Select your language

Suggested languages for you:
Log In Start studying!
StudySmarter - The all-in-one study app.
4.8 • +11k Ratings
More than 3 Million Downloads
Free
|
|

All-in-one learning app

  • Flashcards
  • NotesNotes
  • ExplanationsExplanations
  • Study Planner
  • Textbook solutions
Start studying

Medical Physics

Save Save
Print Print
Edit Edit
Sign up to use all features for free. Sign up now

Want to get better grades?

Nope, I’m not ready yet

Get free, full access to:

  • Flashcards
  • Notes
  • Explanations
  • Study Planner
  • Textbook solutions
Medical Physics

If you’ve ever had an X-ray or an MRI, you’ve encountered medical physics. This is the branch of physics that deals with healthcare. It offers solutions and practical applications from physics and physics engineering in the medical field. Two areas that stand out are optics and imaging.

Medical physics covers many different areas, from technologies used to improve eyesight and hearing to help with the diagnosis of diseases (internal imaging techniques), the creation of tools to improve surgical methods (endoscopy), and disease treatment, such as radiotherapy.

Physics of the eye and ear

In any animal species, organs that help to sense the environment are the most important tools for survival. For humans, two of these sensory systems are hearing and vision.

Both mechanisms translate incoming signals into electrical impulses that are delivered to the brain. Evolution has made these systems so complex that they allow us to detect colours, the direction of sounds, and the intensity of both sound and light. The physical mechanisms that rule their functioning are important, and understanding them from the perspectives of physics and biology allows us to develop a range of healthcare solutions.

The eye

We can see the things around us because of light entering our eyes. This light undergoes a series of optical transformations to produce an image that we can see. Let us understand how it works.

  • Light enters the eye through a clear dome called the cornea, which is a refractive medium that bends the entering light.
  • The light then passes through the pupil, an aperture controlled by a muscle that expands and contracts to allow more or less light to pass.
  • After passing the pupil, the light enters the lens, which focuses the light beam to the back of the eye with the help of the cornea.
  • The image focused on the back of the eye is then projected onto the retina. This possesses a sensitive array of nerves that conduct the light signal to the brain.

Many of the processes in the eye are impacted by light, including focusing, lenses, and image processing. Thus, many applications from optics, a branch of physics that deals with light, have been used in corrections of eyesight problems.

The ear

We can hear the sounds around us because of the functioning of the ear. The ear can be split into three parts, each with its own set of functions. Looking at its structure, we find:

  1. The outer ear, which collects and transmits the sound to the middle ear.
  2. The middle ear, which converts the energy of a sound wave into internal vibrations of the middle ear’s bone structure. These vibrations are then converted into compressional waves in the inner ear.
  3. The inner ear, which transforms the energy of the compressional waves into nerve impulses that can be transferred to the brain.

See the image below for the different components of the ear.

Medical Physics. Ear system. StudySmarterFigure 1. Anatomy of the human ear. Source: Lars Chittka and Axel Brockmann, Wikimedia Commons (CC BY 2.5).

The role of physics in the medical field

Physics has a great impact, providing solutions and technology to help people in many areas of medicine and healthcare. Lenses and lens implants to correct vision and optical instruments to conduct surgeries via endoscopy use results and techniques from optics.

Areas such as hearing benefit from applications in acoustics and electronics. These help to develop mechanisms to translate audio to electrical impulses and to amplify them. Other applications of physics can be found in disease treatments, such as the use of radiation to kill cancer cells and shrink tumours. Other areas using applications of physics are electrocardiography and imaging.

Cancer treatment

Nuclear physics has been one of the main tools used in the fight against cancer. Treatments use a beam of particles (electrons, photons, or protons) directed towards the tumour to aim to kill it and stop it from spreading further.

In some cases, radiation sources can be internal (inside your body), a treatment that is known as radiotherapy.

Medical Physics. Cancer therapy. Radiation. StudySmarterFigure 2. During radiotherapy, cancer cells are targeted with doses of radiation to damage their DNA and stop their growth. Source: Manuel R. Camacho, StudySmarter.

Cells carry instructions in their genome to produce daughter cells and replace tissue when it is damaged, or other cells have died.

Cancer cells carry damage in their genome that affects the instructions for growth and division (cancerogenesis). This leads to cancer cells multiplying without end and forming tumours.

Radiation is used to damage the DNA of these cells further. After some sessions, the DNA is so damaged that the cells cannot reproduce anymore. Radiotherapy is used in combination with other treatments, such as surgery and chemotherapy, to ensure high success in beating cancer.

An aid to hearing

Human hearing has a mechanism that translates sound first into mechanical vibrations and then into electrical impulses that are sent to the brain. As people age, parts of these mechanisms are lost or damaged.

