ASNT RT II Flashcards
Low voltage x-ray tubes are generally fitted with windows made of?
Berylium
Monochromatic x-ray beam is?
a beam consisting of a single wavelength
The general method of producing x-rays involves the sudden deceleration of high velosity electrons in a solid body called a?
target
If it were necessary to radiogragh a 7 in. thick steel product. which of the following gamma ray sources would most likely be used?
Co-60
A Co-60 gamma ray source has an approximate practical thickness limit of?
9 inches of steel or its equivalent
The absorption of gamma rays from a given source when passing through matter depends on the?
atomic number,density,and thickness of the matter
The fact that gasses, when bombarded by radiation,ionize and become electrical conductors make them useful in?
radiation detection equipment
The velocity of electrons striking the target in an x-ray tube is a function of the?
voltage difference between the cathode an anode
The uneven distribution of developed grains within the emulsion of a processed x-ray film causes the subjective impression of?
graininess
Co-60 is reported to have a half-life of 5.3 years.By how much should exposure time be increased when the source is two years old?
31% longer
A source of ir-192 provides an optimum exposure of a given test object today in a period of 20 minutes.what exposure time is needed 5 months from now?
1 hour and 20 minutes
- The gamma ray intensity at 30 cm (1ft) from a 37 GBq (1 Ci) source of radioactive Co-60 is nearest to:
15 roentgens per hour
The focal spot in a X-ray tube:
should be as small as possible without unduly shortening the life of the tube
In an X-ray tube, the filament and focusing cup are the two essential parts of the:
cathode
The quantiy or radiation which will produce, by mean of ionization, on electrostatic unit of electricity in 0.001293 g of dry air is known as
roentgen
The specific activity of an isotopic source is usually measured in:
curies per gram (Ci/g)
Which of the following isotopes has the longest half-life?
cs-137
The primary form of energy conversion when electrons strike a target in an X-ray tube results in the production of:
heat
The slope of a straight line joining two points of specified densities on a characterisitc curve of a film is known as the:
average gradient
An X-ray film having wide latitude also has by definition:
low contrast
The purpose for circulatng oil in some types of X-ray tubes is to:
dissipate heat
An X-ray tube with a small focal spot is considered better than one with a large focal spot when it is desired to obtain:
better definition
one method of reducing radiographic contrast is to:
decrease the wavelength of the radiation used
Thin sheets of lead foil in intimate contact with X-ray film during exposure increase film density because they:
emit electrons when exposed to X and gamma radiation which helps darken the film
X-ray tubes are often enclosed in a shockproff casing in order to:
protect the operator from high-voltage shock
An X-ray tube is rated for a maximum of 250 kVp. This tube may be operated at a miximum of:
250,000 V peak
A voltage selector consisting of an iron core transformer with a single winding having a series of taps at various points on the winding is called:
an autotransformer
In X-ray radiography, alternatin current must be changed to pulsating direct current in order to satisfy the neeed for unidirectional current. This chance may be accomplished by
recitfiers
When radiographing to the 2-2T quality level, an ASTM penetrameter for 63 mm (2.5in.) steel has a thickness of:
a. 13 mm (0.5 in.)
