Unit 21 Applied Science BTEC aims AB and C up to Distinction level (Distinction achieved on the assignment)
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AB. D1 Justify the choice of non-ionising and ionising radiation techniques in medical applications.
A. M1 Compare the principles, production and uses of different non-ionising radiation techniques in
medical applications.
A. P1 Explain how the principles and production of non-ionising radiation technologies are used in
medical applications.
A. P2 Explain why non-ionising radiation technologies are used for diagnosis and treatment of the
human body
B. M2 Compare the principles, production and uses of different ionising radiation techniques in
medical applications.
B. P3 Explain how the principles and production of ionising radiation technologies are used in medical
applications.
B. P4 Explain why ionising radiation technologies are used for diagnosis and treatment of the human
body.
AB. D1 Justify the choice of non-ionising and ionising radiation techniques in medical applications.
A. M1 Compare the principles, production and uses of different non-ionising radiation techniques in
medical applications.
A. P1 Explain how the principles and production of non-ionising radiation technologies are used in
medical applications.
A. P2 Explain why non-ionising radiation technologies are used for diagnosis and treatment of the
human body
B. M2 Compare the principles, production and uses of different ionising radiation techniques in
medical applications.
B. P3 Explain how the principles and production of ionising radiation technologies are used in medical
applications.
B. P4 Explain why ionising radiation technologies are used for diagnosis and treatment of the human
body.
Medical Physics Applications: Radiation Use in Medical Diagnosis and Treatment
A. Non-Ionising Radiation Technologies
P1- Explain how the principles and production of non- ionising radiation
technologies are used in medical applications.
Non-ionising radiation technologies like ultrasound and MRI utilize various
physical principles to generate detailed images of the human body without the
risks of ionising radiation exposure (Stoeva, 2016).
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Ultrasound imaging uses high-frequency sound waves, typically above 20 kHz,
to safely visualize internal body structures (FDA, 2024). A transducer probe is
placed on the patient's skin and emits pulses of ultrasound waves that
propagate through the underlying tissues. As the sound waves encounter
changes in tissue density or composition, some of the wave is reflected to the
transducer. Based on the time interval between the initial pulse and the
reflected wave, the ultrasound machine can determine the depth of the tissue
interface causing the reflection (Wild and Neal, 2018). This allows a two-
dimensional image to be constructed showing tissue, organ boundaries, and
other structures (Scott P. Grogan; Cristin A. Mount, 2023).
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Different modes of ultrasound utilize additional physical properties of sound waves to
garner further diagnostic information. For example, Doppler ultrasound detects the
change in frequency of reflected ultrasound waves from moving objects like red blood
cells. This change in frequency provides details on blood flow velocity and direction,
allowing assessment of arterial blockages, heart valve function, and identification of
risky arterial plaques (Webb, 2003). Elastography tracks the propagation time of
ultrasound waves through tissues which varies based on the tissue stiffness. This
allows benign and malignant tumours to be distinguished and can guide needle
biopsies (Dewey, 2024). Overall, ultrasound provides versatile, real-time imaging
without any ionising radiation exposure.
MRI leverages the magnetic properties of protons, primarily in water and fat,
within the body's tissues (Zagoudis, 2022). Within the strong magnetic field of
an MRI scanner, many protons align their spin with the field. Radiofrequency
pulses are then applied which disturb this equilibrium and cause the protons
to absorb RF energy (Kahn and Liney, 2018). When the pulse is turned off, the
protons release this absorbed energy as they realign to the magnetic field; this
release is detected by the MRI scanner. Additional magnetic gradients applied
in sequence allow for the spatial encoding of the released energy signals to
reconstruct a detailed cross-sectional image (Bushberg et al., 2021).
MRI provides exceptional soft tissue contrast allowing clear visualization of
anatomical structures, joints, organs, tumours and more without ionising
radiation risks.
P2- Explain why non-ionising radiation technologies are used for diagnosis and
treatment of the human body.
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Non-ionising radiation technologies like ultrasound and MRI are extensively
utilized for diagnostic imaging and some treatment applications in the human
body due to their inherent safety and lack of damaging ionising radiation
exposure (Hendee and Ritenour, 2002).
