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Transcript
Film Screen Q & A
Robert Metzger, Ph.D.
RAPHEX General
Question 2001
D10: Flood replenishment of a processor involves all
of the following except:
A. Draining and refilling the developer tank each day.
B. Putting starter solution into the replenishment
tank.
C. Replenishment of developer on a timed basis
(e.g. every 15 min).
D. Stabilization of sensitometry for low volume
pressures.
E. A possible compromise in film contrast.
RAPHEX Answer to 2001
General Question D10
A. Flood replenishment uses timed
replenishment to stabilize the processor
in low film volume situations. It requires
the addition of starter to the developer
replenishment tank, which may not
result in optimum processing of film. It
does not involve daily draining.
RAPHEX General
Question 2001
D15: If the absorption efficiency of each
intensifying screen in a dual screen system is
30%, what percentage of x-rays is stopped by
the screens together?
A.
B.
C.
D.
E.
9%
30%
51%
60%
70%
RAPHEX Answer to 2001
General Question D15
C. 30% is absorbed in the first screen,
70% passes through. The second
screen absorbs 30% of that 70% (or
21%). Total stopped is 30% + 21%.
RAPHEX General
Question 2003
D25: A radiograph with an optical density
(OD) of 3.0.
A. Transmits 1/3 times as much light as a film with
an OD of 1.0.
B. Has a combined OD of 6.0 when placed over
another film of OD 2.0.
C. Looks “light gray” on a standard view box.
D. Transmits 0.1% of the light incident upon it.
RAPHEX Answer to 2003
General Question D25
D. Optical densities are additive, so the
net OD of both films is 5.0. An OD of
3.0 looks black on a standard view box.
OD = log10(I/T), where I and T are the
incident and transmitted light intensities.
For OD = 3.0, T = 0.001, and OD = 1.0,
T = 0.1.
RAPHEX General
Question 2001
G72: A radiograph transmits 10% of the light
from a viewbox with an illumination level of
400 lux. The optical density of the radiograph
is ________ .
A.
B.
C.
D.
E.
10
2
1
0.1
1/400
RAPHEX Answer to 2001
General Question G72
C. Optical density (OD) = log (incident
intensity / transmitted intensity) = log
(1/0.1) = log10 = 1.0.
RAPHEX General
Question 2002
G75: A grid improves the quality of a
diagnostic x-ray primarily by attenuating
________ .
A.
B.
C.
D.
E.
Primary photons
Compton scattered photons
Compton electrons
Photoelectrons
Coherent scattered photons
RAPHEX Answer to 2002
General Question G75
B. Compton-scattered photons travel in
random directions, and contain no
useful diagnostic information. The grid
absorbs most of these photons, and
thus improves image contrast.
RAPHEX General
Question 2003
G80. There are approximately _______ bits
in a megabyte.
A.
B.
C.
D.
E.
1024
2048
8000
2,000,000
8,400,000
RAPHEX Answer to 2003
General Question G80
E. 1 byte = 8 bits, 1 Mbyte = 1024 x
1024 = 1,044,448,575 bytes =
8,388,608 bits.
RAPHEX General
Question 2003
G81: For protection purposes, the absorbed
dose is multiplied by a “radiation weighing
factor” wR is ______.
A.
B.
C.
D.
E.
1
5
10
20
50
RAPHEX Answer to 2003
General Question G81
D. See NCRP Report 116.