Devices that can amplify incoming sounds have been developed to improve the hearing of anyone with hearing impairments. Using a microcontroller, these devices transform sounds into electrical signals and send them to the ear canal after they have been amplified.

Some hearing issues require specific and more direct solutions, which may include the implant of devices below the skin, such as:

  • Bone-anchored hearing aids, which transmit the vibration through the inner ear.
  • Cochlear implants, which send the electrical signal to the cochlea, the organ that translates the vibration into electrical signals.
  • Auditory brainstem implants, which send the signal directly to the brain.

Lenses and optics

Optics has been one of the main areas of medical physics, enabling us to produce devices such as telescopes and microscopes. Optics also helps us to produce lenses to correct vision. Defects in vision caused by a deformation of the eye curvature modify the image that is acquired by the brain. Glasses and lenses correct the light entering the eyes, thereby providing a solution for vision defects.

Medical Physics. Myopia. Eyesight. Optics. StudySmarterFigure 3. Sight disorders such as myopia are caused by the deformation of the eye. Source: Manuel R. Camacho, StudySmarter.

In myopia, the image focuses before it reaches the back of the eye, making it blurry. Glasses help to refocus the image before it enters your eye, thereby correcting this defect.

In many cases, myopia can be also be treated by implanting lenses inside the first layer of the eye. These intraocular lenses can also help with cataracts, replacing the natural lenses of the eye when they become cloudy.

Electrocardiography

A test called an electrocardiogram allows doctors to measure a patient’s heartbeat. This technique is known as electrocardiography.

The electric potentials in the heart muscle produce a measurable electrical trace, an electrocardiograph or ECG. The analysis of the signal delivered can show the heart’s performance and give valuable information on any strange behaviour.

Non-ionising imaging

This includes the study of ultrasound imaging and magnetic resonance imaging (MRI), techniques that use low energy photons or sound to produce images of internal components of the body.

Ultrasound imaging

This works by transferring sound waves to the body and detecting their reflection waves. We cannot detect these ultrasound waves, which have a sound range of 20kHz and above that is beyond our hearing capacity.

With ultrasounds, doctors can get detailed images in real-time at a relatively low cost without causing any harm to the patient. Ultrasound imaging allows medics to diagnose a variety of medical conditions, including heart valve disorders, possible tumours, and other organ abnormalities.

Magnetic resonance scanning

Magnetic resonance imaging, commonly known as ‘MRI scans’, is used for producing a detailed image of a cross-section of a patient’s body. It utilises strong magnetic fields and radio waves to produce images by inducing rapid small changes into the body’s hydrogen atoms.

Medical Physics. MRI. Non-ionising imaging. StudySmarterFigure 4. MRI devices allow doctors to obtain detailed images of the inner body without using high energy radiation. Source: Navy Medicine, Flickr (Public Domain).

Ionising imaging

Imaging techniques also use high-power radiation, utilising small doses of electromagnetic radiation to recreate images of the body as x-rays or gamma rays for tracing. Other processes of imaging can also use the emission of beta particles.

In general, these techniques can produce very accurate images of internal parts of the body. However, exposure to them should be limited to ensure the security of the patients.

X-ray imaging

X-rays are waves with short wavelengths and high intensities. They are used in medicine to create black and white images of the inside of the body. The image colours and tones are a product of the absorption of the x-ray photons.

X-rays have high energy and thus penetrate matter more easily, but their absorption and penetration depend on the density of the material.

Medical Physics. X-ray imaging. Ionising imaging. StudySmarterFigure 5. X-rays were discovered by the German scientist Wilhelm Röntgen. Source: Yale Rosen, Flickr (CC BY-SA 2.0).

On the images, bones, which absorb the x-rays, appear in white. Tissues, which absorb fewer x-rays, are displayed in grey, while air, which absorbs only a very small number of x-rays, shows as black.

The technique of creating, processing, and interpreting x-rays is called radiography. X-rays are routinely used for checking fractures, but they can also spot pneumonia and even breast cancer. More recently, x-rays have been used to check for possible signs of COVID-19 complications.

Radionuclide imaging

A radionuclide is a nucleotide that is radioactive in nature. It is an isotope of an element with an unstable nucleus. Its decay results in the emission of subatomic particles or electromagnetic radiation.

A radionuclide scan is a type of imaging that employs a small amount of an isotope called a tracer to identify cancer, injuries, infections, and other conditions. The tracer is either injected into a vein or eaten. Once within the body, the tracer travels through circulation to the organ of interest, such as the thyroid, heart, or bones. The radiation is then detected and interpreted by a camera or sensor.

