Image Production - Chapter 8

Physics II

The radiation that exits the patient is composed of varying energies and interacts with the image receptor to form

The Latent (invisible) image

____ ___ creates an image that structurally represents the anatomic area

Differential Absorption

True or False: Anatomic parts absorb the primary beam to the same degree

False - they do not

Defined as the reduction in the energy or number of photons (quantity) in the primary x-ray beam

Attenuation

What 4 things does attenuation depend on?

Part / Tissue Thickness

Tissue Density

Atomic # / Type of Tissue

Beam Quality / Energy of the beam

During attenuation, which two processes occur in the diagnostic range?

Absorption - photoelectric

Scattering - Compton / Coherent

What two things does total photon absorption depend on?

The energy of the incoming x-ray photon

Atomic # of the anatomic tissue

X-ray photons that pass through the body without any interaction with the atomic structures is called

Transmission

X-rays are attenuated exponentially and reduced by about ___% for each 4-5 cm of tissue thickness

50%

What is the order of attenuation?

Metal, Bone, Muscle, Fat, Air

True or False: Tissue composed of a higher atomic number (bone), attenuates the x-ray beam more than tissue composed of a lower atomic number (fat).

True

True or False: The higher the atomic number, the darker it will appear on a digital image

False: Brighter

Tissue density is defined as

matter per unit volume

True or False: Tissue that is less dense results in decreased attenuation

True

What are higher-penetrating x-rays?

Shorter wavelength, higher frequency

Are more likely to be transmitted through anatomic tissue

results in decreased attenuation

What are lower-penetrating x-rays?

Longer wavelength with lower frequency

More likely to interact with atomic structures and be absorbed

Results in increased attenuation

The remaining radiation of the x-ray beam after it leaves the patient and is composed of both transmitted and scattered radiation

Exit / Remnant Radiation

Unwanted Exposure on the image caused by scatter radiation

Fog

Once the x-ray photons (incident photons) leave the tube and interact with the patient, what 3 things can happen?

Attenuation - absorption of the x-ray photon

Transmission - x-ray photon travel through the patient and interacts with the image receptor

Scatter - x-ray photon interacts with atoms within the tissues and are “scattered” in all different directions.

What is the term for the visible image on the exposed film after processing?

Manifest Image

What is the most common method in radiography to create the radiographic image?

Digital Imaging

Describe the process of digital imaging through the use of digital image receptors

1 - Latent Image Acquisition - Various types of digital detectors record remnant radiation

2 - Computer Image Processing - Exit x-ray intensities are converted to digital data

3 - Display of Digital Image - Radiograph is displayed on a computer monitor and can be altered.

Image composed of numeric data combined in rows and columns is termed

Matrix

Tiny details or bits of information recorded as a single numeric value is called

Pixel

True or False: The larger the pixel the more detail in the image

False - the less detail

As the size of the matrix increases, what other factors increase with it?

Computer Processing time, network transmission time, digital storage space

Range of exposures the system can detect / respond to

Dynamic Range

The narrower range that gives appropriate dose and quality image

Exposure Latitude

A device that receives the radiation leaving the patient

Image Receptor

True or False: A Compton interaction is just as likely to occur in soft tissue as in tissue composed of bone

True

At higher kilovoltages (within the diagnostic range), the percentage of photoelectric interactions _____ whereas the percentage of Compton interactions ____

decreases; increases