Radiographic Technique Evaluation

Radiograph Evaluation We understand how radiographs are made. We understand how to develop our films to have a visible image. Now we will learn how to evaluate the finished radiographic product. The technician needs to have the ability to properly evaluate a radiograph. If you don’t know what is good, then it will be hard to attain a good quality image on film. Will help to minimize re-takes.

Assessing a Radiograph Taking a second radiograph is unavoidable. If you are able to realize what is wrong on the initial radiograph, you can make corrections so that the second attempt is the last attempt. Radiographic quality depends on the technologist’s understanding of the concepts and variables that produce a good radiograph. Quality radiographs are obtained by a understanding of the variables we have discussed so far.

Let’s Review X-ray generation mA is applied to the filament in the cathode. This generates an electron cloud. The electrons are moved to the target on the anode by kV. The collision produces heat and x-radiation. mAs controls the total number of x-rays produced. kVp controls the penetrating power of the x-rays.

And more Review Density and Contrast Density is defined as amount of blackness of the radiograph. Primarily affected by mAs. Contrast is defined as the density differences between two areas of a finished radiograph. Primarily affected by kVp.

Viewing a Radiograph Should be viewed on an evenly lit view box in a semi-darkened room. View box should be clean, and all light bulbs should be in working order.

Film View Position Film position is also important. Usually follow medical viewing protocol. V/D or D/V anatomy should be placed on the top of the view screen. Lateral views should be positioned to face viewer’s left with spine at the top.

Correct Lateral Positioning

Correct V/D positioning

Evaluation of Radiographic Technique Ask two basic questions when evaluating a radiograph. 1. Is the film too light or too dark? 2. Is there proper penetration?

Is the film too light or too dark? The more exposure, the blacker the film. The less exposure, the lighter the film. (opposite from photography). Will most likely need to increase or decrease kVp or mAs. To know which one to adjust, must answer second question.

Is there proper penetration? If there is inappropriate penetration of the x-radiation, then the kVp should be changed. If film is dark, should be decreased. If film is light, should be increased. If penetration of x-radiation is satisfactory, then mAs should be adjusted.

If film is too light Is the film under penetrated? If no: Increase mAs 30-50% If yes: Increase the kVp 10-15%

If film is too dark Is the film over penetrated? If yes: Decrease kVp by 10-15% If no: Decrease mAs by 30-50%.

What determines Adequate Penetration of X-rays? When viewing an abdominal radiograph, should be able to see outlines of liver, spleen, kidneys and bowel. Inadequate penetration has areas that appear almost completely white.

Not good penetration

Good Penetration

Too Dark Radiographs If bone tissue is gray and there is not much contrast between the bone and adjacent soft tissue, there was too much penetration. Decrease kVp by 10-15% If bone tissue is relatively white as compared to surrounding tissues, then there was not too much penetration. Decrease mAs 30-50%

Other Error Considerations Exhausted chemicals Poor development techniques Darkroom issues Not lightproof Film issues