Anniversary Paper: Role of medical physicists and the AAPM in improving geometric aspects of treatment accuracy and precision

The last 50 years have seen great advances in the accuracy of external beam radiation therapy. Geometrical uncertainties have been reduced from a centimeter or more in presimulation, skin-mark guided days to 1-2 mm in today's image-guided radiation therapy treatments. Medical physicists, with the support and guidance of the American Association of Physicists in Medicine (AAPM), have been, and continue to be, at the forefront of research, development and clinical implementation in this area. This article reviews some of the major contributions of physicists to the improvement of treatment accuracy and precision, and speculates as to what the future may bring.