The tracer emits gamma rays, which are comparable to x-rays. A gamma camera detects these gamma rays, which are then processed by a computer to create a picture of the target organ. Potential problem areas emit stronger gamma rays, which show up on the scan as bright patches. PET scans, gallium scans, and bone scans are all examples of radionuclide scans.

Except for a little prick in the case of an injection, a radionuclide scan is painless. The isotope must travel to the target organ, which may take several hours. The patient can normally leave the testing facility during this period and return for the scan, which can take anywhere from one to five hours.

Medical Physics - Key takeaways

  • Medical physics deals with the physics of healthcare and how physics produces applications used in medicine.
  • The eye and the ear are two sensory systems that convert signals, light and sound respectively, into electrical impulses that are then delivered to the brain.
  • Optics and acoustics, both branches of physics, have a great impact on eyesight and hearing healthcare.
  • The analysis of the sensory systems and how they work has helped to create devices and lenses that correct problems with hearing and vision.
  • Cancer treatment uses nuclear physics to combat cancer cells.
  • Medical imaging and monitoring use ionising and non-ionising techniques to monitor and deliver information about internal parts of the body, helping doctors gather more precise information about their patients.

Frequently Asked Questions about Medical Physics

Medical physics deals with the applications of physics to medicine. These include cancer treatment, tracing methods, imaging, and sterilisation.

Medical imaging physics focuses on topics such as radiographic x-rays, fluoroscopy, mammography, angiography, and computed tomography. It also looks at testing, optimisation, and quality assurance in the diagnostic radiology industry.
Imaging physics uses different sources of radiation like X-rays; or emission of particles, as in emission tomography. The radiation is observed by a media that is very sensitive to this emission. Images are then created from the observations.

Medical physics covers a broad range of topics from imaging techniques to radiotherapy, processes to enhance surgical procedures, such as endoscopy, and improving hearing and eyesight.

Final Medical Physics Quiz

Question

What's the retina?

Show answer

Answer

The part of the eye where the image is focused.

Show question

Question

How does the iris work?

Show answer

Answer

It regulates the amount of incoming light.

Show question

Question

Can we see colors in the dark?


Show answer

Answer

No, because the cells operating in the night don't distinguish colors.

Show question

Question

What's myopia?

Show answer

Answer

A defect in the focus inside the eye

Show question

Question

What allows us to see colors?

Show answer

Answer

We have specialized cells that catch a range of colors.

Show question

Question

What's the cornea?

Show answer

Answer

The most external part of the eye.

Show question

Question

What's the difference between the iris and the pupil?

Show answer

Answer

The iris is responsible for the aperture of the pupil.

Show question

Question

What is the shape of the eye, and why does it have liquid inside?

Show answer

Answer

The eye is spherical, and the liquid inside causes the light to refract on the retina.

Show question

Question

What are cone cells?

Show answer

Answer

Cone cells are used to see colors and are highly sensitive to light.

Show question

Question

Why rod cells aren't involved in color vision?

Show answer

Answer

Because rod cells are of one kind.

Show question

Question

How can vision defects occur?

Show answer

Answer

When the eye's structure is altered, misalignments of the focus can occur, leading to vision defects.

Show question

Question

What do we do to correct focus-related vision problems?

Show answer

Answer

By applying lenses in the front of the eye, we correct the angle of incidence of the light, allowing it to reach the correct point in the retina.

Show question

Question

What's hypermetropia?

Show answer

Answer

It is the condition that causes the focus of the eye's lens to be in front of the retina.

Show question

Question

How many types of cone cells exist?

Show answer

Answer

Three, they perceive light of different wavelengths.

Show question

Question

Are cones useful for night vision?

Show answer

Answer

Yes, because they are more sensitive to light than the rod cells.

Show question

Question

Does non-ionizing radiation conserve enough energy to cause an electron to break away from the atom?

Show answer

Answer

No, it doesn't.

Show question

Question

Non-ionizing radiation waves have a long wavelength. True or false?


Show answer

Answer

True.

Show question

Question

What is another name for ultrasound imaging?


Show answer

Answer

Sonography.

Show question

Question

Which one of the techniques in non-ionizing imaging does not capture the interior of the human body in real time?


Show answer

Answer

Magnetic resonance imaging (MRI).

Show question

Question

An endoscope is a device that provides lighting and visibility into the interior of a joint. True or false?

Show answer

Answer

True.

Show question

Question

Radiation waves with which wavelength value are considered ionizing radiation?


Show answer

Answer

λ <125nm.

Show question

Question

Which non-ionizing imaging technique can be used to see internal organ movement?

Show answer

Answer

 Ultrasound imaging.

