Properties of X-rays and Their Interaction with Tissue in Medical Imaging

What are the characteristics of X-rays as discovered by Roentgen?

1. X-rays are polyenergetic and heterogeneous

2. highly penetrating

3. invisible

4. produce chemical and biological changes

5. can ionize gas

6. produce secondary radiation

7. cannot be focused by a lens

8. travel in a straight line and diverge from a source

9. electrically and magnetically neutral

10. affect photographic film

What does it mean that X-rays are polyenergetic and heterogeneous?

X-rays consist of a range of energy levels; for example, at 90 kV, the beam includes photons with energies from 30 kV to 90 kV.

Why are X-rays considered highly penetrating?

They are highly penetrating due to the high atomic number of the tungsten target used in X-ray tubes.

What are some biological effects of X-ray exposure?

Long-term effects include erythema, alopecia, cataracts, and leukemia. Short-term effects can include skin burns, nausea, and fatigue.

What is the significance of the Geiger counter in relation to X-rays?

Geiger counters use the property of X-rays to ionize gas, allowing for the detection of radiation.

What is the difference between leakage radiation and scatter radiation?

Leakage radiation is emitted from the X-ray tube housing in all directions, while scatter radiation is radiation that has interacted with an atom and is redirected.

Why can't X-rays be focused by a lens?

X-rays cannot be focused by a lens because they are not influenced by electric or magnetic fields; the focusing cup in the X-ray tube only directs the electron stream.

How do X-rays interact with tissue?

Weaker X-ray quanta are absorbed or attenuated by tissue, while higher quanta penetrate bones and muscles to form images on radiographs.

What factors influence the absorption or attenuation of X-rays?

Factors include the thickness of the material and the density and atomic number of the material.

How does the thickness of a material affect X-ray absorption?

Thicker materials absorb more X-rays than thinner materials; for example, three inches of bone will attenuate more radiation than one inch.

What is the relationship between atomic number and X-ray attenuation?

Materials with higher atomic numbers will attenuate more X-rays than those with lower atomic numbers.

How does bone appear on a radiograph due to X-ray attenuation?

Bone appears white on a radiograph because it attenuates X-rays, resulting in fewer X-rays interacting with the image receptor.

What shade does air produce on a radiograph and why?

Air produces black shades on a radiograph because it is thin and has a low atomic number, allowing X-rays to pass through and interact with the image receptor.

How do muscle and fat affect X-ray images?

Muscle and fat are less dense; stronger X-rays pass through, while some are attenuated, producing gray shades on the radiograph.

What is the role of kV and mAs in X-ray production?

kV determines the energy or penetrating ability of the X-ray beam, while mAs determines the amount of electrons present and the duration of their flow.

What happens to X-ray photons with energies lower than the selected kV?

Photons with energies lower than the selected kV will not have enough energy to pass through the body and will be absorbed.

What is the effect of X-rays on photographic film?

X-rays ionize silver halide crystals in the film emulsion, resulting in varying degrees of blackness after processing.

What is the speed at which X-rays travel?

X-rays travel at the speed of light.

What are the potential health risks associated with X-ray exposure?

Health risks include radiation-induced afflictions such as cancer and other long-term effects.

What is the significance of the term 'attenuation' in the context of X-rays?

Attenuation refers to the reduction in the number of X-ray photons as they pass through material, affecting the resulting image.

What are secondary radiations produced by X-rays?

Secondary radiations include scatter radiation, which is less energetic than the primary radiation and results from interactions with atoms.

What is the importance of safety standards in X-ray usage?

Safety standards are crucial to protect individuals from the harmful effects of radiation exposure.