Visual linearization of the display of digital radiographs

G. Li, K. Yoshiura, U. Welander, P. Sällström, W. D. McDavid

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


Objectives: To derive and test a method to linearize the visual response of the display of digital radiographs so that equal steps in gray levels will be perceived as equal steps in brightness. Method: A mathematical analysis was performed and expressions for visual linearization were derived. Twenty-four test images were computer generated to confirm that visual linearization may be achieved. Each image had three groups of square areas of different size placed in three rows. The left and right squares in each row were given different gray levels to simulate various contrast levels. The middle squares were initially given the same gray level value as one of the outer squares. The images were examined by ten observers who could change the gray levels of the middle squares so that the step in brightness between the middle square and the outer squares become subjectively equal. The test was performed three times employing two different monitors. Results: The experimental test confirmd that visual linearization could be achieved. Linear regression analyses gave determination coefficients of 0.9926 amd 0.9942 for monitors with γ-values of 1.93 and 2.50, respectively. The mean data from the ten observers perfectly fitted those theoretically calculated. Conclusion: Visual linearization of gray levels can be achieved but further clinical research is needed to determine if this improves diagnosis.

Original languageEnglish
Pages (from-to)131-136
Number of pages6
JournalDentomaxillofacial Radiology
Issue number2
Publication statusPublished - Mar 2002

All Science Journal Classification (ASJC) codes

  • Otorhinolaryngology
  • Radiology Nuclear Medicine and imaging
  • General Dentistry


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