UNIT 21C- MEDICAL PHYSICS
Radiation technologies, both non-ionizing and ionizing, have become an integral
part of modern medicine. These technologies are used for diagnostic imaging,
radiation therapy, and various other medical applications. While these
technologies have revolutionized healthcare and improved patient outcomes,
they also pose significant health and safety risks to both operators and patients.
Poor health and safety practices when using these technologies can lead to
severe consequences, including radiation-induced injuries, long-term health
effects, and even fatalities. Therefore, it is crucial to understand the risks
associated with these technologies and implement appropriate prevention and
safety measures to maximize the protection of operators and patients.
Section 1: Health and Safety Risks, Side Effects, and Limitations of Non-Ionizing
Radiation Technologies
Non-ionizing radiation technologies, such as ultrasound, magnetic resonance
imaging (MRI), and laser therapy, use lower energy radiation that does not have
enough energy to ionize atoms or molecules. While these technologies are
generally considered safer than ionizing radiation, they still pose certain health
and safety risks, side effects, and limitations.
1.1Ultrasound
1.2
Ultrasound is a non-ionizing radiation technology that uses high-frequency sound
waves to create images of the body’s internal structures. It is widely used for
diagnostic purposes, particularly in obstetrics and gynecology. However,
ultrasound exposure can lead to thermal and mechanical effects on tissues.
Risks and side effects:
- Heating of tissues: Prolonged exposure to ultrasound can cause a rise in tissue
temperature, potentially leading to thermal damage
- Cavitation: High-intensity ultrasound can cause the formation and collapse of
gas bubbles in tissues, resulting in mechanical damage
- Fetal effects: Although considered safe for fetal imaging, concerns have been
raised about the potential long-term effects of ultrasound exposure on fetal
development
Limitations:
,- Limited penetration depth: Ultrasound has a limited ability to penetrate deep
tissues, particularly in obese patients or those with dense bone structures [4].
- Operator dependency: The quality of ultrasound images heavily relies on the
operator’s skill and experience [5].
1.3Magnetic Resonance Imaging (MRI)
1.4
MRI uses strong magnetic fields and radio waves to create detailed images of the
body’s internal structures. It is a powerful diagnostic tool for various conditions,
including neurological, musculoskeletal, and cardiovascular disorders.
Risks and side effects:
- Projectile effect: The strong magnetic field can attract ferromagnetic objects,
causing them to become projectiles and potentially injuring patients or operators
[6].
- Tissue heating: Radio frequency (RF) energy used in MRI can cause tissue
heating, particularly in patients with metallic implants or tattoos [7].
- Nerve stimulation: The rapidly switching magnetic fields can induce electrical
currents in the body, potentially causing nerve stimulation and discomfort [8].
- Claustrophobia and anxiety: The confined space of the MRI scanner can trigger
claustrophobia and anxiety in some patients [9].
Limitations:
- Contraindications: MRI is contraindicated in patients with certain metallic
implants, pacemakers, or other devices that can be affected by the magnetic
field [10].
- Long scan times: MRI scans can be time-consuming, which may be challenging
for patients who have difficulty remaining still or those with claustrophobia [11].
1.3 Laser Therapy
Laser therapy uses focused light energy to treat various conditions, such as skin
disorders, eye diseases, and certain cancers. While laser therapy offers many
benefits, it also carries risks and side effects.
,Risks and side effects:
- Eye damage: Direct or reflected laser light can cause eye injuries, including
retinal damage and permanent vision loss [12].
- Skin damage: Improper use of lasers can lead to skin burns, scarring, and
pigmentation changes [13].
- Photosensitivity reactions: Some medications and substances can increase the
skin’s sensitivity to laser light, leading to adverse reactions [14].
Limitations:
- Limited tissue penetration: The penetration depth of laser light depends on the
wavelength and power used, which may limit its effectiveness for deeper tissues
[15].
- Potential for misuse: Lasers can be misused or used inappropriately, leading to
unintended harm to patients or operators [16].
Section 2: Health and Safety Risks, Side Effects, and Limitations of Ionizing
Radiation Technologies
Ionizing radiation technologies, such as X-rays, computed tomography (CT), and
radiation therapy use high-energy radiation that can ionize atoms or molecules.
These technologies are widely used in medical imaging and cancer treatment.