1270 um (50 mils
Valve tubes are used in X-ray equipment to:
provide necessary rectification
When sharp, black, bird-foot shaped marks which are known not to correspond with an discountinuities appear at random on radiographs, they are probably caused by:
static charges caused by friction
The adjustment of tube current in a conventional X-ray tube circuits is made by:
adjusting the filament heating current
In comparison with lower-voltage radiographs, high-energey radiographs show:
greater latitude
Filters used at the port of the X-ray tube:
filter out “soft” radiation to provide a more homogeneous X-ray beam
An ASTM penetrameter for use when inspecting a 13mm (0.05in) thick steel plate to the 2-2T quality level using a 41cm (16in) source-to film distance would be made of:
254 um (10 mil) thick steel
Filters placed between the X-ray tube and specimen tend to reduce scatter radiation undercutting the specimen by:
absorbing the longer wavelength components of the primary beam
Besides serviingt as a filter, screens of high atomic numbers, such as lead and lead antimony also
provide some images intensifying action
The range of thickness over which densities are obtained that are satisfactory for interpretation is a measure of the:
latitude of a radiograph
Almost all gamma radiography is performed with:
Ir-192 or Co-60
The amount of unsharpness or blurring of a radiograph is:
directly proportional to to the zie of the focal spot and inversly proportional to the source-to-object distance
Images of discontinuties close to the source side of the specimen become less clearly defined as:
the thickness of the specimen increases
The inherent filtration of an X-ray tube is a function of the:
thickness and composition of the X-ray tube port
X-ray films with large grain size:
have higher speeds than those with relatively small grain size
Aa the effective energy of the radiation increases up to about 250 kV:
film graininess increase
The specific activity of Co-60 depends on the:
time the material has been in a reactor
The most commonly used target material in an X-ray tube is:
tungsten
The prupose for including a disc-shaped target that rotates rapidly during operation in some X-ray tubes is to:
increase the permissible load
A device which is basically a combination of magnet and transformer designed to guide and accelerate electrons in a circular orbit to very high energies is called a:
betatron
Two isotropic sources of a given strength have two different specific activity values. The source with the higher specific activity value will:
have a smaller physical size than the source with a lower specific activity
A gas-filled region located in an electrical field created by electrodes across which a potential difference is applied forms the major portion of:
an ionization chamber
Two serious obstacles to high-intensity fluoroscopy are:
the limited brightness and large grain size of fluoroscopic screens
In general, the quality of fluoroscopic equipment is best determined by:
penetrameter sensitivity measurements
In fluoroscopic testing, a fundamental difficulty is the relative low brightness level of the images. One method for increasing brightness utilizes one of the following which converts light energy from the initial phosphor surface to electrons which are accelerated and focused onto a smaller fluroescent screen.
image amplifier or intensifier
A general rule governing the application of the geometric principles of shadow formation states that the:
central ray should be as nearly perpendicular to the film as possible to preserve spatial relationships
In order to utilize the principles of geometric enlargment (placing the film at the distance from the specimen):
the source of the radiation must be extremely small
The radiographic absorption of a material will tend to become less dependent upon the composition of the material when:
the kilovoltage is increased
The formula (milliamperes X time) / distance^2 is:
the exposure factor
The load that can be handled by an X-ray tube focal spot is governed by:
the size of the focal spot and the efficiency of the cooling system of the anode
X-ray exposure holders and cassettes often incorporate a sheet of lead foil in teh back which is not in intimate contact with the film. The purpose of this sheet of lead foil is:
protect the film from backscatter
A lead sheet containing a pinhole may be placed halfway between the X-ray tube and the film in order to:
determine the approximate size of the focal spot
In certain cases, it may be advantageous to pack lead shot around a specimen. The purpose for doing this is to:
prevent movment of the specimen
When radiographing steel with a thickness less than 25mm (1in):
a 250 kV X-ray machine would give greater radiographic sensitivity than co-60
The absorption of radiation by a material varies:
in an approximately exponential manner with the thickness of the material
In the microradiographic technique:
a. soft X-rays are usually used
b. a kilovoltage range 5-50 kV is usually used
c. the photographic material is often finer grained than an ordinay X-ray film
In order for a radiograph to have a penetrameter sensitivity of 2-2T or better:
the radiographic procedure must be able to define the 2T hole in a penetrameter which is 2% of the thickness of the specimen
For practical purpose, the shape of the characteristic curve of an X-ray film is:
independent of the quality of X or gamma radiation
The term which describes the total absorption of the useful beam caused by the X-ray tube wall, the wall of the tube housing, and any material between the tube and the housing is:
inherent filtration
The interval between the time a film is placed in a fixer solution and the time when the original diffuse, yelow milkiness disappears is known as:
clearing time
Improper geometric factors, poor contact between film and lead foil screens, and graininess of film are possible causes of:
poor definition
In fluoroscopy, the most common way to minimize operator fatigue is to:
change operators periodically
Which of the following X-ray generators would produce the narrowest cone of X-radiation?
