CT scanners use a rotating X-ray tube and a row of detectors placed in a gantry to measure X-ray attenuations by different tissues inside the body. The multiple X-ray measurements taken from different angles are then processed on a computer using tomographic reconstruction algorithms to produce tomographic (cross-sectional) images (virtual "slices") of a body. CT scans can be used in patients with metallic implants or pacemakers, for whom magnetic resonance imaging (MRI) is contraindicated. Since its development in the 1970s, CT scanning has proven to be a versatile imaging technique. While CT is most prominently used in medical diagnosis, it can also be used to form images of non-living objects. The 1979 N ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iodine
Iodine is a chemical element with the Symbol (chemistry), symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at , and boils to a violet gas at . The element was discovered by the French chemist Bernard Courtois in 1811 and was named two years later by Joseph Louis Gay-Lussac, after the Ancient Greek 'violet-coloured'. Iodine occurs in many oxidation states, including iodide (I−), iodate (), and the various periodate anions. It is the least abundant of the stable halogens, being the sixty-first most abundant element. As the heaviest essential mineral nutrient, iodine is required for the synthesis of thyroid hormones. Iodine deficiency affects about two billion people and is the leading preventable cause of intellectual disabilities. The dominant producers of iodine today are Chile and Japan. Due to its high atomic number and ease of attachment to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cadmium Telluride
Cadmium telluride (CdTe) is a stable crystalline compound formed from cadmium and tellurium. It is mainly used as the semiconducting material in cadmium telluride photovoltaics and an infrared optical window. It is usually sandwiched with cadmium sulfide to form a p–n junction solar PV cell. Applications CdTe is used to make thin film solar cells, accounting for about 8% of all solar cells installed in 2011. They are among the lowest-cost types of solar cell, although a comparison of total installed cost depends on installation size and many other factors, and has changed rapidly from year to year. The CdTe solar cell market is dominated by First Solar. In 2011, around 2 GWp of CdTe solar cells were produced; For more details and discussion see cadmium telluride photovoltaics. CdTe can be alloyed with mercury to make a versatile infrared detector material ( HgCdTe). CdTe alloyed with a small amount of zinc makes an excellent solid-state X-ray and gamma ray detector ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Convolutional Neural Network
In deep learning, a convolutional neural network (CNN, or ConvNet) is a class of artificial neural network (ANN), most commonly applied to analyze visual imagery. CNNs are also known as Shift Invariant or Space Invariant Artificial Neural Networks (SIANN), based on the shared-weight architecture of the convolution kernels or filters that slide along input features and provide translation- equivariant responses known as feature maps. Counter-intuitively, most convolutional neural networks are not invariant to translation, due to the downsampling operation they apply to the input. They have applications in image and video recognition, recommender systems, image classification, image segmentation, medical image analysis, natural language processing, brain–computer interfaces, and financial time series. CNNs are regularized versions of multilayer perceptrons. Multilayer perceptrons usually mean fully connected networks, that is, each neuron in one layer is connected to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deep Learning
Deep learning (also known as deep structured learning) is part of a broader family of machine learning methods based on artificial neural networks with representation learning. Learning can be Supervised learning, supervised, Semi-supervised learning, semi-supervised or Unsupervised learning, unsupervised. Deep-learning architectures such as #Deep_neural_networks, deep neural networks, deep belief networks, deep reinforcement learning, recurrent neural networks, convolutional neural networks and Transformer (machine learning model), Transformers have been applied to fields including computer vision, speech recognition, natural language processing, machine translation, bioinformatics, drug design, medical image analysis, Climatology, climate science, material inspection and board game programs, where they have produced results comparable to and in some cases surpassing human expert performance. Artificial neural networks (ANNs) were inspired by information processing and distr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Algorithm
In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific problems or to perform a computation. Algorithms are used as specifications for performing calculations and data processing. More advanced algorithms can perform automated deductions (referred to as automated reasoning) and use mathematical and logical tests to divert the code execution through various routes (referred to as automated decision-making). Using human characteristics as descriptors of machines in metaphorical ways was already practiced by Alan Turing with terms such as "memory", "search" and "stimulus". In contrast, a heuristic is an approach to problem solving that may not be fully specified or may not guarantee correct or optimal results, especially in problem domains where there is no well-defined correct or optimal result. As an effective method, an algorithm can be expressed within a finite amount of spac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Histogram
