Introduction to Medical
Imaging
Jeff Benseler, D.O.
Objectives
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Medical Imaging: What to expect in your first 2
years at OUHCOM
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Overview: How do x-rays create an image of
internal body structures?
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What are the advantages of CT, MRI and
Ultrasound?
Medical Imaging (Radiology)
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Nearly all medical disciplines utilize medical
imaging
As you move from block to block we will learn:
How each modality works to create an image of
internal body structures
 Selecting the best imaging tests for a given clinical
presentation
 Develop a stepwise repeatable pattern of evaluating
medical images
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Method for learning medical image
interpretation
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Most blocks will contain recorded presentations
These recordings last approximately 10 to 30
minutes each
Most blocks will have 2 to 4 recordings to view
before the live class
The recordings can be viewed and reviewed as
needed anytime 24/7
In class, we will learn by interpreting unknown
cases
Questions about medical imaging
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Please feel free to contact me with questions
My preferred contact method is email
benseler@ohio.edu
Objective 2
What are x-rays?
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No mass
No charge
Energy
X-rays are a type
of electromagnetic
energy
How do x-rays passing through the
body create an image?
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X-rays that pass through the body render the
image dark (black)
X-rays that are totally blocked render the image
light (white)
Air = low atomic # = x-rays get through =
image is dark (black)
Metal = high atomic # = x-rays blocked =
image is light (white)
5 Basic Radiographic Densities
1.
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Air
Fat
Soft tissue/fluid
Mineral
Metal
2.
3.
Name these radiographic densities.
4.
5.
Optimal environment for visual
perception
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Dedicated source of light (5 to 9 mega pixel
monitors)
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Darkened environment (like a movie theater)
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Limit distraction
X-ray viewing station
Can you recognize
shapes and density?
Find the pathology
What clues do you have?
Medical Imaging Interpretation
3 basic steps
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First learn how each modality creates an image
of internal body structures
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Next, be able to accurately label normal
anatomy (body structures)
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Then, search for structures that don’t belong
and for body structures that are abnormal in
size, shape, position and/or density
History: 11 year old twisting
injury of the foot
Naming the parts of a long bone
Distal
3.
2.
1.
Proximal
Word bank: epiphysis, metaphysis, diaphysis, cortex, medullary cavity
Review: What are the 5 basic
radiographic densities from black to
bright white?
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Air
Fat
Soft tissue/fluid
Bone/mineral
Metal
Summary for objective 2: How do x-rays create
an image of internal body structures?
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X-rays pass through the body to varying degrees
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Higher atomic number structures block x-rays
better, example bone
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Lower atomic number structures allow x-rays to
pass through, example: air in the lungs
Objective 3
Advantages of CT, MRI and
Ultrasound
These modalities are cross sectional imaging
Cross sections are like slices
X-ray studies are a 2 dimensional representation of
3 dimensional structures can result in
undesirable overlapping densities and artifacts
CT
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Advantages
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Eliminates overlapping
densities
Excellent resolution
Excellent for detecting
intracranial bleeding
Excellent in the neck,
chest and abdomen
Excellent for evaluating
fractures
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Disadvantages
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More expensive than xray and ultrasound
Much more radiation
Dense bone (petrous
ridge for example) and
metal cause severe
artifacts
air
CT scan of the abdomen
X-rays used
skin
What density is this?
MRI
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Advantages
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No overlapping artifact
Excellent resolution
Very good at detecting
fluid
Excellent for imaging the
brain, spine and joints
No radiation
Multiple imaging tests
within the same study
(T1, T2, IR, GE)
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Disadvantages
Very expensive
 Patients cannot have a
pacemaker or
ferromagnetic material
 Slower to acquire images
(approximately 45 minutes)
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Ultrasound
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Advantages
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No radiation
Portable
Instantaneous (real time)
Excellent for cysts and fluid
Doppler ultrasound is excellent
to assess blood flow
Excellent for newborn brain,
thyroid, gall bladder, female
pelvis, scrotum, pregnancy
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Disadvantages
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Does not work well in large or
obese patients
Resolution less than CT and
MRI
Air or bowel gas prevents
visualization of structures
Ultrasound of the
gall bladder showing
a gall stone
X-rays, CT, MRI and ultrasound help us
see into the body
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Internal body structures are composed of varied
material (fat, muscle, bone, gland) or contain air,
water or minerals that “show up” differently on
each type of imaging test.
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Each modality has its own advantages allowing
us the choose the best one for each medical
circumstance.
What an excellent medical student at
your level can do:
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Be able to describe how x-rays can create an
image of internal body structures
Recognize and label the 5 basic densities on an
x-ray
Be familiar with the advantages for CT, for MRI
and for ultrasound
List of Potentially Helpful
Radiology Websites
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http://www.med-ed.virginia.edu/courses/rad/
Online tutorial series.
http://radiopaedia.org/
A free educational radiology resource with one of the
web's largest collections of radiology cases and
reference articles.
http://www.radiologyassistant.nl/en/p42023a885587e
/welcome-to-the-radiology-assistant.html
Websites Continued
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http://learningradiology.com/index.htm
Seems to have some good stuff but difficult to navigate
the site.
http://www.swansea-radiology.co.uk/index.html
http://bubbasoft.org/
Strange name but the website is useful. Breaks it into
radiologic anatomy (identification of structures) and
clinical radiology (identification of pathology).
Websites continued
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http://eradiology.bidmc.harvard.edu/index.html
This source seems really valuable. Includes sections on
primary care radiology, representative images of classic
cases, interactive tutorials, and living anatomy
http://www.radiologyeducation.com/
List of radiology resources
http://www.med.wayne.edu/diagRadiology/TeachingF
ile.html
Collection of interesting cases
Websites continued
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http://headneckbrainspine.com/
Neuroradiology anatomy and cases.
https://3s.acr.org/CIP/Default.aspx
Case in point. American College of Radiology’s
case of the day.