Diagnostic X-Rays
Diagnostic X-rays are a form of electromagnetic radiation used in medical imaging to create detailed images of the inside of the body. They are produced by directing a controlled amount of radiation through the body, with different tissues absorbing or transmitting the radiation to varying degrees. These images help in diagnosing and monitoring various medical conditions.
7 Key excerpts on "Diagnostic X-Rays"
eBook - ePubMethods and Applications of Statistics in Clinical Trials, Volume 2
Planning, Analysis, and Inferential Methods
- Narayanaswamy Balakrishnan, N. Balakrishnan(Authors)
- 2014(Publication Date)
- Wiley(Publisher)
...In general, the imaging modalities create diverse forms of radiations that interact with the tissues and then the relevant image receptors (IR) in different ways. Creating an X-ray image, in particular, is a three-step process (Figure 2). In the first of these, an X-ray tube, such as Roentgen’s, creates a fairly uniform X-ray beam, directed at the patient. Figure 2 : The three-step process of creating a radiograph or a digital X-ray transmission image with a beam of probes. An (ideally) uniform X-ray beam is directed at the chest; some of the X rays incident on it are either absorbed or scattered through interactions with its atoms and molecules, predominantly in the dense bones. The differential attenuation of X rays by the various body tissues is revealed in the (no longer uniform) residual beam emerging from its far side and captured by the image receptor (IR). This process is the basis for all X-ray imaging, including CT Second, dissimilar materials absorb and scatter this high-energy electromagnetic (EM) energy at different rates—X rays tend to interact more readily with bone or pieces of metal than with soft tissues, because they are generally denser and happen to be composed of higher-atomic number (Z) atoms. The body thereby imprints a primary X-ray image in the previously flat beam. For such X-ray transmission imaging, the body must be partially, but only partially, transparent to the X-ray probes. In the third step, the pattern of X-ray intensities emerging from the patient can be captured by film or by a digital IR as a shadowgram that reveals such differences...
eBook - ePub- Charles A. Kelsey, Philip H. Heintz, Gregory D. Chambers, Daniel J. Sandoval, Natalie L. Adolphi, Kimberly S. Paffett(Authors)
- 2013(Publication Date)
- Wiley-Blackwell(Publisher)
...CHAPTER 12 Radiation Biology of Diagnostic Imaging Keywords Diagnostic radiology, biology of diagnostic radiology, fluoroscopy, planar imaging, mammography, CT Topics Biological effects of planar X-ray imaging Biological effects of fluoroscopic imaging Biological effects of mammographic imaging Biological effects of computed tomographic imaging Equipment and techniques to acquire diagnostic X-ray images Diagnostic Procedures Almost all medical imaging procedures come from one of the six major diagnostic procedures: planar, fluoroscopic, computed tomographic, mammographic, magnetic resonance, or ultrasound imaging. The first four modalities use X-rays, magnetic resonance imaging uses radio frequency radiation, and ultrasound imaging uses high-frequency sound waves. Only procedures using X-rays are covered in this chapter. Medical diagnostic procedures expose more people to radiation than any other source of man-made radiation. In the United States, almost half (48%) of the population exposure is from diagnostic X-ray procedures. The frequency and amount of radiation the population gets from medical exposure increases with patient age. The geometry of the four X-ray modalities is similar. A radiation source outside the patient sends X-rays through the patient to an image receptor on the other side of the patient's body. The transmitted radiation is detected, converted into a digital image, and presented on a video monitor. Less than 2% of the incident radiation reaches the detector on the exit side of the patient...
