20. Medical physics techniques

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					20. Medical physics techniques

          BTEC level 3
                      Aim
• The aim of this unit is to enable learners to
  develop, through a practical vocational skills
  approach, an understanding of the important
  fundamental physics concepts behind medical
  physics techniques such as x-rays, ultrasounds,
  diagnostic imaging and magnetic resonance
  imaging (MRI) and radiotherapy.
• Learners will also understand the importance of
  radiation safety.
• Diagnostic medicine has come a long way since
  the time when the best diagnosis occurred
  during the postmortem examination. Surgery
  today is faster, less invasive and more effective
  than ever – thanks in part to improvements in
  medical imaging technology. Imaging gives the
  doctor a clearer understanding of the patient’s
  condition so treatment can be planned more
  effectively and therapy delivered more precisely.
• Nuclear medicine is providing hope for the
  cure of the most serious diseases,
  especially cancer. Radioactive materials
  are used in this rapidly developing branch
  of medicine. At the cutting edge of
  developments in nuclear medicine is the
  precise targeting needed to get the
  radiation to the exact site of the cancer.
• Future prospects are even more exciting. Medical
  imaging is extending human vision into the very nature of
• disease; at the cellular level it will permit diagnosis
  before symptoms even appear. Surgery in the future will
  be bloodless, painless and non-invasive. It will be
  powered by medical imaging systems that focus on the
  disease and use energy to destroy the target but
  preserve healthy tissue. Researchers are testing the use
  of highintensity ultrasound to destroy tumours identified
  and targeted while the patient lies in an MRI scanner.
• This unit introduces learners to some of
  the established practices in medical
  physics imaging. It aims to deliver the
  underpinning knowledge of several of the
  fundamental techniques and provide a
  basic introduction to the more complicated
  theory of magnetic resonance imaging.
          Learning outcomes
• Know atomic structure and the physical
  principles of ionising radiation and ultrasound
• Understand how radiopharmaceuticals are used
  in diagnostic imaging
• Know the basic principles of magnetic
  resonance imaging
• Understand the importance of radiation safety to
  the treatment of malignant disease with
  radiotherapy.
1. Know atomic structure and the physical principles of
          ionising radiation and ultrasound

• Radioactivity: industrial applications; atomic structure;
  characteristics of alpha, beta, and gamma, random
  nature of decay, half-life, decay constant, and activity
• X-rays: industrial applications e.g. production of x-rays
  from a target; x-ray spectrum and effect of tube voltage,
  tube current, target material and filtration; interaction of
  x-rays with matter; attenuation, inverse square law,
  absorption and scattering, intensity and half value
  thickness
• Ultrasound: industrial applications; production of
  ultrasound and basic principles of e.g. pulse echo
  technique, reflection and refraction, interaction with
  tissue, scattering and absorption; intensity measurement
  in decibels; specific acoustic impedance; sonar principle
  and ultrasonic scanning eg A-scan, B-scan and M-scan;
  Doppler effect; measurement of blood flow using Doppler
  ultrasound
2. Understand how radiopharmaceuticals
     are used in diagnostic imaging
• Radionuclides: industrial applications eg
  radionuclides; radionuclide generators and
  preparation of radiopharmaceuticals; the
  need for quality control, sterility and
  apyrogenicity; advantages and
  disadvantages of radionuclide imaging
• The gamma camera: operating principles
  of main components; function as a
  detector
 3. Know the basic principles of
  magnetic resonance imaging
• Nuclear magnetic resonance: industrial
  applications; proton spin, energy levels and
  precession; resonance; overview of process,
  e.g. block diagram; factors influencing signal
  intensity; relaxation, contrast and resolution
• Instrumentation and equipment: magnets,
  gradient field coils, radio frequency coils
• MRI applications and safety: abnormal body
  water, joints, abdomen, head and spine;
  instruments and equipment, implants, patient
  tolerance and quenching
4. Understand the importance of radiation safety to the
   treatment of malignant disease with radiotherapy

