Management of pediatric radiation dose using Agfa computed radiography

Abstract

Radiation dose to patients and its management have become important considerations in modern radiographic imaging procedures, but they acquire particular significance in the imaging of children. Because of their longer life expectancy, children exposed to radiation are thought to have a significantly increased risk of radiation-related late sequelae compared to adults first exposed to radiation later in life. Therefore, current clinical thinking dictates that dose in pediatric radiography be minimized, while simultaneously ensuring sufficient diagnostic information in the image, and reducing the need for repeat exposures. Dose management obviously starts with characterization and control of the exposure technique. However, it extends farther through the imaging chain to the acquisition system, and even to the image processing techniques used to optimize acquired images for display. Further, other factors, such as quality control procedures and the ability to handle special pediatric procedures, like scoliosis exams, also come into play. The need for dose management in modern radiography systems has spawned a variety of different solutions, some of which are similar across different manufacturers, and some of which are unique. This paper covers the techniques used in Agfa Computed Radiography (CR) systems to manage dose in a pediatric environment.

Evaluation of exposure index (IgM) in orthopaedic radiography

“…The analysis of the results shows that lgM is far above the recommended target of 1.96 (5) . At least 42% of evaluated exposures were above the limit of 2.26, which indicates that the IP receives at least double the exposure necessary to produce an adequate image.…”

“…The lgM reference value used for this study is 1.96 (5) and a reference standard deviation of 0.2 (6) was selected for the upper and lower limits for statistical analysis. A significance level of P 0.05 was used for statistical tests.…”

“…The analysis of the segmented histogram produces the AGFA dose feedback number that indicates how close the average detector dose in some region of interest behind the patient was to the average detector dose expected from the speed class (SC) used for acquiring that image (5) . The relationship between pixel value and exposure must be known: the expected lgM value for any SC, according to vendor specifications is about 1.96 and should be consistent to a 2.5 mGy exposure measured at the detector (5) . Each change of 0.3 (log) *Corresponding author: luis.lanca@estesl.ipl.pt in lgM corresponds to doubling or halving of dose because of its logarithmic nature.…”

“…This problem should be avoided in routine clinical practice. If dose is maintained at a relatively constant IP, at a value that is considered to be appropriate for the exam or patient type, then dose consistency in the CR environment could be achieved (5) .…”

“…LgM is in relation to the absorbed dose at the phosphor plate and is determined by the pixel values (3) . For AGFA CR systems, the lgM provides the dose feedback indicator (5) .…”