A histogram is an approximate representation of the distribution of numerical data. The term was first introduced by Karl Pearson. To construct a histogram, the first step is to " bin" (or " bucket") the range of values—that is, divide the entire range of values into a series of intervals—and then count how many values fall into each interval. The bins are usually specified as consecutive, non-overlapping intervals of a variable. The bins (intervals) must be adjacent and are often (but not required to be) of equal size. If the bins are of equal size, a bar is drawn over the bin with height proportional to the frequency—the number of cases in each bin. A histogram may also be normalized to display "relative" frequencies showing the proportion of cases that fall into each of several categories, with the sum of the heights equaling 1. However, bins need not be of equal width; in that case, the erected rectangle is defined to have its ''area'' proportional to the frequenc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tomographic Reconstruction
Tomographic reconstruction is a type of multidimensional inverse problem where the challenge is to yield an estimate of a specific system from a finite number of projection (linear algebra), projections. The mathematical basis for tomographic imaging was laid down by Johann Radon. A notable example of applications is the operation of computed tomography#Tomographic reconstruction, reconstruction of CT scan, computed tomography (CT) where cross-sectional images of patients are obtained in non-invasive manner. Recent developments have seen the Radon transform and its inverse used for tasks related to realistic object insertion required for testing and evaluating computed tomography use in airport security. This article applies in general to reconstruction methods for all kinds of tomography, but some of the terms and physical descriptions refer directly to the reconstruction of X-ray computed tomography. Introducing formula The projection of an object, resulting from the tomograph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Compton Scattering
Compton scattering, discovered by Arthur Holly Compton, is the scattering of a high frequency photon after an interaction with a charged particle, usually an electron. If it results in a decrease in energy (increase in wavelength) of the photon (which may be an X-ray or gamma ray photon), it is called the Compton effect. Part of the energy of the photon is transferred to the recoiling electron. Inverse Compton scattering occurs when a charged particle transfers part of its energy to a photon. Introduction Compton scattering is an example of elastic scattering of light by a free charged particle, where the wavelength of the scattered light is different from that of the incident radiation. In Compton's original experiment (see Fig. 1), the energy of the X ray photon (≈17 keV) was significantly larger than the binding energy of the atomic electron, so the electrons could be treated as being free after scattering. The amount by which the light's wavelength changes is called t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X-ray Notation
X-ray notation is a method of labeling atomic orbitals that grew out of X-ray science. Also known as IUPAC notation, it was adopted by the International Union of Pure and Applied Chemistry in 1991 as a simplification of the older Siegbahn notation. In X-ray notation, every principal quantum number is given a letter associated with it. In many areas of physics and chemistry, atomic orbitals are described with spectroscopic notation (1s, 2s, 2p, 3s, 3p, etc.), but the more traditional X-ray notation is still used with most X-ray spectroscopy techniques including AES and XPS. Conversion Uses *X-ray sources are classified by the type of material and orbital used to generate them. For example, CuKα X-rays are emitted from the K orbital of copper. *X-ray absorption is reported as which orbital absorbed the x-ray photon. In EXAFS and XMCD the L-edge or the L absorption edge is the point where the L orbital begins to absorb x-rays. * Auger peaks are identified with three orbital d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charge Sharing
Charge sharing is an effect of signal degradation through transfer of charges from one electronic domain to another. Charge sharing in semiconductor radiation detectors In pixelated semiconductor radiation detectors - such as photon-counting or hybrid-pixel-detectors, charge sharing refers to the diffusion of electrical charges with a negative impact on image quality. Formation of charge sharing In the active detector layer of photon detectors, incident photons are converted to electron-hole pairs via the photoelectric effect. The resulting charge cloud is being accelerated towards the readout electronics via an applied voltage bias. Because of thermic energy and repulsion due to the electric fields inside such a device, the charge cloud diffuses, effectively getting larger in lateral size. In pixelated detectors, this effect can lead to a detection of parts of the initial charge cloud in neighbouring pixels. As the probability for this cross talk increases towards pixel edge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pulse Pileup
In medicine, a pulse represents the tactile arterial palpation of the cardiac cycle (heartbeat) by trained fingertips. The pulse may be palpated in any place that allows an artery to be compressed near the surface of the body, such as at the neck (carotid artery), wrist ( radial artery), at the groin ( femoral artery), behind the knee ( popliteal artery), near the ankle joint ( posterior tibial artery), and on foot ( dorsalis pedis artery). Pulse (or the count of arterial pulse per minute) is equivalent to measuring the heart rate. The heart rate can also be measured by listening to the heart beat by auscultation, traditionally using a stethoscope and counting it for a minute. The radial pulse is commonly measured using three fingers. This has a reason: the finger closest to the heart is used to occlude the pulse pressure, the middle finger is used get a crude estimate of the blood pressure, and the finger most distal to the heart (usually the ring finger) is used to null ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
