Linearity and uniformity response as an indicator of performance for Agfa ADC-MD10 computed radiography plates.

Computed radiography (CR) plates are currently used in radiation therapy clinics to acquire digital radiographic images for the purpose of verifying the treatment field size, shape, and location. Each CR plate may be used numerous times, and the use of these digital images allows for easy storage and retrieval of patient data. Over prolonged repeat exposures of the CR plates, however, the image quality begins to degrade, making it increasingly more difficult for the therapists and physicians to determine where one anatomical structure begins, and the other ends. The purpose of this project was to analyze and compare the linearity and uniformity responses of new CR plates, versus CR plates that have been used clinically for a period of 2 years, and determine whether linearity or uniformity response may be used as an indicator of image quality degradation. To determine this, 44 old Agfa MD10 CR plates and 56 new Agfa MD10 CR plates were tested. When comparing the results of the uniformity test, we found both the old and the new plates varied from approximately 0.5% to 3.2%. When comparing the results of the linearity test, we found that the correlation coefficient, R(2), for both the old and the new plates varied from approximately 0.996 to 0.998, with the mean values being 0.9972 and 0.9979, respectively. We concluded that linearity and uniformity response cannot be used as an effective method for the evaluation of CR plate performance. Additional research is currently underway to evaluate various other methods of assessing CR plate performance.