Digital Image Processing

Question 1

What is digital image processing.

Answer 1

Digital image processing is the manipulation of an image to enhance it or extract useful information from it.

Question 2

What is a digital image?

Answer 2

A matrix of pixels. each pixel is represented by a numerical value

Question 3

What is a pixel in the context of digital images?

Answer 3

A pixel (short for “picture element”) is the smallest unit of a digital image, forming part of the digital image matrix. Pixels are arranged in rows and columns to create the grid of an image. The arrangement and size of the pixels determine the image resolution and quality; smaller, more densely packed pixels result in higher resolution and sharper image quality

Question 4

How is the pixel value significant in digital images?

Answer 4

• The pixel value is a numerical representation of the brightness or color of a pixel, which defines what will appear when the image is displayed.
• These values are critical for visualising contrast and fine details in digital images.

Question 5

Define pixel bit depth.

Answer 5

Pixel bit depth refers to the number of bits available to represent each pixel, determining the number of different values (brightness levels or shades of grey) a pixel can have.

Question 6

Describe the significance of bit depth in digital displays.

Answer 6

Higher bit depths, better representation of brightness or colour variations per pixel, enhancing image quality with more shades and details

Question 7

What is a computer language?

Answer 7

Bit

Question 8

Pre-processing?

Answer 8

Pre-Processing:

• Operations applied to raw data before the image is formed.
• Purpose: To correct or improve raw data quality for accurate image reconstruction.

-Examples:
Noise reduction.
Beam hardening correction.
Detector calibration.

Question 9

Post - Processing?

Answer 9

Post-Processing:

• Operations applied to enhance or adjust an already reconstructed image for better visualisation or interpretation.
• Purpose: To improve diagnostic utility of the image.
• Examples:
  Contrast adjustments.
  Image sharpening or smoothing.
  Multi-planar reformatting (MPR).
  3D rendering.

Question 10

List the categories of image post-processing techniques used in CR and DR?

Answer 10

• grey scale procesing
• spatial filtering
• dynamic range control

Question 11

List the categories of image post-processing techniques used in CT?

Answer 11

• image plane reformating
• windowing
• Region of interest
• 3D volume rendoring
• Multi-planar reformats (MPR)

-Maximum Intesity Projection (MIP)

Question 12

List the categories of image post-processing techniques used in fluoroscopy?

Answer 12

• Digital subtraction angiography
• Subtraction of images out of a sequence
• greyscale processing
• temporal frame averaging
• edge enhancement
• pixel shifting

Question 13

What are the 2 types of grey scale processing?

Answer 13

• LUT
• Windowing

Question 14

what is a look up table and how does it work?

Answer 14

• A Look-Up Table (LUT) is a set of pre-calculated pixel value data (mappings) stored in the computer, used to substitute the original pixel values of an image to modify its display properties.
• LUTs are commonly used to adjust brightness and contrast efficiently without altering the raw data of the image.
• Instead, they modify how the image is displayed to enhance contrast and make fine details more visible.

Question 15

What is an exposure index?

Answer 15

• measure of the amount of exposure that reaches the detector

Question 16

what is image windowing?

Question 17

What is spatial frequency and the 3 types?

Answer 17

series of different algorithms used to post process the image.

1- edge enhancement
2 -unsharp masking (eg. DSA)
3-smoothing/blurring

Question 18

DSA?

Answer 18

Digital Subtraction Angiography (DSA) is a fluoroscopic technique used to visualize blood vessels by digitally removing radiopaque structures like bones.

check fluoro cards

Question 19

what is geometrical processing?

Answer 19

Geometrical processing involves techniques that change the position or orientation of pixels without altering contrast or brightness, such as scaling, sizing, centering, cropping, and rotation.

Question 20

MPR and MIP

Answer 20

MPR is a technique that allows viewing images in multiple planes, enhancing the analysis of anatomical structures.

MIP is a method that highlights the brightest areas in a set of images, aiding in the visualization of significant features.