X-Ray Film Quality Issues & How to Resolve Them
X-rays are extremely important diagnostic tools integral to treatment planning. Practitioners commonly have trouble with films coming out of the processor too light, too dark, or with an otherwise poor appearance.
This months issue of Tech Tips discusses many of the common problems with x-ray films and the solutions to resolve them.
|Films coming out too light
|First, we must separate the two areas that can be the source of the problem: the x-ray producer itself and the darkroom, which includes the processor as well as the environment.
Step 1: Try another x-ray machine. If you still get light films, the problem is probably in the darkroom, skip to step 4. If films are good from the other machine, proceed to Step 2.
Step 2: Check the settings on the control. Most of the later model machines have only a timer setting. Turn the timer up several steps and try again. If you have an older model with mA, KVP, and timer controls, make sure that these are where they ought to be. Higher KVP settings will result in darker radiographs, mA affects density. Do not just start turning knobs. Always go up with just one control at a time.
Step 3: Make sure that you are holding the exposure button down until it cuts off. X-ray machines are required to have “dead man’s switches” so that the emission of radiation stops when the button is released. Occasionally an operator will be in a hurry and release the button early. If this happens, you will get a light film.
Step 4: Several things in the darkroom will cause a light film. Cold solutions in the processor or dip tank, weak or depleted solutions, and film being processed too rapidly. Ideal temperature for solutions is 80°-82° F. The solution should be changed at least monthly, more often for busy practices. A chart displaying date of change is a must. Even better, put a calendar next to the processor to record all maintenance complete with check boxes to verify it has been performed.
Most automatic film processors have some sort of solution heater (usually a pad that goes under the tanks or some sort of bar/probe that goes into them). If the solutions are cool, the solution heater is usually the cause. You will need a multi-meter to check for power or appropriate resistance of the heater. Specifications will vary depending on the make and model of processor. (Some developers also have a separate temperature sensor – see below under “films too dark” for more info on these). Consult your owner’s manual or call American Dental Accessories, Inc. and our tech support staff can assist you with a determination.
Step 5: Check the speed. 4.5 minutes is prescribed. If running too short– the speed can often be calibrated. Consult your owner’s manual or call American Dental Accessories, Inc. tech support line and we can assist you with calibration. Worn or dirty transports may not move freely and could slow down processing as well.
Step 6: Contaminated chemistry. Many times contaminated chemistry causes poor quality film. Thoroughly clean all tanks and racks/rollers and change the chemistry. Rinse everything with distilled water.
Evidence of contaminated chemistry:
• Dark developer solution.
• Black deposits in the bottom of the developer solution pan/tub.
If these problems exist the processor must be cleaned thoroughly, rinsed with distilled water, and the chemicals replenished.
Note: Depleted chemistry can also cause light films. Replenish your chemistry with 6–8 oz. solutions daily. During the day you may top off the solutions with distilled water (1-2 oz. only– more will dilute the chemistry).
|Films come out too dark.||You must be sure where the dark films are being damaged. Most of the time it is not the machine, but a light leak (see below).* If the processor developer is too warm, it will certainly cause dark radiographs. Check the temperature– it should be approximately 80°-82° F. (You can also check it quickly by putting your finger in the developer solution. If it is warm to the touch, it is probably overheated.) If the solution is too warm, unplug the heater, lift off the covers, and allow the solution to cool off. (You can pour in 8 or 10 ounces of fresh solution to cool it off faster). Some processors (notably Dent-X) use a separate temperature sensor which controls activation of the solution heater. Overheating is usually due to a worn temperature sensor for those processors with a separate sensor.
If your processor has a separate sensor, you can use a multimeter to check it. Specifications will vary depending on the make and model of processor. Consult your owner’s manual or call American Dental Accessories, Inc. tech support line and we can assist you with a determination.
The Air Techniques AT2000 processors have the temperature sensor built in to the solution heater so you will need to replace the heater if the sensor is bad.
|Films are spotted and grainy||Check the wash water. Make certain that your wash water is clean. Scrub and rinse out the wash water tub as above. For those processors with an automatic replenishment of the wash water, make certain the water flow is not blocked. Verify that water is flowing into the processor. Some processors (like the Dent-X 810) also spray water through the wash rack. Make certain that the spray tubes are not blocked or clogged.
For roller-type processors, make certain the rollers are clean. One of the most common causes of marks on film is dirty transports.
|Film is totally clear (also see “Light Films” above)||Step 1: Fixer and developer solutions are switched in the processor, developer has leaked out of the processor, or the solutions are totally depleted. To check the processor, expose a film to light and process, it should come out black.
Step 2: The x-ray producer is not emitting. Try another machine. If you still get a clear film, suspect the film, or go back to Step 1, above.
Note: “A friend in need….” If you still cannot get to the root of the problem, and help is not available, try this: Using your x-ray and your film, take a picture. Go to a nearby dentist’s office, (if pan film, you must be extra careful to protect it from light). Process the film with his/her processor. If you can, take a film at his/her office and bring it back, and process it in your processor. This should really tell you where your problem lies.
|Brownish tint on films||Usually due to depleted fixer. Also can be attributed to inadequate wash water in the processor (also see “Check wash water” above).|
|Jagged streaks or lightning-like streaks on film||Static electricity (more prevalent in dryer climates). There is an anti-static spray available to help overcome this problem. If you do not have some on hand, touch a metal faucet repeatedly while handling the film/cassette and “ground out” the static while you are working.|
NOTE: The machine that is taking the x-rays does not cause dark films. Dark films are only caused by the chemistry being too warm or light leaks. The slightest crack in the safelight filter will cause dark pan or ceph films (disregard periapical films, pan & ceph films are 200 times more sensitive to light). A very slight leak under or around the door (or into a daylight loader) will cause dark films. To test for light leaks, lay a fresh film out on the counter, place a coin on the film, wait a minute or two and then develop the film. If you can see the image of the coin, you have light leaks. If using a daylight loader, try using the processor in the dark. If this corrects the problem, your daylight loader leaks. To check for light leaks around a darkroom door, stand in the middle of the darkroom and turn all the lights off. Close your eyes for 60 seconds. Open your eyes and look for the source of light.
Also, make certain you have a safelight with a GBX filter. Many times one may be tempted to use a red bulb but this is not a true safelight and could expose your films. Using a dedicated safelight with a low wattage bulb and separate GBX filter is essential to film quality.
Last of all is the film itself. Make certain that your film is safely stored and is not expired. Always make certain to rotate your stock so that the oldest film is used first. When re-stocking film (and supplies in general), always put the newest supply behind the older stock on your shelf.
There are additional checks and possibilities for panoramic films as well. These are detailed in our equipment repair and maintenance guide Doctor, Did You Check the Breaker Too? available from American Dental Accessories, Inc. in hard copy or on interactive CD.
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