However, ionizing radiation poses significant health and safety risks due to its
ability to damage living tissues and cause long-term health effects.
2.1 X-rays
X-rays are a form of ionizing radiation used for diagnostic imaging of the body’s
internal structures, such as bones, lungs, and teeth. While X-rays are an
essential tool in medical diagnosis, they also carry risks and side effects.
Risks and side effects:
- Radiation exposure: X-rays expose patients and operators to ionizing radiation,
which can damage living tissues and increase the risk of cancer [17].
,- Skin reactions: High doses of X-rays can cause skin reddening, itching, and
burns [18].
- Fetal effects: X-ray exposure during pregnancy can increase the risk of birth
defects and childhood cancers [19].
Limitations:
- Limited soft tissue contrast: X-rays have limited ability to differentiate between
soft tissues, which can make it difficult to diagnose certain conditions [20].
- Ionizing radiation exposure: The use of X-rays always involves exposure to
ionizing radiation, which carries inherent risks [21].
2.2 Computed Tomography (CT)
CT uses X-rays to create detailed cross-sectional images of the body. It is a
powerful diagnostic tool for various conditions, including cancer, trauma, and
cardiovascular diseases. However, CT scans deliver higher doses of ionizing
radiation compared to conventional X-rays.
Risks and side effects:
- High radiation exposure: CT scans deliver significantly higher doses of ionizing
radiation than conventional X-rays, increasing the risk of radiation-induced
cancers [22].
- Contrast media reactions: Some patients may experience allergic reactions or
adverse effects from the contrast media used in CT scans [23].
Limitations:
- Ionizing radiation exposure: The higher doses of ionizing radiation used in CT
scans increase the risk of long-term health effects [24].
- Artifacts: Metallic implants or patient movement can cause artifacts in CT
images, reducing image quality and diagnostic accuracy [25].
2.3 Radiation Therapy
,Radiation therapy uses high-energy ionizing radiation to kill cancer cells and
shrink tumors. It is a critical component of cancer treatment, often used in
combination with surgery and chemotherapy.
Risks and side effects:
- Radiation-induced tissue damage: Healthy tissues surrounding the tumor can
be damaged by radiation, leading to side effects such as skin reactions, fatigue,
and organ-specific complications [26].
- Secondary cancers: Exposure to high doses of ionizing radiation can increase
the risk of developing secondary cancers later in life [27].
- Long-term health effects: Radiation therapy can cause long-term health effects,
such as cardiovascular disease, endocrine disorders, and infertility [28].
Limitations:
- Limited specificity: Radiation therapy can damage both cancerous and healthy
cells, leading to side effects and complications [29].
- Cumulative radiation exposure: Patients undergoing radiation therapy receive
high cumulative doses of ionizing radiation, which can have long-term health
consequences [30].
Section 3: Prevention and Safety Measures
To maximize the protection of operators and patients, hospitals and healthcare
facilities must employ a range of health and safety measures when using non-
ionizing and ionizing radiation technologies.
3.1 Education and Training
- Provide comprehensive education and training to all personnel involved in the
use of radiation technologies, including physicians, technologists, and nurses
[31].
- Ensure that operators are knowledgeable about the risks, side effects, and
limitations of each technology and are competent in their safe operation [32].
3.2 Safety Protocols and Guidelines
,- Develop and implement clear safety protocols and guidelines for the use of
each radiation technology, including patient screening, equipment maintenance,
and emergency procedures [33].
- Regularly review and update safety protocols to incorporate the latest
evidence-based practices and regulatory requirements [34].
3.3 Radiation Protection Measures
- Use appropriate shielding materials, such as lead aprons and barriers, to
minimize radiation exposure to operators and patients [35].
- Implement the ALARA (As Low As Reasonably Achievable) principle, which
emphasizes using the lowest radiation dose necessary to achieve the desired
diagnostic or therapeutic outcome [36].
- Regularly monitor and record radiation doses to ensure compliance with dose
limits and identify areas for improvement [37].
3.4 Equipment Maintenance and Quality Control
- Establish a comprehensive equipment maintenance and quality control
program to ensure that radiation technologies are functioning properly and
delivering accurate doses [38].
- Perform regular calibration, testing, and inspection of radiation equipment to
identify and correct any issues that may compromise patient safety or image
quality [39].