Diagnostically, the superb soft tissue contrast and detail provided by
ultrasound and MRI make them well-suited for identifying and characterizing
abnormalities in organs, muscles, joints, tumours and more without exposing
patients to ionising radiation (Kowalik and Ödman, 2019). Repeated ionising
radiation exposure builds up lifetime risk for cancer and other stochastic
effects. By avoiding this, ultrasound and MRI allow for regular ongoing imaging
for diagnosis and surveillance without cumulative radiation risk.
For example, obstetric ultrasound is considered very safe, allowing
developing fetuses to be visualized and monitored closely through pregnancy
without concern over radiation (Juhl and Crummy, 1993). Cardiac ultrasound
and MRI can assess heart structure and function to detect abnormalities
without ionising exposure (Thrall, 2021). For joints and muscles, ultrasound
and MRI safely image complex anatomy to pinpoint ligament tears, tendon
damage and other injuries (Mettler and Guiberteau, 2020). MRI in particular
provides exquisite neurological tissue differentiation utilized in diagnosing
multiple sclerosis, brain tumors and more (Drixler et al., 2021).
The lack of ionising radiation also means ultrasound and MRI can be used
routinely for surveillance of known conditions, tracking changes over time.
Ultrasound monitors uterine fibroids, with MRI adjunct imaging, to determine if
surgical treatment is warranted based on
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growth (Zaidi, 2019). MRI is routinely used to monitor treatment response for
brain tumours and check for concerning recurrence (Curry et al., 1990).
Overall, the safety and imaging capabilities make non-ionising radiation
technologies ideal for diagnostic medical imaging applications.
Therapeutically, options like UV lamps for seasonal affective disorder and
ultrasound to speed musculoskeletal healing represent some non-ionising
treatment options. However, the predominant medical application of these
technologies is in leveraging their imaging abilities for safe, serial diagnostic
use without ionising radiation exposure risks.
P3 Explain how the principles and production of ionising radiation technologies are
used in medical applications.
Ionising radiation technologies including x-rays, CT scans, and radiation
therapy utilize forms of high- energy electromagnetic radiation or particle
radiation that carry enough energy to ionise atoms and molecules within the
body (Wong, 2008). This allows unique medical imaging and cancer treatment
capabilities despite some potential risks.
Medical x-rays take advantage of ionising radiation produced when electrons
are accelerated across a high voltage potential and strike a metal target
(Bushberg et al., 2021). This generates a broad beam of high frequency x-rays
that can penetrate through body tissues before exposing an image receptor
film or digital detector. As x-rays pass through the body, some are absorbed
while others pass through. Denser tissues like bone absorb more x-rays,
resulting in those areas appearing lighter on the final image. Soft tissues
absorb fewer x-rays and show up darker. This differential
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absorption allows body structures like the lungs, fractures, foreign objects,
organ outlines and more to be distinguished.
CT scans acquire multiple x-ray images rapidly from different angles rotating
around the patient (Stoeva, 2016). A computer uses tomographic
reconstruction algorithms to process this projection data into a three-
dimensional model of the body's internal structures. CT provides more detail
than standard x-rays because the variable absorption of ionising radiation by
different tissue densities provides superior contrast between bone, muscle,
fat, organs, tumours, and other structures. This allows clearer visualization of
lesions, organ anatomy and the presence or spread of pathology.
In radiation therapy, tightly focused beams of ionising radiation like x-rays,
protons or electrons are directed at cancerous tissues to damage their DNA
and destroy tumour cells' ability to divide and replicate (Zagoudis, 2022).
External beam radiation is delivered from a machine outside the body.
Brachytherapy uses implanted radioactive sources like iridium or cesium
directly within tumours to irradiate from the inside out. The radiation induces
strand breaks in cancer cell DNA, leading to apoptosis and cell death. Normal
tissues are exposed as well, but higher cancer cell susceptibility provides a
therapeutic window.
