radio final lec 1

7/30/2019 Radio Final Lec 1

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Dr. Louie Hammad

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Quality Assurance and Infection Control

*Quality Assurance

-Quality assurance is mainly a plan of action to ensure a

diagnostic X-ray facility will constantly produce high-quality

images with minimal radiation exposure to the patient and

personnel

-so radiation protection is a part of quality assurance .This plan

depends upon professional judgment and standards, which differ

among specialties (each specialty has its own standards).

-It might also be defined as regular testing to detect equipment

malfunctions, or any variables affecting image quality.

For dentistry, diagnostic images must permit the detection of

caries, periodontal problems, and periapical pathosis.

-There are qual ity assurance tests, which are collections of

devices for quality assurance that are sold together that are used

for regular maintenance of X-ray equipment. They are

expensive, however, and if you can't (or don't want to) buy

them, you can ask for help from a technician who has this test

and whose job it is to inspect X-ray equipment.

-By checking your equipment regularly you benefit greatly; you

improve diagnosis, you reduce exposure, and you save time.

*Quality Control Tests

-We have quality control tests for dental X-ray equipment,

supplies, and film processing. Some must be done daily; others

must be done weekly, others monthly and others yearly.

(Check the table).


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Dr. Louie Hammad

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-You need to have a book in your clinic, it is called "retake

book or retake log". If you want to retake any image recorded

in a book, you write the reason for the retake in order not to do

this mistake again.

*Equipment and Supplies

*Dental X-ray Machines

-A quality assurance kit contains

many devices to monitor the

machine; a dosimeter to monitor X-

ray output, kilovoltage meter to

monitor kilovoltage, and others for

milliamperage linearity, half-valuelayer, timer accuracy, focal spot size,


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beam alignment and tube head stability.

-The little timer-accuracy testing device measures the number

of impulses.

*A beam-alignment test is

performed by exposing four

numbered films simultaneously

to make sure the diameter is no

more than 2.7

Dental X-ray Film

-A simple test: fresh film test unwrap a new and unexposed

film from a newly-opened box and process it properly using

fresh chemicals. The film must appear clear with a slight blue

tint (because of emulsion).

-Outdated film is usually foggy (cloudy) due to inappropriate

storage conditions or exposure to radiation. Fogged films should

not be used.

-You can use this test if you're buying films from any suppliers and you

want to make sure the films are really new.

Screens and Cassettes

-Intensifying screens should be checked for dirt and scratches.

They should be cleaned monthly with commercially available

cleansers.

-screens that appear visibly scratched should be replaced.


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Dr. Louie Hammad

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-Cassette holders must be examined for worn closures, light

leaks and warping which may result in fogged and blurred

radiographs these cassettes must be

repaired or replaced

-Cassette must also be checked for adequate film-to-screen

contact.

Screen-Film Contact

- If the film and intensifying screen surfaces do not make good contact,the light will spread, as shown below, and will produce image blurring.

-This is an abnormal condition that occurs when a cassette or film

changer is defective and does not apply sufficient pressure over the entire

film area. Inadequate film-screen contact usually produces blurring inonly a portion of the image area.

(Sources of Blur in Screen-Film receptors)

-The conventional test for film-screen contact is to radiograph a wiremesh. Areas within the image where contact is inadequate will appear to

have a different density than the other areas.


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-This variation in image density is most readily seen when the film isviewed from a distance of approximately 6 ft and at an angle.

* Film-to-screen contact test: this test is used to check the distancebetween the film and the screen...If they have intimate contact or not.

1. You place a film between the screens in the cassette holder,

2. Place a wire mesh on top of the cassette,

3. Expose it at a target-film distance of40 inches using 10 mA, 70 kVp,

and 15 impulses (memorize these numbers!) while directing the centralray perpendicular to the cassette.

4. Process the exposed film,

5. View it on a view box in a dimly-lit room at a distance of6feet.

-the results of the film screen contact test can be interpreted as follow:

*Adequate contact: if the "wire mesh" image seen on the film exhibits a

uniform density.

*Inadequate contact: if the "wire mesh" image seen on the film exhibits

varying densities.areas of poor film-screen contact appear darker than

good contact areas

-cassettes that provide inadequate film-screen contact must be repaired orreplaced.


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Dr. Louie Hammad

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Dr. Louie Hammad

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View box Equipment

-The view box "illuminator": a light source that is used to view dental

radiographs

-the view box contains fluorescent light bulbs that emit light through an

opaque plastic or plexiglass front

-the view box should emit a uniform and subdued light when it is

functioning properly.

-The view box must accommodate the size of the film. So if you have a

white area on your view box (if the view box is larger than the film) you

must cover it before viewing your film.

-The view box should also have adequate lighting in order for you to seethe images clearly.

- A view box must be cleaned.


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Dr. Louie Hammad

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Film Processing

*Darkroom LightingThe darkroom must be checked every six months for light leaks,

processing solutions, and safe lighting.

