临床直线加速器用于电子FLASH放疗的快速可逆适应性改造。

Rapid and reversible adaptation of a clinical linear accelerator for electron FLASH radiotherapy.

作者信息

Schneider Frank, Bauer Cornelius J, Göbel Ida D, King Clarence, Spadea Maria Francesca, Seco Joao, Giordano Frank A, Fleckenstein Jens

机构信息

Department of Radiation Oncology, University Medical Centre Mannheim, University of Heidelberg, Germany.

Institute of Biomedical Engineering, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany; Division of Biomedical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg 69120, Germany; Department of Physics and Astronomy, Heidelberg University, Heidelberg 69120, Germany.

出版信息

Phys Med. 2025 Jun 23;136:105032. doi: 10.1016/j.ejmp.2025.105032.

DOI:10.1016/j.ejmp.2025.105032

PMID:40554908

Abstract

PURPOSE

The aim of this work was to establish a procedure that allows the conversion of a standard clinical LINAC into a "FLASH" LINAC capable of delivering ultra-high dose rates above 40 Gy/s, with minimal, fully reversible modifications to the device. A dosimetric characterization of the resulting treatment beam is presented.

METHODS

A LINAC was modified to emit a 10 MeV electron FLASH beam. Modifications included the integration of a pulse control unit which consisted out of a scintillation detector and a transistor circuit. Beam parameters were optimized to maximize dose output. Beam characterization measurements were performed with different detectors in water: ionization chamber, diamond detector, radiographic films and scintillation detector. The resulting doses per pulse (DPP) and dose rates at different source-surface-distances (SSD) as well as the output reproducibility were determined. The beam was characterized with depth dose curves and lateral profiles.

RESULTS

Conversion of a LINAC to FLASH mode was feasible in less than 30 min. Output was between DPP = 1.69 ± 0.02 Gy and DPP = 0.53 ± 0.01 Gy or dose rates between 676 ± 8 Gy/s and 213 ± 4 Gy/s. Reproducibility of DPP was better than 0.8 %. FLASH depth dose curves showed a higher range (R80 = 39.8 mm vs. 34.6 mm) and lateral beam profiles had a reduced flatness (from 5.5 % to 12.7 %) at SSD = 56 cm.

CONCLUSION

We present a fully reversible conversion method requiring minimal modifications to a LINAC to produce electron FLASH beams. The achieved DPP and mean dose rates demonstrated high reproducibility, meeting criteria for FLASH applications, and markedly simplifying access to this technology for broader implementation.

摘要

目的

本研究的目的是建立一种方法，能够将标准临床直线加速器转换为“FLASH”直线加速器，使其能够在对设备进行最小程度的、完全可逆的修改的情况下，实现高于40 Gy/s的超高剂量率输出。文中给出了所得治疗束的剂量学特征。

方法

对一台直线加速器进行改造，使其能够发射10 MeV的电子FLASH束。改造内容包括集成一个脉冲控制单元，该单元由一个闪烁探测器和一个晶体管电路组成。对束参数进行优化，以最大化剂量输出。使用水中的不同探测器进行束特征测量：电离室、金刚石探测器、射线照相胶片和闪烁探测器。确定了不同源皮距（SSD）下的每个脉冲剂量（DPP）和剂量率以及输出重复性。通过深度剂量曲线和横向剂量分布对束进行特征描述。

结果

在不到30分钟的时间内将直线加速器转换为FLASH模式是可行的。输出剂量在DPP = 1.69±0.02 Gy至DPP = 0.53±0.01 Gy之间，或剂量率在676±8 Gy/s至213±4 Gy/s之间。DPP的重复性优于0.8%。FLASH深度剂量曲线显示射程更大（R80 = 39.8 mm对34.6 mm），在SSD = 56 cm时横向束剂量分布的平坦度降低（从5.5%降至12.7%）。