Image quality and clinical efficacy of electronic and film portal images

This study compares, quantitatively, the image quality and clinical efficacy of film and electronic portal images. The study consisted of three phases. In the first, the clarity of anatomical landmarks was measured for film and EPID portal images. Next, oncologists reviewed the film and EPID portals with their respective simulation images and rated, on a scale of 1 to 5, their level of confidence in the review. Finally, the physicians reviewed film and EPID portals of treatments containing setup errors to an anthropomorphic phantom. The accuracy of the physicians´ review was compared for the two modalities. The image quality was statistically equivalent between film and EPID for portals of abdomen, extremity, and AP pelvis, while EPID was slightly inferior for lateral pelvis. Most physicians were less confident in their review of treatment portals with the EPID system by an average of 0.5 points, on a scale of 1 to 5. Finally, the physicians´ accuracy in detecting translational setup errors was equivalent between the two modalities, but with the EPID they were more likely to detect subtle errors such as rotations or field aperture changes. The clarity of film and EPID portal images is similar for most treatment sites. The oncologists´ lower confidence level in performing EPID review may be due to lack of experience with the system, as they were more accurate in detecting setup errors with EPID