MODULE 8: Digital Medical Imaging Flashcards
What is a two-dimensional function Function f(x,y) where x and y are spatial coordinates and f at any x,y is related to the brightness at that point?
Image
What is a 2D representation of a continuous image by a 2D array of discrete samples?
Digital Image
What is each element of the 2D array called?
Pixel
If the digital image f (x, y, z) is 3D, then the picture element is called a ?
Voxel (Volume element)
What is the fourth dimension?
t = time
What comprises a 3D image?
Height, Width and Volume
What is a rectangular arrangement of numbers into rows & columns
Matrix
What is each number in a matrix referred to as?
Matrix element or entry
What is the order of the dimensions of a matrix?
Number of rows and columns of the matrix (y, x)
What is it called if the image is obtained through a digitizer?
Digitized
If it is generated digitally, what is the image called?
Digital Image
If it is generated digitally, what is the image called?
Digital Image
Represent physical, chemical, & physiological properties of the state of anatomical structures or physiological processes when the image was captured
Gray Levels
The most radiolucent structure in the anatomy
Air
What is the device used to measure penetrating abilities of x-rays
Penetrometer
What represents the optical density of the small square area of the film?
Digitizer
Represents the relative linear attenuation coefficient of the tissue
Computed Tomography
How many Hounsfield Units does the Air have?
-1000
How many Hounsfield Units does the Water have?
0
How many Hounsfield Units does the Bone have?
1000
How many Hounsfield Units does the Muscle have?
50
How many Hounsfield Units does the Brain White have?
45
How many Hounsfield Units does the Brain Gray have?
40
How many Hounsfield Units does the Fat have?
-100
How many Hounsfield Units does the Lung have?
-200
Corresponds to the MR signal response of the tissue
MRI (Magnetic Resonance Imaging)
In MRI; what are the signals in these colors?
White Matter Gray -
Bone Dark -
CSF Bright -
Intermediate Signal
Low Signal
High Signal
Echo signal of the utz
beam when it penetrates
the tissues
UTZ or Ultrasound
The four image results of UTZ
Isoechoic
Hypoechoic
Hyperechoic
Anechoic
2D projection image is the ordered pair (M, N) signals, it is the product of M x N bits where 2k is the gray level range
Image size
2D projection image is the ordered pair (M, N) signals, it is the product of M x N bits where 2k is the gray level range
Image size
A digital image can be printed on film or paper as a hard copy or displayed on a CRT & LCD as a soft copy,
Image Display
What is done to when the pixel values are first converted to analog-signals, to digital-to-analog conversion
To display a soft copy digital medical image.
What are the three parameters to measure the Quality of a digital image
Spatial Resolution, Density Resolution and Signal-to-Noise Ratio
related to the number of pixels
and the range of pixel values used
to represent the object of interest
in the image
Spatial Resolution & Density Resolution
means that the image has strong
signal with little noise
A high signal-to-noise ratio
Provide a standardized way to store the information describing an image in a computer file
Image File
One or more images representing the projection of an anatomical volume onto an image plane
Projection or planar imaging
A series of images representing thin slices through a volume
tomographic or multi-slice 2D imaging
A set of data from a volume
volume or 3D
Multiple acquisition of the same tomographic or volume image
over time to produce a dynamic series of acquisitions
4D
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.
File Format
4 MAJOR FILE FORMATS USED IN MEDICAL IMAGING
- Analyze
- Nifti
- Minc
- Dicom
Representation of the internal structure or function of an anatomic region in the form of an array of picture elements called pixels or voxels.
Medical Image
NUMERICAL VALUE OF A PIXEL DEPENDS ON:
- Imaging Modality
- Acquisition Protocol
- Reconstruction
- Post-processing
Number of bits used to encode the information of each pixel
Pixel Depth
In Pixel depth, Every image is stored in a file & kept in the memory of a computer as a group of ?
bytes (group of 8 bits)
The amount of information per pixel is?
Color Depth
1 bit of information per pixel
monochrome
8 bits of information per pixel
grey-scale
8 or 16 bits of information per pixel
color (RGB)
24 or 32 bits of information per pixel
true color (RGB)
Specifies how the pixel data should be
interpreted for the correct image
display as a monochrome or color
image; Each pixel of the image is associated with color in a predefined color map
Photometric Interpretation
What kind of Photometric Interpretation does X-ray, CT, & MRI use?
gray scale photometric interpretation
What kind of Photometric Interpretation does Nuclear Medicine, PET, & SPECT?
color map or color palette/LUT
Stored at the beginning of the file as a header & contains at
least the image matrix dimensions, spatial resolutions, pixel
depth, & photometric interpretation
Metadata
Numerical values of the pixels are stored
Pixel Data
2 Categories for Medical Image File Formats:
- DICOM
- Analyze, Nifti & Minc
Formats intended to standardize the images generated by
diagnostic modalities
DICOM
Formats born with the aim to facilitate & strengthen post-processing analysis
Analyze, Nifti & Minc
1980’s, Mayo Clinic in Rochester, MN, USA and consists of two binary files: image file with extension
Analyze
The Two binary files; image file with an extension of Analyze
______ = contains the voxel raw data
______ = header file, contains metadata
.img
.hdr
What does NIFTI stand for?
Neuroimaging Informatics Technology Initiative
2000s | National Institute of Health
and can be thought as revised Analyze format
NIFTI
Merging the header & image information into one file extension
.nii
1992 | Montreal Neurological Institute (MNI) and functions to provide a flexible data format for medical
imaging
MINC
When was DICOM developed?
1990s
Who developed DICOM?
ACR - American College of Radiology
NEMA - National Electric Manufacturers Association
“an image
that is separate from its metadata becomes _________ as medical image”
meaningless
contains the most complete
description of the entire procedure
DICOM header
