Transcript Lecture1_bri

Introduction to Medical Imaging
Instructors: Brian Fleming and Ioana Fleming
[email protected], [email protected]
Lecture 1
• Meet and greet
• A brief history of everything
• Break
• Intro to Death Rays X-Rays
In the Beginning…
Where to put the Leeches
• Hippocrates (460 - 377 BCE)
– Muscles, skeleton, kidneys
– Observation only
• Pesky “Oath” prevented human dissection
• Aristotle and Friends (4th century BCE)
– Animals aren’t people
• Herophilos and Erasistratus (4th century BCE)
– First human cadavers
– Criminals aren’t people either
Where to put the Leeches
• Dark Ages - Europe
– Balance the “humors”
– Bleed, burn, drown, or exorcise
• Dark Ages – Arabia/Persia
– Avicenna (1020 AD) Canon of Medicine
• Premier book of medicine everywhere for 500 years
– Ibn Zuhr (1100 AD)
• Invented Autopsy and discovered parasites
• Would have killed the idea of humors if logic and fact had
been considered a valid argument
Where to put the Leeches
• Printing Press – 17th century
– Sharing of ideas brings renaissance (murder?)
History of Medical Imaging
Wilhelm Röntgen (Roentgen)
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The father of diagnostic radiology
German physicist (1845-1923)
Discovered x-rays in 1895
X was for "unknown“
First Nobel Prize in physics 1901
Discovery of X-rays
How to Irradiate Yourself
• Step 1 – Force electrons to go where no
electron would ever want to go
– In air, would cool by giving off light
How to Irradiate Yourself
• Step 2 – Get rid of the air
– Air quenches electron escape
• Unless you really ramp up the voltage…
– Try Neon
– Or try nothing…
How to Irradiate Yourself
• Step 3 – Run those electrons into a target
“Instant” Success
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Nov 8, 1895: Accidental discovery of x-rays
Dec 22, 1895: Bertha’s hand
Dec 28, 1895: first publication of results
Jan 1, 1896: Roentgen mailed copies to
leading scientists
• Jan 5, 1896: Austrian newspaper story
• Jan 23, 1896: society presentation
• Feb 8, 1896: 1st clinical use (in US!)
Within One Year ...
• 49 serious books on x-rays
• 1,044 scientific papers
• Known to:
– spot cancer
– treat cancer
– cause cancer
• Numerous patents
What it REALLY Did…
Fluoroscopy
Fluorescence
Filmed in X-ray!
Early Popularity of Fluoroscopy
• Simple fluoro equipment:
– x-ray tube
– electrical generator
– scintillation screen
• Convenience of real-time
• Note: early film required 12 hours of exposure
– (where was intensifier
screen????)
Red Goggles
• Fluoroscopy images were dim
• 1899: Beclere showed that dark adaptation is
a function of the retina
• 1901: Williams suggested 10-minute dark
adaptation
• 1916: scientific basis of sensitivity of retinal
rods in the range of red light
• 1916-1950’s: red goggles standard gear
X-ray Hazards
• Early 1896: reports of hair falling out
• Early 1896: skin reddening, inflammation
• Early 1896: some severe burns (attributed to high
voltage in tubes)
• Early 1896: delayed burns
• 1902: Edison clear on dangers of x-rays
– Clarence Dally’s oozing ulcers, lost fingers, left
hand, died in 1904 (Edison never x-rayed again)
• The use of X-rays for medical purposes (to develop into
the field of radiation therapy) was pioneered by Major
John Hall-Edwards in Birmingham, England. In 1908,
he had to have his left arm amputated owing to the
spread of X-ray dermatitis
Some More Landmarks
• 1896: Becquerel discovered radioactivity
• 1896: stereoradiography developed
• 1901: contrast agents
described
• 1904: lead glass protection
devised
• 1904: exposure badge
invented
First angiogram
Coolidge X-ray Tube: 1913
• Properties of new tube:
– high vacuum
– hot cathode
– tungsten-target
• Five outstanding properties
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accurate adjustment
stable
reproducible
range of x-ray energies
less scattered radiation
William Coolidge
(expense prevented routine use until 1930’s)
Potter-Bucky Grid: 1913-1920
• Scattered x-rays cause blurring
• 1913: Gustav Bucky: metal collimator grid
– reduce scatter blur
• 1920: Hollis Potter: movable grids
– reduce image of grid
Conventional Tomogram: 1929
• Overlapping tissues blur tissue of interest
• Jean Kieffer invented conventional tomogram
to image an interior slice
– to help diagnose his own TB!