Show question

Question

Do non-ionizing radiation waves have the potential to excite molecules and atoms, thus causing them to vibrate faster?

Show answer

Answer

Yes, they do.

Show question

Question

Which non-ionizing imaging technique is used to diagnose digestive system illnesses?


Show answer

Answer

Endoscopy.

Show question

Question

Which optic principle is used by endoscopy?

Show answer

Answer

The total internal reflection principle.

Show question

Question

The general consensus is that you can successfully scan tissue to a depth of around which number?


Show answer

Answer

500 times the wavelength of the wave.

Show question

Question

Which non-ionizing imaging technique uses fiber optics and advanced lens systems?


Show answer

Answer

 Endoscopy.

Show question

Question

 Are X-rays non-ionizing or ionizing?


Show answer

Answer

 Ionizing.

Show question

Question

Which non-ionizing imaging technique is used to see a baby inside the womb?


Show answer

Answer

Ultrasound imaging.

Show question

Question

Is infrared radiation non-ionizing or ionizing?


Show answer

Answer

 Non-ionizing.

Show question

Question

When a radiation wave's wavelength increases, does its energy increase or decrease?


Show answer

Answer

 It decreases.

Show question

Question

Which non-ionizing imaging technique uses strong magnetic fields and radio waves?

Show answer

Answer

Magnetic resonance scanning (MRI).

Show question

Question

Are gamma rays non-ionizing or ionizing?


Show answer

Answer

 Ionizing.

Show question

Question

Which non-ionizing imaging technique is used to get a better image of the human brain?


Show answer

Answer

 Magnetic resonance imaging (MRI).

Show question

Question

What distinguishes non-ionizing waves from ionizing waves?

Show answer

Answer

Having enough energy to cause ionization.

Show question

Question

Can radionuclides be created by humans?

Show answer

Answer

Yes, they can.

Show question

Question

What is the given name to a radionuclide's pace in emitting radiation? 


Show answer

Answer

Half-life.

Show question

Question

The half-life is the amount of time it takes for one-half of the atomic nuclei in a radioactive sample to do what?

Show answer

Answer

Decay.

Show question

Question

 Which radionuclide imaging technique is the most precise and noninvasive technique available?


Show answer

Answer

Positron emission tomography (PET).

Show question

Question

 Can nuclear species spontaneously transform into other nuclear species by releasing particles and energy?

Show answer

Answer

Yes, they can.

Show question

Question

 To minimize unwanted irradiation, should the half-life be short or long?


Show answer

Answer

 It should be short.

Show question

Question

 Which technique gives a unique chance to monitor and quantify in vivo physiological molecular interactions in real time?


Show answer

Answer

Positron emission tomography (PET).

Show question

Question

What is the technique that uses radiation to regulate or destroy fast-dividing cancer cells?


Show answer

Answer

 Radiotherapy.

Show question

Question

What do we call it when nuclear species spontaneously transform into other nuclear species by releasing particles and energy?

Show answer

Answer

Decay.

Show question

Question

SPECT and planar scintigraphy use gamma cameras for detection, with collimated detectors registering emitted gamma rays. True or false?


Show answer

Answer

 True.

Show question

Question

PET necessitates the use of a radiopharmaceutical that contains what?


Show answer

Answer

A positron-emitting radionuclide

Show question

Question

Are gamma cameras used in SPECT?


Show answer

Answer

Yes, they are.

Show question

Question

 What detects optical photons?


Show answer

Answer

Photomultiplier tubes.

Show question

Question

In hybrid techniques, what is used combined with SPECT and PET?

Show answer

Answer

Computed tomography (CT).

Show question

Question

Does SPECT have the advantage of three-dimensional imaging? 


Show answer

Answer

 Yes, it does.

Show question

60%

of the users don't pass the Medical Physics quiz! Will you pass the quiz?

Start Quiz

Discover the right content for your subjects

No need to cheat if you have everything you need to succeed! Packed into one app!

Study Plan

Be perfectly prepared on time with an individual plan.

Quizzes

Test your knowledge with gamified quizzes.

Flashcards

Create and find flashcards in record time.

Notes

Create beautiful notes faster than ever before.

Study Sets

Have all your study materials in one place.

Documents

Upload unlimited documents and save them online.

Study Analytics

Identify your study strength and weaknesses.

Weekly Goals

Set individual study goals and earn points reaching them.

Smart Reminders

Stop procrastinating with our study reminders.

Rewards

Earn points, unlock badges and level up while studying.

Magic Marker

Create flashcards in notes completely automatically.

Smart Formatting

Create the most beautiful study materials using our templates.

Just Signed up?

Yes
No, I'll do it now

Sign up to highlight and take notes. It’s 100% free.