IT: medical image Flashcards
What is an image?
An array or matrix of square pixels (picture element) arranged in columns and rows
What does each picture element in a greyscale image (8-bit) have?
Assigned intensity that ranges from 0 to 255
What is an image (descriptive)?
- Measurements at multiple spatial locations
- Spatial measurements = measurements of distance, area and volume, these involve the first 2 dimension of image its width and height
- The measurements are often, but not always arranged on a 2D/3D grid
What is the key feature of an image?
Each measurement relates to a physical location in the patient
What can a 2D medical image be?
Either tomographic or a projection through a 3D object
What is tomographic image?
A slice through the object
What does projection images do?
Aggregate data over long lines
What are the 2 characteristic of projection images?
- Summation (projection x-ray)
2. Surface reflection and scattering in a photograph
What is an element of image usually called?
Pixel (single 2D slice/projection) or voxel (3D image)
What is each voxel sampling?
Some kind of average (usually a summation) of the contents of finite volume of object
What is point spread function?
Response of an imaging system to a point source or point object
What are examples of spatial size of samples?
- Partial volume effects
- Point spread function
- Slice profile
What does an image metadata involve?
Details relevant to image itself as well as information about its production
How is some metadata generated?
Automatically by device capturing image
What can image metadata be useful for?
Cataloging and contextualising visual information
How can you make an image more meaningful?
Store extra information alongside image array itself
Often stored in an image ‘header’
What are examples of image metadata?
- Geometry
- Patient details
- Exam logistics
- Exam parameters
- Relationship to other slices, series,exams,
- Archiving information
- Display information
Examples of geometry
- Sample spacing (voxel size, resolution, slice thickness)
- Orientation repetition
- Standard orientation to display
Example of patient details
- Name
- Hospital number
- Date of birth
- Ward
- History
- Indication
Example of exam logistics
- Hospital
- Scanner
- Date and time
- Radiographer
- Referring clinician
Examples of exam parameters
- Modality
- Flip angle
- TE/TR
- B value
- Dynamic timing
- RF pulse type
- Filters
Example of display information
- Window/level
2. colourmap
How are radiological images normally displayed?
As if the patient were in a standard orientation
What must you be certain about?
- Anatomy orientation
- Displayed orientation
- Handedness