25 MeV
A radiograph is taken at a voltage of 500 kv.if the voltage is increased:
there will be little significant change in the graininess of the film
A radiograph of a steel weldment is made using a 15 MeV betatron. When the radiograph is developed, there is an overall film motting. A possible cause for such mottling is:
failure to use a lead screen during exposure
A basic difference between a radiography and a fluoroscopic image is:
the fluoroscopic image is a positive whereas the radiograph is a negative transparency
Which of the following factors will not materially influence the image density of a radiograph?
the size of the film
A 1,000 kVp X-ray machine used in conjunction with a lead foil screen has an approximate practical thickness limit of:
127 mm (5in) of steel or its equivalent
Because of geometrical factors such as source size, source-to-specimen distance, and specimen-to-film distance, there can be a lack of perfect sharpness at the edges of indications. The unsharpness caused by geometrical factors may be referred to as the:
penumbral shadow
Two factors which greatly affect the suitability of the target material in a X-ray tube are:
atomic number and melting point
The reason the exposure time must be increase by a factor of four when the source-to-film distance is doubled is that:
the intensity of radiation is inversely proportional to the square of the distance from the source to the film
The most important factor for determining the amount of X-ray absorpton of a specimen is the:
atomic number of the material
Which of the following technique variables is most commonly used to adjust suject contrast?
kilovoltage
Films that are left between lead screens too long in a high temperature and high humidity atmosphere may:
become fogged
The quantitative measure of film blackening is referred to as:
photographic density
a curve that relates density with the logarithm of exposure or of relative exposure is called:
an H&D curve
subject contrast is affected by:
a. thickness differences in specimen
b. radiation quality
c. scattered radiation
Which of the following instruments would exhibit the best sensitivity and most likely be used to detect small leaks in a radiation barrier?
a Geiger counter
At voltages above 400 kV, the use of lead to provide protection may present serious problems. If this is a serious problem, which of the following materials would most likely be used as a substitute?
concrete
A qualitative term often used to indicate the size of the smallest detail that can be seen in a radiograph is:
radiographic sensitivity
The slope (steepness) of a characteristic curve is a measure of:
film contrast
A special radiographic method requiring two radiographs taken during separate exposures from two different position to give the visual impression of a three-dimensional display when viewed in an optical device simultaneously is called:
stereoradiography
The depth of a discontinuity can be estimate by making two exposures on a single film from two different positions of the X-ray tube. The depth of the discontinuity is computed from the shift in the shadown of the discontinuity with respect to the images of fixed markers on the fron and back of the specimen. The method is called:
the parallax method of depth location
Constant agitation of the developer during the development process by means of machanical stirrers or circulating pumps may:
cause undesirable, preferential flow of the developer along certain paths
The activity of the fixer diminishes after being used for a period of time because the:
fixer solution accumulates soluble silver salts
In processing radiographs, the hourly flow of water in the wash tank should be:
4-8 times the volume of the tank
a zinc cadmium sulfide fluoroscopic screen that is continually exposed to bring daylight, sunlight, or other sources of ultraviolet radiation will:
become discolored and lose some of its brilliance
Increasing the X-ray or gamma ray energy will:
have little effect on the shape of a characteristic curve
As the development time increase:
the characteristic curve grows steeper and moves to the left
A distinctive characteristic of high-voltage radiography is that:
it is applicable to comparatively thick or highly absorbing specimens
Lead screens are used for almost all exposures when using:
high-voltage radiography
Which of the following glasses would most likely be used as an X-ray barrier window on fluoroscopic equipment?
lead glass
The maximum practical speed of scanning a test object for convertional fluoroscopic has been estimated to be about:
76 mm (3in) per s
When other operating conditions are held constant, a change in tube current causes a change in radiatino intensity emitted from an X-ray tube, the intensity being approximately proportional to tube current. What is the primary factor that prevents this from being exactly proportional?
the voltage and voltage waveform of an X-ray machine transformer varies with load
When viewing a radiograph, an image of the back of the cassette superimposed on the image of the specimen is noted. This is most likely due to:
backscatter
The half-value layer of lead for Co-60 is approximately 13mm (0.5in). If the radiation level on the source side of a 38 mm (1.5in) lead plate is 64 R/h, the radiation level on the opposite side is:
8 R/h
Which of the following is not a factor in determining subject contrast?
