Enhancing Precision in Radiotherapy Delivery: Validating Monte Carlo Simulation Models for 6 MV Elekta Synergy Agility LINAC Photon Beam Using Two Models of the GAMOS Code

The most crucial requirement in radiation therapy treatment planning is a fast and accurate treatment planning system that minimizes damage to healthy tissues surrounding cancer cells. The use of Monte Carlo toolkits has become indispensable for research aimed at precisely determining the dose in radiotherapy. Among the numerous algorithms developed in recent years, the GAMOS code, which utilizes the Geant4 toolkit for Monte Carlo simula-tions, incorporates various electromagnetic physics models and multiple scattering models for simulating particle interactions with matter. This makes it a valuable tool for dose calculations in medical applications and throughout the patient’s volume. The aim of this present work aims to vali-date the GAMOS code for the simulation of a 6 MV photon-beam output from the Elekta Synergy Agility linear accelerator. The simulation involves mod-eling the major components of the accelerator head and the interactions of the radiation beam with a homogeneous water phantom and particle information was collected following the modeling of the phase space. This space was po-sitioned under the X and Y jaws, utilizing three electromagnetic physics mod-els of the GAMOS code: Standard, Penelope, and Low-Energy, along with three multiple scattering models: Goudsmit-Saunderson, Urban, and Wentzel-VI. The obtained phase space file was used as a particle source to simulate dose distributions (depth-dose and dose profile) for field sizes of 5 × 5 cm2 and 10 × 10 cm2 at depths of 10 cm and 20 cm in a water phantom, with a source-surface distance (SSD) of 90 cm from the target. We compared the three electromagnetic physics models and the three multiple scattering mod-els of the GAMOS code to experimental results. Validation of our results was performed using the gamma index, with an acceptability criterion of 3% for the dose difference (DD) and 3 mm for the distance-to-agreement (DTA). We achieved agreements of 94% and 96%, respectively, between simulation and experimentation for the three electromagnetic physics models and three mul-tiple scattering models, for field sizes of 5 × 5 cm2 and 10 × 10 cm2 for depth-dose curves. For dose profile curves, a good agreement of 100% was found between simulation and experimentation for the three electromagnetic physics models, as well as for the three multiple scattering models for a field size of 5 × 5 cm2 at 10 cm and 20 cm depths. For a field size of 10 × 10 cm2, the Penelope model dominated with 98% for 10 cm, along with the three multiple scattering models. The Penelope model and the Standard model, along with the three multiple scattering models, dominated with 100% for 20 cm. Our study, which compared these different GAMOS code models, can be crucial for enhancing the accuracy and quality of radiotherapy, contributing to more effective patient treatment. Our research compares various electro-magnetic physics models and multiple scattering models with experimental measurements, enabling us to choose the models that produce the most reli-able results, thereby directly impacting the quality of simulations. This en-hances confidence in using these models for treatment planning. Our re-search consistently contributes to the progress of Monte Carlo simulation techniques in radiation therapy, enriching the scientific literature.

基于国产加速器URT-Linac 506c的计划复杂度分析和患者计划质量保证预测

目的 探讨基于国产联影URT-Linac 506c加速器的容积弧形调强放射治疗(Volumetric Modulated Arc Therapy,VMAT)计划复杂度参数与患者计划质量保证(Patient Specific Quality Assurance,PSQA)间的关系,并建立机器学习模型对PSQA结果进行评估和预测。方法 随机选取150例在URT-Linac 506c加速器上行VMAT治疗计划的患者为研究对象,在该加速器上对所有计划进行基于机载电子射野影像系统探测器的PSQA剂量验证。对剂量验证结果进行阈值为10%、标准为2%/2 mm的伽马通过率分析。同时对每个计划基于多叶准直器位置和跳数,提取其中的11个复杂度参数。分析复杂度参数和PSQA结果间的关系,并建立机器学习模型对PSQA结果进行预测。结果 计划复杂度参数与PSQA结果的相关性分析表明二者并不严格呈线性相关,但计划的复杂程度越高,PSQA通过率相对越低。梯度提升决策树(Gradient Boosting Decision Tree,GBDT)模型和随机森林(Random Forest,RF)模型对基于复杂度参数的PSQA结果预测水平相当,GBDT模型和RF模型的平均预测误差分别为0.55%和0.54%。由于PSQA结果分布严重不平衡,更改过权重后的模型对低通过率部分的预测能力有所提升。结论 对于国产加速器URT-Linac 506c,这2种基于决策树结构的机器学习模型对PSQA结果的预测可提供一定的帮助,建立更精准的模型需要进一步完善采集患者的样本量。

