PHYSICAL PRINCIPLES
An x ray is similar to light and has both particle and wave nature. That basic working of a x ray CT scan is the photons of x ray radiation comes in contact with the electron clouds in atoms. This can happen either by photo electric effect or by scattering.
COMPTON SCATTERING
The first type of interaction of x rays in CT energy range is scattering and one of it is Compton scattering. In Compton scattering photons interact with the outer shell electrons of the atom an ejects it from the atom thereby ionising the atom. The ejected electron is then absorbed by a neighbouring atom. The probability of scattering depends on the electron density of the atom that is more the electron density more the chance of scattering.
…show more content…
The filament adjacent to the cathode is heated up and the energy is absorbed by the electrons and gets ejected of the cathode. The electrons travel towards the anode and hits the tungsten target and rapid deceleration of electrons occurs and this deceleration results in production of electromagnetic radiation that is x-rays. The anode keeps on rotating so that the heat will be lost to a larger area.
SENSORS /DETECTORS
The x-rays leaving the object must be studied to create images. Basically there are three types of detectors.
• Ionisation chamber filled with gas
• Scintillation multiplier tube
• Solid state scintillation detector
IONISATION CHAMBER
Here a chamber is filled with compressed gas. Two electrodes with high potential difference between them is present. As the x-rays enter the chamber the atoms in the gas ionizes and current flows between the electrodes and detection takes place. The advantages of the gas chamber is that it is easier to manufacture and the response to beam density is linear.
SCINTILLATION MULTIPLIER TUBE.
Here a bismuth germinate crystal is used. When this crystal is struck by x-ray photon light is produced with is proportional to the energy of the hitting photon. Near to this is a photo emissive plane. The light produced from the crystal hits this plane and electrons are ejected from this plane. The intensity of the ejected electrons depends on the
X-ray tube is designed to lower the amount of heat produce, this can be accomplished by the rotating of the anode which gives off heat. The X-ray tube is designed with the anode attach to the rotor and cathode on the other side of anode. This design determines the characteristics of X-ray beam.
In both X-rays and CT scans, a form of radiation is emitted and travels through the body, and a detector receives the unabsorbed rays and transmits them to a computer. The physics behind PET scanning is quite different. Basically, a person is injected with a radioactive substance. This substance begins the process of
of the first subatomic particle. In order to do this successfully, Thompson constructed a cathode ray tube that allowed him to determine the ratio of the cathode ray particle’s charge to its mass. The cathode ray tube Thompson constructed was an “air tight” glass tube that had a cathode and an anode (with a small slit) attached to a power source, an electromagnet, a pair of charged plates, and a zinc sulfide coating at the front of the tube. The cathode is a negatively charged metal electrode which produces cathode rays, whereas the anode is a positively charged electrode that allows electrons
One of the first radiology departments was created at the Glasgow Royal Infirmary in 1896. Dr. John Macintyre, head of radiology at Glasgow, created the first x-ray of a kidney stone, an image showing a penny in the throat of a child, as well as an image of a frog’s legs in motion. An American physiologist experimented with x-rays in order to trace food as it traveled through the digestive system (Waters, 2011). In 1896, Dr. Hall-Edwards became one of the first physicians to use x-rays to diagnose a patient, when an x-ray revealed that a needle was embedded in the patient’s hand. X-rays quickly became a vital tool used by doctors, to diagnose patients (Roentgen’s discovery of the X-Rays, 2006). In 1897, x-rays were first used to locate bullets
X-rays are used for medical purposes. They are a form of radiation named electromagnetic waves (EM Radiation). They are used to take pictures of the insides of the human body which come out in black and white. The X-ray was first developed in 1895 by a man named Wilhelm Conrad Roentgen. While He was working with a cathode-ray tube in his laboratory, Roentgen observed a fluorescent glow of crystals on a nearby table close to his tubes. The tube that he was working with consisted of a bulb with positive and negative electrodes enclosed within it, when the air inside of the tube left and when a high voltage was applied to it , the tube produced a fluorescent glow. Roentgen then shielded the tube with heavy