Only amateur in >100
years to make a significant
discovery in medical
imaging
Tomography
• Much as any light/camera, there
is a focal plane
• My moving source and camera
in opposite directions, focal
plane becomes sharp
• Basis for almost all modern
medical 3-D devices except
Ultrasound.
– CAT = Computed Axial Tomography
– PET = Positron Emission
Tomography
Tomography (Again!)
Tomography was hard
• So it really
wasn’t used all
that much…
• Until 1972, when
computers and
motors led to the
development of
CAT
Impact of X-rays
• Widespread detection of tuberculosis
in 1917
• 1898: American Roentgen Ray
Society
• 1927: proof of cell damage caused
by x-rays
• 1935: radiologist required to interpret
radiograph in court (anybody could
previously)
• Shoe fluoroscopes from 1920’s to
1960’s
Out with the old, In with the nukes
• X-rays were (and still are) limited.
– Dim, for one (unless subject already dead)
– Cannot track temporal events well
• Blood flow
• Brain activity
• Etc
• Enter nuclear medicine
Radioactive Decay
• Antoine Henri Becquerel (1852 – 1908)
• Shared Nobel Prize of 1903 with Marie and Pierre
Curie for discovery of radioactivity
– Studying phosphorescence in Uranium salts on one side of
his desk and the effect of bright sunlight on fluorescent coated
photographic plates on the other.
Nuclear Physics in a Slide
Isotope
Mass
C12
12
C13
13.00335
N13
13.0057
N14
14.0031
N15
15.0001
O15
15.0031
Neutron
1.0087
Proton
1.0073
Electron
0.00055
Alpha (He) 4.0026
Spontaneous Decay
• Every atom in the universe has a chance of
spontaneously decaying
– p+  0 + e+
• Happens about once every universe
• Generally, large isotopes ( > Fe) Alpha decay
– Nucleus binding energy is unstable
– Mass products have lower mass than parent
– 238U  234Th + 4He
• Beta Decay = emission of electron or positron
– p+  n0 + e + + ν
– Electronic Transmutation – 15O 
15N-
+ e+ + ν
• Gamma Decay – excess from β decay
Back to Nuclear Imaging
• Radiopharmaceuticals are injected
• Biodistribution process causes
– absorption, distribution, metabolism, excretion
• Radioactive decay occurs, producing:
– gamma rays (single photons), or
• Single Photon Emission Computed Tomography
(SPECT)
– positrons (which yield paired photons)
• Positron Emission Tomography (PET)
• Location and counts are recorded as images
Positron Annihilation
• Positrons are Anti-matter (anti-electrons)
– When matter and anti-matter collide, they
annihilate
– Mass energy of electron + positron released as
two photons
– Total energy = 2*0.511 MeV + extra conserved
energy
Nuclear Medicine
• Step 1 – Inject patient with a
radioactive substance
•Alpha, Beta, or Gamma?
•PET, SPECT
•Step 2 – Wait for body to
distribute
•Choose radiopharmaceutical
depending on target
• Step 3 – Take photos, make
scrapbook
Gallium scintigraphy looks for recurrence of
malignant melanoma
Radiopharmaceuticals?
Isotope
Beta Decay
Gamma
Decay
Half Life
Product
15O
Β+
N*
122 s
15N
234Th
Β-
Y
24 d
234Pa
18F
Β+
N*
110 m
18O
111In
Β-
Y
122 s
111Sn
14C
Β-
N*
5730 y
14N
99mTc
N
Y
6h
99Tc
Tc = Technitium, In = Indium
Nuclear Medicine Landmarks
Single-photon imaging
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1896: Becquerel discovered radioactivity
1930’s: Hevesy mapped internal organs
late 1930’s: discovery of technetium
1946: AEC allowed isotopes for medical use
1950’s: Anger invented gamma camera
1968: SPECT introduced by Kuhl
1980’s: Dual/triple headed SPECT systems
Gamma Camera
For:
•planar imaging
•SPECT imaging
SPECT =
single photon emission
computed tomography
Commercial Gamma Cameras
Siemens
Toshiba
For planar
imaging and
SPECT
[Normal male, Tc-99m HMPAO,
for cerebral blood flow, Brighamrad]
normal Tc-99m MDP bone scintigram (5 mCi injected dose).
Commercial PET Scanners
CTI/Siemens
PET Images
Parkinson's Disease
Huntington's disease
Dopamine receptors
Myocardial perfusion
Ultrasound Imaging
Medical Ultrasound
• 1940’s – Ultrasound used to ease pain
– Dr. George Ludwig, Naval Medical RI, Bethesda
• 1949 - Dr. John Wild measures how thick
your colon (wall) is
– “Father of Medical Ultrasound”
• 1953 – Inge Edler asks Carl Hertz if he can
use radar to see inside the body.
