1.0 INTRODUCTION:

In our today’s country, radiation protection has turned out to be one of

the most alarming issues in majority of our radiological diagnostic centres.

Though radiography is gaining wide acceptance in nearly all part of the

continent, it is equally important that the radiation protection of staffs and

patients is taken into consideration and this is the sole responsibility of the

radiographer operating the x-ray equipment. For this reason, quality control

was considered one of the tools in optimizing best practice in the area of

radiation protection of both the patient and the staff and also in maintaining

the production of consistently high-quality diagnostic radiographs. (Martin,

2007).

According to ICRP (1991), there are two basic principles of radiological

protection. There are; justification of the practice and optimization of

protection. In the area of optimization of protection, there is considerable

scope for reducing doses to patient without any loss of diagnostic

information, but the extent to which the measures available are used varies

widely. Optimization of radiation protection does not necessarily mean the

reduction of doses to the patient or by operating in the absence of a

demonstrable threshold for stochastic effects but by trade-off between the

benefits of dose reduction and the costs of achieving these reductions. A

number of factors facilitate this trade-off. One of such factors is the quality

control measurements and practices of the department. (Saure and

Hagemann, 1995).

This quality control as noted by Maccia and Moores (1997), involves a

quantitative and qualitative measurements and test of the performance of x-

ray equipments, programs and practices of that diagnostic centre. Hence, in

instituting a good quality control system in our x-ray department, a quality

control program which will monitor the basic components of the imaging

process at a low cost through the use of simple, inexpensive tools and

minimal staff time must be put in place. This quality control will now

determine their adequacy in terms of production of high-quality diagnostic

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radiographs and also evaluates their contribution to all the radiation

protection practices therefore outlining their role in the optimization of the

radiation protection of that centre.

2.0 DEFINITION OF TERMS

Quality Control (QC): These are specific actions designed to keep

measurable aspects of the process involved in manufacturing a product or

providing a service within specified limits. These actions typically involve

measurement of a process variable, checking the measured value against a

limit, and performing corrective action if the limit is exceeded. (CRCPD Pub.,

2001).

Quality Assurance (QA): These are planned and systematic actions that

provide adequate confidence that a diagnostic x-ray facility will produce

consistently high quality images with minimum exposure of the patients and

healing arts personnel. The determination of what constitutes high quality

will be made by the facility producing the images. Quality assurance actions

include both quality control techniques and quality administration

procedures. (CRCPD Pub., 2001).

Quality Control Program: allows a facility with limited resources and

personnel to monitor the basic components of the imaging process at a low

cost through the use of simple, inexpensive tools and minimal staff time.

Quality Assurance Program: Is an organized entity designed to provide

quality assurance for a diagnostic radiology facility. The nature and extent of

this program will vary with the size and type of the facility, the type of

examinations conducted, and other factors. (CRCPD Pub., 2001).

Optimization: Optimization in the field of diagnostic radiology simply

means any process or procedure which ensures that doses due to

appropriate medical exposure for radiological purposes are kept as low as

reasonably achievable (ALARA) consistent with obtaining the required

diagnostic information, taking into account economic and social factors.

(IAEA Pub., 2004).

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Cost-Effectiveness: Chesney (1981) defined Cost-Effectiveness as “the

ratio of spending to the efficiency of production that follows the result”. It

compares the relative expenditure (costs) and outcome (effects) of two or

more courses of action.

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3.0 AIMS AND OBJECTIVES:

The main aim and objective of this colloquium is to promote awareness

creation about the practical implementation of quality control protocols and

image quality evaluation by consistently implementing simple and

inexpensive actions such as the use of appropriate screen/film combination,

use of secondary radiation grids when necessary, etc.

It also aims to create pools of expertise in the area of radiation

protection of patients, hence alleviating the dangerous practices of

unnecessary irradiation of our patients.

A further objective of this research seminar is to offer assistance and

guidance to an imaging scientist implementing and operating a quality

assurance program any in diagnostic radiology department across the globe.

4.0 SIGNIFICANCE OF QUALITY CONTROL:

All medical facilities using x-ray equipment, from a simple intra-oral

dental unit to an image intensified special procedure system, will benefit

from adopting a good quality control program because;

I. It will monitor the imaging process from start to finish revealing

potential problems that may otherwise go unrecognized and

achieving reduction of dose to patient and consistent production of

high-quality diagnostic radiographs.

