Proton therapy using mini-beams is a promising method to reduce radiation damage to normal tissue. However, distribution measurements of mini-beams are difficult due to their small structures. Since optical imaging is a possible method to measure high-resolution two-dimensional dose distribution, we conducted optical imaging of an acrylic block during the irradiation of mini-beams of protons. Mini-beams were made from a proton pencil beam irradiated to 1 mm slits made of tungsten plate. During irradiation of the mini-beams to the acrylic block, we measured the luminescence of the acrylic block using a charge-coupled device camera. With the measurements, we could obtain slit beam images that have slit shapes in the shallow area while they were uniform in their Bragg peaks, which was similar to the case of simulated optical images by Monte Carlo simulations. We confirmed that high-resolution optical imaging of mini-beams is possible and provides a promising method for efficient quality assessment of mini-beams as well as research on mini-beam therapy.

使用微型束的质子治疗是减少辐射对正常组织损伤的一种很有前景的方法。然而，微型光束的分布测量由于其结构小而困难。由于光学成像是测量高分辨率二维剂量分布的一种可能方法，我们在质子微束照射期间对丙烯酸块进行了光学成像。微型光束由质子笔形光束照射到由钨板制成的 1 毫米狭缝制成。在微型光束照射到亚克力块期间，我们使用电荷耦合器件相机测量了亚克力块的发光。通过测量，我们可以获得在浅层区域具有狭缝形状而在其布拉格峰中均匀的狭缝光束图像，这类似于通过蒙特卡罗模拟模拟光学图像的情况。我们证实了微型光束的高分辨率光学成像是可能的，并为微型光束的有效质量评估以及微型光束治疗的研究提供了一种有前途的方法。