Image Acquisition and Processing in Digital Radiography

PSP exposure field border recognition

The image analysis includes data outside the border, causing histogram and rescaling errors.

Causes of histogram analysis and rescaling errors

Inappropriate collimation margins and/or beam alignment.

Requirement for appropriate multiple field distribution on a PSP

Center each field to a plate segment with clean collimation between fields and the plate's edge.

Indication of poor exposure field recognition

Gray or dark areas outside the exposure field, often from scatter or off-focus radiation.

Quantization in digital imaging

Assigning a unique value to each pixel sample during analog-to-digital conversion.

Types of histogram analysis

Priori Histogram Analysis and Neural Histogram Analysis.

Causes of histogram analysis errors

1) Incorrect anatomic menu selection, 2) Presence of metal prosthesis.

Automatic rescaling

Matching captured image values to standardized 'values of interest' to maintain consistent brightness and appearance.

Moiré effect

A grid error when grid frequency is close to the Nyquist frequency, causing visible interference patterns.

Methods to control scatter in digital radiography

1) Beam limiting, 2) Optimal exposure, 3) Use of grids.

Automatic rescaling in digital imaging

Consistent brightness across a wide range of exposures.

Window level

Used to adjust the brightness of the digital image.

Window width

Adjusts the contrast (dynamic range) of the digital image.

Limitations of contrast resolution in digital detectors

Dynamic range and quantization (bits per pixel).

Purpose of low-pass filtering

To remove high-frequency noise and smooth the image, but it may reduce contrast.

Downside of smoothing/noise suppression

It reduces visibility of fine detail and does not improve edge sharpness.

High-pass filtering

Enhances edges by increasing contrast at boundaries (edge enhancement).

Disadvantage of edge enhancement

It can create halo artifacts that may mimic pathology.

Equalization in imaging

Used to balance brightness across an image by darkening light areas and lightening dark areas.

Effect of excessive equalization

It can degrade image quality and create artifacts like 'metal mottle.'

Effect of excessive processing on an image

It can obscure anatomical details and lead to misdiagnosis.

inappropriate collimation

inappropriate beam alignment

quantization

Prior to image creation, the exposure values extracted from the PSP plates are subject to a process know as:

sampling frequency

Quantization may sometimes be referred to as:

values of interest

The predetermined values used to create the digital image are known as:

60 micro-roentgens

PSP's respond to an exposure as low as ____________ micro-roentgens.

beam limiting

Ways at reducing scatter radiation include which of the following:

optimal exposure (use of)

Ways at reducing scatter radiation include which of the following:

grid use

Ways at reducing scatter radiation include which of the following:

utilizing compression bands

Ways at reducing scatter radiation include which of the following:

aperture diaphragms

Examples of beam limiting devices include all of the following except:

grids

Examples of beam limiting devices include all of the following except:

brightness

____________ describes the concept of density as it is displayed on a soft-copy monitor for digital image viewing.

Halo

Excessive edge enhancement may cause this type of artifact:

frequencies

Digital filtering transforms images into their corresponding _____________.

metal mottle

This term describes excessive equalization caused by a metal prosthesis.

histograms

_____________ graphically represent a collection of exposure values extracted from the digital image receptor.