midterms Flashcards
Cassettes may vary because of screens of different manufacture, age, or front panel materials. If there is any doubt or question as to the equality of radiographic speeds among cassettes or screens, the following simple test should be performed.
Test for Assessing the Speed of Film and Film-Screen Combination
Equipment: Speed of Film and Film-Screen Combination
- cassettes (of the same size)
- Unexposed films
- Densitometer
Procedure
- Procedure: Place no more than four cassettes, preferably all the same size, on the x-ray table with the corners touching.
- One of the four should be a known standard cassette/screen combination.
- All cassettes should be loaded with film from the same box.
- The x-ray tube is centered perpendicular to the intersection of the four cassettes and an exposure made which will produce a film density between ____
0.8 to 1.5
Evaluation
- For the speed test, compare the resulting densities on the four processed test films close to the central ray.
- Visual densities should be the same.
- If a densitometer is used to compare densities the maximum density variation should be ____
plus or minus 0.2
The light-tightness of the darkroom is important because a non-insulated darkroom can ruin all the films in a department or significantly degrade their quality.
Test for DR Fog and Safelight
Possible Sources of DR fog
- Safelight filters (old or compromised)
- Safelight housing
- Safelight too close to work area
- Light bulb of incorrect wattage or type
- Ancillary indicator lights on processor
- Timers
- Radios
- Fluorescent light afterglow
- Light leaks
- Suspended ceilings
- Any place there is a hole cut in the wall
- Excessive ambient light through the tinted viewing windows of daylight loading systems
Frequency: Test for DR Fog and Safelight
- Semi-annually
- When a fault in the light-tightness of the darkroom is suspected.
- After a bulb or filter replacement
- After changing or adding types of film
Equipment: Test for DR Fog and Safelight
- most sensitive film available (the film with the highest speed)
- Cardboard box
- Six coins
- Watch
- Lead sheet
Visual inspection:
- Step into the darkroom.
- Shade the windows, if any, and make the darkroom light-tight as usual.
- Turn off all the lights in the darkroom, including the safelight.
- Allow sufficient time (approximately ____) for your eyes to adjust to the low light conditions.
- Check for any spots letting white light into the room through the doors, processor, film exchange boxes, extractors or ceiling.
5 min
Qualitative Measurement
- Load a film into a cassette.
- Always use a new package of films because a package opened earlier may be already foggy.
- Expose half of the film to x-rays, choosing exposure settings to obtain an optical density of ___
- The other half of the film may either be covered by a lead sheet or the film could be cut into half to observe the differences.
- Place the sensitized film on a workbench in the darkroom.
1 (sensitization exposure)
Next Procedure
- Place the six coins at approximately the same distance from each other along the longer side of the film.
- Use cardboard to cover the area of the film containing five of the coins. Wait for ___ and move the cardboard to reveal one more coin.
- Repeat until the film and all coins are completely uncovered.
- When the last ___ have elapsed and none of the coins is covered, process the film.
- Repeat steps (1 to 6) to test with any safelight illumination used.
30 s
Baseline Tolerances: Test for DR Fog and Safelight
No coins should be visible on the film
Corrective Actions: Test for DR Fog and Safelight
- The darkroom should be insulated against stray light and the safelight should be checked to ensure that it is not leaking white light.
- If needed, replace the filter of the safelight and check the power rating of the bulbs
Film should only be handled in correct safelight conditions. White light should not be allowed to leak into the darkroom.
White Light Fogging Test
Frequency of White Light Fogging Test
- Semi-annually
- As needed
Equipment: White Light Fogging Test
- 1 unexposed film
- 1 cardboard (same size with the film)
Procedure White Light Fogging
- Turn on all the lights in areas adjacent to darkroom.
- Switch off darkroom lights including safelights.
- Ensure that any doors are closed.
- Place the sheet of film on the workbench.
- Cover half of the film with the sheet of card.
- Leave for ___. Process the film.
3 minutes
Evaluation: White Light Fogging Test
- If the density of the uncovered part of the film is greater than the covered part, then some fogging has occurred.
Action: White Light Fogging Test
- Seal any areas of light leakage.
- Repeat the white light leakage test. File a report.
A darkroom should be fitted with appropriate safelighting.
Safelight Efficiency Test
Frequency: Safelight Efficiency Test
Semi-annually or annually
Equipment: Safelight Efficiency Test
- 1 unexposed film
- 2 cardboards (same size with the film)
- Timer
- 1 sheet of lead or lead rubber (same size)
Procedure: Safelight Efficiency Test
- Place cassette face up on the X-ray
table.
- Set a FFD (SID) of ___. Cover one third of the cassette with lead rubber, lengthways (area C).
- Collimate to the uncovered area of the cassette.
- Expose the film using a minimum exposure (suggested exposure ____.)
100 cm
45 kV 2 mAs
Procedure: Safelight Efficiency Test
- Unload the cassette in the darkroom in total darkness.
- Place the film on the workbench.
- Cover one third of the exposed side of the film with the sheet of card, lengthways (area A).
- Cover areas B and C of the film, horizontally, with the second sheet of card, except for a ___ strip at the top.
3cm
Procedure: Safelight Efficiency Test
- Switch on the safelights.
- Start clock immediately.
- Wait __ seconds.
- Move second sheet of card down 3 cm (the first sheet of card must remain in place throughout). Wait __ seconds.
