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Physics
That branch of science that deals withmatter and energy and their relationshipto each other.
Examples:MagnetismElectricityElectromagnetism
Equivalencies – English, Metric, Scientific Notation
Some Relationships You Must Know:
Fundamental Units of Measure
Consist of measurements relating tolength, mass and time.
Length:Fundamental unit – Meter (approx. 3 ft)
100 cm in meter = .01 meter, 10-2, 1/100
1 inch = 2.54 cm
Conversion from English to metric system(# Total inches X 2.54) – 4 inches X 2.54 = 10.16 c.m.
Conversion from metric to English system(# Total c.m. / 2.54) 10.16 c.m./ 2.54 = 4 inches(40 inch SID X 2.54 = 101.6 c.m.)
In radiology, the angstrom is often used to measure wavelength of x-rays and light.1 A = 1 X 10-10 meters
Fundamental Units of Measure
Mass – The quantity of matter in a body(inertia) • Determined by weighing• unit of mass = kilogram• 1 kg = 2.2 lb
• conversion from English to metric ( # total lbs/ 2.2), 120 lbs/ 2.2 = 54.54 kg
• conversion from metric to English (# total kg X 2.2), 54.54 kg X 2.2 = 119.988 lb
Fundamental Units of Measure
Time• unit of measure is seconds• milliseconds are used often in radiology• milli = 1/1000 sec., .001 s, 10 -3
• To convert milliseconds to seconds, move the decimal point 3 places to the left.• To convert seconds to milliseconds, move the decimal point 3 places to the right
Other Commonly Used Units of Measurement inRadiology
Amps – # of electrons flowing per second• Often expressed in milliamps• 300 mA = .3 A
ExposureREM – Measures biologic effect of radiation• Often given in millirem (mrem) 50 mrem = .05 remRAD – Measures absorbed doseRoentgen – Ionization in air
Voltage – Energy (push) behind electrons• Usually given in kilovoltage (kVP)• 100 kVp = 100,000 volts
Know what each of the above units measure
Energy
The ability to do work
Potential Energy – The ability to do workby virtue of position
Kinetic Energy – Energy in motion
Law of Conservation of Energy
Energy can neither be created nor destroyed
• If may change forms, but will not cease to exist
• Examples: - Production of x-ray results in changing electron’s energy to x-ray and heat
- Interaction between x-ray and body matter results in transferring original energy of radiation to electrons or nucleus of atoms