introduction to medical imaging instructors: brian fleming and ioana fleming [email protected],...
TRANSCRIPT
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Introduction to Medical Imaging
Instructors: Brian Fleming and Ioana Fleming
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Lecture 1
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In the Beginning…
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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
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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
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Where to put the Leeches
• Printing Press – 17th century– Sharing of ideas brings renaissance (murder?)
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History of Medical Imaging
Wilhelm Röntgen (Roentgen)
• The father of diagnostic radiology• German physicist (1845-1923)• Discovered x-rays in 1895• X was for "unknown“• First Nobel Prize in physics 1901
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Discovery of X-rays
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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
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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…
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How to Irradiate Yourself
• Step 3 – Run those electrons into a target
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“Instant” Success
• 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!)
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Within One Year ...
• 49 serious books on x-rays• 1,044 scientific papers• Known to:
– spot cancer– treat cancer– cause cancer
• Numerous patents
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What it REALLY Did…
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Fluoroscopy
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Fluorescence
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Filmed in X-ray!
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Early Popularity of Fluoroscopy
• Simple fluoro equipment:– x-ray tube– electrical generator– scintillation screen
• Convenience of real-time• Note: early film required 1-
2 hours of exposure– (where was intensifier
screen????)
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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
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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
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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
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Coolidge X-ray Tube: 1913
• Properties of new tube:– high vacuum– hot cathode– tungsten-target
• Five outstanding properties– accurate adjustment– stable– reproducible– range of x-ray energies– less scattered radiation
William Coolidge
(expense prevented routine use until 1930’s)
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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
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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 >100years to make a significantdiscovery in medicalimaging
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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
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Tomography (Again!)
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Tomography was hard
• So it really wasn’t used all that much…
• Until 1972, when computers and motors led to the development of CAT
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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
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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
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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.
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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
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Spontaneous Decay
• Every atom in the universe has a chance of spontaneously decaying– p+ π0 + 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
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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
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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
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Nuclear Medicine
Gallium scintigraphy looks for recurrence of malignant melanoma
• 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
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Radiopharmaceuticals?
Isotope Beta Decay Gamma Decay
Half Life Product
15O Β+ N* 122 s 15N234Th Β- Y 24 d 234Pa18F Β+ N* 110 m 18O111In Β- Y 122 s 111Sn14C Β- N* 5730 y 14N99mTc N Y 6 h 99Tc
Tc = Technitium, In = Indium
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Nuclear Medicine LandmarksSingle-photon imaging
• 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
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Gamma Camera
For:•planar imaging•SPECT imaging
SPECT = single photon emission computed tomography
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Commercial Gamma Cameras
ToshibaSiemens
For planarimaging andSPECT
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[Normal male, Tc-99m HMPAO, for cerebral blood flow, Brighamrad]
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normal Tc-99m MDP bone scintigram (5 mCi injected dose).
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Commercial PET Scanners
CTI/Siemens
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PET Images
Parkinson's Disease
Huntington's disease
Myocardial perfusionDopamine receptors
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Ultrasound Imaging
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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
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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
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Medical Ultrasound
• 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
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How Does Ultrasound Work?
• Send a pulse -- receive the pulse• Map time-of-arrival to round-trip distance• Scan transducer in a plane
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Ultrasound
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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 ?
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Ultrasound Images
heart
Fetal head
kidneyCorotid artery
Fetalspine
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3D Ultrasound
Kretztechnik AG
Voluson 530D Gallbladder stone
prostate
Fetal face
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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
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Computerized Tomography
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CT Landmarks
• 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)
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Early Commercial CT Scanner
Siemens Siretom CT Scanner, 1975 Compareto modernCT image
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Fast and High Resolution CT
• 2 revs/s• 8 slices/s• 2.5mm slices• 58 s total time
Data collected usingusing Picker Mx8000TM
This image followsimage processing and 3D rendering
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3D Anatomy from CT
Facial fractures Lumbar spine CT endoscopy
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Magnetic Resonance Imaging
CT MRI
Same patient:
acute cerebral infarct
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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
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MRI Landmarks
• 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
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Some Modern Systems
[Siemens, MAGNETOM 42SP]
GE 0.5T open magnet(“double donut”)
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MR Images
Tagged MRI
Breast implants
knee
heart
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What is Next?
• MEG: magneto-encephalography• EEG: electro-encephalography• fMRI: functional magnetic resonance• micro-PET• optical imaging• molecular imaging• Photo acoustic imaging
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Why We’re are Afraid to Fly
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