II. It will also form a learning process for those taking part and will also

provide them with tools and practical protocols which can be used

in the implementation of a national quality control program in

diagnostic radiology in future.

III. Another most important benefit of a close control of the x-ray

department can be summarized by saying that, the overall cost-

effectiveness of the department will be improved. (Chesney, 1981).

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Some details which add up to improved cost-effectiveness includes;

a. The number of repeated radiographs is reduced.

b. The rate of flow of patients through the department is improved.

c. The department’s ability to meet the demands made upon its

services is raised.

d. Quality of radiograph produced is higher.

e. Standardization of the radiographic results is achieved and

maintained.

f. The reliability efficiency of automatic processors and of x-ray

equipment is improved.

5.0 QUALITY CONTROL PROGRAM

According to Stewart (1993), essentially, three steps are involved in a

quality control program. There are;

i. Acceptance Testing : These are test conducted on every new x-

ray facilities e.g. the x-ray machine, cassettes, intensifying screens,

grids, to name but a few. This test is carried out prior to it clinical

usage to show if the equipment is performing within the

manufacturer’s specification. This test must be done by someone

other than the manufacturer or his representative.

ii. Routine Performance Evaluation : With use, these x-ray

equipments deteriorate. This necessitates the periodic quality

control evaluation of these equipments. That is, these are the

quality control tests conducted on these equipments to see if the

equipment will meet predestined requirements.

iii. Error Corrections : When these equipment performances are not

optimal or do not meet predetermined requirements, or errors

found after the quality control test has been conducted, actions are

taken to effect corrections on them.

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5.1 General Consideration:

An adequate quality control program for any individual facility will

depend on a number of factors which include, but may not necessarily be

limited to, items such as the type of procedures performed, type of

equipment utilized, and patient workload. This program is developed under

the guidance and supervision of a medical physicist qualified in this area of

expertise by education, training, and experience.

5.2 Equipment Log:

An individual equipment log should be maintained on each x-ray unit in

the department. This equipment log must be kept at some convenient

location where anyone using the facility (physicians, technologists,

physicists, service engineer, etc.) can get ready access. The log should

contain;

1. Equipment Data Specifications

a. Technical specifications, including tube loading charts.

b. Equipment operating instructions.

c. Detailed identification of major components of the system

including name, serial number, and date of installation.

2. An outline of the applicable quality control program.

3. A log of the quality control test results.

4. A record of service on the equipment including a description of

system

malfunctions and description of what service was carried out. The

service record should also include identification of the individual

performing the service and the date.

5.3 Recording Test Data:

All quality control test data should be recorded on standardized forms. It

is suggested by AAPM (1981), that each institution develops its own forms

suitable to its own needs.

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1. The use of standardized forms will assure that all of the required data

will be obtained.

2. Forms should be filed as part of the room log.

3. The charting of trend data is a recommended procedure which will

allow easy identifications of variation with time. This is of particular

value in the case of film processors.

5.4 Conditions of the X-Ray Equipment:

5.4.1Mechanical Integrity: As noted in ICRU Report 54 (1996), a general

observation of the diagnostic system should be made. Key items to

look for are the presence of loose or absent screws, bolts, or other

structural elements that may have been improperly installed or have

worked loose due to use. The functioning and operation of meters,

dials, and other indicators like the pilot lights should be checked.

5.4.2Mechanical Stability: To obtain a diagnostic quality radiograph, it is

important to minimize patient motion. The availability and adequacy of

patient support devices such as the table or immobilizing devices

should also be checked. ICRP Pub. 60 (1991) added that, it is equally

important to check the reproducibility of positioning of the source and

image receptor that may be indicated or controlled by physical marks

or detents. A check of the accuracy of angulations scale should also be

made.

5.4.3Electrical Integrity: The external condition of the high voltage cables

should also be observed. Check to make sure that the retaining rings

at the termination points are tight and that there are no breaks in the

insulation. (ICRU Report 54, 1996). It is important to observe the "lay"

of the cables, how they are being hanged, so that they don’t interfere

with tube positioning.

5.4.4Alignment and SID: Source to image receptor distance (SID)

indicators should be checked. The consistency between multiple SID

indicators (indicators on the tube support and the collimator) should be

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verified. The accuracy of these indicators should also be verified with a

tape measure. Verification of proper grid installation should be made.

