fund ch 24, 28, 29
What is the spatial frequency for a gamma camera?
.1 lp/mm
What is the spatial frequency for CT?
1.5 lp/mm
What is the spatial frequency for MRI?
1.5 lp/mm
How many lp/mm can an 8X10 CR system show?
10
How many microns are in a millimeter?
1000
What is the common matrix size for digital radiography?
1024X1024
What is the common matrix size for diagnostic ultrasonography?
128X128
How many lp/mm can detail film-screens resolve?
15
What is the spatial frequency for mammo?
15 lp/mm
When and how was digital imaging first used?
1970's for computed tomography
What is the spatial frequency for sonography?
2 lp/mm
What does a true black and white image have a bit depth of?
2 or 2^1
What is the common matrix size for computed radiography?
2048X2048
What is the common matrix size for computed tomography?
256X256
What is the bit depth of the x-ray beam exiting the patient?
2^10
What is the bit depth and number of shades of gray s in NM?
2^10, 1024
What is the bit depth and number of shades of gray in CT?
2^12, 4096
What is the bit depth and number of shades of gray in MRI?
2^12, 4096
What is the bit depth and number of shades of gray in DR?
2^14, 16384
What is the bit depth and number of shades of gray in DM?
2^16, 65536
What is the bit depth and number of shades of gray in DMS?
2^8, 256
What is the spatial frequency for fluoroscopy?
3 lp/mm
How many shades of gray can the human eye differentiate between?
32 shades of gray; 2^5
What is the spatial frequency for DR?
4 lp/mm
How many lp/mm can a 14X17 system show?
5
How many lp/mm can the human eye discern?
5-20
What is the common matrix size for magnetic resonance imaging?
512X512
What is the spatial frequency for CR?
6 lp/mm
What is the common matrix size for nuclear medicine?
64X64
How many lp/mm can 400 speed systems resolve?
7
How many lp/mm can a 10X12 system show?
7
How do you calculate the number of shades of gray in 2n systems?
8 bits can have 256 different shades of gray; 2^n=2^8=256
What is the spatial frequency for radiography?
8 lp/mm
What is a pixel?
A picture element
What is the official computer language used by the US department of defense?
ADA
What is contrast resolution?
Ability to distinguish many shades of gray from black to white; smallest exposure change (signal difference) that can be captured by a detector; limited by dynamic range (number of bits per pixel) of the detector
Compare digital and analog imaging systems.
An analog system is in which values are represented along a continuous scale, can have a value in between that; a digital is a system of discrete or discontinuous values
What is an image matrix?
An arrangement of pixels in rows and columns, this is what a digital image is
How did fluoroscopy advance in the 1970's?
Analog-to-digital converters allowed real-time images to be viewed on TV monitors, and fluoroscopic images could be stored on a computer
What is digital imaging?
Any image acquisition process that produces an electronic image that can be viewed and manipulated on a computer
What is a tape, diskette, hard disk or optical disk used to do?
Archive files
State the tissue qualities used to determine pixel value for radiographic and fluoroscopic imaging.
Atomic number and mass density
What are the tissue qualities used to determine pixel size for CT?
Atomic number, mass density
What is a computer language used to write some application programs?
BASIC
What computer systems do automatic bank tellers use?
Batch processing
What is it called when a computer processes data without human input or intervention?
Batch processing
What represents zero or one?
Bit
Compare the relationship in bit-rate to shades of gray.
Bit depth refers to the gray scale for image acquisition and display, bit depth is equal to 2 where n is the number of bits
What are line pairs?
Black line on white background, one line pair consists of a line and an interspace of the same width
How were early PACS systems used in the 1980's?
By the military to send images between Veterans Administration hospitals, development was encouraged and supported by the US government
How can a matrix be described?
By the number or pixels along the horizontal axis, or columns; and the number of pixels along the vertical axis, or rows
What is the programming language developed for coding business data?
COBOL
What controls the data transfer between the main memory and the input and output hardware?
Central processing unit
What is the active storage of a computer stored in?
DRAM, SRAM, and ROM chips
What is the computer file a record of?
Each pixel's location and value
What range of exposures do typical digital systems respond to?
Exposures as low as 100 micro Roentgens and as high as 100mR
What is the oldest compute language for writing scientific and mathematical programs?
FORTRAN
What is the determining factor of spatial resolution for film-screen systems?
