Whether CCD digitizers can provide image quality comparable to that of expensive laser digitizers has been a topic of discussion among x-ray film digitizer manufacturers, systems integrators, and radiologists. A recent study concluded that there were no significant differences in image quality between laser-based and CCD-based methods.
Using comparisons between the DiagnosticPro CCD digitizer from Vidar Systems (Herndon, VA) and the Lumiscan 75 laser digitizer from Lumisys (Sunnyvale, CA), radiologists either preferred images scanned on the DiagnosticPro or had no preference between CCD- and laser-scanned images in nearly 60% of the image pairs viewed. During this study, more than 2800 image pairs were viewed by 170 radiologists of varying backgrounds and technical expert levels.
According to Brian Beardslee, director of medical business for Vidar, the study was the largest of its kind conducted to date, reflected real-world scenarios, and used a diverse sampling of radiologists. The results demonstrated that there were no strong preferences for laser-scanned images, and there were no clinically significant differences in the quality of images digitized using the two techniques.
Image Smiths (Germantown, MD), a provider of soft-copy-display quality-assurance products and image-display workstations, designed the study. The Mallinckrodt Institute of Radiology (St. Louis, MO) selected the cases, certified that both digitizers met factory specifications, and digitized the films used in the preference study.
In addition, Image Smiths developed the study software to allow pairings of images to be displayed randomly on high-resolution dual-screen display systems. To ensure optimum image presentation, Image Smiths calibrated the monitors according to the DICOM gray-scale standard display function using its Veri-Lum product.
Interestingly, many modern imaging systems such as computed-tomography and magnetic-resonance-imaging systems already use digital interfaces. However, in traditional x-ray systems, when direct digital or analog feeds are not available, the x-ray film must be digitized. To date, more than five companies supply such digitizers as front-ends for medical picture archiving and communication systems (see table on p. 9).
Both laser digitizers and CCD digitizers are readily available. And whereas laser digitizers provide a generally higher optical density a measurement of the digitizer's ability to discern details in the dark areas of an image—they are typically more expensive than CCD-based designs.
—ANDREW WILSON