Oolbekkink Stijn, Wolthaus Jochem W H, van Asselen Bram, van den Dobbelsteen Madelon, Raaymakers Bas W
Department of Radiotherapy, University Medical Center Utrecht, Utrecht, Netherlands.
J Appl Clin Med Phys. 2025 Feb;26(2):e14604. doi: 10.1002/acm2.14604. Epub 2024 Dec 25.
For the development and validation of dynamic treatment modalities and processes on the MR-linac, independent measurements should be performed that validate dose delivery and linac behavior at a high temporal resolution. To achieve this, a detector with both high temporal and spatial resolution is necessary.
This study investigates the suitability of a Delta4 Phantom+ MR (Delta4) detector array for time-resolved dosimetry in the 1.5 T MR-linac and characterizes the Delta4's performance with dynamic dose delivery, such as beam gating and field modulation during radiation.
A Delta4 detector was used, including software for time-resolved dosimetry. First validation experiments were performed and compared to reference measurements. Subsequently, demonstrator measurements were performed to show use cases of the Delta4's time-resolved dose readouts. An example of such an experiment is the determination of the field speed during a sliding window experiment, traveling between 0.7 and 6.8 cm/s in the cranial-caudal direction.
Validation experiments of the dose reproducibility and dose rate dependency showed no difference relative to the standard static delivery. The field speed measured by the Delta4 showed an average field speed difference of -0.3% relative to MR-linac log files. The Delta4 was capable of measuring the dose with high accuracy and temporal resolution during dynamic radiation delivery.
The Delta4 can be used for time-resolved dosimetry in a 1.5 T MR-linac.
为了开发和验证磁共振直线加速器上的动态治疗模式和过程，应进行独立测量，以在高时间分辨率下验证剂量输送和直线加速器的行为。要实现这一点，需要一个具有高时间和空间分辨率的探测器。
本研究调查Delta4体模+磁共振（Delta4）探测器阵列在1.5T磁共振直线加速器中用于时间分辨剂量测定的适用性，并通过动态剂量输送（如辐射期间的射束门控和场调制）来表征Delta4的性能。
使用Delta4探测器，包括用于时间分辨剂量测定的软件。进行了首次验证实验，并与参考测量进行比较。随后，进行了演示测量，以展示Delta4时间分辨剂量读数的用例。此类实验的一个例子是在滑动窗口实验中确定场速，在头-尾方向上以0.7至6.8cm/s的速度移动。
剂量再现性和剂量率依赖性的验证实验显示与标准静态输送相比没有差异。Delta4测量的场速相对于磁共振直线加速器日志文件显示平均场速差异为-0.3%。Delta4能够在动态辐射输送期间以高精度和时间分辨率测量剂量。
Delta4可用于1.5T磁共振直线加速器中的时间分辨剂量测定。