Geometric factor of OID, SID, and FSS
What does a larger dynamic range mean for contrast resolution?
Greater contrast resolution
What is the relationship between pixel density and spatial resolution?
Greater pixel density results in greater spatial resolution*What is spatial frequency?** Line pairs, it relates the number of line pairs in a given length usually line pairs per mm or lp/mm
What is the purpose of a line pair?
Helps determine spatial frequency
In what ways can spatial frequency be organized?
Horizontally or vertically and to be useful it must exist in both dimensions
What is the formula for pixel size?
Image size (mm)/matrix size (pixels)
What are the tissue qualities used to determine pixel size for ultrasound?
Interface reflectivity
Explain the purpose of a modulation transfer function (MTF)?
It's the overall ability to show accuracy of detail; mathematical expression that describes the ability of an imaging system to capture, and display signal contrast present in radiation beam from object, describes fraction of each component that will be preserved in the captured image; it is the ideal expression of the image quality provided by a detector
What does the value of each cell correspond to?
Its brightness or intensity
What are the primary characteristics of a digital image?
Its matrix, spatial resolution, contrast resolution, signal-to-noise-ratio, and temporal resolution
What does computer hardware include?
Keyboard, central processing unit, and motherboard
What became available in the 1980's?
Magnetic resonance imaging
What eventually converted to a digital format?
Mammography
What is pixel pitch measured in?
Microns
What does increased dynamic range allow?
More anatomical structures to be captured during an exposure
Compare matrix size, and pixel size, and spatial resolution.
More pixels in same area allow better spatial resolution; larger pixel size and matrix size smaller spatial resolution
What does higher lp/mm mean for spatial resolution?
More spatial resolution
What is an example of computer input hardware?
Mouse
What type of systems are MAC-OS, Windows, and UNIX?
Operating
Compare pixel density and pixel pitch.
Pixel density describes the number of pixels/mm in an image, it's determined by pixel pitch; and pixel pitch is the space from the center of a pixel to the center of the adjacent pixel
What is the determining factor of spatial resolution for digital imaging systems?
Pixel size
What are the tissue qualities used to determine pixel size for MRI?
Proton density, spin relaxation
What are the tissue qualities used to determine pixel size for nuclear medicine?
Radionuclide uptake
What is dynamic range and compare this to image contrast?
Range of exposures over which a detector can acquire image data; contrast enables us to distinguish objects
What type of processing do computers use for computerized medical image equipment such as CT scanners?
Real-time
What film-screen concept is spatial resolution equivalent to?
Recorded detail
What did ultrasound and nuclear medicine use for digital imaging?
Screen capture to grab the image and convert it digitally
What do modern day computers use to store information?
Silicon chips
How do you calculate the spatial resolution in lp/mm when given a matrix size and image size?
Spatial resolution=number of pixels/FOV
What program does the computer first use when it is turned on?
Systems software
What is spatial resolution?
The ability of an imaging system to resolved and render a small, high contrast object
What is the number of pixels in a matrix the product of?
The columns and rows
What happens when the latent image is made manifest?
The film is capable of displaying any shade of gray between the darkest (black) and the lightest (white), which is one reason film-screen is an analog image system
What is the spatial frequency of a system equal to?
The film size (FOV) divided by the matrix
What do more pixels in the same area mean for spatial resolution?
The image contains more information, which means it has more spatial resolution
How were radiographs read in between the time of conventional radiography and the discovery of computed and digital radiography?
The initial method required scanning radiographs into a computer, and images were then stored in PACS
How do you calculate the quantity of pixels in a matrix when given the matrix size?
The number of pixels in a matrix is the product of the columns and rows. Ex. 256X256= 65,536 pixels
What happens to the objects that can be seen as spatial frequency increases?
They get smaller
What type of systems do large research facilities use?
Time sharing
What was the first commercially successful general-purpose stored-program electronic digital computer developed in 1951?
UNIVAC
What was the first generation computer run with?
Vacuum tubes
How are film screen images produced?
When x-rays strike phosphors in an intensifying screen, each crystal can emit light of any intensity from none to its maximum output, the silver halide crystals in the film record the light
What is the maximum spatial frequency of a digital imaging system equal to?
½ the number of pixels/mm; if a system has a pixel density of 5 pixels/mm, the maximum spatial frequency is 2.5 lp/mm
