An evaluation of the signal and noise characteristics of four CCD‐based film digitizers

Abstract

Film digitizers are common devices in radiology departments involved with picture archive and communication systems (PACS) and teleradiology. In this paper, we studied the performance of film digitizers based on charge-coupled device detectors (CCD digitizers), and compared this with the performance of a laser digitizer (the de facto standard). Our focus was on the assessment of signal, noise and useful optical density range performance. A function (L* delta D) derived from the Rose model was used to evaluate these parameters in absolute terms, based their predicted ability to detect objects of specific size and optical density difference with respect to background. We studied CCD digitizers from four different vendors and found that none was able to reliably operate up to the maximum density of 3.0 required to digitize plain radiographs, while the laser digitizer was capable of this task. Our analysis also indicated that two of the four CCD digitizers were adequate for digitizing laser-printed cross-sectional images in certain cases. Finally, our analysis indicated that digitization of SMPTE pattern films along with visual assessment of the 5% and 95% contrast patches was not sufficient for determining the utility of film digitizers for clinical tasks. Computation of the L* delta D function provides a useful means of assessing the performance of film digitizers (e.g., for acceptance testing and quality control), and this technique may be adaptable for evaluation of other digital imaging modalities.

Digital images obtained with a digital camera are not associated with a loss of critical information – a preliminary study

“…[3][4][5] In one study that compared four different fi lm scanners and addressed the possible loss of information during scanning, the authors concluded that the scanners could not produce a reliable digital conversion of plain fi lm because of their density range limitation. 6 These fi ndings agree with another study that indicated a significant loss of information in scanned radiographs, particularly in the dark zones. 7 However, others have found no differences in resolution between digitised images and the fi lm-based radiographs, 8 although the digitised radiographs demonstrated higher density.…”

“…This shows a major advantage of digitising radiographs over conventional radiographs as previously reported. [1][2][3][4][5][6] However, the reason for the difference may originate from another source. The outcome of the digitisation of fi lm-based radiographs may be subject to a number of variables, including the type of camera and exposure resolution selected.…”

Developments in digital radiography: an equipment update

“…This makes it possible to compare with confidence the performance of X-ray imaging systems of completely different design. It is noteworthy that DQE is now a practical tool for evaluating X-ray image quality not only in the laboratory but also increasingly of systems operating in clinical 2 can be estimated from the image receptor entrance dose and knowledge of the radiographic factors used. With digital radiography systems [SNR out ] 2 can be calculated using digital test image data derived by the device itself.…”

“…The higher the density the blacker the film. Laser digitisers have a density range extending above 3.0, and thus have improved image reproduction at these high levels of optical density [2].…”

Computational adjustment technique for digital mammographic images based on the digitizer characteristic curve

“…6,7 However, due to such a technology, the cost of these scanners is high, which is their main disadvantage. Alternatively, other groups use scanners with charge-coupled device ͑CCD͒ technology and white light sources.…”