eBook - ePub- Christopher Clarke, Anthony Dux(Authors)
- 2020(Publication Date)
- Wiley-Blackwell(Publisher)
...I Introduction to X‐rays 1 Introduction to X‐rays What are X‐rays? X‐rays are a form of ionising radiation. Radiation is the transfer of energy in the form of particles or waves. Visible light, radio waves, and ultraviolet waves are all examples of radiation and form part of the electromagnetic spectrum. X‐rays contain more energy than visible light and ultraviolet waves. In fact, X‐rays have sufficient energy to cause ionisations, which is a process whereby radiation removes an outer‐shell electron from an atom, hence the term ionising radiation. In this way, ionising radiation is able to cause changes on a molecular level in biologically important molecules (e.g. DNA). Uses of ionising radiation include conventional plain radiographs (often simply referred to as X‐rays), fluoroscopy, computed tomography (CT), nuclear medicine, and positron emission tomography (PET). How are X‐rays produced? X‐rays are produced by focusing a high‐energy beam of electrons onto a metal target (e.g. tungsten) (Figure 1.1). The electrons hit the metal target and some will have enough energy to knock out another electron from the inner shell of one of the metal atoms. As a result, electrons from higher energy levels then fill up this vacancy and X‐rays are emitted in the process. Producing X‐rays this way is extremely inefficient (~0.1%), so most of the energy is wasted as heat. For this reason, X‐ray tubes need to have advanced cooling mechanisms. The X‐rays produced then pass through the patient and onto a detector mechanism which produces an image. Figure 1.1 X‐ray production. How do X‐rays make an image? X‐rays can either pass through the body or be absorbed by tissues. While passing through a patient, the X‐ray beam is absorbed in proportion to the cube of the atomic number of the various tissues through which it passes...
eBook - ePub- Euclid Seeram(Author)
- 2019(Publication Date)
- Wiley-Blackwell(Publisher)
...2 Diagnostic X‐Rays : Essential Physical Factors Chapter at a Glance X‐Ray Production Mechanisms for Creating X‐Rays X‐Ray Spectrum Form of an X‐Ray Emission Spectrum X‐Ray Beam Quality and Quantity Controlling Beam Quality and Quantity X‐Ray Attenuation Definition Factors Affecting Attenuation X‐Ray Interactions Photoelectric Absorption Compton Scattering Increasing kV and Scatter Production X‐rays are produced when high‐speed electrons strike a target. In diagnostic radiology, an X‐ray tube is used to produce X‐rays to image patients. The X‐ray tube consists basically of an anode and a cathode. The cathode consists of a filament that when heated emits electrons. In turn, the electrons are accelerated at high speeds to strike a small spot on the anode, called the target. The electron–target interaction results in the production of heat and X‐rays. The purpose of this chapter is to outline several physical factors relating to the basic physics of X‐ray production, X‐ray interactions with matter, and X‐ray attenuation, all of which are important to radiation protection. An understanding of how the X‐ray beam is produced, how it interacts with the patient, and what happens when the beam is transmitted through the patient is key to optimizing image quality and minimizing radiation dose. The technologist has control over several parameters that affect X‐ray production, attenuation, and interaction with the patient. This chapter is pivotal in ensuring that the technologist/radiographer has the fundamental cognitive skills that are required for good radiation protection practices. X‐Ray Production To produce X‐rays for a particular examination, the technologist sets up the appropriate voltage (kV), current (mA), and time (in seconds [s]) on the control panel. These exposure technique factors determine the type of radiation beam that will be produced by the X‐ray tube...
eBook - ePubModern Diagnostic X-Ray Sources
Technology, Manufacturing, Reliability
- Rolf Behling(Author)
- 2021(Publication Date)
- CRC Press(Publisher)
...Chapter 3 The interaction of X-ray with matter Interaction of X-ray photons with human tissue is a great source of information. Contrast bolus in cerebral vessels helps differentiate ischemic from hemorrhagic stroke and direct the therapy. Understanding the fingerprints of X-ray attenuation, scattering, and refraction is essential to gain the most information from the lowest dose of ionizing radiation. (Courtesy of Philips.) The explosion of scientific and clinical works immediately after Conrad Roentgen’s discovery was an indicator for the huge lack of knowledge about the interior morphology of patients. “More light” were supposedly Johann Wolfgang von Goethe’s last words. This is what Roentgen has generated. By the same medium of the invisible light, anatomic, and functional information is transmitted. The major interactions of X-ray photons with matter will be discussed in the following section to get a glimpse of the information, which can be expected by measuring them. X-ray photons interact with tissue, fat, bone, water, or air. They are either extinguished or scattered out of the initial direction, or generate secondary photons depending on the elementary composition of the object and the material density. In all these cases, photons disappear from the primary beam. Usually, only a small fraction in the order of a percent will reach the detector. Refraction of X-rays is very small compared to visible light for photons of the relevant energies. Differentiation between direct radiation, which originates in the focal spot, and indirect radiation, which originates elsewhere, is therefore the key for the interpretation of the spatial pattern of X-ray flux sensed by the detector. Although X-ray phase shifts are comparatively large refraction and phase shift of X-rays have not (yet?) been utilized in day-to-day clinical routine...