This check should also include a verification of the alignment of the x-

ray source and the center of the grid.

5.5 The Radiograph As A Quality Control Tool:

Patient’s radiographs are also considered one of the quality control

tools of which they are being checked on periodic basis and should be

factored into any departmental evaluation program.

5.5.1Rejected Films Analysis: Rogers (2008) defined Film Reject as “a

film deemed useless and discarded with another film being taken” and

A Repeat Film as “a film retaken to provide extra/missing diagnostic

information sent with the original for reporting”.

Film Reject Analysis according to Suleiman and Showalter (1984)

are periodic assessment and checks on rejected films as well as the

accepted ones usually on monthly intervals so as to identify the

problem, determine it cause and find solutions to it, all aiming at

reduction of film reject rate.

The causes of rejection of films are analyzed according to the

following;

- Too dark, too light (under/over exposure)

- Positioning/Collimation errors

- Patient movement

- Processing errors

- Others

Reference data should also be assigned to this analysis e.g. date/time,

operator ID code, room, exam type, reject or repeat, etc.

5.5.2Accepted Films Analysis: Good practice should always question the

adequacy of radiographs of less than optimal quality for their

acceptability in making a diagnosis. Repeating a procedure to get a

film of optimal quality is often not necessary and should be evaluated

in terms of the radiation exposure and cost of the retake. Since one

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should expect to find films of less than optimal quality in a

departmental file, an analytic review of these films should be made on

a regular basis.

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6.0 FACTORS IN OPTIMIZATION OF CONVENTIONAL RADIOGRAPHY

The formation of image of the body involves interplay between many

different factors. To achieve the correct balance between patient dose and

image quality, it is necessary to understand the way in which images are

formed, and to know the factors that influence the image quality and the

radiation dose received by the patient, so that appropriate options can be

selected. These factors include;

6.1 Screen/Film Combination:

The most important factor in the optimization of conventional

radiography is the choice of screen/film combination. (Martin, 2006). For a

screen-film typed film, the x-ray film is sandwiched between two screens

inside a light-tight cassette. Each screen has a layer of a fluorescent

phosphor, such as calcium tungstate or gadolinium oxysulphide, which

converts x-ray photons into visible light photons. The spectral emission of

the phosphor must be matched to the sensitivity of the film. This therefore

means that the wavelength of light emitted by the phosphor of the

intensifying screens must be within the range of wavelengths of light to

which the films is sensitive to and will record as latent image. (Maccia,

1995). Hence, blue light and green light emitting phosphors must be used

with monochromatic and orthochromatic films respectively.

Martin (2006) continued that, the thickness chosen for the phosphor

layer is a compromise between radiation dose and image quality. That is, a

thick film will have high efficiency in the conversion of x-rays to light but with

blurred image. But thin screens results in better resolution but requires

higher radiation exposure.

Hence, in choosing a screen/film combination, factors such as; the

spectral sensitivity of the film, the sensitivity of screen/film which is

quantified in terms of speed index, image contrast and range of exposure

levels to be produce; etc must be put into consideration. (Gray and Winkler,

1983).

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6.2 Exposure Control:

To produce an image on a film with an acceptable level of contrast, the

exposure must be within a relatively narrow range of doses. This is to say

that all exposures must be as low as reasonably achievable. (ICRP Pub. 60,

1990).

Two major factors according to Martin and McKenzie (1993) are

involved in the quantity of radiation produced by the tube. These are; the

tube potential difference (kVp) and the beam filtration. They also noted that,

the exposure factors used will be optimized through the experience of the

radiographers and exposure charts employed for each X-ray unit. The charts

provide a guide to the best factors for different examinations for a patient of

standard build. But however, adjustments will need to be made for patients

of different sizes.

To achieve a consistent exposure level, an automatic exposure control

(AEC) device is usually employed in fixed radiographic imaging facilities. This

comprises a set of X-ray detectors behind the patient that measure the

radiation incident on the cassette. The detectors are usually thin ionization

chambers. Exposures are terminated when a pre-determined dose level is

reached, thereby ensuring that similar exposures are given to the image

receptor for imaging patients of different sizes. The important parameter

involved in radiographic image formation is optical density, so film is used in

setting up the AEC to give a constant optical density. (Shrimpton and Jones,

1984).