基于DICOM的3D C-arm控制服务协议(RoboLINK)设计与实现

三维成像技术辅助骨科机器人进行术前规划能够提高手术精确性和高效性,但目前基于三维数据的传统外科导航系统需要预先术前采图,再经过图片导入和人工配准,使得手术步骤愈加繁琐,且患者在采图和手术过程中的位置不同可能导致新的配准误差,导致精确度的降低。鉴于这一需求,本文设计一种基于DICOM协议的3D C-arm控制服务协议(RoboLINK),能将手术机器人和CT连接,可在手术过程中进行CT采图,为当前问题提供新的解决方案。在支持三维C臂与手术机器人进行数据传输的基础上,也可传输运动控制指令,达到设备相互协作的效果。根据以上设计,协议以一影医疗的3D C-arm和模拟手术机器人为实验环境,对协议进行测试。结果表明,RoboLINK协议能够有效完成数据传输和设备控制任务,具有可行性和安全性。

瓦里安Clinac 23EX常见GFIL连锁系统故障分析

根据加速器电子枪控制系统原理,利用数字万用表、示波器、高压棒等进行有关参数的测量对比,对该机器出现GFIL连锁故障进行测量和比较分析,找出其根本原因,总结该机器GFIL连锁,实现GFIL连锁出现时进行快速维修,为患者缩短等候时间。瓦里安23EX加速器常见的GFIL连锁故障维修效果较好,提高了机器的稳定性能、显著减少相关联故障的发生,提高了开机率。

Design of 10 MeV electron linear accelerator for space environment simulation

A compact 10 MeV S-band irradiation electron linear accelerator(linac)was developed to simulate electronic radiation in outer space and perform electron irradiation effect tests on spacecraft materials and devices.According to the requirements of space environment simulation,the electron beam energy can be adjusted in the range from 3.5 to 10 MeV,and the average current can be adjusted in the range from 0.1 to 1 mA.The linac should be capable of providing beam irradiation over a large area of 1 m^(2) with a uniformity greater than 90% and a scanning rate of 100 Hz.A novel method was applied to achieve such a high beam scanning rate by combining a kicker and a scanning magnet.Based on this requirement,a design for the10 MeV linac is proposed with an RF power pulse repetition rate of 500 Hz;it includes a thermal cathode electron gun,a bunching-accelerating section,and a scanning transport line.The detailed physical design and dynamic simulation results of the proposed 10 MeV electron linac are presented in this paper.

基于LINAC慢正电子源的EGS4模拟

介绍基于BEPCLINAC和BFELLINAC（北京正负电子对撞机和北京自由电子激光装置电子直线加速器）慢正电子束设备中正电子源部分的Monte－Carlo模拟过程。结果表明，从Ta靶出射的快正电子产额在BEPCLINAC和BFELMNAC运行于兼容模式时分别为184×1010/s和3．9×1011/s。若慢化体慢化效率在10-4量级，基于BEPCLINAC和BFELLINAC慢正电子束的慢正电子产额分别为106－107/s和107－108/s。

Clinical Study of Accelerated Rehabilitation Concept Combined with Tianji Robot-Assisted Surgery in Lumbar Degenerative Diseases

