An obese patient needs an AP abdomen. The first image at 80 kVp and 40 mAs with a grid is underexposed with high noise. What is the best change?

Increase kVp to about 90 and keep a suitable mAs

Remove the grid and halve the mAs

Which of the following digital image display errors is corrected by changing the window width, not by repeating the exposure?

Image contrast that looks too flat

Which change would decrease patient dose while keeping receptor exposure the same?

Raising the kVp and reducing the mAs

Lowering the kVp and raising the mAs

Daily mobile AP chest radiographs are taken on an intensive care patient to follow heart size and the position of lines and tubes. Why should the same SID and patient position be used each day?

It keeps magnification constant, so changes in heart size are real

It removes the magnification of the heart seen on AP projections

It keeps the exposure index the same whatever the patient's condition

It keeps the entrance dose identical, the main aim of follow-up films

Exposure factors and image quality

50 Gulf Prometric Radiographer (DHA, DOH, MOH, SCFHS, QCHP) practice questions on Exposure factors and image quality, part of Radiography and Positioning. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Hard
An obese patient needs an AP abdomen. The first image at 80 kVp and 40 mAs with a grid is underexposed with high noise. What is the best change?
1. AIncrease kVp to about 90 and keep a suitable mAs
2. BRemove the grid and halve the mAs
3. CUse the small focal spot
4. DReduce the SID to 70 cm
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Answer: A · Increase kVp to about 90 and keep a suitable mAs
A thick abdomen needs more penetration and the photon count at the detector is low, causing quantum noise. Raising the kVp improves penetration and reduces noise, with the mAs adjusted. Removing the grid increases scatter fog, and a short SID would cause magnification and grid cutoff.
- B: Removing the grid and halving mAs makes noise worse and adds scatter.
- C: The small focal spot has less heat capacity and is not the cure.
- D: A short SID gives magnification and cutoff and does not help penetration.
Remember this
A thick abdomen needs more penetration and the photon count at the detector is low, causing quantum noise.
Question 2 · Medium
Which of the following digital image display errors is corrected by changing the window width, not by repeating the exposure?
1. AImage contrast that looks too flat
2. BSevere patient motion
3. CUnderexposure with heavy noise
4. DA foreign object in the field
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Answer: A · Image contrast that looks too flat
Window width adjusts the displayed contrast, and window level adjusts brightness; both are postprocessing steps. Motion, foreign bodies and quantum noise from low exposure are acquisition problems and cannot be fixed after the fact. Repeats are justified only for these.
- B: Motion blur cannot be removed by display changes.
- C: Heavy noise from underexposure remains.
- D: A foreign object needs the image to be repeated if it obscures the anatomy.
Remember this
Window width adjusts the displayed contrast, and window level adjusts brightness; both are postprocessing steps.
Question 3 · Medium
Which change would decrease patient dose while keeping receptor exposure the same?
1. ALowering the kVp and raising the mAs
2. BRemoving the filtration
3. COpening the collimators fully
4. DRaising the kVp and reducing the mAs
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Answer: D · Raising the kVp and reducing the mAs
A higher kVp penetrates tissue better so fewer photons are absorbed in the patient; the mAs can be lowered, but contrast also falls. Lower kVp with more mAs increases skin dose. Filtration and collimation should never be removed.
- A: That change raises patient dose.
- B: Removing filtration lets low-energy photons add to skin dose.
- C: A wide collimation increases the irradiated volume and scatter.
Remember this
A higher kVp penetrates tissue better so fewer photons are absorbed in the patient; the mAs can be lowered, but contrast also falls.
Question 4 · Medium
Which term describes the range of exposures that a digital detector can record and still produce a useful image?
1. ADynamic range
2. BPixel pitch
3. CModulation transfer
4. DSpatial frequency
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Answer: A · Dynamic range
Dynamic range is the span between the lowest and highest exposures the detector responds to. Digital systems have a wide range, which gives forgiveness in technique but can hide overexposure. Film had a narrow latitude.
- B: Pixel pitch is the spacing of detector elements.
- C: Modulation transfer function describes resolution performance.
- D: Spatial frequency describes detail size, not exposure range.
Remember this
Dynamic range is the span between the lowest and highest exposures the detector responds to.
Question 5 · Medium
Daily mobile AP chest radiographs are taken on an intensive care patient to follow heart size and the position of lines and tubes. Why should the same SID and patient position be used each day?
1. AIt removes the magnification of the heart seen on AP projections
2. BIt keeps magnification constant, so changes in heart size are real
3. CIt keeps the exposure index the same whatever the patient's condition
4. DIt keeps the entrance dose identical, the main aim of follow-up films
Show answerHide answer
Answer: B · It keeps magnification constant, so changes in heart size are real
Magnification depends on the SID and on how far the heart lies from the receptor. If both are kept the same, any change in the cardiac outline or in line position between films reflects the patient, not the geometry. An AP film is still magnified, but by the same amount each day, and the SID is recorded on the image.
- A: An AP chest at 100 cm is still magnified; a constant SID makes it consistent, not removed.
- C: The exposure index also depends on patient size, fluid and exposure factors, not on SID alone.
- D: Dose consistency is welcome, but the main aim is comparable images for diagnosis.
Remember this
Constant SID and position on serial mobile chests make the films comparable.
Question 6 · Easy
A radiographer plans an AP lumbar spine on an adult. Above what part thickness is a grid generally used?
1. AAbout 4 cm
2. BAbout 30 cm
3. CAbout 20 cm
4. DAbout 10 cm
Answer and explanation in LearnFree account
Question 7 · Medium