-This is done by simply going into the darkroom, looking at doors,

keyholes, and cracks to check if there is any light coming in.

-Light leaks must be correcting with weather stripping or black tapebefore proceeding with film processing.

# Safe lighting test

-The coin test is used to make sure that

the safelight is safe; in which a coin is

placed on an unwrapped, unexposed film,

,4 minutes-3the safelight is turned on for

and then the film is processed. If the light

is not safe, the film will be fogged except

for the area under the coin; because it will

be masked by the coin.

-If the safelight is safe, there will be no

exposure, and after processing, the film

will be completely clear with a slight blue

tint (because of emulsion).

-If a positive coin test is persistent, white-light leaks should be looked for

(through cracks, under-door spaces, keyholes...), or the safelight's

position, filter, and bulb wattage.


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are used in this test because they're more sensitive thanPanoramic films-

intraoral films.

-Processing Equipment

Automatic Processor

-The automatic processor can be checked by processing two films, one of

which is exposed to light.

-After processing, one must be dark (the exposed one), the other must belight (the unexposed film). Otherwise, the processor is not working well.

Processing Solutions

-Developer strength and fixer strength must be checked.

-Processing solutions must be replenished daily and changed every 3 to4 weeks as recommended by the manufacturer.

Developer Strength

-when the developer solution loses strength, the time-temp

recommendations of the manufacturer are no longer accurate

**There are three tests used to check for developer strength:

-Reference filmIt is a film that is processed under ideal conditions (ideal exposure, freshchemicals, correct duration and temperature) and kept to compare to

radiographs processed dailythe results of this test are as follow:

1- A matched density between the two films means that daily

radiographs are good.

2-If the daily radiograph is lighter than the reference radiograph, this

.coldorweakmeans the developer is


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tooortoo concentrated, the developer solution isdarkerIf they're-3

.warm

-weakened or concentrated developer solution must be replaced

-if the developer solution is too cool or too warm, the temp must be

adjusted.

- Step wedge radiographs*A step wedge: is a device constructed of layered aluminum steps or it is

an aluminum block that has multiple graduated thicknesses.

-Different thicknesses result in different densities on a radiograph. So a

step wedge radiograph will give an image of adjacent bands of different

shades (black, shades of gray, and white), corresponding to different

thicknesses of aluminum in the step wedge.


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-Twenty films are usually exposed, but only one is processed Using fresh

chemicals (this processed radiograph will exhibit different densities as a

result of step wedge and it is known as "standard step wedgeradiograph")

-The remaining 19 films are processed one film per day. Then compare

the density of the "daily step wedge radiograph" with the" standard stepwedge radiograph".

-This radiograph (standard radiograph) can be used as a reference film.

Compared to other films, if there is a difference ofmore than twodensities (two steps), the solution must be changed.

-If the films are darker than the reference step wedge film, the developer

solution is hot or concentrated.

-If they are lighter, the developer solution is cold or weak.

-An unmatched density by more than two steps on the step wedge the

developer solution is depleted.

-Normalizing device-It can be used to monitor the developer strength and film density.

-Expose a "D"or"E"speed intraoral film, using your usual settings,

while inserted under a copper filter provided with the "Dental

Radiographic Normalizing and Monitoring Device".

-The instrument used is called "Dental Radiographic normalizing andmonitoring device", also called "Crabtree device".


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Dr. Louie Hammad

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-Process test film. Compare the processed film with the 7step film strip

provided with the device as a standard. The processed film should match

the midrange of the standard film strip.


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-If results are substandard, recheck x-ray unit settings and processor

temperature. If both are correct, CHANGE CHEMICALS and repeatsteps

- It has one slot for exposing the film, beneath a copper plate. After

processing, the film is inserted into another slot and compared with

numbered densities on the device.

Fixer strength

-Test: clearing test.

*An unexposed film is unwrapped and immediately placed in the fixer

solution. If it becomes white (clear) in 2-3 minutes, the fixer is workingproperly; if it doesn't, the fixer solution is depleted.

-the results of clearing test can be interpreted as follow:

*fast clearing: If the film clears in 2 minutes then the fixer is of adequatestrength

*slow clearing: If the film is not completely clear in 2 minutes, re-

immerse it in the fixer solution, if the film does not completely clear in 3-

4 minutes then the fixer solution is depleted!


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Dr. Louie Hammad

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Operator Competence

-The X-ray technician must be competent in taking radiographs; because

retaking radiographs means exposing the patient to additional radiation.-each dental radiographer must be competent in both exposure and

processing techniques.

- A retake logs mustbe kept torecord all retakes and their reasons to avoid them in the future.

-As a student, you can do the simple tests listed above. It is good to have

a sense of what a machine (or processing solution) malfunction is, and

correct it whenever possible, or call the technician to do it.

radio final lec 1

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