{"title":"用于 FLASH 放射治疗的瓦里安 ProBeam PBS 系统产生的 250 MeV 质子的特性。","authors":"Serdar Charyyev, Chih-Wei Chang, Mingyao Zhu, Liyong Lin, Katja Langen, Anees Dhabaan","doi":"10.14338/IJPT-22-00027.1","DOIUrl":null,"url":null,"abstract":"<p><p>Shoot-through proton FLASH radiation therapy has been proposed where the highest energy is extracted from a cyclotron to maximize the dose rate (DR). Although our proton pencil beam scanning system can deliver 250 MeV (the highest energy), this energy is not used clinically, and as such, 250 MeV has yet to be characterized during clinical commissioning. We aim to characterize the 250-MeV proton beam from the Varian ProBeam system for FLASH and assess the usability of the clinical monitoring ionization chamber (MIC) for FLASH use. We measured the following data for beam commissioning: integral depth dose curve, spot sigma, and absolute dose. To evaluate the MIC, we measured output as a function of beam current. To characterize a 250 MeV FLASH beam, we measured (1) the central axis DR as a function of current and spot spacing and arrangement, (2) for a fixed spot spacing, the maximum field size that achieves FLASH DR (ie, > 40 Gy/s), and (3) DR reproducibility. All FLASH DR measurements were performed using an ion chamber for the absolute dose, and irradiation times were obtained from log files. We verified dose measurements using EBT-XD films and irradiation times using a fast, pixelated spectral detector. R90 and R80 from integral depth dose were 37.58 and 37.69 cm, and spot sigma at the isocenter were σ<sub>x</sub> = 3.336 and σ<sub>y</sub> = 3.332 mm, respectively. The absolute dose output was measured as 0.343 Gy*mm<sup>2</sup>/MU for the commissioning conditions. Output was stable for beam currents up to 15 nA and gradually increased to 12-fold for 115 nA. Dose and DR depended on beam current, spot spacing, and arrangement and could be reproduced with 6.4% and 4.2% variations, respectively. Although FLASH was achieved and the largest field size that delivers FLASH DR was determined as 35 × 35 mm<sup>2</sup>, the current MIC has DR dependence, and users should measure dose and DR independently each time for their FLASH applications.</p>","PeriodicalId":36923,"journal":{"name":"International Journal of Particle Therapy","volume":null,"pages":null},"PeriodicalIF":2.1000,"publicationDate":"2023-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10166018/pdf/","citationCount":"0","resultStr":"{\"title\":\"Characterization of 250 MeV Protons from the Varian ProBeam PBS System for FLASH Radiation Therapy.\",\"authors\":\"Serdar Charyyev, Chih-Wei Chang, Mingyao Zhu, Liyong Lin, Katja Langen, Anees Dhabaan\",\"doi\":\"10.14338/IJPT-22-00027.1\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p><p>Shoot-through proton FLASH radiation therapy has been proposed where the highest energy is extracted from a cyclotron to maximize the dose rate (DR). Although our proton pencil beam scanning system can deliver 250 MeV (the highest energy), this energy is not used clinically, and as such, 250 MeV has yet to be characterized during clinical commissioning. We aim to characterize the 250-MeV proton beam from the Varian ProBeam system for FLASH and assess the usability of the clinical monitoring ionization chamber (MIC) for FLASH use. We measured the following data for beam commissioning: integral depth dose curve, spot sigma, and absolute dose. To evaluate the MIC, we measured output as a function of beam current. To characterize a 250 MeV FLASH beam, we measured (1) the central axis DR as a function of current and spot spacing and arrangement, (2) for a fixed spot spacing, the maximum field size that achieves FLASH DR (ie, > 40 Gy/s), and (3) DR reproducibility. All FLASH DR measurements were performed using an ion chamber for the absolute dose, and irradiation times were obtained from log files. We verified dose measurements using EBT-XD films and irradiation times using a fast, pixelated spectral detector. R90 and R80 from integral depth dose were 37.58 and 37.69 cm, and spot sigma at the isocenter were σ<sub>x</sub> = 3.336 and σ<sub>y</sub> = 3.332 mm, respectively. The absolute dose output was measured as 0.343 Gy*mm<sup>2</sup>/MU for the commissioning conditions. Output was stable for beam currents up to 15 nA and gradually increased to 12-fold for 115 nA. Dose and DR depended on beam current, spot spacing, and arrangement and could be reproduced with 6.4% and 4.2% variations, respectively. Although FLASH was achieved and the largest field size that delivers FLASH DR was determined as 35 × 35 mm<sup>2</sup>, the current MIC has DR dependence, and users should measure dose and DR independently each time for their FLASH applications.