CH 1 Principles of Imaging

X-rays

High energy electromagnetic radiation with short wavelengths and high frequencies.

Discovery of X-rays

X-rays were discovered on November 8, 1895, by Dr. Wilhelm Conrad Roentgen.

First radiograph

The first radiograph was of Mrs. Roentgen's hand.

Nobel Prize

Roentgen received the first Nobel Prize presented for physics in 1901.

Crookes tubes

Roentgen was using Crookes tubes when he discovered X-rays.

Roentgen rays

X-rays were called Roentgen rays at first.

Fluorescence

The instantaneous production of light caused by interaction between a type of energy and some element or compound.

Barium platinocyanide

A fluorescent material that glowed when the tube was energized.

X in X-ray

A symbol for unknown.

Erythema

Reddening of the skin, early sign of biological damage due to X-ray exposure.

Xray Properties are:

electrical and magnetic

Static image exposure time of 1st xray

It took 15-minutes of exposure.

Issue with Roentgen's first xray-

You could see his bones-his Hand was between the tube & barium platinocyanide-coated paper, also took 15 min.

X-ray Wavelength measurement

Angstroms

Wavelength

Distance between two successive crests of a sine wave.

Frequency

Measure in Hertz - the number of waves passing a given point per given unit of time.

Hertz

Unit of frequency, representing cycles per second.

Angstroms

wavelength measurements (A)

X-ray Movement

Moves in waves that have wavelength and frequency, longer wavelengths mean shorter frequencies

Wavelength and Frequency Relationship

Inversely related and proportional, longer wave=shorter freq.

Tighter Wavelengths

If Wavelengths are tighter together it means more energy, farther away, less wavelengths less energy

Poly

Many

Radiation Units of Measurement

Two systems for quantifying radiation - conventional and international (si)

Si

International System

Absorbed Dose Units of Measure

Radiation absorbed dose (rad) -Conventional

Gray (Gy) - International (si)

Exposure Units of Measurement

Roentgen (R)- Conventional

Air Kerma (Gy)- International (SI)

Dose Equivalent Units of Measure

Radiation Equivalent in man (Rem)- Conventional

Sievert (Sv) - International

Radioactivity Units of Measure

Curie (ci) - Conventional

Becquerel (Bq) - international

Roentgen (R)

A Conventional measure of the intensity of radiation EXPOSURE.

Absorbed dose

Measures the transfer of radiation energy into matter aka tissue.

Gray (Gy)

One gray equals 100 rads. (international absorbed dose measurement)

Dose Equivalent

The units used in measuring occupational radiation exposure. Such as 1 rad or 0.01 Gy is equal to 1 rem or 0.01 Sv.

Unstable Atoms

will spontaneously emit particles andenergy from the nucleus in an effort to reach stabilitycalled radioactive disintegration or decay

Photon

small discrete bundle of energy

Size Matters in X-rays

Need to have enough energy to penetrate the person properly.. More energy for larger ppl.

Half-life

Describes the time it takes for the radiation activity to reduce to 50% of its original activity.

Properties of X-rays

X-rays are electrically neutral, have no mass, and form a polyenergetic or heterogeneous beam.

ALARA principle

As low as reasonably achievable principle. (limit time, maintain distance, maximize shielding)

Limit, Maintain, Maximize what...

Limit- Time

Maintain- Distance

Maximize- Shielding

Radiation exposure units

Radiation exposure is typically expressed in smaller units by adding the prefix 'milli,' where 1 R = 1000 mR and 1 Gy = 1000 mGy.

Cathode

- Negative End - of xray tube where xray photons are created

Anode

+ Positive End + of xray tube, target where xray photons are directed. photons hit the target.

Percentage of Xray production

1% produces xrays, 99% is heat