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. The open questions 41 and 42 are awarded the indicated maximal number of points if both derivation and answer are correct.

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

Complete the sentence correctly: The number of electrons in an electrically neutral atom is equal to the...
1. neutron number
2. atomic number
3. mass number
4. difference between mass number and atomic number
Complete the sentence corectly: Characteristic X-radiation arises...
1. if an electron returns from one shell to a lower-energy shell
2. if an electron is decelerated
3. if an electron is accelerated
4. during the process of Compton effect
Complete the sentence corectly: The probability of the photo-electric effect to occur...
1. hardly depends on the photon energy
2. hardly depends on the atomic number of the material
3. increases if the photon energy becomes higher
4. increases if the atomic number of the material becomes larger
During X-ray diagnostics, the X-ray technicians 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 and a thyroid collar
2. an apron with a thickness of 0.25 lead-equivalent without a thyroid collar
3. an apron with a thickness of 0.35 lead-equivalent and a thyroid collar
4. an apron with a thickness of 0.35 lead-equivalent without a thyroid collar
To answer the next question, you may use the transmission of X-radiation through plaster given in Figure A .
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. 100 mm
2. 120 mm
3. 150 mm
4. 190 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 B .
What is the transmission of the stone wall?
1. 0.000 01
2. 0.0001
3. 0.001
4. 0.01
Complete the sentence corectly: Protection against X-radiation usually relatively simple because...
1. the penetration depth of X-radiation into the body is very small
2. the radiation weighting factor w_R for X-radiation is very small
3. the dose rate of an X-ray device is always very small
4. X-radiation usually can be shielded with a thin layer of lead
Complete the sentence correctly: If one decreases the voltage across the tube while not changing the other settings of the X-ray device, then...
1. the energy of the characteristic X-ray radiation decreases
2. the energy of the characteristic X-ray radiation remains the same
3. the energy of the characteristic X-ray radiation increases
4. the yield of the X-ray tube remains the same
The half-value thickness is the amount of material needed to reduce the dose rate by a factor of two.
Which property holds for the radiation that is generated by an X ray device?
1. the half-value thickness of the primary beam is larger than the half-value thickness of the scattered beam
2. the half-value thickness of the primary beam is smaller than the half-value thickness of the scattered beam
3. the half-value thickness increases when the exposure time increases
4. the half-value thickness decreases when the exposure time increases
Which combination of tube current and exposure time produces the largest output dose of an X-ray device, all other settings remaining the same?
1. 4 mA during 0.4 seconds
2. 5 mA during 0.3 seconds
3. 6 mA during 0.2 seconds
4. 7 mA during 0.1 seconds
In an organ with a mass of 100 grams, an energy of 2 joules is deposited by X-rays.
How high is the absorbed dose in that organ?
1. 0.02 Gy
2. 0.05 Gy
3. 20 Gy
4. 50 Gy
Complete the sentence corectly: The tissue weighting factor w_T is used for the conversion from...
1. only equivalent dose to effective dose
2. only absorbed dose to equivalent dose
3. neither equivalent dose to effective dose nor absorbed dose to equivalent dose
4. both equivalent dose to effective dose and absorbed dose to equivalent dose
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 type of source.
Which type of radiation source is this?
1. soil
2. cosmic radiation
3. radon
4. food
What does the precise working of an ionization detection depend on?
1. the dimensions of the detector
2. the pressure of the counting gas
3. the composition of the counting gas
4. the voltage between anode and 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.

