Each pixel has an - intensity value and location address.
An image - is a two dimensional function
A digital image - is a 2D representation
Each element of the 2D array is a - pixel
If the digital image is 3D, then the picture element is called a - voxel
Matrix - is a rectangular arrangement of numbers into rows and columns
Matrix A has 2 rows and 3 columns, it is called a 2x3 matrix.
DIGITIZED - if the image is obtained through a digitizer
DIGITAL IMAGES - if it is generated digitally
0-255 (8-bit)
0-511 (9-bit)
0-1023 (10-bit)
0-2045 (11-bit)
0-4095 (12-bit)
Gray levels - represent physical, chemical, & physiological properties of the state of anatomical structures or physiological processes when the image was captured
penetrometer - is a device used to make gray levels
radiolucent - is dark or black
radiopaque - is white
Digitizer - represents the optical density of the small square area of the film
Computed Tomography - Represents the relative linear attenuation coefficient of the tissue
Water - 0
Air - (-1000)
Bone - 1000
MRI - Corresponds to the MR signal response of the tissue
Ultrasound - Echo signal of the utz beam when it penetrates the tissues
Quality of a digital image, is measured by three parameters: Spatial Resolution, Density Resolution, Signal - to - noise ratio
Image File Format - Provide a standardized way to store the information describing an image in a computer file
MEDICAL IMAGE DATA SET CONSISTS: projection or planar imaging, tomographic or multi-slice 2D imaging, volume or 3D, 4D
File Format - Describes how the image data are organized inside the image file and how the pixel data should be interpreted by a software for the correct loading and visualization.
4 MAJOR FILE FORMATS USED IN MEDICAL IMAGING: Analyze, Nifti ,Minc, Dicom
Medical Image - Representation of the internal structure or function of an anatomic region in the form of an array of picture elements called pixels or voxels.
NUMERICAL VALUE OF A PIXEL DEPENDS ON:
- Imaging Modality
- Acquisition Protocol
- Reconstruction
- Post-processing
pixel depth - Number of bits used to encode the information of each pixel
the amount of information per pixel is called a color depth
monochrome - 1 bit of information per pixel
grey-scale - 8 bits of information per pixel
color (RGB) - 8 or 16 bits of information per pixel
true color (RGB) - 24 or 32 bits of information per pixel
Photometric Interpretation - specifies how the pixel data should be interpreted for the correct image display as a monochrome or color image
metadata - Information that describes the image
metadate stored at the beginning of the file as a header & contains at least the image matrix dimensions, spatial resolutions, pixel depth, & photometric interpretation
Numerical values of the pixels are stored is called pixel data
2 C A T E G O R I E S F O R M E D I C A L I M A G E F I L E F O R M A T S : DICOM and Analyze, Nifti, Minc
Medical image files are typically stored using one of the following two possible configurations: One in which a single file contains both the metadata and image data, with the metadata stored at the beginning of the file. The second configuration stores the metadata in one file and the image data in a second one.
Analyze consists of two binary files: image file with extension: .img and .hdr
Nifti - Neuroimaging Informatics Technology Initiative
MINC - To provide a flexible data format for medical imaging
Montreal Neurological Institute (MNI)
Backbone of every medical imaging department is DICOM
DICOM - ACR and NEMA
ACR - American College of Radiology
NEMA - National Electric Manufacturers Association