6.3 Scattered Radiation And Use Of Low Attenuation Components:

Scattered radiations are produced when x-rays are attenuated at

angles different from the incident rays by the body tissue. These scatter is

increased with increase thickness of body part examined, e.g. skull, pelvis,

lumbar spine examinations.

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As noted in IAEA Publication (1995), radiation scatter has adverse

effects on our radiographs which are;

i. Decreases the light transmitting ability of our film.

ii. Decreases slightly the sharpness of the recorded detail.

iii. Increases the random background noise of the film and all these

will result in

iv. a reduction in the contrast of the film.

The amount of scattered radiation can be reduced by means of an anti-

scatter

grid. (Bauer, 1998). The grid consist of a plate containing thin strips of lead

lying perpendicular to the plated surface, which are sandwiched between a

low attenuation inter-space material which are radiolucent materials made of

either aluminium or polyester. X-ray photons are more likely to be

attenuated by the lead strips. (Sandborg and Carisson, 1993).

Secondary radiation grids are not used for examination of the body

parts but only parts intended to produce scatter maybe as s result of

increase in the tube potential difference (kVp).

6.4 Beam Collimator and X-Ray Projection:

Collimation of the X-ray beam is an important factor in optimization.

Good collimation will both minimize the dose to the patient and improve

image quality, because the amount of scattered radiation will increase if a

larger volume of tissue is irradiated.

Hart and Shrimpton (2000) noted that, collimation is particularly

important in pediatric radiography since the patient’s organs are closer

together and larger fields are more likely to include additional radiosensitive

organs. Collimation in most cases depends on the technique of the

radiographer, but regular quality control by checking that the X-ray beam

and the field from the light beam diaphragm are accurately aligned is

important, particularly for mobile equipment.

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6.3 Film Processing :

The final stage in the production of a radiograph is processing the film.

If processing conditions are not optimal, the film will require a higher

radiation dose in order to provide an acceptable film density. Chemicals

should be changed regularly, and the processing conditions, such as

temperature and development time should be carefully optimized. A system

of quality control that involves checking temperatures of processing

chemicals and carrying out sensitometry, involving development of a test

strip of film exposed to a range of light levels ensures optimal performance.

(BIR Pub. 2001). These checks should be carried out daily to monitor

performance in terms of film density, contrast and background fog level. The

performance levels of processors that have a relatively low workload need to

be monitored carefully.

Gray and Winkler (1983) noted that, film processing affects the film

density; therefore, it influences the speed index. Thus, the measurements of

the characteristic curve for a film will also reveal problems with processing. If

a film is taken with optimized processing, it can be considered the reference

standard. Checks can then be made by comparing future results with the

reference standard to identify any deterioration.

7.0 RECOMMENDED QUALITY CONTROL TESTS

This section describes the recommended quality control tests that

should be carried out in a radiological diagnostic centre. The frequency and

brief procedure of the test is also described in this section.

To successfully carry out a good quality control tests on our x-ray

equipments, many test tools and equipments of which some could be made

by the user are required. Such items include; test phantoms, mesh patterns,

alignment fixtures and timing tools, densitometers, etc. Other test tools,

such as the test cassette, require calibration and adjustment which is

feasible only when a quantity can be made.

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According to CRCPD Pub. 01-5 (2001), the recommended guidelines

and steps on implementing a good quality control test on our x-ray facilities

are as follows;

7.1 Processor Quality Control (Sensitometry):

Objective: The objective of this test is to determine if the processor is

working optimally.

Frequency: This test should be carried out daily, prior to processing patient

films

Required Equipment: Includes; a) Sensitometer b) Dedicated box of

control film c) Densitometer.

Steps:

1. Expose the control film with the sensitometer.

2. Develop the film.

3. Determine the average optical density of the mid-density step and record

it on a form.

4. Determine the average optical density difference and record.

5. Measure the background optical density (base + fog) and record. Verify

that the measured values are within a suggested optimal performance

criteria.

Corrective Action:

The tests should be repeated if the values are outside the performance

criteria. If, after repeating, the results are still out of limits, look for

processing problems and contact the processor service supplier.

7.2 System Constancy Test :

Objective: To assure that the radiographic system is operating consistently.

Suggested Performance Criteria: Optical density on test film within 1

step of comparison film.

