Test examination

RPO THK-basic

Tag one of the four alternatives (a, b, c or d) for each of the multiple-choice questions. Only one answer is correct. For the open questions 41 and 42, the complete calculations must be attached.

The examination is based on the syllabus Radiation Protection Officer - dental radiology - basic, written by dr. F. Pleiter and dr. H.F. Boersma. You will find the correct answers here .

Complete the sentence: The number of electrons in an electrically neutral atom is equal to the...
1. atomic number
2. mass number
3. difference between mass number and atomic number
4. neutron number
What is characteristic X-radiation?
1. radiation that is emitted if an electron returns from one shell to a lower-energy shell
2. radiation that is emitted if an electron is decelerated
3. radiation that is emitted if an electron is accelerated
4. radiation that is emitted during the process of Compton effect
Complete the sentence: The probability of the photo-electric effect to occur...
1. increases if the atomic number of the material becomes larger
2. hardly depends on the atomic number of the material
3. increases if the photon energy becomes larger
4. hardly depends on the photon energy
During X-ray diagnostics, the workers wear personal protective clothing? Which of the following choices offers usually the best protection?
1. an apron with a thickness of 0.25 lead-equivalent without a thyroid collar
2. an apron with a thickness of 0.25 lead-equivalent and a thyroid collar
3. an apron with a thickness of 0.35 lead-equivalent without a thyroid collar
4. an apron with a thickness of 0.35 lead-equivalent and a thyroid collar
To answer the next question, you may use the transmission of X-radiation through plaster given in Figure C .
The tube voltage of an X-ray tube is 90 kV. How many mm plaster is needed to reduce the intensity of the X-ray beam by a factor of 50?
1. 190 mm
2. 150 mm
3. 120 mm
4. 100 mm
The tube voltage of an X-ray device is 70 kV. Each time an X-ray photo is taken, the dentist takes position behind a stone wall with a thickness of 10 cm, thus reducing his effective dose by a factor equal to the transmission of the wall. To answer the next question, you may use the transmission of X-radiation through stone given in Figure D .
What is the value of this transmission?
1. 0.01
2. 0.001
3. 0.0001
4. 0.000 01
Why is protection against X-radiation usually relatively simple?
1. because X-radiation usually can be shielded with a thin layer of lead
2. because the radiation weighting factor w_R for X-radiation is very small
3. because the dose rate of an X-ray machine is always very small
4. because the penetration depth of X-radiation into the body is very small
The voltage across the X-ray tube is reduced while the other settings of the X-ray apparatus remain unchanged.
Which of the following statements is correct?
1. the energy of the characteristic X-ray radiation increases
2. the energy of the characteristic X-ray radiation decreases
3. the energy of the characteristic X-ray radiation remains the same
4. the intensity of the emitted radiation remains the same
The half-value thickness is the amount of material needed to reduce the dose rate by a factor of two.
Which of the following properties holds for the radiation that is generated by an X-ray device?
1. the half-value thickness increases when the exposure time increases
2. the half-value thickness decreases when the exposure time increases
3. the half-value thickness of the primary beam is larger than the half-value thickness of the scattered beam
4. the half-value thickness of the primary beam is smaller than the half-value thickness of the scattered beam
Which of the following combinations of tube current and exposure time produces the largest output dose of an X-ray device, all other settings remaining the same?
1. 7 mA during 0.1 seconds
2. 6 mA during 0.2 seconds
3. 5 mA during 0.3 seconds
4. 4 mA during 0.4 seconds
In a radiation field, an energy of 2 joules is absorbed in an organ with a mass of 100 grams.
How big is the absorbed dose?
1. 50 Gy
2. 20 Gy
3. 0.05 Gy
4. 0.02 Gy
For which calculation is the tissue weighting factor w_T used?
1. the conversion of absorbed dose to equivalent dose
2. the conversion of equivalent dose to effective dose
3. both of the conversions named at [a] and [b]
4. none of the conversions named at [a] and [b]
Two of the six salivary glands receive each an equivalent dose of 3 mSv while an intra-oral X-ray picture is taken by the dentist. The tissue weighting factor of the salivary glands is w_salivary = 0.01.
What is the contribution of this exposure to the effective dose received by the patient?
1. 0.01 mSv
2. 0.03 mSv
3. 1 mSv
4. 3 mSv
Almost half of the radiation dose due to natural radiation in the Netherlands is caused by a single source.
Which is this radiation source?
1. radon
2. food
3. soil
4. cosmic radiation
What does the precise working of an ionization detection depend on?
1. the composition of the counting gas
2. the pressure of the counting gas
3. the dimensions of the detector
4. the voltage between anode en cathode
The grey shade describes the average brightness of a photo: an underexposed photo is too light and an overexposed photo is too dark.

