Digital Imaging and Radiography Fundamentals

Comprehensive vocabulary flashcards covering digital imaging terminology, radiography physics, and system components based on the provided lecture notes.

Noise

Photon dependent, visible brightness fluctuations and graininess in an x-ray image; occurs when there are fewer photons and negatively affects visibility related to exposure.

Signal to noise ratio (SNR)

The strength of radiation exposure compared with the amount of noise in an image.

Exposure latitude

The range of exposure values to the image which represents the acceptable range of densities for diagnostic purposes.

Detective quantum efficiency (DQE)

A measurement of the efficiency of an Image Receptor (IR) in converting the x-ray exposure it receives into a quality x-ray image.

Brightness

The amount of luminance on a display monitor.

Magnification

An increase in the image size of the object compared with its true or actual size, also known as distortion.

Shape distortion

Images that appear longer or shorter than the true objects.

Sharpness

The accuracy of structural lines and well-defined edges on a final image.

Histogram

A graphic display of pixel values where the computer analyzes the shape to build the final visible image.

Nyquist theorem

The speed limit for digital sampling which states that one must scan/sample twice as fast as its high frequency.

Aliasing

A digital pattern glitch also known as a moire pattern.

Look up table (LUT)

A pre-calculated math function or digital structure used during post-processing to map pixel values to new output pixel values.

Edge Enhancement

A post-processing technique that improves the visibility of small, high contrast structures.

High Pass Filtering

An edge boosting trick where a computer math filter blocks low frequencies.

Digital Imaging

A computer communication standard language for information sharing, picture archiving, and communication systems (PACS).

Tele-radiology

An electronic system that allows patient electronic records and images to be accessed offsite or within a facility for remote interpretation.

Photostimulable Phosphor (PSP)

A plate made of several layers (barium fluoride crystals doped with europium) that store x-ray energy as a latent image for cassette-based digital systems used in Computed Radiography (CR).

Flat Panel Detector (FPD)

A solid-state image detector used in modern Digital Radiography (DR) using a large area active matrix array of electronic components.

Direct Capture Radiography

A process that converts incoming x-ray photons straight into an electrical charge, typically using an amorphous selenium photoconductor.

Indirect Capture Radiography

A two-step process where x-rays are first turned into visible light by a scintillator, which is then converted into an electrical signal.

PACS

Picture Archiving and Communication System; a secure network for transmitting, exchanging, and storing patient images and data.

DICOM

Digital Imaging and Communications in Medicine; the global, universal standard computer language that allows different systems of a PACS to communicate.

Analog

A continuous signal or image that has not been broken down into digital pixels, such as traditional film radiography.

Air Kerma

Kinetic energy released in matter; the intensity of x-rays at a given point in air at a known distance from the focal spot, expressed in Grays ($Gy$) or milligrays ($mGy$).

Deviation Index (DI)

A value reflecting the difference between the target exposure and the actual exposure to the IR; perfect is $0$, with a range from $-3$ to $+3$.

Pixel

Short for "picture element"; the smallest individual component of a digital image matrix representing a single brightness level.

Pixel Bit Depth

The number of bits that determines the number of shades of gray available for image display.

Field of View (FOV)

The overall physical area or dimensions of the patient anatomy that is imaged and displayed on the monitor.

Exposure Index (EI)

A numerical value representing the total amount of radiation received by the digital image receptor.

Spatial Resolution

The ability of an imaging system to distinguish and clearly display small, distinct objects that are close together; evaluates the accuracy of structural lines.

Dynamic Range

The range of exposure intensities that an image receptor can respond to and acquire image data.

Modulation Transfer Function (MTF)

A measurement of the imaging system’s ability to display the contrast of anatomic objects varying in size; a value of $1.0$ indicates perfect reproduction.

Smoothing

A post-processing digital filter that suppresses image noise and softens an image by blurring sharp edges, though spatial resolution is degraded.

Window Width

The control that adjusts image contrast by defining the range or number of shades of gray visible on the digital image.

Window Level

The control that adjusts image brightness by setting the center point of the range of brightness.

Shuttering

A digital cropping tool used to black out white, unexposed borders around an image to reduce glare.

Image Orientation

The way an image is turned or flipped on the screen to match standard medical viewing perspectives.

Image Stitching

The process of seaming multiple smaller x-ray images together into one continuous picture, commonly used for full spine or leg length imaging.

Annotation

Typing digital notes, labels (like "Left" or "Right"), or arrows directly onto the x-ray image.

Patient Demographics

Basic personal information attached to an image, including full name, birth date, gender, and unique identification number.

Archive Query

A digital search command used to find and retrieve old x-rays or medical records from a long-term storage database.

Imaging Plate

The physical, reusable sheet inside a protective cassette in CR systems that houses the PSP material to capture photon intensities.

Protective Layer

A tough, clear plastic top coating that shields imaging materials from scratches, dust, and wear.

Reflective Layer

A layer that acts like a mirror to bounce emitted light forward during laser reading to make the image brighter.

Conductive Layer

An antistatic layer that drains away static electricity to prevent image distortion or background fuzziness.

Support Layer

A semi-rigid, durable base layer that provides physical strength and structure to the flexible imaging plate.

Absorption/Color Layer

A layer that absorbs laser scanning light while letting image light pass through to prevent blurring.

Backing Layer

A soft, protective bottom coating on the back of the plate that stops light leakage and guards against damage.

Fast scan

The rapid movement of a laser beam back and forth across an imaging plate.

Slow scan

The steady, continuous movement of the imaging plate itself through the laser in the reader.

Photodetector

A light sensor that catches flashes of light released from the PSP during scanning and changes them into electrical signals.

Quantum mottle

A grainy or "staticky" look on an image, also called quantum noise, caused by an insufficient number of x-ray photons.

Grid frequency

The number of lead lines packed into one unit of length (inches or cm) of an x-ray grid.

Grid ratio

The ratio of the height of the lead strips compared to the distance between them.

Focused grid

A grid with lead lines angled (canted) to match the angle of divergence of the primary x-ray beam.

Collimation

A decrease in the size of the projected radiation field, also known as beam restriction.

Artifact

Any fake mark, smudge, or shadow on an image that does not belong there, such as patient movement or clothing zippers.

Thin Film Transistor (TFT)

A microscopic electronic switch or gatekeeper located at every pixel on a detector that holds an electrical charge until the computer is ready to read it.

Analog to Digital Converter (ADC)

A device that takes an analog signal and divides it into a series of bits ($1s$ and $0s$) for computer processing.

Binary code

The language of computers using only two digits, $1$ and $0$, to store information.

Bit

A computer's basic unit of information, represented as a $0$ or a $1$.

Byte

A combination of $8$ bits.