type of film used
Developer solution should be discarded when the quantity of replenisher added equals:
2-3 times the original quantity of developer
If a specimen is radiographer at 40 kV and again at 50 kV with time compensation to give the radiographs the same density, which of the following statements would be true?
the 50 kV exposure would have a lower contrast and a greater latitude than the 40 kV exposure
A 250 kVp X-ray machine used in conjunction with a lead foil screen has an approximate practical thickness limit of:
51 mm (2in) of steel or its equivalent
the degree of concentration of the radioactive material in a gamma ray source is referred to as the:
specific activity of the source
In million-volt radiography, filtration at the tube:
offers no improvement in radiographic quality
Film selection for an X-ray exposure depends on”
a. the thickness of the part
b. the material of the specimen
c. the voltage range of the X-ray machine
While using an X-ray tube for radiography, the operator wants to increase the radiation intensity. To do so, the:
tube current should increased
Lead screens are put in direct contact with film to:
a. increase the photographic action on the film
b. absorb the longer wavelength scattered radiation
c. intensify the photographic effect of primary
Because of geometrical factors such as source size, source-to-specimen distance, and specimen-to-film distance, there can be a lack of perfect sharpness at the edges of indications. the unsharpness caused by these factors may be called the:
penumbral shadow
The main purpose of the X-ray generator controls on the equipment is to:
enbale the operator to obtain the intensity, quality and duration of exposure desired
Fluoroscopic screen, as mounted and used, are easily damaged by which of the following?
exposure to ultraviolet radiation or sunlight
When X-ray, gamma rays, light, or electrons strike the photographic emulsion, a change takes place in the sliver halide crystals. This change is called:
latent image
If 3.7 GBq (1 Ci) of Ir-192 produces a dose rate of 5900 mR/h at 0.3m (1 ft), how many mR will 3700 GBq (10 Ci) produce at the same distance?
59,000
With respect to quality, what three factors must be considered in selecting a source-to-film distance?
source size, specimen thickness, geometric unsharpness
On a radiograph of a pipe weld, there is a very light irregularly-shaped small image in the weld. this image would most likely be due to the presence of:
tungsten incluison
A larger physical size source may produce an equivalent quality radiograph if:
the source-to-film distance is increased
- A light image of backing “B” on processed radiograph is probably caused by:
backscatter
Co-59 becomes Co-60 when it is placed in a nuclear reactor where it captures:
a neutron
When a faster speed film is substituted for a slower one to improve the economics of the exposure, which of the following conditions occur?
the image resolution will be reduced
FOr a given change in the radiation exposure, film contrast is the inherent ability to show:
adifference in density
The ability of a material to block or partially block the passage of X-rays and gamma rays is called:
absorption
Source size, specimen thickness, and source-to-specimen distance are the factors that determine the:
unsharpness recorded on the radiograph
The range of specimen thickness that can be adequately recorded on the radiograph is called:
latitude of the radiograph
Approximately how long would it take for a 370 GBq (10 Ci) Co-60 source to decay to 93 GBq (2.5 Ci)?
10.6 years
The “photoelectric” effect involves:
complete absorption of a photon
Radiographic undercutting is caused by:
side scatter
The developer solution is:
alkaline
a general rule governing the application of the geometric principles of shadow formation states that the:
central ray should be as nearly perpendicular to the film as possible to perserve spatial relationships
The half-life of radioactive Cs-137 is nearest to:
30 years
The slope of the H&D curve of a radiographic film is called:
gamma or gradient
The projected area of the target of the X-ray tube is called:
effective focal spot
The correct equation for determining geometric unsharpness UG is:
UG = ft/d
An exposure technique is established to obtain a 2.0 density using type “D” film and automatic processing at 27Deg C (81F). In order to obtain comparable results using manual processing at 20 deg C (68deg F) and 5-minute development time, it would be necessary for the original exposure time to be:
increased by approximately 99%