The ionising nature of these technologies does carry some risks, notably the
potential for secondary cancers due to DNA mutations. However, when utilized
appropriately with strict dosimetry guidelines, the substantial benefits of x-
rays, CT imaging, and radiation therapy for diagnosis and cancer treatment
typically outweigh the risks. But cumulative exposures should
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always be limited and radiation safety principles followed to minimize
potential hazards.
M1- Compare the principles, production and uses of different non-ionising
radiation techniques in medical applications.
[Institute for Quality and Efficiency in Health Care, 2020]
• Transducer: This is the probe-like device that is placed on the skin to send and
receive sound waves. It is made of piezoelectric crystals that vibrate when an
electric current is applied, creating sound waves. The sound waves travel through
the body and bounce off organs and tissues. The echoes are then picked up by
the transducer and converted back into electrical signals.
• Gel: This is a water-based substance that is applied to the skin between the
transducer and the body. The gel helps to transmit sound waves more
efficiently and reduces air pockets that could interfere with the image.
• Computer: The computer processes the electrical signals from the transducer
and converts them into an image that can be displayed on the screen. It also
controls the settings of the ultrasound machine, such as the frequency of the
sound waves and the depth of the image.
• Screen: The screen displays the ultrasound image, which allows the sonographer
to see the internal organs and tissues.
• Controls: The controls allow the sonographer to adjust the settings of the
ultrasound machine, such as the image depth, zoom, and gain.
Principles:
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Ultrasound imaging relies on high-frequency sound waves, typically above 20
kHz, to generate images (Juhl and Crummy, 1993). Sound waves are produced
by supplying alternating electrical currents at ultrasonic frequencies to
piezoelectric crystals in the transducer probe. This stimulates vibrations and
pulsed emission of sound waves that propagate through tissue. Reflected
waves occur at tissue interfaces and are detected by the transducer to discern
anatomical structures (Webb, 2003).
[Haynes, Heather & Holmes, William, 2013]
Magnet: This is the largest and most powerful component of an MRI machine. It creates a strong magnetic
field that aligns the protons in the body's atoms. The strength of the magnetic field is measured in teslas (T),
and most clinical MRI machines have magnetic fields ranging from 1.5T to 3T. The magnet is usually
superconducting, meaning it uses special materials that conduct electricity with no resistance at very low
temperatures.
Gradient coils: These are coils of wire that generate rapidly changing magnetic fields. These changing fields
cause the protons to precess (wobble) at different rates depending on their location in the body. This allows
the MRI machine to create detailed images of different tissues.
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Radiofrequency (RF) coils: These coils transmit and receive radio waves. The RF waves excite the protons,
causing them to absorb energy. When the RF waves are turned off, the protons release the energy they
absorbed, and the RF coils detect this signal. The strength and timing of the RF signals are carefully controlled
to create different types of MRI images.
Bore: This is the cylindrical opening in the magnet where the patient lies. The bore is usually quite narrow, and
patients with claustrophobia may find it uncomfortable.
Patient table: This table slides in and out of the bore so that the patient can be positioned for the scan. The
table may also have built-in coils to improve image quality.
Computer system: This complex system controls all of the other components of the MRI machine and
processes the signals from the RF coils to create the images.
Monitor: This is where the MRI technologist views the images and controls the scan.
MRI utilizes strong static magnetic fields, pulsed radiofrequency waves, and
additional magnetic gradients to exploit the magnetic properties of protons
within the body's tissues, primarily in water and fat molecules (Thrall, 2021).
In the strong field, many protons align their spin magnetically. Radiofrequency
pulses disturb this equilibrium and cause proton energy absorption.
Subsequent energy release during realignment is detected to construct images
(Kahn and Liney, 2018).
Production:
In ultrasound, the alternating electrical signals used to stimulate the
piezoelectric crystals originate from a voltage generator within the
ultrasound machine (Wild and Neal, 2018). The frequency, amplitude, and
pulse timing can be controlled to optimize the sound waves for the imaging
application. The crystals emit high- frequency mechanical vibrations
producing the sound beam.
MRI scanners use an electromagnet consisting of coiled wire conducting
electricity to generate a strong static
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