This document provides an introduction to medical imaging for first and second year medical students. It outlines objectives to learn how different imaging modalities like x-rays, CT, MRI, and ultrasound create images of internal structures. X-rays pass through the body to varying degrees based on atomic number, allowing visualization of different tissues. CT provides cross-sectional images to eliminate overlapping densities, while MRI and ultrasound have advantages for certain applications like detecting fluid or evaluating blood flow without radiation. Students are encouraged to learn normal anatomy and identify any abnormal structures.

1. Introduction to Medical
Imaging
Jeff Benseler, D.O.

2. Objectives
 Medical Imaging: What to expect in your first 2
years at OUHCOM
 Overview: How do x-rays create an image of
internal body structures?
 What are the advantages of CT, MRI and
Ultrasound?

3. Medical Imaging (Radiology)
 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

4. Method for learning medical image
interpretation
 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

5. Questions about medical imaging
 Please feel free to contact me with questions
 My preferred contact method is email
 benseler@ohio.edu

6. What are x-rays?
 No mass
 No charge
 Energy
X-rays are a type
of electromagnetic
energy
Objective 2

7. How do x-rays passing through the
body create an image?
 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)

8. 5 Basic Radiographic Densities
 Air
 Fat
 Soft tissue/fluid
 Mineral
 Metal
1.
2.
3.
4.
5.
Name these radiographic densities.

9. Optimal environment for visual
perception
 Dedicated source of light (5 to 9 mega pixel
monitors)
 Darkened environment (like a movie theater)
 Limit distraction

10. X-ray viewing station

11. Can you recognize
shapes and density?

12. Find the pathology
What clues do you have?

13. Medical Imaging Interpretation
3 basic steps
 First learn how each modality creates an image
of internal body structures
 Next, be able to accurately label normal
anatomy (body structures)
 Then, search for structures that don’t belong
and for body structures that are abnormal in
size, shape, position and/or density

14. History: 11 year old twisting
injury of the foot

16. Proximal
Distal
1.
2.
3.
Word bank: epiphysis, metaphysis, diaphysis, cortex, medullary cavity
Naming the parts of a long bone

17. Review: What are the 5 basic
radiographic densities from black to
bright white?
 Air
 Fat
 Soft tissue/fluid
 Bone/mineral
 Metal

18. Summary for objective 2: How do x-rays create
an image of internal body structures?
 X-rays pass through the body to varying degrees
 Higher atomic number structures block x-rays
better, example bone
 Lower atomic number structures allow x-rays to
pass through, example: air in the lungs

19. 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

20. CT
 Advantages
 Eliminates overlapping
densities
 Excellent resolution
 Excellent for detecting
intracranial bleeding
 Excellent in the neck,
chest and abdomen
 Excellent for evaluating
fractures
 Disadvantages
 More expensive than x-
ray and ultrasound
 Much more radiation
 Dense bone (petrous
ridge for example) and
metal cause severe
artifacts

21. CT scan of the abdomen
X-rays used skin
What density is this?
air

23. MRI
 Advantages
 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)
 Disadvantages
 Very expensive
 Patients cannot have a
pacemaker or
ferromagnetic material
 Slower to acquire images
(approximately 45 minutes)

25. Ultrasound
 Advantages
 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
 Disadvantages
 Does not work well in large or
obese patients
 Resolution less than CT and
MRI
 Air or bowel gas prevents
visualization of structures

26. Ultrasound of the
gall bladder showing
a gall stone

27. X-rays, CT, MRI and ultrasound help us
see into the body
 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.
 Each modality has its own advantages allowing
us the choose the best one for each medical
circumstance.

28. What an excellent medical student at
your level can do:
 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

29. List of Potentially Helpful
Radiology Websites
 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

30. Websites Continued
 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).

31. Websites continued
 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

32. Websites continued
 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.