Objective: To compare the effectiveness and safety of two surgical methods for lumbar degenerative diseases;the combination of the concept of accelerated rehabilitation with the assistance of Tianji Robotics and the concept of accelerated rehabilitation combined with manual pedicle screw placement assisted by conventional C-arm fluoroscopy. Methods: A retrospective analysis was performed on 70 patients who received the concept of accelerated rehabilitation combined with spinal surgery for lumbar degenerative diseases in Baise People’s Hospital from January 2022 to January 2024. Among them, 35 patients in the robot group received accelerated rehabilitation concept combined with robot-assisted surgery;In the conventional C-arm group, 35 patients received the accelerated rehabilitation concept combined with manual pedicle screw placement assisted by conventional C-arm fluoroscopy. VAS score (preoperative/postoperative), ODI score (preoperative/postoperative), intraoperative bleeding volume, postoperative hospital stay, postoperative complications and the accuracy rate of screw placement were compared between the two groups. Result: There was no statistically significant difference in preoperative VAS scores between the robot group and the conventional C-arm group (6.45 ± 0.82 VS 6.63 ± 0.81, P = 0.6600). The postoperative VAS score of the robot group was better than that of the conventional C-arm group (1.69 ± 0.80 VS 2.45 ± 0.85, P = 0.0000*). There was no statistically significant difference in preoperative ODI scores between the robot group and the conventional C-arm group (32.11 ± 3.18 VS 31.66 ± 2.25, P = 0.4900). The postoperative ODI score of the robot group was better than that of the conventional C-arm group (22.68 ± 1.94 VS 24.57 ± 2.25, P = 0.0000*). The postoperative complications in the robot group were less than those in the conventional C-arm group (2.7778% VS 28.5724%, P = 0.0030*). The intraoperative bleeding in the robot group was lower than that in the conventional C-arm group (320.85 ± 276.28 VS 490.00 ± 395.34, P = 0.0420*). The postoperative hospital stay of the robot group was shorter than that of the conventional C-arm group (10.00 ± 9.32 VS 14.49 ± 7.55, P = 0.0300*). The screw placement inaccuracy score of the robot group was lower than that of the conventional C-arm group (0.17 ± 0.51 VS 1.45 ± 1.46, P = 0.0000*). Conclusion: The combination of the concept of accelerated rehabilitation and Tianji Orthopedic robot-assisted surgery is more effective and safer in posterior lumbar decompression and internal fixation surgery with a screw rod system, and is worthy of promotion and application.

医用电子直线加速器生产环节风险分析及现场体系核查要点

医用电子直线加速器具有系统结构复杂、核心部件多、控制精度要求高等特点,对产品质量控制和监管都提出了较高的要求。该研究通过对医用电子直线加速器技术特点及生产环节风险分析,结合医疗器械生产质量管理规范要求,提出了此类产品现场体系检查要点,对企业的质量管理人员和监管部门的检查员具有一定参考意义。

Clinac iX和Trilogy加速器束流匹配计划验证分析

通过对束流匹配的加速器进行计划设计,比较计划参数,验证交叉执行的差异及通过率,验证束流匹配的可行性及可靠性。选取头颈、胸部和腹盆部共15例病例,分别设计Clinac iX和Trilogy两个不同治疗机的三维适形计划(3D-CRT);另选头颈、胸部和腹盆部共15例病例,分别设计两个不同治疗机的调强计划(IMRT)。比较相同计划类型不同治疗机的计划差异,评价指标包括靶区PTV的D98%、D2%、Dmax,晶体Dmax、脑干Dmax、左右肺V5 Gy、双肺V20 Gy、脊髓Dmax、膀胱D50%、小肠D2 cc、股骨头V40 Gy等危及器官及治疗机跳数MU。并对治疗机执行计划进行点剂量和面剂量验证。PTV的D98%、D2%、Dmax剂量差异最大平均值标准差分别为-0.52%±0.30%、0.53%±0.45%、-0.55%±0.17%,危及器官剂量差异最大平均值为膀胱D50%(0.94%±0.84%);Clinac iX和Trilogy治疗机执行所有计划的最大绝对剂量偏差分别为2.36%和-2.80%。MatriXX和PV的γ验证通过率结果平均值分别在97.00%和96.00%以上,Clinac iX最小值为95.40%,Trilogy最小值为95.90%。两台经过束流匹配的治疗机之间交换执行计划的剂量学偏差在临床可接受的范围内,各项参数能精准执行,必要时可以在两台治疗机之间交换执行计划,保证病人放疗疗程完整。

Visual Analysis of the Daily QA Results of Photon and Electron Beams of a Trilogy Linac over a Five-Year Period

