LESSON 1 Flashcards
Images can be:
(Aspect: Signal Type)
Analog Images:
Digital Images:
Continuous signal (analog)
Discrete numerical values (digital)
Images can be:
(Aspect: Image Formation)
Analog Images:
Digital Images:
• Single exposure using light-sensitive
film
• Multiple samplings converted to digital values
Images can be:
(Aspect: Processing Method)
Analog Imagesv
Digital Images:
• Chemical development of film
• Computer algorithms
Images can be:
(Aspect: Storage)
Analog Images:
Digital Images:
• Physical storage (films, cassettes)
• Digital storage (hard drives, cloud
services)
Images can be:
(Aspect: Quality and Resolution)
Analog Images:
Digital Images:
• Dependent on film quality and
processing
• Improved through multiple samplings and higher bit depth
Images can be:
(Aspect: Transmission)
Analog Images:
Digital Images:
• Requires physical transfer of films
• Easily shareable electronically
formed in an analog fashion
Radiographic Image
it sensitive to the light that is produced by the screens, and is exposed to radiation and then processed in
chemical solutions.
film
containing fluorescent screens
cassette
In an _____ such as film/screen radiography, xray energy is converted to light, and the light waves are recorded just as they are
analog system
In digital radiography, it is converted into numbers that are recorded
analog system
formed through multiple samplings of the signal
rather than the one single exposure of an analog image.
Digital images
it begins as an analog signal.
digital images
Through this, the image becomes digitized and is sampled multiple times.
computer data
processing
it can be described with respect to several characteristics
or fundamental parameters, including the matrix, pixels, voxels, and the
bit depth
digital image
A digital image can be described with respect to several characteristics
or fundamental parameters, including the ___, ___, ____, and ____.
matrix
pixels
voxels
bit depth
A digital image is made up of a two-dimensional array of numbers called a
____.
matrix
The matrix consists of ____ and ____ that define pixels
columns (M)
rows (N)
The dimensions of the image are described by:
M (columns)
N (rows)
When M=N, the image is _____; typically, diagnostic images are ____.
square
rectangular
The matrix size (or FOV) is ____.
selected during imaging
it also take longer to transmit to remote locations
Larger images
it require more processing time and storage space.
Larger images
it is necessary to facilitate efficient storage and
transmission
Image compression
(Matrix size and typical bit depth)
Nuclear medicine:
128 x 128 x 12
Matrix size and typical bit depth
Magnetic resonance imaging:
256 x 256 x 12
(Matrix size and typical bit depth)
Computed tomography:
512 x 512 x 12
(Matrix size and typical bit depth)
Digital subtraction angiography:
1024 x 1024 x 10
(Matrix size and typical bit depth)
Computed radiography:
2048 x 2048 x 12
(Matrix size and typical bit depth)
Digital radiography (flat-panel imagers):
2048 x 2048 x 12
(Matrix size and typical bit depth)
Digital mammography:
4096 x 4096 x 12
it is
the smallest element in a digital
image.
A pixel, or picture element
pixel or
picture element
If
you
have
ever magnified a digital picture to
the point that you see the
image as small squares of
color, you have seen ___.
pixels
it represents the smallest sampled
2D element in an image.
pixel
It has dimensions given along two axes in
millimeters, dictating in-plane spatial
resolution
Pixel
it makes up the matrix and are generally square
pixel
Each ___ contains a discrete number representing a brightness level.
pixel
in this modalities, the numbers relate to the atomic number and
mass density of tissues
Radiography
CT
In this modality, the numbers represent other tissue characteristics like proton
density and relaxation times.
MRI
A typical digital chest x-ray might contain ____ of pixels and
______ of pixels for a total of _____ pixels.
2000 columns
2500 rows
5 million
Each pixel contains a series of ____ defining the grayscale or shade
of that particular point on a digital x-ray image
1s
0s
Each space available or a 1 or 0 is called a __. A group of 8 bits is called
a ___.
bit
byte
Each ___ is coded with numbers to show different shades, helping to
create the detailed digital image you see
pixel
The pixel size can be calculated using the relationship:
Pixel size = FOV/matrix size
For ____, the larger the matrix size, the smaller the
pixel size (for the same FOV) and the better the spatial resolution.
digital imaging modalities
it is the number of bits per pixel
bit depth
An image that is described as having a bit depth of 8 will have ___ shades
of gray
256 (2⁸)
The term ___, is synonymous with the x-ray field.
field of view, or FOV
FOV
field of view
it is the amount of body part or patient included in the image.
field of view
The _____, the more area is imaged
larger the FOV
Changes in the __ will not affect the size of the ___ ; however, changes in the ___ will affect ___.