Only one setting of the X-ray device is changed. The other settings remain the same.
In which way can one reduce the contrast of an X-ray photo?
1. by increasing the voltage across the X-ray tube
2. by decreasing the voltage across the X-ray tube
3. by increasing the current through the X-ray tube
4. by decreasing the current through the X-ray tube
To make a specific X-ray image, the extra filter is removed, so that only the intrinsic filter remains. Tube voltage and mAs value remain unchanged.
What is the consequence of this for an X ray image?
1. the average grey shade decreases
2. the skin dose decreases
3. the contrast increases
4. the contrast 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. by increasing the tube voltage
2. by reducing the tube current
3. by reducinge the length of the position indicating device
4. by reducing the opening of the position indicating device
In which type of tissue are cells most sensitive to ionizing radiation?
1. tissue that receives the largest dose
2. tissue that is located in the abdominal region
3. tissue with cells that no longer divide
4. tissue with cells that divide quickly
Which effect of ionizing radiation occurs with a probability that is not proportional to the received radiation dose?
1. a genetic effect
2. a stochastic effect
3. a tissue reaction
4. leukemia
Which disease can be regarded as a stochastic effect due to ionizing radiation?
1. leukemia
2. permanent sterility
3. temporary sterility
4. reduction in the number of white blood corpuscles
An unborn child receives an absorbed dose of 0.5 Gy during the first ten days after the conception.
What is the possible consequence of this irradiation?
1. a tumor in later life
2. malformation of an organ
3. death shortly after birth
4. prenatal death
The average effective dose in the Netherlands due to background radiation is about 4 μSv per day.
Complete the sentence correctly: The risk of this is comparable with the risk from...
1. 1 intra-oral photo or less
2. 1 - 100 intra-oral photos
3. 100 - 10 000 intra-oral photos
4. 10 000 intra-oral photos or more
What does the ALARA principle mean?
1. preference for any alternative method in which no ionizing radiation is applied
2. the received dose must be kept as low as reasonably achievable
3. the application must be justified, which means that the benefits outweigh the disadvantages
4. no dose limit shall be violated
According to the Decree on Basic Safety Standards Radiation Protection, which is the annual limit for the effective dose of an exposed category-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 category-A worker?
1. 20 mSv
2. 50 mSv
3. 150 mSv
4. 500 mSv
According to the Decree on Basic Safety Standards Radiation Protection, an area in which ionizing radiation is applied must be designated as a supervised or controlled area. The criterion for this is the maximum effective annual dose that may be received in this area.
What criterion must the effective annual dose in a supervised area meet?
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 registered radiation protection expert
3. no, this may only be done by radiation protection experts
4. no, this may in principle be done by everyone
There is no other X-ray device in the dental office besides a cone-beam CT-scanner.
Complete the sentence correctly: This cone-beam CT-scanner...
1. may be used without any restrictions
2. is subject to a license
3. may be used without a radiation protection officer
4. must be registered with the ANVS
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
According to the Regulation Basic Safety Standards Radiation Protection, a diagnostic X-ray device in the dental practice must be equipped with a position indicating device (PID).
What does one want to limit with the PID?
1. only the area exposed to the beam
2. only the distance between focus and skin
3. neither the area exposed to the beam nor the distance between focus and skin
4. both the area exposed to the beam and the distance between focus and skin
In order to comply with the specific justification for a cone-beam CT-scan, the oral surgeon asks his female patient about a possible pregnancy.
Complete the sentence correctly: In order to comply with the individual justification, this question is...
1. understandable, but was not necessary if it is irrelevant in the opinion of the oral surgeon
2. understandable, but may not be asked under the Decree on Basic Safety Standards Radiation Protection
3. in violation of the General Regulation on Data Protection (AVG)
4. justified because it must always been asked under the Decree on Basic Safety Standards Radiation Protection
Consider the following two instructions to new employees:
Instruction I: Introducton into the house rules.
Instruction II: Introduction into the written instructions.
Which instruction belongs and which does not belong to the duties of the radiation protection officer?
1. instruction I and instruction II are both duties
2. neither instruction I nor instruction II are duties
3. instruction I is not to a duty, but instruction II is
4. instruction I is a duty, but instruction II is not
For a medical procedure, one often uses a diagnostic reference level (DRL).
Complete the sentence correctly: For medical procedures, ...
1. the DRL is a means to apply ALARA
2. the dose for the patient should be higher than the DRL
3. the dose for the patient should be lower than the DRL
4. the dose for the patient should be about equal to the DRL
Complete the sentence corectly: The annual effective dose of the dentist due to his/her work is almost entirely determined by...
1. direct radiation
2. scattered radiation
3. neither direct nor scattered radiation
4. both direct and scattered radiation
Which measure leads to the largest dose reduction for the dentist?
1. increase the distance to the radiation source by a factor of 2
2. increase the distance to the radiation source by a factor of 3
3. decrease the exposure time by a factor of 2
4. decrease the exposure time by a factor of 2 and also increase the distance to the radiation source by a factor of 2
A six month old child complains about sudden pain in the jaw. The mother brings the child to the clinic Oral and Maxillofacial 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. the mother
3. a nurse practitioner
4. someone with a diploma Radiation Protection Officer
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. It may be assumed here 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. about 0.09 mSv
2. about 0.13 mSv
3. about 0.30 mSv
4. about 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 = 20 cm and opening = 30cm²
3. length = 30 cm and opening = 15 cm²
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 C .

What is the correcty new mAs value?

about 1.0 mA·s
about 1.6 mA·s
about 4.0 mA·s
about 6.4 mA·s

To answer questions 41 and 42, the full calculation must be given. Clearly indicate the calculation method and/or reasoning you use to arrive at the solution. Always state the quantities and units used.

Data for question 41
tube voltage	90 kV
filter	3 mm aluminum
tube current	6 mA
exposure time	0.15 seconds
yield of X-ray tube	see Figure C
distance focus - skin	25 cm

An X-ray image is taken in the Oral Surgery department.

Calculate the equivalent skin dose per X-ray photo.
(maximal 4 points)

Data for question 42
number of photos per year	2000
average tube voltage	70 kV
average mAs value	1.5 mA·s per photo
filter	3 mm aluminum
yield of X-ray tube	see Figure C
distance focus - road	3 meters
thickness double glass	11 mm
transmission of glass	see Figure D
the contribution of scatter radiation can be neglected

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.

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:12 December 2025 1.01 p.m.

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Test examination

To answer questions 41 and 42, the full calculation must be given. Clearly indicate the calculation method and/or reasoning you use to arrive at the solution. Always state the quantities and units used.

Data for question 41

Data for question 42