RTCA111 Chapter 7: Image Production and Digital Imaging

Vocabulary terms and definitions from Chapter 7 regarding image production, exposure factors, and digital radiography systems.

Primary Radiation

Radiation that exists before reaching the patient.

Absorbed Radiation

Radiation that is absorbed by tissues within the patient's body.

Scatter Radiation

Radiation that changes direction, causes fog, and lowers image contrast.

Remnant Radiation

Radiation that reaches the Image Receptor (IR) to form the image.

Attenuation

The reduction of the X-ray beam as it passes through matter, calculated as $\text{Absorption} + \text{Scatter}$.

Radiolucent

Materials like air and fat that allow X-rays to pass through easily, appearing black or dark gray on an image.

Radiopaque

Materials like bone that absorb X-rays, appearing white on an image.

mAs

Milliampere-seconds; the primary factor controlling receptor exposure and X-ray quantity, calculated as $mA \times \text{seconds}$.

kVp

Kilovoltage peak; the factor that controls the penetrating power of the beam and image contrast.

SID

Source-to-Image Distance; controls the intensity of the radiation beam and image magnification.

mAs Reciprocity Law

The principle that different combinations of mA and time that result in the same mAs will produce the same receptor exposure, such as $200\text{ mA} \times 0.25\text{ s} = 50\text{ mAs}$.

15% Rule

A rule stating that a $15\%$ increase in kVp doubles receptor exposure, while a $15\%$ decrease halves it.

Filtration

The removal of low-energy X-rays from the beam to reduce patient dose.

Collimation

The restriction of the X-ray beam size to reduce scatter radiation.

Grids

Devices used to absorb scatter radiation and improve image contrast.

High Contrast

An image with few shades of gray, also referred to as short-scale contrast.

Low Contrast

An image with many shades of gray, also referred to as long-scale contrast.

Spatial Resolution

Also called Sharpness, Detail, or Definition; it is improved by less motion, a small focal spot, long SID, and small OID.

Size Distortion

Magnification of the image, which is controlled by SID and OID.

Shape Distortion

Misalignment of the X-ray tube, part, or IR, resulting in foreshortening or elongation.

Foreshortening

A type of shape distortion where the image appears shorter than the actual object.

Elongation

A type of shape distortion where the image appears longer than the actual object.

Latent Image

The invisible image stored on the receptor after exposure but before processing.

Manifest Image

The visible image seen after the receptor has been processed.

PSP

Photostimulable Phosphor; the active component in Computed Radiography (CR) plates.

PACS

Picture Archiving and Communication System; used to store, retrieve, and share digital images.

MIMPS

Medical Image Management and Processing System; used to manage, process, and integrate imaging data.

Flat Panel Detector (FPD)

The detector system used in Digital Radiography (DR) with a weight limit of $320\,lbs$ and a cost of approximately $\$90,000$.

Direct DR

A digital radiography system that uses a photoconductor and Amorphous Selenium to capture the image.

Indirect DR

A digital radiography system that uses a scintillator combined with $CsI$ or $Gd_2O_2S$ to capture the image.