Non Ionising Imaging

4 Key excerpts on "Non Ionising Imaging"

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  eBook - ePub

  Practical Medical Physics

  A Guide to the Work of Hospital Clinical Scientists

  • Debbie Peet, Emma Chung, Debbie Peet, Emma Chung(Authors)
  • 2021(Publication Date)
  • CRC Press

    (Publisher)

  Part I Non-Ionising Imaging

  The NHS performs millions of imaging tests each year, with the most common being plain X-ray radiography, followed by diagnostic ultrasound, X-ray computerised axial tomography (CT scans) and magnetic resonance imaging (MRI). Part 1 of this book covers non-ionising (MRI and ultrasound) imaging. Ionising imaging using X-rays and molecular imaging techniques in Nuclear Medicine are reserved for Part 2 .

  Ultrasound and MRI represent the second and fourth most performed imaging modalities used in the UK. Of 3.6 million imaging tests taking place in England in November 2019, ultrasound accounted for 860,000 scans and MRI for 310,000.

  Both ultrasound and MRI were pioneered in the UK but require fewer hospital physicists than the use of X-rays due to their exemplary safety profiles. Therefore, the roles of physicists specialising in non-ionising imaging tend to focus on research and teaching as an adjunct to hospital support. As the fundamental physics underlying MRI and ultrasound techniques are very different, non-ionising specialists tend not to have studied both in detail.

  MRI physicists are often recruited at post-doctoral level and then asked to apply for Clinical Scientist registration through demonstrating equivalence. Larger hospitals will often employ a small “non-ionising” team responsible for QC and safety checks of hospital imaging equipment; however, it is also common for services to be offered regionally or outsourced to external companies.

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  Principles of Science for Nurses

  • Joyce James, Colin Baker, Helen Swain(Authors)
  • 2008(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  It is now an important method used to evaluate blood vessels and blood flow, providing the opportunity for real-time imaging that assists in monitoring the functioning of the major arteries and veins of the body and the heart. It is also used to check the blood flow to the placenta in fetal monitoring. Choice of imaging techniques The technique of choice for non-invasive imaging will depend both on the clarity and nature of the information provided by the image formed and also safety considerations. Both X-ray methods and MR imaging are avoided in pregnancy but otherwise they are considered safe as long as appropriate precautions are taken. Ultrasound has been used in fetal moni-toring for over 30 years and there is no evidence of damage to fetus or mother. The applicability of these methods is summarised in Table 11.6. Summary • The electromagnetic spectrum describes the different types of energy that are transmit-ted in the form of waves, ranging from gamma rays to radiowaves • The sun is a major source of electromag-netic radiation • The energy of a waveform is directly pro-portional to its frequency • We distinguish between ionising radiation and non-ionising radiation in terms of the effect the radiation has on matter • Radioisotopes are atoms with unstable nuclei that emit particles and ionising radia-tion as they decay • The half-life of a radioisotope is the time taken for 50% of the sample to decay • Ionising radiation is useful in its ability to kill cancerous cells • Ionising radiation is used in a variety of diag-nostic and imaging techniques – e.g. X-ray, CT and PET scans • Imaging techniques that do not use ionising radiation are MRI and ultrasound • Control of dosage (time, distance shielding) is essential in minimising the harmful effects of ionising radiation on patients and workers. Review questions 11.1. What type of radioactive decay do you think is occurring in the following examples? i) radium-226 Æ radon-222? ii) sodium-24 Æ magnesium 24? 11.2.

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  Occupational Ergonomics

  Theory and Applications, Second Edition

  • Amit Bhattacharya, James D. McGlothlin(Authors)
  • 2012(Publication Date)
  • CRC Press

    (Publisher)

  827 C H A P T E R 31 Nonionizing Radiation John Cardarelli II 31.1 NONIONIZING RADIATION Nonionizing radiation (NIR) is a form of electromagnetic energy that is too weak to break chemical bonds in molecules. It takes many forms, including television and radio signals, radar, pager and cordless and cellular phone signals, microwaves, visible light, infrared and ultraviolet light, and lasers. Everyone is exposed to NIR from both naturally occurring and man-made sources. It can be beneficial or detrimental to those exposed. You cannot see it except for visible light (wavelength = 400–760 nm), taste it, or smell it; but you may be able to feel it by sensing heat or through electrostimulation. The phenomenon of hearing certain radiofrequencies is also a well-established biological effect with no known adverse health consequences. A quiet environment is needed for these radiofrequency-induced sounds (similar to other common sounds) to be heard. The presence of NIR is growing, fueling anxiety and speculation about its possible adverse health effects. Levels of exposure will continue to grow as technology advances and as society increasingly demands the conveniences it brings. The electromagnetic spectrum includes ionizing and NIR (Figure 31.1). This chapter explains the characteristics of NIR radiation, with a focus on ways to measure it and its CONTENTS 31.1 Nonionizing Radiation 827 31.1.1 Exposure Limits 832 31.1.2 Interpreting RF Measurement Data 834 31.1.3 Spatial Averaging 835 31.1.4 Time Averaging 835 31.2 Protective Measures 835 31.2.1 Engineering Controls 835 31.2.1.1 Administrative Controls 837 31.2.1.2 Health Effects Associated with EMF below 100 kHz 837 31.2.1.3 Health Effects Associated with EMF above 100 kHz 838 31.2.1.4 Infrared and Ultraviolet Radiation 839 31.2.1.5 Laser Radiation 840 References 842 828 ◾ Occupational Ergonomics: Theory and Applications associated safety standards for occupational environments.

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  Definitions, Conversions, and Calculations for Occupational Safety and Health Professionals

  • Edward W. Finucane(Author)
  • 2016(Publication Date)
  • CRC Press

    (Publisher)

  8-1 Chapter 8 Ionizing & Non-Ionizing Radiation Interest in this area of potential human hazard stems, in part, from the magnitude of harm or damage that an individual who is exposed can experience. It is widely known that the risks associated with exposures to ionizing radiation are significantly greater than compa-rable exposures to non-ionizing radiation. This fact notwithstanding, it is steadily becom-ing more widely accepted that non-ionizing radiation exposures also involve risks to which one must pay close attention. This chapter will focus on the fundamental characteristics of the various types of ionizing and non-ionizing radiation, as well as on the factors, parame-ters, and relationships whose application will permit accurate assessments of the hazard that might result from exposures to any of these physical agents. RELEVANT DEFINITIONS Electromagnetic Radiation Electromagnetic Radiation refers to the entire spectrum of photonic radiation, from wave-lengths of less than 10 –5 Å (10 –15 meters) to those greater than 10 8 meters — a dynamic wavelength range of more than 22+ decimal orders of magnitude! It includes all of the segments that make up the two principal sub-categories of this overall spectrum, which are the “Ionizing” and the “Non-Ionizing” radiation sectors. Photons having wavelengths shorter than 0.4 μ (400 nm or 4,000 Å) fall under the category of Ionizing Radiation; those with longer wavelengths will all be in the Non-Ionizing group.

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