Luminescence imaging of non-uniform phantoms during irradiation of protons

Although luminescence imaging during irradiation of protons is a useful method for range and dose estimations, it has only been attempted for uniform phantoms. Since luminescence imaging inherently has high resolution, we will be able to measure the images with non-uniform phantoms. Therefore, we measured the luminescence images for a non-uniform structured acrylic block during irradiation of protons. Imaging was conducted using a cooled charge-coupled device (CCD) camera during the irradiation of 129-MeV protons to an acrylic block with a 10-mm diameter hole in which an acrylic rod, air, or a titanium rod was inserted. Under these three different conditions, we could obtain different luminescence images for protons. The luminescence images with the acrylic rod showed uniform Bragg peaks in the lateral direction. In the luminescence images with air, a part of the Bragg peak under the hole was elongated. In the luminescence images with the titanium rod, the part of the Bragg peak under the hole was shortened. The ranges estimated from the depth profiles of the measured images matched the simulated results within a 1-mm difference. We confirmed that the luminescence imaging of non-uniform phantoms was possible and that ranges could be estimated from the images. We conclude that luminescence imaging is promising not only for uniform phantoms but also non-uniform phantoms.