# Physics Equations and Constants - Part 1

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 Author: Anonymous ID: 166432 Filename: Physics Equations and Constants - Part 1 Updated: 2012-08-19 22:26:16 Tags: Physics Equations Constants Part Folders: Description: Physics Equations and Constants - Part 1 Show Answers:

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1. Compton Equation (Energy)
2. Compton Equation (Wavelength)
3. Capacitor
• Q=CV
4. Resistor
V=IR
5. Inductor
6. Resistance
• R = resistance
•  = resistivity
• L = length
• A = cross-sectional area
7. Doppler Shift
8. T1/T2 images
• T1 = fat bright
• T2 = water/fluids bright
•  (non-paralyzable)
•  (paralyzable)
10. Exposure to Kerma
• X
Na = 6.02x1023 atoms/mol
12. Roentgen to C/kg
R = 2.58x10-4 C/kg
13. Curie to Bq
1 Ci = 3.7x1010 Bq
14. Kerma from attenuation coefficient
15. Bits to Bytes
8 bits = 1 byte
16. Transmission, Attenuation
17. kB, MB, GB, TB
• kB = 210 bytes
• MB = 220 bytes
• GB = 230 bytes
• TB = 240 bytes
19. Film Gamma or Average Gradient
20. Electric Field and Voltage

21. Special Relativity
22. decibels
24. Magnification
25. Dose Equivalent, Effective Dose
26. Average energy of beta decay particle
1/3 of the max energy
27. Gyromagnetic Ratio and Larmor Frequency
• Gyromagnetic ratio for protons (H in water):
• Larmor Frequency:    or
28. Survival Fraction (Single target, Single hit) (Multiple target, Single hit)
(Single target)

(Multiple Target)
29. Ion Chamber Temperature and Pressure Correction
30. Transient Equilibrium Activity of Daughter
• Note: after about 4 Half-lives, the daughter is approximately in equilibrium with the parent. If branching ratio is 1, then the daughter has a slightly higher activity than the parent.
31. Neutron beam activation saturation activity
32. Temperature Conversions (Celsius to Kelvin, Celsius to Fahrenheit)
• T[K] = T[C] + 273.15
• T[F] = 9/5 T[C] + 32
33. MeV/c2 to amu conversion
1amu = 931.5 MeV/c2
34. Sensitivity and Specificity; ROC Curve
• Sensitivity = TP/(TP+FN)
• Specificity = TN/(TN+FP)
• ROC Curve is Sensitivity vs (1-Specificity)
35. Hounsfield Unit
36. Exposure from Gamma Constant

37. Fetal Dose Effects
• During pre-implantation (1st week), the most likely result is death
• During organogenesis (2-8 weeks), the most likely result is growth development and malformations
• During early fetal stage (8-15 weeks), the most likely result is mental retardation
• During mid to late fetal stage (15+ weeks), the most likely result is leukemia and other cancers
• Threshold dose is likely around 10 cGy – 50 cGy
38. What process competes with gamma ray emission?
Internal conversion
39. Optical Density Equation
40. What's the phase difference between the two surfaces of a piezoelectric crystal used in US?
• Quarter-wave matching
• 90-degree phase difference
41. Snell's Law
42. Speed of sound in fat and soft tissue?
• In fat: 1450 m/s
• In soft tissue: 1540 m/s
43. Specific heat equation
• Specific heat transfer:
• Fusion (change in state of matter):
44. Effective half life
45. What standard controls patient demography and billing info?
HL7 (Health Level 7)
46. What regulation controls patient anonymization?
HIPAA
47. What is the lower limit for a fringe field for MRI?
5 Gauss = 0.5 mT
48. An emission has only neutrino and characteristic x-ray, what's the decay scheme?
Electron Capture
49. If a gamma emission from a metastable state to stable state is forbidden, what's the alternative decay?
Internal Conversion
50. Focal Spot Blur
Blur = spotsize*OID/SOD
51. Secular equilibrium ratio of daughter to parent
F = 1-(1/2)n where n is number of half lives
52. Relation between HVL and TVL?
TVL = 3.32 HVL
53. Standard deviation values of Gaussian Distribution
• +/-1 sigma = 68%
• +/-2 sigma = 95%
• +/-3 sigma = 99.7%
54. Electron mass and charge
• Mass = 9.1E-31 kg = 0.511MeV/c2
• Charge = 1.6E-19 C
55. According to NCRP 116 and ICRP report, what is the fatal risk of cancer by radiation for whole population for low dose rate and low LET
5% per Sv of whole body
56. According to FDA, the collimator or jaw of linac is required to be how many HVL layer?
0.5% = 0.005 ~ 8HVL
57. An atom that decays by releasing a positron has an excess of .. (neutrons, protons, electrons)
protons