eBook - ePubX-Ray Diffraction Imaging
Technology and Applications
- Joel Greenberg, Joel Greenberg(Authors)
- 2018(Publication Date)
- CRC Press(Publisher)
...(b) Schematic representation of the system, showing the X-ray source collimated to a fan beam, the tunnel in which the bag resides and the coded aperture (mounted at the top of the tunnel). The detectors have a finite standoff from the top of the tunnel and consist of a linear array of energy-sensitive pixels mounted on a translation stage. The system can produce (c) a multi-energy transmission image of the bag and (d) a map of the threat status (i.e., dangerous, red, or non-dangerous, green) of the materials located within a planar slice of the object (as indicated by the red dashed line in (c)). At a smaller scale, CA-XRDT is also well-suited for isolated, composite items. For example, one can perform bottle liquid scanning (BLS) to determine the material present inside of a container, which is currently of interest with respect to a range of venues, including airports, sporting events, and secure facilities. In contrast to current BLS systems that use Raman scatter or dual energy transmission X-ray imaging, an XRDT-based system can identify the contents of thick, opaque containers in a manner that is independent of the composition of the container itself. 24 1.6.2 Medical Imaging The discovery of X-rays was concomitant with their application to medical imaging over 100 years ago. Despite the development of CT and multi-energy detection, the reliance of medical imaging on photoelectric absorption necessarily limits the contrast and sensitivity that can exist in such images. 99 Different types of soft tissue or chemical compounds can have very similar densities and/or effective atomic numbers, thus fundamentally limiting the capabilities of transmission imaging in the absence of exogenous contrast agents. The structural information revealed via XRD has been shown to reveal important and otherwise unavailable information in a variety of situations...
eBook - ePubPrinciples of Fluoroscopic Image Intensification and Television Systems
Workbook and Laboratory Manual
- Robert J. Parelli(Author)
- 2020(Publication Date)
- CRC Press(Publisher)
...Two x-ray interactions with matter of significant importance, required in the production of a radiographic image, are: 1. Photoelectric effect. When an inner shell electron of an atom is struck by an x-ray photon (A), the photon may give off all of its energy. This photon collision causes photoelectric effect (Figure 6.5). Figure 6.5: Photoelectric effect. The electron struck by the x-ray photon is emitted as a photoelectron and is quickly absorbed. The electron ejected as a photoelectron is quickly replaced by another electron from any outer shell (B) or any free electron. The characteristic radiation (thermal energy) emitted is determined by the binding energies of the shells participating in this event. The vacancy created in the outer shell by the movement of an electron to fill the inner shell results in an atom with a deficiency of one electron (ionized) (C). 2. Compton scatter. When the kilovoltage value is increased, the incoming x-ray photon has increased energy. This photon can strike an electron in an outer shell and be deviated from its original path with a reduction in energy (Figure 6.6). Figure 6.6: Compton scattering. This photon will then travel in a different direction but with less energy. The process can be multiplied if the incident photon retains part of its energy and the remaining energy becomes a recoil electron. This interaction is called Compton effect of scattering, and many secondary collisions may occur with additional Compton and recoil electrons being generated. If the incoming photon is of sufficient energy to dislodge the electron, in addition to giving up some of the photon energy, the recoil electron (ejected electron) causes a vacancy in the outer shell, and the atom becomes unstable (ionized). X-ray photons possess no mass...
