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

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.

Migration of Digital Medical Image Data Stored through Mini-PACS to Full-PACS / 대한의료정보학회지

The purpose of this study was to evaluate the migration of medical image data stored thorough mini-PACS to full-PACS at Yonsei University Medical Center (YUMC). The image data to be migrated were 2.7 TB stored through approximately 4,500 CD archives at Yongdong Severance hospital and 4.7 TB (2:1 compression) stored through 196 digital linear tape (DLT) archives at Severance hospital. Prior to carrying out the migration, principles, methods and expected practical affairs for the migration were discussed and planned to optimize the migration work by considering the cost and the effectiveness of migration work. Migration gateway workstations were set up and a migration software tool was developed. Real migration works were performed based on the results of several migration simulations. Severance hospital decided to migrate all stored image data. The CD image data of 2.7 TB were estimated total 2,250 hr (about 94 days) migration time, but the practical migration work was completed within 3 months by using maximum 5 workstations. The DLT data of 4.7 TB were estimated total 100 days migration time by applying 16 hr working time per day with single workstation, however, the practical migration work was taken 5 months. Meanwhile, 20% of the DLT image data were not able to migrate because the DLT were partially damaged due to frequent access. In conclusion, a migration plan should be carefully prepared by considering the individual hospital environments because the server system, archival media, the network, and the policy of data management may be unique.