Quantitative Assessment on Properties of LASER and CCD-based Film Digitizer / 대한의료정보학회지

ABSTRACT

Picture archiving and communication systems (PACS) has widely been used in many hospitals. Film digitizer has been used in order to create digital image file from conventional plain radiographic films for PACS. In this study, we quantitatively assessed the characteristics of film digitizer for both laser and CCD camera-based type used in Severance hospital. We created three test films to measure the quality of digitized images. The test films were then digitized by both laser and CCD camera-based film digitizer. Finally, the image files were transferred to the PC in which spatial resolution, contrast, and uniformity were evaluated. We also measured digitization time to evaluate the speed of digitizer. Modulation transfer function (MTF) was measured to evaluate the spatial resolution. Contrast was evaluated by measuring of useful range of optical density (OD). Contrast uniformity was calculated by the percentage of difference between minimum and maximum pixel values on the digitized images. Spatial resolution of laser digitizer was ~~5.0cycles/mm, while that of CCD-based unit was ~~1.5cycles/mm of spatial resolution at 10% of MTF. Useful range of OD for CCD unit was ~~77%, while that for laser unit was 100%. Contrast uniformities of laser unit were better than those of CCD-based unit. Digitization time was ~~10sec/film using CCD unit, and ~~60sec/film using LASER unit at film size of 17x14 inches. Laser digitizer can provide relatively higher image quality, while CCD-based unit has the advantage of higher speed than laser unit.