The difference in grey shades of light and dark parts of an X-ray image is called contrast. If the contrast is extremely large, only the shades white and black show up. If the contrast is extremely small, the image shows only a single shade of grey.
In which way can one reduce the contrast of an X-ray photo?
1. by decreasing the voltage across the X-ray tube
2. by increasing the voltage across the X-ray tube
3. by decreasing the current through the X-ray tube
4. by increasing the current through the X-ray tube
The (extra) filter thickness is reduced. What is the consequence of this for an X-ray image?
1. the contrast increases
2. the contrast decreases
3. the skin dose decreases
4. the average grey shade decreases
An X-ray picture turns out to be overexposed. Only one thing in the protocol is altered. How can one ensure that the average grey shade of the next picture is smaller while the contrast remains the same?
1. increase the tube voltage
2. reduce the tube current
3. reduce the opening of the position indicating device
4. reduce the length of the position indicating device
Which type of tissue is most sensitive to ionizing radiation?
1. tissue that receives the largest dose
2. tissue with cells that divide quickly
3. tissue that is located in the abdominal region
4. tissue with cells that no longer divide
Which of the following effects of ionizing radiation occurs with a probability that is NOT proportional to the received radiation dose?
1. tissue reaction
2. stochastic effect
3. genetic effect
4. leukemia
Which of the following diseases can be regarded as a stochastic effect due to ionizing radiation?
1. reduction in the number of white blood corpuscles
2. leukemia
3. temporary sterility
4. permanent sterility
An unborn child receives an absorbed dose of 1 Gy during the first ten days after the conception.
What is the possible consequence of this irradiation?
1. prenatal death
2. death shortly after birth
3. a nonlethal effect such as a deformed organ or mental retardation
4. a tumor after birth
Complete the sentence: The risk of the annual dose due to natural radiation is comparable with the risk from...
1. less than 1 intra-oral photo
2. 1 - 100 intra-oral photos
3. 100 - 10 000 intra-oral photos
4. more than 10 000 intra-oral photos
What does the ALARA principle mean?
1. the application must be justified, which means that the benefits outweigh the disadvantages
2. preference for any alternative method in which no ionizing radiation is applied
3. no dose shall exceed the dose limits
4. the received dose must be kept as low as reasonably achievable
According to the Decree on Basic Safety Standards Radiation Protection, which is the annual limit for the effective dose of an exposed A-worker?
1. 100 μSv
2. 2 mSv
3. 20 mSv
4. 50 mSv
According to the Decree on Basic Safety Standards Radiation Protection, which is the annual limit for the equivalent dose on the lens of the eye of an exposed A-worker?
1. 20 mSv
2. 50 mSv
3. 150 mSv
4. 500 mSv
Complete the sentence: According to the Decree on Basic Safety Standards Radiation Protection, an area is classified as a supervised area if in this area it is possible to receive an annual effective dose that is...
1. higher than 1 mSv, but lower than 6 mSv
2. higher than 6 mSv, but lower than 10 mSv
3. higher than 10 mSv, but lower than 20 mSv
4. higher than 20 mSv
Does a risk inventory and evaluation (RI&E) always have to be carried out by the radiation protection officer?
1. yes
2. no, this may only be done by a radiation protection expert
3. no, this may only be done by a registered radiation protection expert
4. no, this may in principle be done by everyone
Complete the sentence: A cone-beam CT-scanner in the dental practice...
1. may be used without any restrictions
2. may be used without a radiation protection officer
3. must be registered with the ANVS
4. is subject to a license
According to the Decree on Basic Safety Standards Radiation Protection, an X-ray device must be checked regularly for proper operation.
What is here meant with "regularly"?
1. at least once a month
2. at least once in 6 months
3. at least once in 12 months
4. at least once in 24 months
Why must a medical diagnostic X-ray device be equipped with a position indicating device (PID)? Give the best and/or most complete answer.
1. to limit the distance between focus and skin
2. to limit the area exposed to the beam
3. for both reasons named at [a] and [b]
4. for another reason than the ones named at [a] and [b]
In order to comply with the specific justification for a cone-beam CT-scan, the dental surgeon asks his female patient about a possible pregnancy.