Frequency: This test should be carried out monthly and after service of the

equipment

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Required Equipment: Include; Aluminum step wedge, quality control

cassette, film, densitometer

Steps:

1. Set the x-ray unit to the technique factors and source-to-image distance

2. Place the step wedge on the loaded QC cassette on the table top and

center the x-ray beam to the step wedge.

3. Collimate to the edges of the step wedge.

4. Make an exposure of the step wedge and process normally.

5. Using the densitometer, compare the optical densities for Steps 4 through

8 with the comparison film.

6. Record your results on the monthly quality control checklist.

Evaluation: Compare the current film with the comparison film. If the

densities are not within 1 step of the comparison film, constancy has not

been maintained and clinical images should not be taken until the problem

has been identified and corrected.

Corrective Action: Repeat the test to confirm results. Verify that the

processor is in control. Contact your x-ray and processor service engineers.

7.3 Daily And Weekly Darkroom Quality Control

Objective: To keep the darkroom clean and processing optimized.

Frequency:

Daily - Check developer temperature

Daily - Check developer, rinse, fixer levels

Daily - Clean processor feed tray, counter tops

Weekly - Clean darkroom

Required Equipment: Include; non-mercury thermometer, mop, non-

abrasive, liquid cleaning solutions damp, lint-free cloths.

Steps:

Daily: If manual processing, developer temperature must be measured with

non-mercury thermometer for correlation with the time-temperature

chart.

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If auto processing, measure the temperature with a non-mercury

thermometer to verify that the developer is operating within the

temperature range established by the manufacturer, and that the

display, if applicable, is accurate. It may not be necessary to physically

measure the temperature daily if the processor passes the daily QC

test

Daily: If manual processing, replenish following the chemistry manufacturer

guidelines. Replace rinse water.

If auto processing, follow the processor manufacturer

recommendations regarding replenishment.

Daily: Clean processor feed tray and counter top.

Weekly: Damp mop darkroom floor. Clean counters, cabinets, and anywhere

else

dust may accumulate. Clean film hangers.

Corrective Action: If automatic processor can not be maintained at its

optimal operating temperature, call processor service supplier.

7.4 Radiographic Illuminators Quality Control :

Objective: Is to ensure radiographic illuminators (Viewing boxes) are clean

and light levels are kept consistent throughout. A difference in luminance

can create confusion and may effect accurate interpretations.

Suggested Performance Criteria: Illuminator lights are the same “color”

and luminance, and illuminator surfaces are kept clean.

Frequency: This test should be carried out monthly.

Required Equipment: Glass cleaning supplies

STEPS:

1. Clean surface of illuminator.

2. If a bulb or tube fails, it is best to replace all of them.

3. Record results on the monthly quality control checklist.

7.5 Visual Checklist :

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Objective: To assure that all components of the radiographic x-ray system

indicator lights, displays, and mechanical locks and detents are working

properly and that the mechanical rigidity and stability of the equipment is

optimum.

Suggested Performance Criteria: Each of the items listed in the QC

Visual Checklist should pass or receive a check mark. Items not passing the

visual check should be replaced or corrected as soon as possible.

Frequency:

1. Quarterly

2. After service or maintenance on the x-ray system.

Steps:

1. Collimator light brightness and cleanliness.

Determine if light is functioning and is clearly defined under normal

operating conditions, without visible dust or foreign matter shadows.

2. Collimator beam limiting devices (BLDs) available and used.

If unit provides variable collimation, determine that they are

functioning correctly and smoothly. If manual beam limiting devices

are being used, assure they are sufficient for confining the x-ray beam

to the area of clinical interest. Assure that both types are being used

correctly.

3. Locks and detents operable.

Check to make sure all locks and detents are functioning as intended.

Assure that the x-ray tube maintains its position at the clinically used

angles.

4. Boom smoothness of motion.

Determine if boom moves easily without catches or interruptions.

5. Grid condition and operation.

If grids are being used, check that grid lines, grid cutoff, or grid

damage is not visible on films. Assure that grid is properly positioned,

centered to central ray and if a focused grid is being utilized that the

correct focal distance if being used.

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6. Condition of cables.

Inspect all cables for frayed coverings, kinks, and determine that

cables are free from friction from other objects.

7. Tube or generator oil leakage.

Visually inspect areas around x-ray tube and generator for oil or

abnormal collection of dust attaching to oil leaks.

