Warm-up Which of the following is NOT made up of photons?

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Gillian Martin
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1 Warm-up Which of the following is NOT made up of photons? 1. Laser light 2. Radio waves 3. Ultrasonic waves 4. X-rays Radio µwaves fir IR uv x-ray gamma-ray...

the Crookes tube was in a cardboard box.

2 Xrays Discovered by Wm. Roentgen in 1895 First Nobel Prize in Physics (1901) On the evening of November 8, working with a discharge tube, he found that a fluorescent plate across the room glowed, even through the Crookes tube was in a cardboard box. His wife's hand Ring Different materials have different OPACITIES Filling Coins The first medical X-rays were made within months.

$X-radiography Greenstick - an incomplete fracture in which the bone bends Transverse - a fracture that$ $goes at an angle to the axis Comminuted - a fracture of many relatively small fragments Spiral - a$

3 X-radiography Greenstick - an incomplete fracture in which the bone bends Transverse - a fracture that goes across the bone's axis Simple - a fracture which does not break the skin Oblique - a fracture which goes at an angle to the axis Comminuted - a fracture of many relatively small fragments Spiral - a fracture which runs around the axis of the bone Compound - a fracture (also called open) which breaks the skin

4 Sources of X-rays: Radio µwaves fir IR uv x-ray gamma-ray Brehmsstrahlung - high energy electrons accelerate brake A continuous spectrum up to Ke e =ev 2. Transitions among quantum energy levels of HEAVY ATOMS (high Z) Requires an inner shell vacancy incident particle Pb ejects electron K-shell vacancy outer electron fills vacancy Pb K-shell; Xray hf = E i E f K α : L-shell to K-shell K β : M-shell to K-shell L α,β... : Fill L-shell vacancy demo: 137 Cs spectrum shows 32 kev Barium K α xray

5 X-ray Generation Filament Cathode - + e-beam Anode (W, Pb, Mo ) X-rays For a point source I ~ 1/r 2 (inverse square) Brand-X BX-4 Tube

6 Electron Energy Dependence (ev 0 ) di/de L-lines K-lines lower V 0 higher V 0 Brehmsstrahlung endpoint λ 0 = hc ev 0 E di/de L-lines Anode Material same V 0 K-lines E

7 Xrays are penetrating: K-edge µ (cm 2 /gm) 1 Muscle Lead Iodine 0.1 Fat Bone x-ray energy (kev) 120 Air (N 2 ) 0.03 cm 2 /gm (at 50 kev) ρ=1.2x10-3 gm/cm 3 Water 0.21 cm 2 /gm 1 gm/cm 3 Muscle 0.20 cm 2 /gm ~1 gm/cm 3 Fat 0.17 cm 2 /gm ~0.9 gm/cm 3 Bone 0.30 cm 2 /gm 1.9 gm/cm 3 Pb 6 cm 2 /gm 11.3 gm/cm 3 X-rays on film α e µρ Electrons/cm 3 ~ ρ

8 When Xrays reach a film, they turn it BLACK. For a normal diagnostic Xray, which of the following correctly describes the appearance? 1. Bones appear darker than tissue 2. Bones appear lighter than tissue 3. Bones and tissue appear the same 4. None of these X-ray Beam Subject Scattered X-rays Film

9 X-ray Interactions x-rays interact with atomic electrons Energy >> 1 ev : IONIZING Coherent Scattering (non-ionizing) incident scattered Photoelectric absorption incident K-shell vacancy photoelectron K α x-ray (Auger electron) Compton Scattering incident E s = E i *m e c 2 /(m e c 2 +E(1-cos θ)) e + e - pair production (E > MeV) Compton electron θ scattered

10 Chest X-ray

11 Angiogram 1-ascending aorta 2-aortic arch 3-descending aorta Catheter injects iodine contrast agent into the ascending aorta while x-ray image is taken Patient Position adjusted

12 The Unexpected www-personal.umich.edu/~agrxray/index.html

13 Computed Tomography 1. Select Slice 2. Measure 3. Invert (Data -> Image) 8 equations 8 equations 16 unknowns 16 radial measurements detailed algorithms

14 Spiral CT

15 Original and Modern CT Scans

16 Announcements: Exam Dec. 2, tomorrow Practice exams Equation sheet posted Review 3 PM today HERE

17 L i g h t A m p l i f i c a t i o n S t i m u l a t e d E m i s s i o n R a d i a t i o n Monochromatic (temporal coherence): Δλ/λ =< Spatial coherence Diffraction limited spot size : sinθ=λ/1.22d High Intensity (1000 W/m 2 to > W/m 2 ) Versatile: tunable λ, pulsed, high powered

18 Probability of stimulated emission α #phtons in medium (positive feedback)

19 He-Ne Laser LASER CAVITY R=95% Energy Source 2s metastable collisions 3 2p 2s 5 3s 0 2p 5 2s Electron excitation 1s Helium 2p 5 1s (1s 2 2s 2 )2p 6 Neon 3.39µm 0.63µm 1.15µm 2p 5 3p 2p 5 2p STIMULATED EMISSION

$PRK (photrefractive keratectomy) Light from Distant object Myopia: Lens focal length is TOO SHORT P =$ molecular binding Ablates cornea/ no heating stair-step pulses (10 Hz) center is is more ablated

molecular binding Ablates cornea/ no heating stair-step pulses (10 Hz) center is is more ablated

20 PRK (photrefractive keratectomy) Light from Distant object Myopia: Lens focal length is TOO SHORT P = 1 = (n-1) ( 1 ) f R 1 R 1 TOO small -- NEED to flatten the cornea UV 193 nm eximer laser Exceeds molecular binding Ablates cornea/ no heating stair-step pulses (10 Hz) center is is more ablated original Bowman s membrabe removed - regenerates after a few days (ocassional haze) corrected radius of curvature

21 Which of the following is the most important laser feature for corrective eye surgery? 1. Very monochromatic 2. Spatial coherence 3. High Intensity (Power and spot size) 4. Very long wavelengths

22 LASIK (laser-assisted in situ keratomileusis) Corneal flap cut (knife or IR laser) stair-step pulses (10 Hz) center is is more ablated original corrected radius of curvatur UV 193 nm eximer laser Exceeds molecular binding Ablates cornea/ no heating

23 All Laser LASIK developed at UM BME Dept.

Rad T 290 Worksheet 2

Class: Date: Rad T 290 Worksheet 2 1. Projectile electrons travel from a. anode to cathode. c. target to patient. b. cathode to anode. d. inner shell to outer shell. 2. At the target, the projectile electrons