Transcript Computers in Imaging Q & A - Radiation Safety Engineering

Computers in Imaging
Q&A
Robert Metzger, Ph.D.
Raphex General Question 2002
G83-G85: Match the following prefizes with
the correct power of 10:
A. 10 –12
B. 10 –6
C. 10 6
D. 10 9
E. 10 12
G83: micro
G84: mega
G85: giga
RAPHEX Answer to 2002
Questions G83-85
G83: B.
G84: C.
G85: D.
RAPHEX General Question 2003
G77: The computational speed of a computer
is measured in units of:
A. MB
B. MIPS
C. RVU
D. BAUD
E. BPI
RAPHEX Answer to 2003
Question G77
B. MIPS
MIPS stands for Millions of Instructions
Per Second
RAPHEX General Question 2003
G79: Parallel processing refers to:
A. Running multiple tasks simultaneously
B. Using multiple processors to increase
speed
C. Computer networking
D. Sharing peripheral devices between
computers
RAPHEX Answer to 2003
Question G79
B. Using parallel processors to increase
speed.
Parallel processors divide a task into pieces,
with each pieces being solved on a separate
processor to increase speed.
RAPHEX General Question 2003
G80: There are approximately ____ bits in a
megabyte.
A. 1024
B. 2048
C. 8000
D. 2,000,000
E. 8,400,000
RAPHEX Answer for 2003
Question for G80
E. 8,400,000
1 byte = 8 bits
1 Mbyte = 1024 X 1024 =
1,044,448,575 bytes = 8,388,608 bits
RAPHEX Diagnostic Question
2001
D37-D41: Concerning digital subtraction
angiography: (Answer A for True and B for False)
D37: X-rays exiting the patient are normally captured in a cesium
iodide II tube to produce a visible image.
D38: The TV cameras used for DSA normally have a signal-tonoise ratio of about 100:1.
D39: The video signals form the TV camera are processed in a
digital-to-analog converter to obtain a matrix of numbers
corresponding to the image.
D40: Systems with the greatest capability for artifact correction for
re-masking are those which store the subtracted image in
analog form on a video disk.
D41: Compared with film subtraction images, electronically
subtracted images normally have somewhat poorer spatial
resolution, but better iodine contrast resolution.
RAPHEX Answer for 2001
Question D37-D41
D37: TRUE – The x-ray image is captured in high resolution with a CsI
input phosphor.
D38: FALSE – Because the differences signal contains noise
determined by the sum of the noise in the mask and the angiogram, a
very low noise TV camera (SNR 500:1 or higher) is normally employed
in order to prevent additional noise from being added to the image.
D39: FALSE – The analog video signals go to an analog-to-digital
converter (ADC)
D40: FALSE – Image manipulation and enhancement is bets achieved
with systems which store the mask and angiogram separately in digital
form
D41: TRUE – The resolution is limited by the II (4 1p/mm), which has
lower resolution than screen-film (6-10 1p/mm) systems. However,
contrast enhancement (window/level) is easily achieved.
RAPHEX Diagnostic Question
2002
D47: Concerning computed radiography (CR), which
of the following is true?
A. Numerous, small solid-state detectors are used to
capture the x-ray exposure patterns
B. It has better spatial resolution than film
C. It is ideal for portable x-ray examinations, when
phototiming cannot be used
D. It is associated with high reject/repeat rates
E. The image capture, storage, and display are
performed by the receiver
RAPHEX Answer to 2002
Question D47
C. It is ideal for portable x-ray examinations, when
phototiming cannot be used.
Computer radiography has a wide dynamic range, in effect wide
latitude. It produces acceptable films with sub-optimal
technique, such as those obtained with portable x-ray units. It
uses image plages covered with photostimulable phosphor
(Europium activated Barium Fluoride) as a receiver. Resolution
with screen-film systems (5 to 10 1p/mm) is better than that
obtained with CR (2.5 to 5 1p/mm). The reject rate in CR is low
due to post processing techniques available electronically.
Unlike film, CR image capture, storage, and display are all
performed by different component fo the system.
RAPHEX Diagnostic Question
2002
D48: In picture archiving and communications
systems (PACS), large-matrix display stations
(for digitalized radiographs and CR) have all
of the following EXCEPT:
A. A magnification function
B. Interactive window and level functions
C. Ability to measure the linear attenuation coefficient
accurately
D. Ability to invert eh gray-scale values of the image
E. Ability to rotate and flip the image
RAPHEX Answer for 2002
Question for D48
C. Ability to measure the linear
attenuation coefficient accurately
Unlike the case with CT, where CT number
measured in Hounsfield numbers represent
linear attenuation coefficient values relative to
water, in general radiography imaging pixel
values are not referenced to value associated
with any particular tissue or material.
RAPHEX Diagnostic Question
2003
D51: A flat panel digital radiographic detector has a
square 20 X 20 cm image receptor field. The full filed
of the detector is coupled to a nominal 2048 X 2048
CCD array. The relative spatial resolution (
expressed as line pair per mm) when going from a 20
X 20 to a 10 X 10 filed of views is:
A. Four times better
B. Twice as good
C. The same
D. Half as good
E. One fourth as good
RAPHEX Answer for 2003
Question D51
C. The same
Digital radiographic (DR) detectors use a
fixed number of pixels to image the entire
field of view (2048 X 2048 for 20 X 20 cm in
this example). Only some of the pixels are
used when the image is coned down (1024 X
1024 for 10 X 10 in this example). Since the
pixel size is fixed, spatial resolution does not
change with collimation.
RAPHEX