Introduction to Medical Imaging Modalities

Introduction to Medical
Imaging

PAO 5003

3
D. Kotun, NSU Orlando PA Program

Objectives
Recognize various types of imaging
studies
Discuss the mechanism for producing
images with each modality
List th
Li t the common indications for different
i di ti f diff t
imaging modalities
Describe the precautions for ordering
imaging studies
4

Pre – Test
I am looking forward to this test
because:

I want to learn all I can
I am demented
It i a good time to catch a nap
is di h
I heard that Prof. Kotun is a wonderful
lecturer

5

Imaging modalities
X-Ray
Computerized Tomography
Mammogram
M
Nuclear Magnetic Resonance
Positron Emission Tomography
Single Photon Emmission Computerized
Tomography
Ultrasound imaging
6

Terms
Tomography: a cross-sectional image formed from a set of projection
cross-
images. The Greek word tomo means cut.

CT: Computed (or Computerized) Tomography

MR, or MRI: Magnetic Resonance Imaging. This was first called nuclear
magnetic resonance (NMR), but the mention of anything nuclear scared
patients, so the “N” was dropped.

PET: Positron Emission Tomography. Understanding this phenomenon
requires acceptance of the theory that there is antimatter in the universe,
and when antimatter meets matter, then both kinds of matter are
annihilated, and pure energy is formed.

SPECT: Single Photon Emission Tomography

Ultrasound: Sonar in the body

OCT: O ti l C h
OCT Optical Coherent Tomography – th use of infrared light to image
tT h the fi f d li ht t i
(particularity) the walls of an artery.
7

Principle of X-Rays
p X- y

8

The First X-Ray Exam
X-
William Conrad Roentgen
89 Nov 1895
Took a picture of his wife s hand and
wife’s
developed it on photographic film
Ferdinand and Mazwell predicted X-Rays
X-
from Maxwell’s EM radiation theory

9

Bill s
Bill’s Lovely Wife

10

Production of the Radiographic
Image

11

X-Ray Tube

Figure 7-5 Drawing of a typical X-ray tube
75 X ray tube.
12

Bremsstrahlung Radiation

Figure 7-2 Deflection of high-energy electron by nucleus produces white radiation

13

Photon Generation

Figure 3-2 Illustration of the Compton scattering phenomenon

14

Photoelectric Effect

Figure 3-1 Drawing of photoelectric effect (from [Sung et al.]).

15

Spectrum of Densities & Ability to
Attenuate the X-ray Beam
h X-

16

Concept of Subtraction

17

Aortogram Subtraction

18

Magnification

Closest part to the film is in best focus and least magnified
19

In an X-ray tube, the photons are
X-
generated by what?
db h?
A high density nuclear source
1.
1
25%
2. An electron stream onto a metal
25%
target
3. A focused heated metal plate
25%

4. Magic pixies in a glass tube (hence
25%
the name pixels)

20

Posterior Anterior (PA)

The
nomenclature
follows the
direction of the
beam

21

AP Chest

Beam Direction

22

Left Lateral

Nomenclature is
dictated by the closest
body
b d part t the film
t to th fil

23

Lordotic

Nomenclature is
by the position of
the patient.

24

Oblique – LAO and RAO

25

Right Lateral Decubitus

26

AP Recumbant (AP supine)

27

Planes

(Frontal)

28

The left lateral view would mean:

The beam goes from front to back
1.
1
25%
2. The beam goes from left to right
25%
3. Th patient’s left side is closest to the
The ti t’ l ft id i l t t th
beam
25%

4. The patient’s left side is closest to the
25%
film

29

Putting It On Film

Figure 7-7 Scattered X-ray photons can be
removed from the image by positioning a grid
bet ee the patient and the detector (or
between t e pat e t a d t e detecto (o film).
)
30

Putting It On Film
X-Ray Photons are not very good at
exposing film
There is some type of amplification system
Photostimulable cassette
Phospors coat a screen and emit light when struck
by X-Ray photons
X-
These can be catured on film or amplified with an
electronic amplification system
l lf

31

Computerized Axial Tomography
– CT/CAT
/

Several
X-Ray tubes
in an array

32

CAT Scan

33

CAT Scan

34

CT

35

Helical CT

Instead of going
back and forth,
this corkscrews
itself down your
body.

