Comparison of computer workstation with light box for detecting setup errors from portal images

Purpose: Observer studies were conducted to test the hypothesis that radiat ion oncologists using a computer workstation for portal image analysis can detect setup errors at least as accurately as when following standard clini cal practice of inspecting portal films on a light box. Methods and Materials: In a controlled observer study, nine radiation oncol ogists used a computer workstation, called Portfolio, to detect setup error s in 40 realistic digitally reconstructed portal radiograph (DRPR) images. Portfolio is a prototype workstation for radiation oncologists to display a nd inspect digital portal images for setup errors. Portfolio includes tools for image enhancement; alignment of crosshairs, field edges, and anatomic structures on reference and acquired images; measurement of distances and a ngles; and viewing registered images superimposed on one another. The test DRPRs contained known in-plane translation or rotation errors in the placem ent of the fields over target regions in the pelvis and head. Test images u sed in the study were also printed on film for observers to view on a light box and interpret using standard clinical practice. The mean accuracy for error detection for each approach was measured and the results were compare d using repeated measures analysis of variance (ANOVA) with the Geisser-Gre enhouse test statistic. Results: The results indicate that radiation oncologists participating in t his study could detect and quantify in-plane rotation and translation error s more accurately with Portfolio compared to standard clinical practice. Conclusions: Based on the results of this limited study, it is reasonable t o conclude that workstations similar to PortFolio can be used efficaciously in clinical practice. (C) 1999 Elsevier Science Inc.