A radiographer needs to image a thick abdomen. Which is the main purpose of collimating tightly before using a grid?
1. ATo increase the anode heel effect across the field
2. BTo enlarge the effective focal spot on the target
3. CTo make the generator raise the kVp automatically
4. DTo reduce the scatter produced in the patient
Answer and explanation in LearnFree account
Question 8 · Easy
Which change to the X-ray tube gives the best spatial resolution of a small hand bone?
1. ASelecting the small focal spot
2. BUsing a longer exposure time with the same kVp
3. CSelecting the large focal spot
4. DIncreasing the tube current only
Answer and explanation in LearnFree account
Question 9 · Easy
Which exposure factor mainly controls the quantity of x-rays reaching the image receptor, without altering their penetrating power?
1. AmAs
2. BAdded filtration
3. CGrid ratio
4. DkVp
Answer and explanation in LearnFree account
Question 10 · Hard
A fingertip exam at 100 cm SID has an OID of 5 cm and a focal spot of 1.0 mm. What is the approximate penumbra (geometric unsharpness)?
1. A0.05 mm
2. B1.0 mm
3. C0.5 cm
4. D0.5 mm
Answer and explanation in LearnFree account
Question 11 · Medium
A radiographer uses a focused grid with a 100 to 120 cm focal range but performs the exposure at 180 cm SID. What is the expected image result?
1. ALoss of density at the periphery of the image
2. BLoss of density at the centre only
3. CAn increase in contrast with no density loss
4. DGrid lines that are visible as dots
Answer and explanation in LearnFree account
Question 12 · Easy
In digital radiography, the exposure indicator (EI) tells the radiographer about:
1. AThe kVp that the generator delivered
2. BThe amount of radiation that reached the detector
3. CThe age of the detector panel
4. DThe dose absorbed by the patient's skin
Answer and explanation in LearnFree account
Question 13 · Medium
An erect abdomen is shot with a 12:1 grid and the image shows no cutoff, but there is a visible vertical line pattern that looks like a fine mesh. The grid is stationary and the CR reader scans at a similar frequency. This is called:
1. AGhost image
2. BHeel effect
3. CMoire pattern
4. DQuantum mottle
Answer and explanation in LearnFree account
Question 14 · Medium
A mobile AP chest is taken with a 10:1 linear grid whose strips run head to foot. The image shows a lower receptor exposure than usual across the whole field, with no extra fall-off at the edges. The usual exposure factors, SID and centring were used, but the tube had been tilted 15 degrees toward the patient's left to clear a drip stand. What is the most likely cause?
1. AAn upside-down focused grid, with its tube side facing down
2. BOff-focus cutoff, from an SID outside the grid's focal range
3. COff-level cutoff, because the tilt runs across the grid strips
4. DOff-centre cutoff, from lateral decentring of the tube
Answer and explanation in LearnFree account
Question 15 · Medium
On a DR image of the foot, a bright halo appears around a lead marker on the detector. This is best explained as:
1. AQuantum noise from a very low mAs exposure
2. BEdge-enhancement halo at a sharp density change
3. CMoire interference from a stationary grid in the holder
4. DHeel effect from the anode angle of the tube
Answer and explanation in LearnFree account
Question 16 · Hard
A DR detector has a pixel pitch of 0.143 mm. What is its approximate maximum (Nyquist) spatial resolution?
1. AAbout 3.5 lp/mm
2. BAbout 7.0 lp/mm
3. CAbout 1.4 lp/mm
4. DAbout 0.29 lp/mm
Answer and explanation in LearnFree account
Question 17 · Medium
An AP foot is to be taken. The toes are much thinner than the tarsal region and often appear too dark. Which device gives a more even exposure across the foot?
1. AA wedge filter with its thick end over the tarsals
2. BA higher-ratio grid placed under the whole foot
3. CA wedge filter with its thick end over the toes
4. DA larger focal spot to spread the exposure
Answer and explanation in LearnFree account
Question 18 · Easy
On a standard X-ray tube, the intensity of the beam is greatest toward which side because of the anode heel effect?
1. AThe centre only
2. BThe collimator side
3. CThe cathode side
4. DThe anode side
Answer and explanation in LearnFree account
Question 19 · Medium
A large focal spot is chosen for a lumbar spine radiograph and the resulting image shows reduced edge sharpness. The main reason is that a larger focal spot increases the:
1. AGrid cutoff at the edges
2. BGeometric unsharpness (penumbra)
3. CSubject contrast between the tissues
4. DScatter fraction in the beam
Answer and explanation in LearnFree account
Question 20 · Medium
To reduce magnification and edge unsharpness of the heart on a chest radiograph, the standard method is:
1. AIncrease the OID by using AP
2. BUse a large focal spot
3. CUse a short SID of about 100 cm
4. DUse a long SID of about 180 cm
Answer and explanation in LearnFree account
Question 21 · Medium
A technologist wants more contrast between bone and soft tissue on a radiograph of the ankle. Which technique change is correct?
1. AUse a larger focal spot
2. BLower the kVp and raise the mAs to compensate
3. CUse a longer SID only
4. DRaise the kVp and lower the mAs
Answer and explanation in LearnFree account
Question 22 · Hard
A technique of 70 kVp and 20 mAs gives an ideal image. To lower patient dose, a radiographer raises the kVp by 15%, to about 80 kVp. By the 15% rule, what mAs keeps the receptor exposure?
1. A10 mAs
2. B15 mAs
3. C40 mAs
4. D5 mAs
Answer and explanation in LearnFree account
Question 23 · Easy
In computed radiography, how is the imaging plate cleared of the residual latent image after it has been read?
1. ABy heating the plate in a drying unit
2. BBy washing in a chemical bath
3. CBy a second low-dose X-ray exposure
4. DBy exposure to intense white light
Answer and explanation in LearnFree account
Question 24 · Hard
A focused grid is placed upside down for a PA chest. The central part of the film looks acceptable, but both lateral edges show a marked loss of density. What explains this?
1. AThe reversed strips absorb primary rays at the edges
2. BThe tube was centred off the grid midline
3. CThe central ray was angled across the lead strips
4. DThe SID used was shorter than the focal range of the grid
Answer and explanation in LearnFree account
Question 25 · Easy
Which exposure factor setting produces a short-scale (high) radiographic contrast?
1. ALow kVp
2. BHigh kVp
3. CHigh mAs only
4. DLarge focal spot
Answer and explanation in LearnFree account

