[An investigation of the subjective assessment of fluoroscopic imaging using instantaneous detectability]

Instantaneous detectability was introduced in a method for the subjective assessment of fluoroscopic images, particularly in the interventional radiology (IVR) procedure. Quantitatively, instantaneous detectability was obtained by measuring the time required for observers to detect the tip of a linear pattern, such as a guide wire, just after the image is displayed. Dynamic images used in this measurement, which mimic degraded fluoroscopic images, were created in the computer simulation software by adding a low-contrast linear pattern to a noisy background image. Radiological technologists and students in the faculty of computer engineering participated in the assessment, and all measurements were performed using a personal computer system. Even if the contrast-to-noise ratio was identical, instantaneous detectability was remarkably increased when the background noise was dominated by higher frequency components. Also, the sign test suggested that a frame rate of 30 f/s significantly improved detectability compared to a frame rate of 15 f/s. These results enable us to discuss new possibilities for image processing and the optimization of system performance. Although the standard deviation of the measured inter- and intra-observer data was large, statistical significance should be suitably examined by a paired-comparison like the sign test, which will be one of the important analyzers in experiments investigating human performance.