Medical Imaging for
Physiotherapists
24 de setembro de 2025 13:00
Questions
- Difference between scarring and recurrent disc herniation: Hockey stick?? Cannot see it
- Distinguish labrum tear: displaced vs non-displaced
Lesson 1 - Intro and terminology
Lesson 1
Introducti...
What is medical imaging?
Medical Imaging is a specialty that produces images of the (internal) human body to detect and describe
disturbances in anatomy and/or function, and, if possible, to make a (differential) diagnosis of the pathology.
• To diagnose means to catalogue a certain abnormality in anatomy or function as a specific disease entity.
Medical imaging is frequently called radiology or radiographics, since historically mainly X-rays were used to
produce images of the body. Since nowadays other light or energy sources are used to produce images of the
inside of the body, the term medical imaging might be more appropriate. Note that medical imaging is also broader
that just radiology, since some imaging modalities, such as nuclear medicine are not part of radiology.
Disturbances in anatomy
This example shows a more extreme abnormality of the kidney with clear disturbance in shape is clear, different
signal and a potential tumor.
Disturbance of function
Joint abnormality
In the flexion position we can see two black lines in between the facet joints that tell us the distance between facet
joints. We can measure the change in the angle of these lines according to movement. If movement is the lines
doesn't change angle, the mobility is reduced and we have an abnormality in function
Cardiac abnormality
In this cardiac abnormality, a part of the cardiac muscle is not contracting as it should be.
Brain abnormality
Functional MRI is a technique capable of depecting brain activity and visualizing which networks are involved in
Courses and notes Page 1
,Functional MRI is a technique capable of depecting brain activity and visualizing which networks are involved in
each task.
The applications of this can be understanding better the risks of tumor removal and the exact location of the
metasteses.
Example: A study compared healthy subjects and patients with schizophrenia during the task of following a dot
• When changing our focus, the healthy populations overshoot the eye movement a little bit and then correct it.
• Patients with schizophrenia overshoot a lot and then have to correct much more.
With functional MRI, they understood that healthy subjects have more activity on frontal regions for this task, while
patients have much more activation of parleto-temporal regions. This means that the two groups are using
different in networks
Perhaps, if we make a diagnosis early, intervention can start early and improve the outcomes of these patients.
However, this is not yet at this individual level, only at group research level.
Goals of medical imaging
→ Diagnosis: Detection of abnormalities in symptomatic patients = High incidence of disease
→ Screening: Detection of abnormalities in asymptomatic patients = Low incidence of disease
These kind of screenings require high accuracy with high sensitivity (low rate of false negatives) and high
specificity (reliability of the outcome). Techniques still need to improve to reach the desired level.
Example: Mammography screening detects abnormaliteis in the pre- or early stage of breast cancer, in patients with
an increased risk
→ Therapy-planning: Plan the best approach of intervention (how to navigate the surgery)
→ Therapeutic follow-up: Is a fracture healing? Is chemotherapy reducing the size of a cancerous lesion?
→ Therapy: Guidance during operation
Example 1: During and after fixation of plate with screws for a horizontal fracture of the humerus, the surgeons
want to know if they placed it correctly
Example 2: Angiography is an invasive technique that uses x-ray to provide exquisite image detail (check brain part)
Example 3: Stereotactic brain surgery. Imaging is able to map the location of the instrument throughout the surgery
What is an image?
Analog image: Composed of an "infinite" number of elements (details) with a “continuous” color- of gray- scale
(contrast) (more used in the past).
• Example is a conventional X-ray
Digital image: The image is composed of a matrix (NxM) with a finite number (M rows, N colums) of elements
(pixels) and with a discrete number of color- or gray- values with a limited depth (bits)
• Digital Image = Spatial resolution (Matrix (NxM pixels)) x Contrast resolution/Depth (gray scale)
Spatial resolution
More columns and rows = more spatial resolution
The conventional X-ray still has the highest spatial resolution
Courses and notes Page 2
,Contrast Resolution (Depth)
More gray values = more contrast resolution
At 8 bpp you start seeing more differences because of more contrast/depth
The human eye can differentiate about 100 different shades of gray. However, medical images are acquired with
more (> 100) gray values
The “interesting” gray values can be extracted from the image by a procedure called “windowing” or gray value
manipulation
• Windowing is the process where one zooms in onto the medically ‘relevant’ part of the gray values. It helps
make the differences that are not visible to the human eye, visible.