</p>\",\"PeriodicalId\":36923,\"journal\":{\"name\":\"International Journal of Particle Therapy\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":2.1000,\"publicationDate\":\"2023-03-03\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10166018/pdf/\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"International Journal of Particle Therapy\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://doi.org/10.14338/IJPT-22-00027.1\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"2023/1/1 0:00:00\",\"PubModel\":\"eCollection\",\"JCR\":\"Q3\",\"JCRName\":\"ONCOLOGY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"International Journal of Particle Therapy","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.14338/IJPT-22-00027.1","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2023/1/1 0:00:00","PubModel":"eCollection","JCR":"Q3","JCRName":"ONCOLOGY","Score":null,"Total":0}
引用次数: 0
摘要
有人提出了射穿式质子闪烁放射治疗,即从回旋加速器中提取最高能量,以最大限度地提高剂量率(DR)。虽然我们的质子铅笔束扫描系统可以提供 250 MeV(最高能量),但临床上并没有使用这种能量,因此在临床调试过程中,250 MeV 还没有被鉴定出来。我们的目的是描述瓦里安 ProBeam 系统产生的 250 MeV 质子束在 FLASH 中的特性,并评估临床监测电离室 (MIC) 在 FLASH 中的可用性。我们为束流调试测量了以下数据:积分深度剂量曲线、光斑西格玛和绝对剂量。为了评估 MIC,我们测量了输出与束流的函数关系。为了确定 250 MeV FLASH 射束的特性,我们测量了:(1) 中心轴 DR 与电流、光斑间距和排列的函数关系;(2) 对于固定光斑间距,实现 FLASH DR 的最大磁场大小(即 > 40 Gy/s);(3) DR 重现性。所有 FLASH DR 测量均使用离子室进行绝对剂量测量,辐照时间从日志文件中获取。我们使用 EBT-XD 胶片验证了剂量测量结果,并使用快速像素化光谱探测器验证了辐照时间。积分深度剂量的 R90 和 R80 分别为 37.58 厘米和 37.69 厘米,等中心的光斑 sigma 分别为 σx = 3.336 毫米和 σy = 3.332 毫米。在调试条件下测得的绝对剂量输出为 0.343 Gy*mm2/MU。输出量在束流达到 15 nA 时保持稳定,在 115 nA 时逐渐增加到 12 倍。剂量和 DR 取决于光束电流、光斑间距和排列,可再现的变化率分别为 6.4% 和 4.2%。虽然实现了 FLASH,并确定了可提供 FLASH DR 的最大磁场尺寸为 35 × 35 mm2,但电流 MIC 与 DR 有关,用户在应用 FLASH 时应每次独立测量剂量和 DR。
Characterization of 250 MeV Protons from the Varian ProBeam PBS System for FLASH Radiation Therapy.
Shoot-through proton FLASH radiation therapy has been proposed where the highest energy is extracted from a cyclotron to maximize the dose rate (DR). Although our proton pencil beam scanning system can deliver 250 MeV (the highest energy), this energy is not used clinically, and as such, 250 MeV has yet to be characterized during clinical commissioning. We aim to characterize the 250-MeV proton beam from the Varian ProBeam system for FLASH and assess the usability of the clinical monitoring ionization chamber (MIC) for FLASH use. We measured the following data for beam commissioning: integral depth dose curve, spot sigma, and absolute dose. To evaluate the MIC, we measured output as a function of beam current. To characterize a 250 MeV FLASH beam, we measured (1) the central axis DR as a function of current and spot spacing and arrangement, (2) for a fixed spot spacing, the maximum field size that achieves FLASH DR (ie, > 40 Gy/s), and (3) DR reproducibility. All FLASH DR measurements were performed using an ion chamber for the absolute dose, and irradiation times were obtained from log files. We verified dose measurements using EBT-XD films and irradiation times using a fast, pixelated spectral detector. R90 and R80 from integral depth dose were 37.58 and 37.69 cm, and spot sigma at the isocenter were σx = 3.336 and σy = 3.332 mm, respectively. The absolute dose output was measured as 0.343 Gy*mm2/MU for the commissioning conditions. Output was stable for beam currents up to 15 nA and gradually increased to 12-fold for 115 nA. Dose and DR depended on beam current, spot spacing, and arrangement and could be reproduced with 6.4% and 4.2% variations, respectively. Although FLASH was achieved and the largest field size that delivers FLASH DR was determined as 35 × 35 mm2, the current MIC has DR dependence, and users should measure dose and DR independently each time for their FLASH applications.