– No, but they use ultrasound to measure heart
activity, published in 1954
Medical Ultrasound
• 1958 – Prof. Ian Donald treats the wife of one
of the directors of Babcock and Wilcox
– Asks to visit with R&D to see their toys
– Asks to play with ultrasound
– Uses it on volunteers to measure ultrasonic
properties of various people with illnesses
– Publishes "Investigation of Abdominal Masses by
Pulsed Ultrasound”
• The most important medical imaging paper… EVER
– Goes on to study the growth rate of fetuses, first
use of US in obstetrics
Medical Ultrasound
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1965: First real-time ultrasound scanner
1970: commercial systems widespread
mid-1970’s: grayscale and Doppler systems
early-1980’s: phased-array systems
mid-1990’s: 3-D ultrasound
How Does Ultrasound Work?
• Send a pulse -- receive the pulse
• Map time-of-arrival to round-trip distance
• Scan transducer in a plane
Ultrasound
Sound Propagation
• Sound travels through different things at
different speeds
– Speed of sound = cs
– Simple Version :
Material
Cs (m/s)
Air
343
Water
1482
Steel
5960
Muscle
1482
Bone
?
Ultrasound Images
heart
kidney
Corotid artery
Fetal head
Fetal
spine
3D Ultrasound
Fetal face
prostate
Kretztechnik AG
Voluson 530D
Gallbladder stone
Back to X-Ray
• 1955 – Ronald Bracewell did some maths
• X ray source and detector move together
• Pencil thin beam which fans out in 2D
• Each image is a projection of all tissue in beam
• Take images at a full 360 degrees
• Reconstruct using Fourier image analysis
• 1956 – Allan Cormack gives it a try, succeeds in 1963
• 1972 – Godfrey Hounsfied demonstrates first CT
scanner
• Hounsfield and Cormack share Nobel prize
Computerized Tomography
CT Landmarks
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1971: Hounsfield scanned first patient (4min)
1972: EMI dominated Chicago RSNA
1974: 26 EMI scanners worldwide
1974: Shepp-Stein reconstruction formula
1975: Commercial 2G, 3G, 4G CT scanners
1979: Hounsfield and Cormack win Nobel Prize
1985: Imatron, 50-100ms per slice
Late 80’s: Slip-ring technology
1989: first commercial helical CT scanner
1990s: multislice technology (<30s head-toe)
Early Commercial CT Scanner
Siemens Siretom CT Scanner, 1975
Compare
to modern
CT image
Fast and High Resolution CT
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2 revs/s
8 slices/s
2.5mm slices
58 s total time
Data collected using
using Picker Mx8000TM
This image follows
image processing
and 3D rendering
3D Anatomy from CT
Facial fractures
Lumbar spine
CT endoscopy
Magnetic Resonance Imaging
Same patient:
acute cerebral infarct
CT
MRI
How Does MRI Work?
• Human are “ugly bags of mostly water”
• H2O has protons which have magnetic moments
• Protons also spin
• Step 1 – Make protons all spin one way
• Step 2 – Use radio waves at the resonant frequency
to make all the protons suddenly spin the other way
• Step 3 – Turn off radio and let spins go back to normal
• Energy difference between spin up and spin down
states released as a photon
• B-field strength dictates resonance frequency
• Tuned to select individual areas at a time
• Relaxation time, intensity, all Fourier transform
into an image with very high contrast
MRI Landmarks
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1924: Pauli proposed nuclear magnetism
1937: Rabi measured magnetic moments
1946: Bloch and Purcell described relaxation
1971: Lauterbur invented MRI (published 1973)
1973: Mansfield introduced k-space
1975: Ernst invented NMR Fourier imaging
1977: Damadian’s first whole-body MR scanner
1980: Margulis takes lead at UCSF
1997: Damadian wins patent lawsuit against GE
2003: Lauterbur and Mansfield win Nobel Prize
Some Modern Systems
[Siemens, MAGNETOM 42SP]
GE 0.5T open magnet
(“double donut”)
MR Images
knee
Breast implants
Tagged MRI
heart
What is Next?
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MEG: magneto-encephalography
EEG: electro-encephalography
fMRI: functional magnetic resonance
micro-PET
optical imaging
molecular imaging
Photo acoustic imaging
Why We’re are Afraid to Fly