Radiology concepts

History of X-rays

1.) discovered by Wilhelm Roentgen (1895); originally named then X-light and later renamed X-ray or “Roentgen ray” in his honor; won the nobel prize in 1901

2.1910 —> utilization of x-rays in the chiropractic profession

Modern X-ray tube

1.) hot cathode X-ray rube which uses thermionic emission was patented in 1913 and produced in 1917 by GE. Invented by William D Coolidge

2.) design of the modern tuber is often still referred to as the Coolidge tube; design allowed for higher voltages and less fluctuation in the x-rays energy that was produced

Electromagnetic Properties

1.) Wave particle Duality: wave like properties have wavelength and frequency

2.) particle-like properties: have energy and momentum

3.) x-rays travel at the speed of light in a straight line and diverge from their source; processes enough energy to disrupt molecular bonds making ionizing radiation

The Frequency of a Photon determines energy

1.) higher the frequency (shorter the wavelength) = higher energy X-rays —> more likely to pass through or interact with the patient

2.) lower the frequency (longer the wavelength) = lower energy x-rays —> more likely to absorb in patient

3.) weaker (low frequency) x-rays cause more ionization of patient cells due to increased absorption

Patient Interactions

1.) X-rays are either: absorbed, pass through the patient, interact with the patient and are scattered (Deflected)

2.) different shades of gray result from differing amounts of photons making it through the patient (differential absorption)

Radiographic densities

1.) radiograph is a shadow picture of differential absorption/attenuation

2.) low density material such as air is represented as black. Very dense material such as metal or contrast material is represented as white

3.) bodily tissues are varying degrees of grey, depending on density, and thickness

4.) air (least), fat, water, bone, metal

5.) low atomic # = less dense; high atomic #

Differential Absorption → factors

1.) an X-ray is a “map” of X-rays that have either passed through the body or have been variably attenuated (Absorbed) by anatomical structures

2.) X-rays can penetrate (pass through) solid objects dependent on: X-ray wavelength/frequency (kVp), composition of the object (mass, thickness, atomic #)

Mass density of object q

1.) More atoms = more interactions; more interaction = more absorption

2.) more absorption = whiter (less optical density)

3.) the denser the tissue, the more X-rays are attenuated. X-rays are attenuated more by cortical bone than trabecular bone

Atomic # of object

1.) larger atoms = more interactions

2.) more interaction = more absorption

3.) more absorption = whiter (less optical density)

Radiographic tissue densities

1.) four natural tissue densities seen on a chest X-ray; there is a range of grayness

2.) greatest contrast is found in areas of greatest difference in density of adjacent structues

Thickness of objects

1.) more atoms = more interactions

2.) more interaction - more absorption

3.) more absorption = whiter (less optical density)

X-ray tissue densities

1.) radiolucent (lucency): area of blackness; decreased absorption/attenuated of x-rays

2.) radiopaque (opacity): area of whiteness increased absorption/attenuation