• If there are two gray shades that we cannot distinghish, we use contrast to make them more visible - any value
above this interval becomes completely black and below this interval completely white.
• Weasis: software to manipulate gray values
Example: Now we can start to see differences in the lung tissue (left) and the bone (right)
Imaging modalities
Medical imaging makes use of a number of modalities (techniques) to acquire images of the internal human body.
• There are windows to visualize organs/muscles, vessels and bone
• Images are flipped / mirrored. For example, the heart will be on the right side on the image, although it’s on the
left side of the body.
Modalities have to do with the source of energy/light used to obtain the image:
• X-rays: Conventional X-ray (RX) and computer tomography (CT)
• Sound waves: Ultrasound
• Combination of magnetic fields and radiowaves: Magnetic resonance imaging (MRI)
Tissue interaction: The imaging modalities obtain specific and different information about the tissue that is imaged
since the energy source (X-ray, sound, radiowaves) interacts differently with the tissue. Therefore, the obtained
information is fundamentally different.
Courses and notes Page 3
, information is fundamentally different.
Images obtained with various modalities can give new pathophysiological insigths. An abnormality visualised with 1
technique can be ‘invisible’ on another modality
Example: Lunatum with loss of bone marrow
1. X-ray: No changes in density
2. MRI: High signal in the lunatum because the chemical properties changes (no bone marrow compared to the
other bones)
X-ray Detects changes in the density of atoms
Darker image = Lower density (pocket of air)
Lighter image = Higher density (bone)
Not boiled egg: radiation went through more easily in the pocket of air because it had less density
2D projection: When two different densities overlap there is a superposition of X-rays that penetrate
the object to a certain degree, making it difficult to distinghish
CT Detects changes in molecular structure
2D Tomography
Instrument: X-ray tube and detectors at opposite ends with 360ºrotation
Can be mathematically reconstructed as a SLICE through the body
Tomographic cuts
Axial (horizontal) Perpendicular to head-feet axis
Sagittal (vertical AP) Perpendicular to the LR axis
Coronal (vertical LR) Perpendicular to the AP axis
Courses and notes Page 4
Physiotherapists
24 de setembro de 2025 13:00
Questions
- Difference between scarring and recurrent disc herniation: Hockey stick?? Cannot see it
- Distinguish labrum tear: displaced vs non-displaced
Lesson 1 - Intro and terminology
Lesson 1
Introducti...
What is medical imaging?
Medical Imaging is a specialty that produces images of the (internal) human body to detect and describe
disturbances in anatomy and/or function, and, if possible, to make a (differential) diagnosis of the pathology.
• To diagnose means to catalogue a certain abnormality in anatomy or function as a specific disease entity.
Medical imaging is frequently called radiology or radiographics, since historically mainly X-rays were used to
produce images of the body. Since nowadays other light or energy sources are used to produce images of the
inside of the body, the term medical imaging might be more appropriate. Note that medical imaging is also broader
that just radiology, since some imaging modalities, such as nuclear medicine are not part of radiology.
Disturbances in anatomy
This example shows a more extreme abnormality of the kidney with clear disturbance in shape is clear, different
signal and a potential tumor.
Disturbance of function
Joint abnormality
In the flexion position we can see two black lines in between the facet joints that tell us the distance between facet
joints. We can measure the change in the angle of these lines according to movement. If movement is the lines
doesn't change angle, the mobility is reduced and we have an abnormality in function
Cardiac abnormality
In this cardiac abnormality, a part of the cardiac muscle is not contracting as it should be.
Brain abnormality
Functional MRI is a technique capable of depecting brain activity and visualizing which networks are involved in
Courses and notes Page 1
,Functional MRI is a technique capable of depecting brain activity and visualizing which networks are involved in
each task.
The applications of this can be understanding better the risks of tumor removal and the exact location of the
metasteses.
Example: A study compared healthy subjects and patients with schizophrenia during the task of following a dot
• When changing our focus, the healthy populations overshoot the eye movement a little bit and then correct it.
• Patients with schizophrenia overshoot a lot and then have to correct much more.
With functional MRI, they understood that healthy subjects have more activity on frontal regions for this task, while
patients have much more activation of parleto-temporal regions. This means that the two groups are using
different in networks
Perhaps, if we make a diagnosis early, intervention can start early and improve the outcomes of these patients.