8. Cassettes and screens condition.

Cassettes and screens should be cleaned regularly. Check screen

condition for dust particles, scratches, and areas of discoloration.

Assure screens are properly fitted and attached to cassettes. Check

cassette latches to make sure they are functioning properly and are

not broken. Cassettes and screens should be replaced if necessary.

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9. Loaded cassette storage.

Determine that loaded cassettes are stored in an area that is properly

shielded from radiation to prevent exposure. They should be stored off

the ground and kept free from dust.

10. Control panel indicators.

Assure all control panel switches, lights, and meters are functioning

correctly.

11. Technique chart.

Make sure a technique chart is available, current, and appropriate for

all procedures normally performed.

12. Patient view ability.

Determine that means are provided to permit continuous observation

of the patient during the x-ray exposure.

13. Exposure switch placement.

Assure the exposure switch is mounted in such a way that exposure

can only be made with the operator in a protected area during the

entire exposure. If unit is portable or mobile without a portable

protective barrier, assure cable on exposure switch provides means for

the operator to be at least nine feet from the tube housing during the

exposure.

14. Lead aprons, gloves, collars, etc.

Assure proper items are available and stored correctly without bends

or folds. If abnormal areas are found, complete procedure 13.

Corrective Action: Missing items from the room should be replaced as soon

as possible. Malfunctioning equipment should be reported to the x-ray

service engineer for repair or replacement as soon as possible.

7.6 Repeat Analysis:

Objective: To identify ways to minimize patient exposure and reduce costs

by addressing higher than normal repeat rates.

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Suggested Performance Criteria: The criteria associated with repeating a

film is subjective. There is no good way to determine what the repeat rate

should be. Each facility should decide on its own, but should strive for a

repeat rate of no greater than 5 to 7%.

Frequency:

1. Ongoing tracking of films

2. Quarterly data analysis

Steps:

1. Determine the reason for film repeat as compared to the categories listed

on the data sheet.

2. Record these numbers on the Repeat Analysis Form.

3. Determine the total number of repeated films and the total number of

films exposed. The overall repeat rate is the total of repeated films

divided by the total number of films exposed during the test period.

4. By dividing the number of repeats per category by the total number of

repeated films, a facility can determine the repeat rate per category.

Corrective Action: The percentage of repeats should guide the facility to

focus their efforts to those areas needing the most attention. For example,

films that are too light or too dark may be due to processing problems,

equipment problems that require repair or re-calibration, or technique charts

may need updating.

7.7 Film and Chemical Storage:

Objective: To assure film and chemistry quality is maintained and inventory

is rotated on a first in, first out basis.

Frequency: Quarterly

Steps:

1. Maintain inventory so first in is first out.

2. Maintain the temperature and humidity to manufacturer

recommendations.

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3. Follow the chemistry manufacturer guidelines for replacement and

disposal.

4. Record results on the Quarterly QC Checklist.

Corrective Action: If storage conditions exceed manufacturer’s

recommendations, take the necessary steps to resolve the problem.

7.8 Artifact Evaluation :

Objective: To identify and minimize artifacts that may obscure clinical

findings on the radiographs.

Suggested Performance Criteria: No roller marks or artifacts

Frequency:

1. Quarterly

2. When artifacts are noted

Required Equipment: Cassette and film, marking Pen, illuminator.

Steps:

1. Place the loaded cassette in the bucky or cassette holder. Expose the film

to obtain anoptical density of about 1.00 (5-10 mAs, 60 kVp)

2. After unloading the cassette in the darkroom, mark the direction of the

film transport with a pencil and develop as usual.

3. Using the same cassette, repeat Steps 1 and 2, but this time mark and

run the film perpendicular to the previous one.

4. Using a radiographic illuminator, compare the films, comparing any

artifacts seen on them to their direction of travel through the processor.

5. Record results on the Quarterly QC Checklist.

Analysis: If artifacts are present, compare the artifacts with respect to the

direction of film transport. If the artifacts run parallel on both films with

respect to transport direction, they are from the processor. If they are

perpendicular to each other when viewed with respect to transport direction,

they are from somewhere else in the imaging chain.

Corrective Action: Find, identify, and correct the source of artifacts

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7.9 Intensifying Screen Cleaning Procedure :

Objective: To assure that screens and cassettes are free of dust and dirt

particles that may degrade image quality.

