Chapter 12

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One of the challenges for becoming comfortable with radiology is the expected or norm for reading and, thus, interpreting a "plain film," whether hard copy or digital. Importantly, in this text we have used the term radiograph to describe what has traditionally been referred to as a plain film (single plane—plain radiographic image)—today this is more typically a digital form but representing the previous image. By convention, the film is placed on a view box or the digital image is oriented on the monitor as if the person were in the anatomic position (facing toward the reader). This allows the reader to have a relatively constant orientation providing an expected presentation and enhancing the ability to perceive the alteration from the norm to be more obvious. Shadows, image magnifications/distortions (size/shape: elongation or foreshortening related to beam orientation and position of bone and distances to film), and overlapping structures thus are seen in their expected positions and the observer is able to concentrate on seeing the abnormal.

Radiographers have agreed to place L (left) or R (right) anatomic markers onto the film to indicate whether the image is of a right or left extremity or side of body. A common novice error is to orient the image to be able to read the R/L designation rather than placement of the image in the anatomic position as the markers will often be placed onto open space and not related to image orientation (e.g., anteroposterior [AP], posteroanterior [PA]) (Figures 12–1 and 12–2). When looking at an extremity, therefore, the image should be placed upright as seen in the anatomic position, except for the hand and foot which are normally placed with the digits and toes directed upward. Additional markers are sometimes used including rotational indicators (e.g., internally rotated [INT] and externally rotated [EXT], weight bearing [WTB], inspiration [INS], with weights—as in stress views associated with the acromioclavicular joint) (Greathouse, 1998).

###### Figure 12–1

Incorrect orientation of image. In this AP radiograph, the image is incorrectly oriented based on reading the identifying label.

###### Figure 12–2

Correct orientation of image. The same image is correctly oriented according to the anatomical position in reference to the patient.

As a general rule, the bony structure that is at a 90-degree angle to the x-ray tube will appear the most clearly defined and least distorted, whereas the more a bone is angled from the beam, the more it becomes distorted. Also, as a general rule, the closer the structure is to the film plate/receptor, the less distortion and greater definition will be perceived. Loss of image clarity or sharpness can also be related to density and contrast (not using the best combination of exposure time and energy). The radiographer carefully controls these exposure parameters ...

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