Complete the sentence: The question...
1. violates the General Regulation on Data Protection (AVG)
2. is justified if the question is relevant in the opinion of the dental surgeon
3. is understandable, but the question may not be asked under the Decree on Basic Safety Standards Radiation Protection
4. is justified because the surgeon must always ask this question according to the Decree on Basic Safety Standards Radiation Protection
The radiation protection officer has a number of tasks relating to practices with X-ray devices
What belongs to these tasks? Give the best and/or most complete answer.?
1. introducing new employees into the house rules
2. introducing new employees into the written instructions
3. introducing new employees into both the house rules and the written instructions
4. none of the tasks named at [a] and [b] because they are reserved to the radiation protection expert
For medical procedures, one nowadays uses a diagnostic reference level (DRL).
Complete the sentence: For medical procedures, ...
1. the dose for the patient should be lower than the DRL
2. the dose for the patient should be equal to the DRL
3. the dose for the patient should be higher than the DRL
4. the DRL is a means to apply ALARA
What is the largest contribution to the annual effective dose of the dentist due to his/her work?
1. direct radiation
2. scatter radiation
3. neither direct radiation nor scatter radiation
4. both direct radiation and scatter radiation
Which measure leads to the largest dose reduction for the dentist?
1. decrease the exposure time by a factor of 2
2. increase the distance to the radiation source by a factor of 2
3. decrease the exposure time by a factor of 2 AND ALSO increase the distance to the radiation source by a factor of 2
4. increase the distance to the radiation source by a factor of 3
A six month old child complains about sudden pain in the jaw. The mother brings the child to the clinic Dental Surgery where it is decided to take an OPT-recording of the jaw. Someone must keep the child on his or her lap.
Who is the first eligible?
1. the duty radiographer
2. a nurse practitioner
3. someone with a diploma "radiation protection officer"
4. the mother
The old position indicating device (PID) had a length of 30 cm and will be replaced by a new one with a length of 20 cm. In the old situation, the equivalent skin dose was 0.2 mSv. In answering the next questions, you may assume that the length of the PID is equal to the distance between focus and skin.
What is the equivalent skin dose with the new PID, for the same settings of the X-ray device?
1. 0.09 mSv
2. 0.13 mSv
3. 0.30 mSv
4. 0.45 mSv
Which combination of length and opening of the position indicating device gives rise to the largest amount of scatter radiation?
1. length = 20 cm and opening = 15 cm²
2. length = 30 cm and opening = 15 cm²
3. length = 20 cm and opening = 30cm²
4. length = 30 cm and opening = 30 cm²
An X-ray device is equipped with a 3 mm thick aluminum filter. To improve the contrast of the photo, the tube voltage is decreased from 90 kV to 70 kV. In order to obtain the same output dose from the tube, the mAs value has to be changed from the original 2.5 mA s to a new value. To answer the next question, you may use the data given in Figure A .
What is the new mAs value?
1. 1.0 mA s
2. 1.6 mA s
3. 4.0 mA s
4. 6.4 mA s
To answer questions 41 and 42, the full calculation must be given. You may use the data given in Figure A and Figure B .

tube voltage

90 kV

filter

3 mm aluminum

tube current

6 mA

exposure time

0.15 seconds

distance focus - skin

25 cm

tube voltage	90 kV
filter	3 mm aluminum
tube current	6 mA
exposure time	0.15 seconds
distance focus - skin	25 cm

Calculate the equivalent skin dose per X-ray photo using the data in the above table. (maximal 4 points)

the contribution of scatter radiation can be neglected
number of photos per year	2000
average tube voltage	70 kV
average mAs value	1.5 mA s per photo
filter	3 mm aluminum
distance focus - road	3 meters
thickness double glass	11 mm

A dental practice has an intra-oral X-ray device. For 50% of the photos, the X-ray beam is directed perpendicular to the window in the outer wall adjacent to the public road. Use also the data in the above table.

Check by means of calculation whether or not the shielding effect of the double glass in the window is sufficient to comply with the dose limit for the environment. (maximal 6 points)

Last modified:

28 September 2023 2.55 p.m.

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Test examination

To answer questions 41 and 42, the full calculation must be given. You may use the data given in Figure A and Figure B .