• Technique charts are one of the most neglected factors in radiography, for a variety of reasons. Ironically, most repeat exposures are due to errors that could have been avoided if an appropriate technique chart had been consulted prior to exposing the patient. The key word here is “appropriate”. Many facilities post a technique chart that has never been calibrated for the specific x-ray machine they are using, the grid ratio, speed of film, chemicals and other variables. It is not feasible to copy a technique chart out of a book on radiographic techniques and claim it as your own. These are generic examples. Each machine, in each facility, must have a technique chart that is unique to that machine and takes into account all of the variables that make each unit unique. For that reason in order for any technique chart to be valid it must specify on the chart under which conditions these techniques apply. The technique chart must list the specific x-ray generator that was used to establish the techniques, the film type, screens used, processor chemicals, and grid ratios as applicable. Also, since conditions change over time the chart must have a date indicating when it was last reviewed.
• Once you have identified the conditions which apply to the chart you are ready to specify on the chart the actual techniques. The minimum technique information required would be the mA and time (or mAS), kilovoltage, and SID. The technique must also be based on consistent, repeatable measurements of body parts. It must indicate when a procedure is performed without a grid, as for example when x-raying extremities. A separate technique is required for each position. Obviously, a lateral skull position will require different exposure than a PA skull x-ray. A good technique chart will also include guidance on modifications in the technique due to pathology. For example, with pleural effusion normal chest technique will result in an underexposed image. With emphysema normal technique will result in an overexposed image. There are also several differences between a chest x-ray for lungs, ribs, sternum or thoracic vertebra in spite the fact that they are all in the same general part of the body. These differences must be accounted for on an appropriate technique chart.
• Automatic exposure equipment leads some operators to presume that no technique chart is needed because the machine determines the technique for you. That is not correct. Whereas without an automatic exposure controller (AEC) you need to select mA, exposure time and kilovoltage, when you use the AEC you must select sensor chambers, density, and kilovoltage. You must also establish a backup timer setting. In effect, the number of categories of variables required when using the AEC is no less than when not using the AEC. Also, an AEC can fail, and if you have no backup chart for setting manual techniques you should not be using that machine until the AEC is repaired.
• A technique chart is not only good practice, it is essential for the operator to be able to produce consistent results. Without the chart repeat exposures are higher for patients, and since patients are the primary source of exposure to operators it means operators receive more scatter radiation. In addition, tube life is shortened, films and chemicals are wasted, and patient thru-put is reduced. It takes much longer to x-ray a patient twice than it does to do it right the first time. Failure to follow an appropriate technique chart is a costly and high radiation exposure way to do this business. Technique charts also provide a baseline for comparison that enables the operator to identify imminent equipment failures before the failure occurs. If the procedure followed is simply the “hunch” technique it is likely the operator will assume their guess work was just a little off when the image is unsatisfactory. When a technique chart is used and the posted techniques diverge increasingly from what is actually required it provides a good indication that service is needed, while it can be scheduled rather than as a surprise on that busiest of days when the machine just quits. Service repairs performed early may save many dollars from the cost that would have occurred after total failure of the unit.

EXPOSURE TECHNIQUE - FIXED kVp, variable mAs

NON-CHANGEABLE FACTORS			CHANGEABLE FACTORS
Generator: GE 350, 3 phase			kVp fixed at 90
Film Type: Kodak GR200			Grid: 12:1. 110 line, Focus
Screen: Rare earth, 200 speed			Collimation: to part, less half inch
Processing chemicals: Kodak RPX			SID: 100 cm (40 inches)

LUMBAR				mA	Focal Spot	Cells	Density
Vetebral Column	Small	Medium	Large	_	_	(AEC)	(AEC)
Patient size in cm	14-20	21-25	26-32
AP (anterior-posterior)	60 mAs	80 mAs	120 mAs	200	Large	1,2,3	0
LAT (lateral)	65 mAs	86 mAs	130 mAs	300	Large	2	+1
Oblique	65 mAs	86 mAs	130 mAs	200	Large	2	0
L5/S1 Juncture			150 mAs	300	Large	2	0

Date Reviewed: 12/15/2001 Reviewed By: Wilhelm C. Roentgen

Special Considerations: Rotate feet medially for AP projection.