36

CAT Scan
Now multiple heads allow faster imaging
with more resolution
Chest in < 30 sec. with .5cm resolution
sec 5cm
Pictures are reconstructed using a digital
reconstruction algorithm
These must be digitalized
Can be placed on film

37

Reconstruction

38

Mammography
Specific to a woman’s or man’s breasts
woman s man s
Lower dose
Used as cancer screening
Two types
Radiomammography
d h
Uses X-Ray technique
X-
Xeromammography
X h
Electrostatic image production

39

VIEWS
Cranio-caudal (CC) Medio lateral (ML)
()
Latero medial (LM)
()
view and mediolateral
i d di l t l mammographic view mammographic view
oblique (MLO)
mammographic view

Spot compression and cone down views

40

Technique
Mediolateral view

Craniocaudal view

41

Mammography

42

(N)MRI
Uses high strength magnets on hydrogen
bonds (in water)
Magnet strength is in Tesla Units (0.3 – 3)
g g ( )
The magnetic field excites the protons and
as it relaxes, it emits a radiofrequency
, q y
signal
Non-
Non-ionizing (very important)
Fields are aligned in 3 planes but can be
adjusted

43

(N)MRI

44

()
(N)MRI
High Quality three dimensional pictures
Uses Voxels vs Pixels (What is the
vs.
difference?)
Good for soft tissue water filled tissue
tissue,

45

Positron Emission Tomography) PET

Uses a prepared positron emitting nuclide
Positrons are emitted at 180° apart
180°

46

PET
Fair quality pictures
Shows function well

47

PET
Uptake is where the tissue has the most
activity
Increased uptake shows increased tissue
function
f ti
Great for mapping brain activity
Nuclide is usually injected

20 y.o. vs. 80 y.o.

48

SPEC/Nuclear Medicine
Uses a gamma emitting radionuclide to take a
2 dimensional picture
This is gathered on a scintillation camera
picking up the photons
Planar images can be combined from different
angles to reconstruct a 3 – D image
The nuclides are usually injected and are
designed to go to the organ or system in
q
question
49

SPEC/Nuclear Medicine

50

Ultrasound
Uses sound waves higher than detectable by
humans
Non-
Non-invasive and non-painful
non-
Patients aren’t usually afraid of U/S

51

Ultrasound
Early ultrasound was only 1 dimentional
Used for brain diagnoses

52

Ultrasound
2 – D ultrasounds
became more diagnostic
because the transducers
could produce a planar
image

53

Ultrasound
Better hardware and improved technology
made multidimensional images possible
These are safe for fetuses and are not painful
to the parent.

54

If I wanted to see organ function I
would use this type of imaging.
ld hi fi i
Plane X-ray
X-
1.
1
25%

2. Nuclear medicine scan
25%

3. C
Computerized tomography
t i dt h
25%

4. Magnetic resonance tomography
25%

55

To image an unborn fetus, the safest
imaging is:
i ii
Ultrasound
1.
1
25%

2. Nuclear medicine
25%

3. P it
Positron emission
ii
25%

4. Computerized tomography
25%

56

Did Ms Roentgen have a ring on?
Ms.
Yes
1.
1
33%

2. No
33%

3. M b
Maybe
33%

57

In the Future
Cellular imaging uses a combination of MRT,
MRT
CT, and U/S

Mouse done with
cellular imaging

58

Funny Bone…
Bone

59

Acknowledgements
Dove, E. L., 2003, Physics of Medical Imaging – An Introduction. U.
of Iowa, 53pp. Sep. 22, 2003

60

Questions?

61

Introduction to Medical Imaging Modalities

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