Aim and purpose
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...
aim and purpose the aim of this unit is to enable learners to develop
through a practical vocational skills approach
an understanding of the important fundamen
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UNIT
Unit 20: MEDICAL PHYSICS
Medical Physics TECHNIQUES
Techniques
Unit code: F/502/5564
QCF Level 3: BTEC National
Credit value: 10
Guided learning hours: 60
Aim and purpose
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.
Unit introduction
Diagnostic medicine has come a long way since the time when the best diagnosis occurred during the post-
mortem 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 high-
intensity 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
On completion of this unit a learner should:
1 Know atomic structure and the physical principles of ionising radiation and ultrasound
2 Understand how radiopharmaceuticals are used in diagnostic imaging
3 Know the basic principles of magnetic resonance imaging
4 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 (β+ and β–) and gamma
radiations; random nature of radioactive decay, half-life t 1 , decay constant λ and activity A = A0 e − λt ,
A = λN 2
X-rays: industrial applications eg 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
ln 2
square law, absorption and scattering, intensity I = I 0 e − µ x and half value thickness x1 =
2
µ
Ultrasound: industrial applications; production of ultrasound and basic principles of eg pulse echo
technique, reflection α =
( z2 − z1 )
2
and refraction, interaction with tissue, scattering and
( z2 + z1 )2
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, eg 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
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