3.5 Patient Education and Informed Consent
- Provide clear and comprehensive information to patients about the risks, side
effects, and benefits of each radiation technology, allowing them to make
informed decisions about their care [40].
- Obtain informed consent from patients before performing any radiation
procedures, ensuring that they understand the potential risks and complications
[41].
3.6 Dose Optimization Techniques
,- Implement dose optimization techniques, such as automatic exposure control
and iterative reconstruction algorithms, to minimize radiation exposure while
maintaining diagnostic image quality [42].
- Use alternative imaging modalities, such as ultrasound or MRI, when
appropriate to reduce unnecessary radiation exposure [43].
3.7 Occupational Health and Safety
- Provide appropriate personal protective equipment (PPE) to operators, such as
lead aprons, thyroid shields, and protective eyewear [44].
- Implement occupational dose limits and monitoring programs to ensure that
operators’ radiation exposure remains within acceptable levels [45].
- Offer regular health screenings and medical surveillance to operators to identify
and address any potential health effects related to radiation exposure [46].
21C RESUB
M1 - Ionizing Radiation Techniques
X-rays Principles - X-rays are a form of high energy electromagnetic radiation
produced when accelerated electrons strike a metal target, causing rapid
deceleration and emission of x-ray photons with wavelengths capable of ionizing
atoms within the body. Unlike other ionizing techniques like CT, x-rays only
provide a 2D projectional view as the x-ray beam passes through the body and is
attenuated differently by varying tissue densities.
Production - X-ray tubes contain a vacuum chamber with a cathode that emits
electrons towards an angled anode target made of tungsten or another high
atomic number metal. The electrons are accelerated across a high voltage
potential difference, and upon striking the target, their kinetic energy is converted
into x-ray emissions via the Bremsstrahlung process.
Medical Uses - Projection x-ray imaging is widely used due to its simplicity,
relatively low costs, and ability to visualize bony structures, soft tissue masses,
foreign objects, and lung abnormalities. Key applications include chest x-rays,
mammography for breast screening, skeletal x-rays, fluoroscopy, and portable x-
rays. Compared to advanced CT, x-rays provide poorer soft tissue contrast but
require minimal shielding and have very rapid scan times suitable for acute care
settings.
,Advantages over CT include lower ionizing radiation dose, real-time fluoroscopic
guidance, better spatial resolution for bony detail, lower equipment costs, and
more comfortable patient positioning.
Disadvantages compared to CT are inferior soft tissue contrast, limited to 2D
projections of overlapping anatomy, more patient positioning challenges, and
relatively higher radiation doses versus non-ionizing alternatives.
Computed Tomography (CT) Principles - While leveraging x-ray physics, CT
generates 3D volumetric data by acquiring multiple 2D x-ray images from various
angles around the patient's body through rotation of the x-ray source and
detectors, with computer processing used for tomographic reconstruction.
Production - Within the CT scanner's rotating gantry, an x-ray tube on one side
produces a fan-shaped beam towards an arc of x-ray detectors on the opposite
side. As the gantry rotates 360° around the patient, these x-ray projections from
different angles are recorded by the detectors to map tissue attenuations.
Medical Uses - The key advantage of CT over conventional x-rays is the ability to
computationally reconstruct high resolution 3D images from the acquired raw
projection data, allowing unmatched visualization of internal anatomy and cross-
sectional detail ideal for cancer staging, preoperative planning, vascular
assessments, musculoskeletal imaging, neurological conditions like strokes, and
CT-guided interventions.
Advantages over x-ray are the 3D cross-sectional imaging capabilities with
enhanced detail, multi-planar reconstruction options, and widespread availability.
Disadvantages compared to x-ray include much higher ionizing radiation doses,
poorer soft tissue contrast than MRI, noisy images for some patients, and higher
equipment/facilities costs.
Relative to non-ionizing ultrasound and optical methods, CT provides unmatched
spatial resolution and whole body imaging but with ionizing radiation risks.
M2 - Non-Ionizing Radiation Techniques
Ultrasound Principles - Ultrasound uniquely employs non-ionizing high frequency
sound waves above 20 kHz that are transmitted into and reflect off boundaries
between tissues with differing acoustic properties based on changes in acoustic
impedance. Unlike x-ray and CT which rely on ionizing radiation attenuating
through tissues, ultrasound maps these variable reflections.