Suggested Performance Criteria: Minimize artifacts on films from screens

or cassettes.

Frequency:

1. Quarterly or semiannually (depending on workload and amount of dust in

the environment)

2. When a problem is noticed

Required Equipment:

1. Screen cleaner (as recommended by manufacturer)

2. Lint-free gauze pad or cloth, or camel’s hair brush.

3. Canned air (available from photographic supply store)

Steps:

1. Visually inspect the condition of the intensifying screen.

2. Dust the screen with the camel's hair brush and canned air.*

3. If foreign material (e.g. dirt, developer solution) cannot be readily

removed

with the camel's hair brush, use liquid screen cleaner.

4. After cleaning with manufacturer approved cleaners, screens should be

allowed to air-dry, standing vertically, before returning the cassette to

use.

5. Record results on the Quarterly QC Checklist.

Corrective Action: If the screen shows signs of cracking, fading, or

discoloration it should be evaluated for replacement.

Assure that the canned air used to clean the screens is "clean" air. If

the air contains moisture, oil, or other contaminants, you may be introducing

artifacts or damaging the screen.

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7.10 Darkroom Integrity or Fog Test :

Objective: To determine and minimize the amount of darkroom fog.

Suggested Performance Criteria: An optical density increase of 0.05 or

less.

Frequency:

1. Semiannually, with each type of film used clinically

2. After bulb or filter replacement

3. After changing or adding types of film

Required Equipment: Includes; opaque material (manila folder), watch or

timer, attenuation block (aluminum step wedge, phantom, acrylic block) to

create a medium, optical density of about 1.0 on the film, densitometer.

Steps:

1. Load a cassette with film and place on a flat surface.

2. Center the attenuation block and expose the film using an x-ray

technique that will result in an optical density of about 1.0 after the

film is processed.

3. With the safelights on, place the exposed film on the work area in the

darkroom. Cover half the film with opaque material, bisecting the

latent image parallel to the long axis of the film.

4. Leave exposed film on the counter for 2 minutes, then process as

usual.

5. While waiting 2 minutes for darkroom fog test, look for any sources of

extraneous light. Any light leaks identified should be repaired as soon

as possible.

6. Inspect the processed film. If there is no discernible delineation

between the shielded and unshielded sides of the film, there is no fog

problem.

7. If a line is evident, measure the optical densities of both sides of the

line with the densitometer. If the density difference is greater than

0.05, corrective action should be taken.

8. Record results on the Semiannual QC Checklist.

26

Corrective Action: Repeat the test with the safelight off. If the results

remain the same, the problem may be caused by a light leak or extraneous

light. If the fog level disappears, the fog was due to the safelight and

remedial action must be taken to correct the problem.

Possible Sources Of Darkroom Fog:

- Safelight filters (old or compromised) - Radios

- Safelight housing - Fluorescent light afterglow

- Safelight too close to work area - Light leaks

- Light bulb of incorrect wattage or type - Suspended ceilings

- Ancillary indicator lights on processor - Timers

- Any place there is a hole cut in the wall

- Excessive ambient light through the tinted viewing windows of daylight

loading

systems.

7.11 Screen-Film Contact Test :

Objective: To assure that optimum contact is maintained between the

screen(s) and film in each cassette.

Suggested Performance Criteria: No large areas (> 2 cm in diameter) of

poor contact.

Frequency:

1. Acceptance testing for new cassettes

2. Annually

3. As needed, if reduced image sharpness is suspected

Required Equipment:

1. Brass or copper mesh screens (1/8 inch or 3 mm spacing). The mesh

should

be as large as the largest cassette to be tested. The mesh can be placed

between two thin sheets of acrylic or cardboard to protect it.

2. Densitometer

Steps:

27

1. Load cassettes to be tested and let rest for approximately 15 minutes

to allow trapped air to escape.

2. Place the cassette on the table and collimate the beam to the cassette

size.

3. Place the wire mesh on top of the cassette and expose the cassette.

(Suggested technique factors are: 5-10 mAs, 50 kVp; 2 mAs, 70 kVp; or

3-5 mAs, 60 kVp).

4. Process the film. The optical density of the area between the wires of

the mesh on the film should be between 1.5 and 2.0.

