Reformatted method for two-dimensional detector arrays measurement data in proton pencil beam scanning

The spatial resolution of a commercial two-dimensional (2D) ionization chamber (IC) array is limited by the size of the individual detector and the center-to-center distance between sensors. For dose distributions with areas of steep dose gradients, inter-detector dose values are derived by the interpolation of nearby detector readings in the conventional mathematical interpolation of 2D IC array measurements. This may introduce significant errors, particularly in proton spot scanning radiotherapy. In this study, by combining logfile-based reconstructed dose values and detector measurements with the Laplacian pyramid image blending method, a novel method is proposed to obtain a reformatted dose distribution that provides an improved estimation of the delivered dose distribution with high spatial resolution. Meanwhile, the similarity between the measured original data and the downsampled logfile-based reconstructed dose is regarded as the confidence of the reformatted dose distribution. Furthermore, we quantify the performance benefits of this new approach by directly comparing the reformatted dose distributions with 2D IC array detector mathematically interpolated measurements and original low-resolution measurements. The result shows that this new method is better than the mathematical interpolation and achieves gamma pass rates similar to those of the original low-resolution measurements. The reformatted dose distributions generally yield a confidence exceeding 95%.