- Repeat this process every __ seconds until the bottom of the film is reached.
- Switch off the safelights immediately.
- Process the film.
30 seconds
Section A
Sensitized by radiation; not exposed to safelights.
Section B
Sensitized by radiation; exposed to safelights in 8 strips varying in length of exposure from 30 seconds to 4 minutes
Section C
Not sensitized by radiation; exposed to safelights in 8 strips varying in length of exposure from 30 seconds to 4 minutes
Identify the strip in Section B which has a noticeable increase in density compared to its equivalent strip in Section C. Double check by comparing B with A. Note the safelight exposure time of this strip. This exposure is the extreme limit of film handling time. ____ considered to be the limit of the acceptable film handling
3 minutes
Action: Safelight Efficiency Test
- If the identified safe handling time is considered to be too short, consider one or more of the following modifications:
a. Increase the safelight height above the workbench.
b. Reduce wattage of the bulb.
c. Replace filter.
d. Stop white light leak from safelight.
e. Remove one safelight, if more than one. - Re-test after modification.
- File a report.
To ensure viewboxes are clean and light levels are kept consistent throughout. A difference in luminance can create confusion and may affet accurate interpretations.
CLEANING AND INSPECTING THE VIEWBOXES
Suggested performance criteria
Viewbox lights are the same color and luminance, and viewbox surfaces are kept clean.
Frequency: Cleaning viewbox
monthly
Equipment: Cleaning viewbox
Glass cleaning supplies
Steps
- Clean surface of viewbox.
- If a bulb or tube fails, it is best to ____
- Record results
replace all of them
- The film viewer box should produce uniform light to illuminate the films.
- Inhomogeneous white light or flickering from the film viewer box might impact clinical evaluation of the films.
- Nonuniformity of radiographic illuminator brightness most commonly occurs when bulbs are replaced without regard for matching their color or intensity, and when output of the lamps change with age.
TEST FOR ILLUMINATOR BRIGHTNESS AND CONSISTENCY
Undesirable radiographic viewing conditions include:
- Low intensity illuminators
- High ambient room-light levels
- Gross mismatch between viewing conditions used by the radiologist and viewing conditions used by technologists to check films.
- Illuminators in the same viewing area having grossly mismatched intensities and/or color.
Frequency: TEST FOR ILLUMINATOR BRIGHTNESS AND CONSISTENCY
quarterly
Equipment: TEST FOR ILLUMINATOR BRIGHTNESS AND CONSISTENCY
optical photometer calibrated for luminance measurements (in cd/m²) is required for this test.
Procedure
- Clean the viewer box and note any faulty or flickering lights inside.
- Hold the photometer and measure the luminance of the film viewer at approximately ___ from the box on a ____ area
- Record the measured values and then repeat the previous step as many times as necessary to cover the whole area of the x-ray film viewer box.
15 cm from the box on a 15 cm x 15 cm square area
The homogeneity of the brightness should be evaluated by calculating the mean brightness of the sampled areas. This method may also be used to make a
comparison of viewer boxes at the department.
Baseline Tolerances Illumination
- The brightness should be ____ around the average of the measured values of the viewer box.
- No flickering or other artifacts should be observable.
- The baseline value for the average should be measured at commissioning (or soon after it). The typical value of luminance is usually in the range of ____
- However, to evaluate whether the viewing conditions are acceptable, the ambient lighting should also be evaluated.
- plus or minus 20%
- several thousand candelas per square meter
Corrective Action: TEST FOR ILLUMINATOR BRIGHTNESS AND CONSISTENCY
- If the lights flicker or some of them are dim, a technician should _____
- If the average value is significantly lower than the measured value at commissioning, then the glass or plastic plate in front of the lights should be _____
- replace them and check the power supply and the electronics.
- thoroughly cleaned or replaced.
Things to be considered in setting up image quality standards:
- Evidence of proper collimation on all sides of the radiograph
- Evidence of the use of a gonadal shield when appropriate
- Image density and contrast appropriate for the visualization of the anatomy of interest
- Absence of image degradation due to patient motion or artifacts due to poor film processing, old screens, etc.
- Adequate display of anatomy of interest for examination
- Evidence of markers to properly identify the patient’ s left and right anatomy, hospital name, patient number, date, etc.
- One of the main goals of a quality control program is to reduce the number of poor and reject radiographs and to increase the number of good quality radiographs.
- Periodic film analysis determines the problems and analyzes the causes leading to poor and reject radiographs.
RADIGRAPHIC FILM ANALYSIS
Benefits of a film analysis
- identify the main errors and put measures in place to reduce them.
- save money by reducing wastage.
- reduce radiation dose by minimizing the number of repeat films.
- save time and effort by reducing the number of repeat films.
- provide ongoing data for comparison.
- provide possible source of statistics to support claims for more funding to replace, modify, or repair faulty equipment.
Potential Problems Film Analysis
- Staff members do not cooperate fully.
- Radiologist and clinicians tend to retain substandard films on the grounds that they provide some information.
- Reject film records are not always kept up to date.
Frequency of Film Analysis
Monthly basis
Analysis Film Analysis
- Study the data. Compare current data with that of previous programs.
- A reject rate of ____ should be considered unacceptable.
- A reject rate of ____ justifies continued monitoring
10% or more
5% to 10%