FOV, matrix
matrix, pixel size
The characteristics of a digital image can affect the appearance of the digital
image, particularly its ___ and ____.
spatial resolution
density resolution.
it refers to the ability of an imaging modality to differentiate
two adjacent structures as being distinct from one another
Spatial Resolution
it refers to the ability of an imaging system to distinguish
between different levels of radiographic density or optical density (OD)
Density Resolution
it has an effect on the detail or spatial resolution of the image.
matrix size
as the FOV ____, without a change in matrix size, the size of
the pixel ___ as well, thus improving detail.
decreases
decreases
It has an effect on the number of shades of gray, hence the
density resolution of the image
bit depth
it is first essential to understand the fundamental steps to
____, because similar steps apply to any digital imaging modality.
digitizing images
There are three steps to digitizing an image:
• Scanning
• Sampling
• Quantization
In _____, the image is first divided into an array of small square regions
called pixels
scanning
an array of small square regions
called
pixels
The signal from the PMT is an ______ (______)
that must be converted into a digital image for processing by a digital
computer
analog signal(voltage waveform)
The ____, simply involves measuring the brightness level
of each of the pixels using special devices such as a photomultiplier tube
(PMT).
sampling
special devices in sampling that involves measuring the brightness level
of each of the pixel _____.
photomultiplier tube
(PMT)
This is a process
whereby the brightness levels obtained from sampling are assigned an
integer (zero, a negative, or a positive number) called a gray level.
Quantization
integer (zero, a negative, or a positive number) called a ___.
gray level
The third step in digitizing an image is _____.
quantization
The
image is now made up of a range of ____.
gray levels
The total number of gray
levels is called the
gray scale
it plays an important role in the process
of converting an analog signal into digital data for input into a digital
computer
Analog-Digital Converter (ADC)
it consists of several components that will divide up the
analog signal into equal parts.
The Analog-Digital Converter (ADC)
Digital imaging modalities have _____ ADCs
12-13 bit
image quality is better
with __ bit ADCs compared to bit ADCs
higher
lower
it deals with the development of problem specific
approaches to enhance the raw medical data for the
purpose of selective visualization as well as further
analysis.
Basic Image Processing
it concentrates on the development of techniques to
supplement the usually qualitative and frequently
subjective assessment of medical image by human
experts
Basic Image Analysis
Statistics of medical imaging fills the gap and
provides a theoretical framework for statistical
investigation into medical imaging technologies
Statistical Analysis and Entropy
it plays an important role in assessing any new hardware,
software, image acquisition techniques, image reconstruction
or post- processing algorithms
Quality Evaluation
The system is said to be stable only when the output is bounded for
bounded input. For a bounded input, if the output is unbounded in the
system then it is said to be Unstable.
Stable and Unstable Signal Processing
Color information in digital images is used for many
practical purpose, mainly in security fields and also
with gray scale images applications.
Coding and Decoding
it means finite in amplitude.
(Bounded input for Bounded Output)
A stable system satisfies the ___
BIBO
BIBO
(Bounded input for Bounded Output)
Common Image Transforms include:
• Hough Transform
• Radon Transform
• Discrete Cosine Transform
• Discrete Fourier Transform
• Wavelet Transform
it can be applied to an image to convert it
from one domain to another.
image transformation
A principal advantage of digital radiographic imaging over screen-film
radiographic imaging is the ability _______, respectively.
to manipulate the image before and after
display - preprocessing and postprocessing
___ and ___ image processing alter image appearance, usually for the
purpose of improving image contrast.
Pre
Post
_____ describes the manipulation
of radiographic images to derive additional qualitative or
quantitative data
Advanced post-processing
____ of digital images is largely automatic.
Preprocessing
___ is designed to produce artifact-free
digital images
Preprocessing
The adequate and repeatable performance of the image
display system is a key element of information
technology platforms in a modern radiology department.
Medical Image Display