However, this is not yet at this individual level, only at group research level.
Goals of medical imaging
→ Diagnosis: Detection of abnormalities in symptomatic patients = High incidence of disease
→ Screening: Detection of abnormalities in asymptomatic patients = Low incidence of disease
These kind of screenings require high accuracy with high sensitivity (low rate of false negatives) and high
specificity (reliability of the outcome). Techniques still need to improve to reach the desired level.
Example: Mammography screening detects abnormaliteis in the pre- or early stage of breast cancer, in patients with
an increased risk
→ Therapy-planning: Plan the best approach of intervention (how to navigate the surgery)
→ Therapeutic follow-up: Is a fracture healing? Is chemotherapy reducing the size of a cancerous lesion?
→ Therapy: Guidance during operation
Example 1: During and after fixation of plate with screws for a horizontal fracture of the humerus, the surgeons
want to know if they placed it correctly
Example 2: Angiography is an invasive technique that uses x-ray to provide exquisite image detail (check brain part)
Example 3: Stereotactic brain surgery. Imaging is able to map the location of the instrument throughout the surgery
What is an image?
Analog image: Composed of an "infinite" number of elements (details) with a “continuous” color- of gray- scale
(contrast) (more used in the past).
• Example is a conventional X-ray
Digital image: The image is composed of a matrix (NxM) with a finite number (M rows, N colums) of elements
(pixels) and with a discrete number of color- or gray- values with a limited depth (bits)
• Digital Image = Spatial resolution (Matrix (NxM pixels)) x Contrast resolution/Depth (gray scale)
Spatial resolution
More columns and rows = more spatial resolution
The conventional X-ray still has the highest spatial resolution
Courses and notes Page 2
,Contrast Resolution (Depth)
More gray values = more contrast resolution
At 8 bpp you start seeing more differences because of more contrast/depth
The human eye can differentiate about 100 different shades of gray. However, medical images are acquired with
more (> 100) gray values
The “interesting” gray values can be extracted from the image by a procedure called “windowing” or gray value
manipulation
• Windowing is the process where one zooms in onto the medically ‘relevant’ part of the gray values. It helps
make the differences that are not visible to the human eye, visible.
• If there are two gray shades that we cannot distinghish, we use contrast to make them more visible - any value
above this interval becomes completely black and below this interval completely white.
• Weasis: software to manipulate gray values
Example: Now we can start to see differences in the lung tissue (left) and the bone (right)
Imaging modalities
Medical imaging makes use of a number of modalities (techniques) to acquire images of the internal human body.
• There are windows to visualize organs/muscles, vessels and bone
• Images are flipped / mirrored. For example, the heart will be on the right side on the image, although it’s on the
left side of the body.
Modalities have to do with the source of energy/light used to obtain the image:
• X-rays: Conventional X-ray (RX) and computer tomography (CT)
• Sound waves: Ultrasound
• Combination of magnetic fields and radiowaves: Magnetic resonance imaging (MRI)
Tissue interaction: The imaging modalities obtain specific and different information about the tissue that is imaged
since the energy source (X-ray, sound, radiowaves) interacts differently with the tissue. Therefore, the obtained
information is fundamentally different.
Courses and notes Page 3
, information is fundamentally different.
Images obtained with various modalities can give new pathophysiological insigths. An abnormality visualised with 1
technique can be ‘invisible’ on another modality
Example: Lunatum with loss of bone marrow
1. X-ray: No changes in density
2. MRI: High signal in the lunatum because the chemical properties changes (no bone marrow compared to the
other bones)
X-ray Detects changes in the density of atoms
Darker image = Lower density (pocket of air)
Lighter image = Higher density (bone)
Not boiled egg: radiation went through more easily in the pocket of air because it had less density
2D projection: When two different densities overlap there is a superposition of X-rays that penetrate
the object to a certain degree, making it difficult to distinghish
CT Detects changes in molecular structure
2D Tomography
Instrument: X-ray tube and detectors at opposite ends with 360ºrotation
Can be mathematically reconstructed as a SLICE through the body
Tomographic cuts
Axial (horizontal) Perpendicular to head-feet axis
Sagittal (vertical AP) Perpendicular to the LR axis
Coronal (vertical LR) Perpendicular to the AP axis
Courses and notes Page 4
