Development and clinical implementation of an enhanced display algorithm for use in networked electronic portal imaging

Purpose: To introduce and clinically validate a preprocessing algorithm tha t allows clinical images from an electronic portal imaging device (EPID) to be displayed on any computer monitor, without loss of clinical usability. The introduction of such a system frees EPI systems from the constraints of fixed viewing workstations and increases mobility of the images in a depar tment. Methods and Materials: The preprocessing algorithm, together with its varia ble parameters is introduced. Clinically, the algorithm is tested using an observer study of 316 EPID images of the pelvic region in the framework of treatment of carcinoma of the cervix and endometrium. Both anterior-posteri or (AP/PA) and latero-lateral (LAT) images were used. The images scored wer e taken from six different patients, five of whom were obese, female, and p ostmenopausal. The result is tentatively compared with results from other g roups. The scoring system, based on the number of visible landmarks in the port, is proposed and validated. Validation was performed by having the obs erver panel score images with artificially induced noise levels. A comparat ive study was undertaken with a standard automatic window and leveling disp lay technique. Finally, some case studies using different image sites and E PI detectors are presented. Results: The image quality for all images in this study was deemed to be cl inically useful (mean score > 1). Most of the images received a score which was second highest (AP/PA landmarks greater than or equal to 6 and LAT lan dmarks greater than or equal to 5). Obesity, which has been an important fa ctor determining the image quality, was not seen to be a factor here. Compa red to standard techniques a highly significant improvement was determined with regard to clinical usefulness. The algorithm performs fast (less than 9 seconds) and needs no additional user interaction in most of the cases. T he algorithm works well on both direct detection portal imagers and camera- based imagers whether analog or digital cameras. Conclusions: We have demonstrated that it is possible to preprocess EPIs in such a way that the clinically relevant landmarks are easily detected on a generic computer screen. The algorithm is system-independent and fast. Thi s allows for the encoding of EPIs in more generalized commercial formats so that distribution of images is facilitated. (C) 1999 Elsevier Science Inc.