Production - Electrical pulses drive piezoelectric crystals in the ultrasound probe
to mechanically vibrate and generate sound wave pulses that propagate into the
,body. The same crystals then detect returning waves reflected off tissue
interfaces, which are processed into a 2D greyscale image mapping the tissue
density boundaries.
Medical Uses - As a real-time, radiation-free, portable and relatively inexpensive
imaging technique, ultrasound has become indispensable across many medical
specialties including obstetrics for fetal monitoring, abdominal organ evaluations,
musculoskeletal imaging, echocardiography, vascular assessments, interventional
guidance, and ophthalmology. Its unique ability to visualize blood flow using
Doppler techniques provides key hemodynamic data.
Advantages over x-ray/CT include zero ionizing radiation risks enabling unlimited
scanning, unmatched real-time imaging capabilities, superior portable access,
significantly lower costs, and the option to visualize blood flow dynamics.
Disadvantages compared to ionizing modalities are poorer imaging quality for
obese patients and limited imaging windows due to signal attenuation through
gas/bone. Ultrasound also cannot quantify tissue composition and has operator
dependent imaging quality.
Optical Imaging Principles - Rather than utilizing ionizing x-rays or non-ionizing
sound waves, optical imaging techniques like fluorescence and photoacoustics
instead rely on visible and near-infrared light interaction with tissues to glean
functional and anatomical details based on the biochemical and optical properties
of different tissue types.
Production - Specialized light sources like lasers, LEDs or broadband lamps
illuminate the tissue region, with sensitive cameras and detectors then measuring
the optical signals emitted or scattered by the tissues. Additional molecular
probes which fluoresce under light stimulation can enhance the targeting of
specific tissue biomarkers.
Medical Uses - Clinical utility of optical imaging is currently largely restricted to
highly superficial tissue sites like the eye, skin, oral cavity or exposed tissues
during surgery due to limitations in photon penetration depth through the body.
However, at these accessible sites, optical methods excel at capturing detailed
cellular/molecular data on tissue metabolism, composition, and biomarker
expression useful for surgical guidance, cancer detection/monitoring, and
treatment response assessment.
Advantages over other modalities include impressive molecular sensitivity for
functional biochemical processes without ionizing radiation, relatively inexpensive
, optical components, and access to a broad range of light spectra enabling
versatile biomarker targeting.
Disadvantages are the shallow imaging depth possible for most in vivo
applications except optically transparent anatomy, relatively poor spatial
resolution from photon scattering, and the overall modality still being an
emerging clinical option with limited widespread adoption currently.
Overall, while ionizing x-ray and CT methods provide vital structural/anatomic
detail across the entire body, their associated radiation risks position non-ionizing
ultrasound and optical techniques as increasingly important complementary
technologies focused on soft tissue visualization and molecular interrogation
without such hazards when appropriate. Clinicians must carefully weigh the
advantages and limitations of each modality for a given application to optimize
patient outcomes while upholding radiation safety principles.
D1- Justify the choice of non-ionising and ionising radiation techniques in medical
applications.
Determining the most appropriate radiation technique, whether utilizing ionizing
or non-ionizing forms, is a critical decision in modern medical imaging and
therapeutic practices. The optimal choice hinges on carefully weighing the
diagnostic information needs, intended treatment goals, and potential radiation
risks for a given clinical scenario. While both ionizing (e.g. x-rays, CT) and non-
ionizing (ultrasound, optical) methodologies offer vital capabilities, they carry
inherent tradeoffs in terms of Benefits vs Risks that must be judiciously evaluated.
Numerous factors influence this risk-benefit analysis and ultimately guide
clinicians in justifying the selected radiation modality.
Justifying Use of Ionizing Radiation Techniques:
Ionizing radiation-based techniques like x-ray radiography and computed
tomography (CT) scanning derive their diagnostic power from the ability of high
energy x-ray photons to penetrate deeply into the body and interact differently
with structures of varying densities and atomic compositions. This facilitates
unparalleled visualization of high density, high atomic number materials like bone
and calcifications in immense structural detail. In many clinical scenarios where
evaluating osseous anatomy is paramount, the utility of x-ray and CT outweighs
the attendant radiation exposure risks:
