Imaging Technologies I Flashcards
Definition of pixels
Grid elements
Definition of image resolution
Used to refer to the no of pixels along each axis
Definition of intensity/grey scale
No for a pixel
Definition of intensity/grey scale resolution
Image of possible intensity values
Definition of spatial resolution
Measure of smallest discernible details in an image
Depends on properties of imaging devie
Definition of pixel count
No of pixels along each axis
Definition of aspect ratio
Ratio of its width to its height
Definition of dynamic range
Range of intensity values used to display the image
Definition of n bit image
2n different intensity values
Definition of voxels
Pixels in 3D images
Definition of binary values
Only has 2 grey values in a digital image
Definition of fluoroscopy
Moving images w Xray
What is medical imaging
What can it be used for
Technique and process used to create images of the human body
Studying normal populations
Treatment, selection, planning, guidance, evaluation
Scientific research
Diagnosis
What is a digital image
Acquired by imaging device
Overlay grid, assign an integer to each position
Importance of image resolution
Low spatial resolution, cannot resolve small structures
Low intensity resolution, cannot differentiate objects that look similar
Images and matrices
Images can be conveniently represented using matrices
Pixels and voxels
Many medical images are 3D
Because medical images represent real things, pixels/voxels have a size
In most cases, 2D dimensions are the same but z axis is usually larger
Image file types
Many image file formats available
Use DICOM, not compressed, not lossy
Visualisation techniques
Slice mode
Volume mode, involves projecting a 3D dataset onto 2D images
3 main types of visualization techniques
Maximum Intensity projection, can see surfaces and internal structures
Surface rendering
Volume rendering
Generation of Xrays
Ionising radiation, cause biological damage
Produced when high speed electrons strike a target material (tungsten)
Max energy of X-rays depends on electron speed (30-100KeV)
Radiographical contrast
Arises due to differences in density
5 Xray densities
Air Fat Soft tissue/water Bone Metal
Detection of xrays
Screen film combinations
Image intensifiers
Flat panel detectors static imaging
Dynamic imaging
Modern X-ray systems
Chest xrays Portable xrays Mobile C arm X-rays Fixed C arm single plane Fixed C arm bi plane Robotic C arm single plane
Problems with projective xrays
All estrutures are superimposed
Cannot know depth of objects
CT scanners used today
Gen 3 of 5
Single motion, fan beam rotating detector
(single/multislice)
Methods of scanning in CT
Conventional scanner
Spiral scanner
Multislice scanner
Trends in CT
Faster scanning, more images/sec Lower radiation does, less mSr Interventional, real time imaging Spectral, resolve xray energies Multisource, more than 1 tube