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Exposure factors and image quality

An obese patient needs an AP abdomen. The first image at 80 kVp and 40 mAs with a grid is underexposed with high noise. What is the best change?

Which of the following digital image display errors is corrected by changing the window width, not by repeating the exposure?

Which change would decrease patient dose while keeping receptor exposure the same?

Which term describes the range of exposures that a digital detector can record and still produce a useful image?

Daily mobile AP chest radiographs are taken on an intensive care patient to follow heart size and the position of lines and tubes. Why should the same SID and patient position be used each day?

A radiographer plans an AP lumbar spine on an adult. Above what part thickness is a grid generally used?

A radiographer needs to image a thick abdomen. Which is the main purpose of collimating tightly before using a grid?

Which change to the X-ray tube gives the best spatial resolution of a small hand bone?

Which exposure factor mainly controls the quantity of x-rays reaching the image receptor, without altering their penetrating power?

A fingertip exam at 100 cm SID has an OID of 5 cm and a focal spot of 1.0 mm. What is the approximate penumbra (geometric unsharpness)?

A radiographer uses a focused grid with a 100 to 120 cm focal range but performs the exposure at 180 cm SID. What is the expected image result?

In digital radiography, the exposure indicator (EI) tells the radiographer about:

An erect abdomen is shot with a 12:1 grid and the image shows no cutoff, but there is a visible vertical line pattern that looks like a fine mesh. The grid is stationary and the CR reader scans at a similar frequency. This is called:

On a DR image of the foot, a bright halo appears around a lead marker on the detector. This is best explained as:

A DR detector has a pixel pitch of 0.143 mm. What is its approximate maximum (Nyquist) spatial resolution?

An AP foot is to be taken. The toes are much thinner than the tarsal region and often appear too dark. Which device gives a more even exposure across the foot?

On a standard X-ray tube, the intensity of the beam is greatest toward which side because of the anode heel effect?

A large focal spot is chosen for a lumbar spine radiograph and the resulting image shows reduced edge sharpness. The main reason is that a larger focal spot increases the:

To reduce magnification and edge unsharpness of the heart on a chest radiograph, the standard method is:

A technologist wants more contrast between bone and soft tissue on a radiograph of the ankle. Which technique change is correct?

A technique of 70 kVp and 20 mAs gives an ideal image. To lower patient dose, a radiographer raises the kVp by 15%, to about 80 kVp. By the 15% rule, what mAs keeps the receptor exposure?

In computed radiography, how is the imaging plate cleared of the residual latent image after it has been read?

A focused grid is placed upside down for a PA chest. The central part of the film looks acceptable, but both lateral edges show a marked loss of density. What explains this?

Which exposure factor setting produces a short-scale (high) radiographic contrast?