Purpose
Exposure creep is the gradual increase in x-ray exposures over time that results in increased radiation dose to the patient. It has been theorized as being a phenomenon that results from the wide-exposure latitude of computed radiography (CR) and direct/indirect digital radiography (DR). This project evaluates radiographic exposures over 43 months to determine if exposure creep exists and if measures can be applied to halt or reverse exposure creep trends.
Methods
Exposure indices were initially recorded over 29 months between August 2007 and December 2009 from the intensive and critical care unit (ICCU) and the emergency department (ED) departments where manual CR exposures were used. The data from this period were then assessed and the exposure indexes (EI) values from the radiographic images were compared to the radiology department criteria of EI values between 1400 to 1800 as being in the optimal exposure range. EI values below this were considered underexposed and over this as overexposed. An intervention was required to be used in ICCU and implemented in January 2010 to halt a noted trend of overexposure. The EI value for each chest x-ray (CXR) was recorded in the patients’ ICCU records and was to be used by radiologic technologists/radiographers in determine exposure factors in subsequent CXR. After the intervention, EI values were recorded and evaluated for an additional 15 months between February 2010 and March 2011.
Results
Between August 2007 and December 2009, 17,678 ICCU CXR images and 69,327 ED x-ray examinations were evaluated for over- and underexposure. A trend was noted in ICCU that showed a significant increase ( P = .023) in EI values from the beginning to the end of the evaluation. No such trend was seen in the ED EI values ( P = .120). After the intervention in ICCU, the overexposure trend was halted.
Conclusions
Exposure creep has been show to exist. It is surmised that this occurs where judgment to determine the correct radiographic exposure factors is needed when taking into account a large range of patient sizes. It has also been shown that providing radiologic technologists/radiographers with previous EI values for the same x-ray examination can halt a trend of exposure creep.
Computed radiography (CR) and direct/indirect digital radiography (DR) have many benefits over film/screen (FS) radiography. One of the greatest advantages is the wider dynamic range or latitude that CR/DR exhibits . Radiologic technologists/radiographers are able to produce diagnostic images using a greater range of exposure factors . This eliminates one of the primary reasons in FS radiography for repeating an examination: an overexposure to the image plate.
The phenomenon of exposure creep is described in previous studies, though its existence has yet to be shown . Exposure creep is the gradual increase over time of the radiologic technologists/radiographers “usual” exposures for a given radiographic anatomical projection. Exposure creep commenced with the introduction of digital radiographic techniques such as CR and DR. As CR and DR became more widespread, radiologic technologists/radiographers have learned that overexposure in these imaging modalities actually improves image quality. In FS radiography, over- or underexposure resulted in an unacceptable image. When choosing radiographic exposure factors for CR and DR, particularly manual exposures, the tendency of some radiologic technologists/radiographers is to choose toward the high exposure levels because it is more likely to result in a better quality image. Lower radiographic exposure factors can result in noisy or lower quality images. CR and DR images that are over or underexposed image can still be displayed on a monitor with adequate brightness and contrast because of the large dynamic range of the digital detectors and the ability to manipulate window widths and levels. These higher radiographic exposure factors then become the norm.
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Methods
Inclusion Criteria
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Data Collection
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Determination of Optimal, Under-, and Overexposures
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Intervention
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Results
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Discussion
Preintervention
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Postintervention
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Conclusion
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Acknowledgment
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References
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