5. View the film on a in a room with low ambient lighting. Stand 6 to 8

feet away from the illuminator to evaluate the film.

6. Areas of poor contact will appear as dark areas on the film.

7. Record results on the Annual QC Checklist.

Corrective Action:

Large areas (>2 cm in diameter) of poor contact may indicate the need for

corrective action. Clean the cassettes and retest. Areas of poor contact

around the periphery of the cassette may indicate faulty latches or worn

seals on the cassettes. If the area of poor contact is not eliminated by

cleaning, consider replacing the cassette.

7.12 Collimator Test:

Objective: To assure that the light field accurately defines the x- ray field.

Suggested Performance Criteria: The light and x-ray field misalignment

does not exceed 2% of the source-to-image distance (SID) in either the

length or the width of the film.

Frequency:

1. Annually

2. After service or maintenance on the x-ray system (e.g., changing the light

bulb)

Required Equipment: Includes; i) 8 coins, ii) measuring tape.

Steps:

28

1. Place a 10 x 12 inch (24 x 30 cm) loaded cassette at a known SID (e.g., 28

inches).

2. If possible, adjust the field size to 6 x 8 inches (15 x 20 cm). The field

must be smaller than the film. If your system is not equipped with a

variable collimator, attach a beam limiting device (BLD) that provides a

field size smaller than the cassette.

3. Place the coins.

4. Expose (65 kVp, 4 mAs) and develop the film. If field edges are not well

defined, adjust techniques accordingly and repeat this step.

5. Measure the distances between the light (where the coins touch) and x-

ray fields for all coin locations.

6. Add differences for each set of coins along and across the film, and divide

each set of differences by the SID (Example: (1.5" along table / 28")(100)

= 5.38% and (0.5" across table / 28")(100) =1.79%).

7. Percentage differences greater than 2.0% in either direction should be

corrected as soon as possible.

8. Using the same exposed film, determine the center of the x-ray field

(darkened portion of film) using a straight edge.

9. In the same manner, determine the center of the film.

10. Measure distance between the two centers and calculate the difference as

a percentage of the SID. If the percentage difference is greater than 2.0%,

corrective action is necessary.

11. Measure the dimensions of the x-ray field on the film. If the difference

between the indicated and measured field size exceeds 2% of the SID,

corrective action is required.

12. Record on the Annual QC Checklist.

Corrective Action: Malfunctioning equipment should be reported to the x-

ray service engineer to correct the problem.

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7.13 Protective Device Integrity Check:

Objective: To assure that the various protective devices such as lead

aprons, gloves, gonadal shields, and thyroid collars provide

optimal protection when positioned appropriately.

Suggested Performance Criteria: No breaks in lead lining of protective

garments.

Frequency: Annually

Required Equipment: Lead aprons, gloves, gonadal, and thyroid shields

Steps:

Option 1: If an image intensified fluoroscopy unit is available, this is the

preferred way to inspect the aprons, gloves, and collars.

1. Lay out the item to be checked on the table.

2. Examine the entire item using the fluoroscope.

3. Record results on the Annual QC Checklist.

Option 2: If an image intensified fluoroscopy unit is not available:

1. Closely inspect each item for kinks and irregularities.

2. Take a radiograph of suspect areas.

3. Process the film and look for breaks in the lead lining.

4. Record results on the Annual QC Checklist

Corrective Action: Any item displaying breaks in the lead lining should be

replaced.

30

5.0 CONCLUSION:

In conclusion, based on patient dose measurements, comparison with

reference values, assessment of image quality, the introduction of quality

control and corrective actions, if needed, and re-evaluation of patient doses

and image quality, has demonstrated its effectiveness for optimization of

radiological protection program.

Finally, a ‘culture’ of regular patient dose measurements, film reject

analysis, and image quality assessment need to become part of diagnostic

radiology.

6.0 RECOMMENDATION:

From all the information outlined in our colloquium, it has been proven

beyond reasonable doubt that quality control programs and protocols form

an essential part of the optimization process. Therefore, such programs

covering physical and technical parameters associated with the types of x-

ray examination being carried out needs to be instigated in every medical x-

ray facility. For that reason, we strongly recommend that all state radiation

control personnel should be encouraged to promote quality control as a

proven means to reduce doses of exposure, increase and maintain

diagnostic image quality, and limit health care costs.

31

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