Geometrical verification system using Adobe Photoshop in radiotherapy.

PURPOSE: Adobe Photoshop is used worldwide and is useful for comparing portal films with simulation films. It is possible to scan images and then view them simultaneously with this software. The purpose of this study was to assess the accuracy of a geometrical verification system using Adobe Photoshop. MATERIALS AND METHODS: We prepared the following two conditions for verification. Under one condition, films were hanged on light boxes, and examiners measured distances between the isocenter on simulation films and that on portal films by adjusting the bony structures. Under the other condition, films were scanned into a computer and displayed using Adobe Photoshop, and examiners measured distances between the isocenter on simulation films and those on portal films by adjusting the bony structures. To obtain control data, lead balls were used as a fiducial point for matching the films accurately. The errors, defined as the differences between the control data and the measurement data, were assessed. RESULTS: Errors of the data obtained using Adobe Photoshop were significantly smaller than those of the data obtained from films on light boxes (p < 0.007). CONCLUSION: The geometrical verification system using Adobe Photoshop is available on any PC with this software and is useful for improving the accuracy of verification.