• Effect of x-rays: effect on cells and tissue in relation to
  malignant disease; absorbed and effective doses
• Radiotherapy: types eg megavoltage and superficial
  therapy; beam characteristics, multiple and rotational
  beams, wedges and compensators; linear accelerator;
  industrial applications
• Radiation safety: major effects of ionising radiation on
  the body; outline of the need for legislative requirements
  and dose limits; use of film badges and
  thermoluminescent dosimeters; procedures for reducing
  radiation hazards
     Assessment and grading
• Snipping tool
     Assessment activity 20.1
         (P1, M1, D1, P2)
• Scenario: your work as a junior technician
  in the radiography section of a large
  hospital involves working with other highly
  qualified personnel, talking to patients
  undergoing therapy and periods of
  personal study. You must show that you
  have a clear understanding of the terms
  used and an understanding of the basic
  science principles involved in your
  department
               For a pass
• Draw sequences which show what
  happens to radioactive elements when
  they lose: an alpha particles, a beta
  particle. What happens to an atom when
  gamma rays are emitted? P1
• Draw a fully labelled diagram
  demonstrating the principles of: an x-ray
  tube; production of ultra-sound. P2
               For a merit
• Using graph paper, show a decay curve
  and mark on :
  – The axis showing the fraction of undecayed
    nuclei remaining
  – The axis showing time
  – Half-life intervals
  – Fractions of original number of undecayed
    nuclei remaining M1
          For a distinction
• Use a suitable diagram to analyse what
  happens to an x-ray spectrum when the
  tube voltage is changed. Show some
  known x-ray peaks in your diagram. What
  do these peaks tell you? D1
              Grading tips
• Include labels of protons and neutrons in
  your answer and at least two element
  sequences for each decay to achieve P1
• To achieve M1 you could add a simple
  demonstration set of results using dice to
  illustrate the random aspect of decay
      Assessment activity 20.2
          (M2, D2, P3, P4)
• Scenario: As a recent addition to the
  technical and nursing staff of a large city
  hospital, you must show that you are
  familiar with the radiopharmaceuticals
  used and the way in which they are
  detected within the body of a patient
              For a pass
• Make a list of the most common
  pharmaceuticals used in medicine,
  describe how they are produced and
  briefly describe what happens when these
  substances enter the body P3
• Explain how the gamma camera works
  using a fully labelled diagram P4
               For a merit
• Using your list from P3, provide details of
  what qualities you are looking for when
  choosing a suitable radiopharmaceutical.
  Remember that patients have to inhale or
  be injected with these substances M2
           For a distinction
• Use information in chapter 20.2 (pg 374-
  377) and your own research to evaluate
  which radiopharmaceuticals are best for a
  given purpose D2
              Grading tips
• You should include the formulas for your
  radiopharmaceutical in your answer for P3
  and what the images received by the
  gamma camera tell use for P4. Additional
  research is necessary for M2 and D2,
  which should provide information on the
  choices made by doctors for particular
  radiopharmaceutical in specific parts of the
  body. Health if the patient is vital and the
  image produced is very important
     Assessment activity 20.3
          (M3, D3, P5)
• Scenario: You are called upon to provide
  an explanation of the procedure of an MRI
  scan to a patient as part of your duties as
  a technician within the radiology
  department of a major hospital
              For a pass
• Describe how the MRI scanner works in
  simple terms and list the main components
  with a brief description of each P5
               For a merit
• Provide an explanation of the principles of
  nuclear magnetic reasonance and how
  different factors change the signal intensity
  M3
          For a distinction
• Use a variety of images of the same body
  parts to evaluate the similarities and
  differences between x-ray and MR images
  D3
              Grading tips
• Include some mention of proton spin and
  what happens to particles in a magnetic
  field in your answer for P5 with a more
  detailed explanation for M3. To complete
  D3, you will need to put yourself into the
  role of an image analyst and become
  familiar with the detail of individual images
     Assessment activity 20.4
          (M4, D4, P6)
• Scenario: working in the x-ray department
  of a busy hospital means that you will
  need to attend regular specific additional
  training sessions for health and safety as
  part of your continuing professional
  development
               For a pass
• Provide a slide demonstration explaining
  the way in which x-rays are used to treat
  malignant disease. Provide a brief
  explanation of equipment which may be
  used P6
               For a merit
• Explain the physical effects of being
  exposed to a lot of radiation M4
           For a distinction
• Evaluate the various types of radiotherapy
  practices that are currently in use and
  explain the function of equipment that
  allows these kinds of treatment D4
                Grading tips
• List the components of the equipment which
  focus x-rays onto the target with a simple
  explanation of how they work and highlight what
  can happen to cells during radiotherapy for P6
• Link the doses of radiation to the symptoms of
  radiation exposure and comment on
  preventative measures to achieve M4
• You will need to include specific radiation types
  used for particular diseases for D4 and the
  equipment used to produce and target the
  radiation

				
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