Next, researcher used a Varian Clinac 6EX Linear Accelerator to produce 6MV photon for the study. Researcher then used an Exradin A2 Farmer chamber to measure the ionization of each material, and used a Keithley 35614 digital dosimeter with no temperature or pressure corrections made to read the measurements. The current in the dosimeter set to
X-rays are of two kinds within the ems, the two kinds are the soft x-rays and the hard x-rays. The soft x-rays as the name suggests refers to a higher and bigger wavelength compared to hard x-rays but has a very small wavelength compared to the others and one of the largest frequency and energy but lesser than the hard x-rays. The wavelength starts at 10-7 to 10-10 meters and the average size is between a protein and a water molecule, the frequency of soft x-rays is between 1016 and 1018 and the energy ranges from anywhere between 102 and 104 electric volts. The hard x-rays have lesser wavelength with less size but higher frequency and energy. The energy starting from 104 and going up, and the frequency starting from 1018 and going up from
In this project report, we investigate X-ray as one of the categories under Modern Optics by looking at different aspects of it. After providing background information regarding X-rays, we provide its uses in medicine, security, and astrology. Information regarding the advantages and disadvantages of X-rays was then explored and we found that the benefits out shine the drawbacks. We followed by comparing X-ray to other diagnosis equipment in the medical field such as the MRI, the CAT scan, and the Ultrasound. We found that X-ray diagnosis is generally better than the other types of diagnosis but there are cases in which the other forms of diagnosis are much better.
With the use of filters there is an increase in the quality of x-ray beam but a reduction in the intensity (Ball and Price, 1995). Therefore filtration is necessary but photons from the low end of spectrum if they are not
X-rays are defined as an electromagnetic wave of high energy and very short wavelength. X-rays are able to pass through many materials opaque to light. Visible light is electromagnetic radiation responsible for the sense of sight to humans. Infrared light, microwaves, and radio waves are categories of invisible light that all have the same type of electromagnetic energy.
X-Ray’s are used to generate pictures that show the inside of the human body such as finding broken bones. In Otto Zhou of the University of North Carolina, Dr Zhou and his colleagues are bringing X-radiography into the world of modern electronics. In doing so, there is a hope to create X-ray
When electrons emitted from a heated cathode filament are accelerated by a potential difference U and impinge onto an anode target (for example tungsten), the motions of the electrons with in the target are influenced by the strong Coulomb fields of the atomic nuclei. As a result, the electrons are decelerated within small distances and; consequently, a broadband bremsstrahlung or continuous radiation is produced.
X-rays are the form of ionizing radiations that function to make the diagnosis of any diseases or injuries in patient body. By introducing high penetrating power, the ionizing radiation may pass trough to patient body. In using radiations, an appropriate procedure is crucial to provide important information so that it can assist doctor to diagnose about patient problems. Clinicians and practitioners must be trained to use the low amount of radiation necessary for certain procedure. Thus, patient dose and image quality criteria are being concerning matters in performing certain examinations. According to Carlton & Adler (2014) they said that the recommended dose limits for general public which are considered as
CT scanning is a form of digital radiography that employs the processing power of computers to produce a 3-Dimensional (3D) representation of a given component or specimen by combining multiple x-ray images. This allows the operator to analyse the component as a whole and determine if it is fit to be used for the given task.
There are two methods to investigate the energies. The first method is Qualitative analysis which can be made by investigating the wavelengths of the fluorescence X-rays and the other method is quantitative analysis by investigating the X-ray dose. One is for optical separation to them and the other is to use the energy separation characteristic of the X-ray detector. The former is called the wavelength dispersive method an: the latter the energy dispersive method. The element analyzer employs the latter method. As seen from the figure, since the energy dispersive X-ray spectrometer has no moving parts uses a simple optical system, its structure is simple and compact. And since the detector can be installed the specimen, the X-ray solid angle of collection can be made large, thus presenting many features such as