Yamamoto Seiichi, Toshito Toshiyuki, Okumura Satoshi, Komori Masataka
Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya 461-8673, Japan.
Department of Proton Therapy Physics, Nagoya Proton Therapy Center, Nagoya City West Medical Center, Nagoya 462-8508, Japan.
Med Phys. 2015 Nov;42(11):6498-506. doi: 10.1118/1.4932630.
Proton therapy has the ability to selectively deliver a dose to the target tumor, so the dose distribution should be accurately measured by a precise and efficient method. The authors found that luminescence was emitted from water during proton irradiation and conjectured that this phenomenon could be used for estimating the dose distribution.
To achieve more accurate dose distribution, the authors set water phantoms on a table with a spot scanning proton therapy system and measured the luminescence images of these phantoms with a high-sensitivity, cooled charge coupled device camera during proton-beam irradiation. The authors imaged the phantoms of pure water, fluorescein solution, and an acrylic block.
The luminescence images of water phantoms taken during proton-beam irradiation showed clear Bragg peaks, and the measured proton ranges from the images were almost the same as those obtained with an ionization chamber. Furthermore, the image of the pure-water phantom showed almost the same distribution as the tap-water phantom, indicating that the luminescence image was not related to impurities in the water. The luminescence image of the fluorescein solution had ∼3 times higher intensity than water, with the same proton range as that of water. The luminescence image of the acrylic phantom had a 14.5% shorter proton range than that of water; the proton range in the acrylic phantom generally matched the calculated value. The luminescence images of the tap-water phantom during proton irradiation could be obtained in less than 2 s.
Luminescence imaging during proton-beam irradiation is promising as an effective method for range estimation in proton therapy.
质子治疗能够选择性地将剂量传递至靶肿瘤，因此应通过精确且高效的方法准确测量剂量分布。作者发现质子辐照期间水会发出荧光，并推测这种现象可用于估计剂量分布。
为实现更准确的剂量分布，作者在带有点扫描质子治疗系统的工作台上放置水模体，并在质子束辐照期间用高灵敏度的冷却电荷耦合器件相机测量这些模体的荧光图像。作者对纯水、荧光素溶液和丙烯酸块的模体进行了成像。
质子束辐照期间拍摄的水模体荧光图像显示出清晰的布拉格峰，从图像中测得的质子射程与用电离室测得的结果几乎相同。此外，纯水模体的图像与自来水模体的图像显示出几乎相同的分布，这表明荧光图像与水中的杂质无关。荧光素溶液的荧光图像强度比水高约3倍，质子射程与水相同。丙烯酸模体的荧光图像质子射程比水短14.5%；丙烯酸模体中的质子射程总体上与计算值相符。质子辐照期间自来水模体的荧光图像可在不到2秒内获得。
质子束辐照期间的荧光成像有望成为质子治疗中射程估计的有效方法。