Data visualization technique was applied to analyze the daily QA results of photon and electron beams. Special attention was paid to any trend the beams might display. A Varian Trilogy Linac equipped with dual photon energies and five electron energies was commissioned in early 2010. Daily Linac QA tests including the output constancy, beam flatness and symmetry (radial and transverse directions) were performed with an ionization chamber array device (QA Beam Checker Plus, Standard Imaging). The data of five years were collected and analyzed. For each energy, the measured data were exported and processed for visual trending using an in-house Matlab program. These daily data were cross-correlated with the monthly QA and annual QA results, as well as the preventive maintenance records. Majority of the output were within 1% of variation, with a consistent positive/upward drift for all seven energies (^+0.25% per month). The baseline of daily device is reset annually right after the TG-51 calibration. This results in a sudden drop of the output. On the other hand, the large amount of data using the same baseline exhibits a sinusoidal behavior (period = 12 months;amplitude = 0.8%, 0.5% for photons, electrons, respectively) on symmetry and flatness when normalization of baselines is accounted for. The well known phenomenon of new Linac output drift was clearly displayed. This output drift was a result of the air leakage of the over-pressurized sealed monitor chambers for the specific vendor. Data visualization is a new trend in the era of big data in radiation oncology research. It allows the data to be displayed visually and therefore more intuitive. Based on the visual display from the past, the physicist might predict the trend of the Linac and take actions proactively. It also makes comparisons, alerts failures, and potentially identifies causalities.

C-arm Lipiodol CT in transcatheter arterial chemoembolization for small hepatocellular carcinoma

AIM:To investigate the value of C-arm Lipiodol computed tomography(CT) for intra-procedural hepatocellular carcinoma(HCC) lesion detection during transcatheter arterial chemoembolization(TACE).METHODS:Forty patients(37 male,3 female;mean age,52.6 ± 12.5 years,age range:25-82 years) diagnosed with HCC were enrolled in this study.All patients underwent 64-slice CT 1-2 wk before TACE.During the procedure,hepatic angiography was performed first.Following diagnostic embolization with Lipiodol injected into the hepatic artery,a C-arm CT scan was immediately conducted(C-arm Lipiodol CT).If new HCC lesions were confirmed,gelfoam particles were super-selectively injected into the tumor-nourishing blood vessel.A Lipiodol CT scan was performed 7-14 d after TACE.All images acquired from 64-slice CT,digital subtraction angiography(DSA),C-arm Lipiodol CT and Lipiodol CT were retrospectively reviewed by four radiologists and the number of detected lesions in each examination was counted,respectively.The results of Lipiodol CT were taken as the diagnostic reference.Alpha-fetoprotein values were examined both before and after TACE.This study only takes into account the lesions that were not found or were considered suspicious on 64-slice CT before TACE.RESULTS:Preprocedural 64-slice CT detected a total of 13 suspicious lesions in the 40 patients.DSA detected ten definite and four suspicious lesions.C-arm Lipiodol CT detected 71 lesions in total and Lipiodol CT confirmed 67 lesions with a diameter range of 3-12 mm.Four false-positive lesions,which were detected by C-arm Lipiodol CT,were considered to be hepatic artery-portal vein fistulas.The average alpha-fetoprotein values before and after TACE were significantly different(452.3 ± 192.6 ng/m L vs 223.8 ± 93.2 ng/m L;P = 0.039).CONCLUSION:C-arm Lipiodol CT has a higher diagnostic sensitivity for small HCC lesions.This technique may help physicians make intraproceduraldecisions to provide patients with earlier treatment.

Proton linac-based therapy facility for ultra-high dose rate (FLASH) treatment

As an advanced treatment method in the past five years,ultra-high dose rate(FLASH)radiotherapy as a breakthrough and milestone in radiotherapy development has been verified to be much less harmful to healthy tissues in different experiments.FLASH treatments require an instantaneous dose rate as high as hundreds of grays per second to complete the treatment in less than 100 ms.Current proton therapy facilities with the spread-out of the Bragg peak formed by different energy layers,to our knowledge,cannot easily achieve an adequate dose rate for FLASH treatments because the energy layer switch or gantry rotation of current facilities requires a few seconds,which is relatively long.A new design for a therapy facility based on a proton linear accelerator(linac)for FLASH treatment is proposed herein.It is designed under two criteria:no mechanical motion and no magnetic field variation.The new therapy facility can achieve an ultrahigh dose rate of up to 300 Gy/s;however,it delivers an instantaneous dose of 30 Gy within 100 ms to complete a typical FLASH treatment.The design includes a compact proton linac with permanent magnets,a fast beam kicker in both azimuth and elevation angles,a fixed gantry with a static superconducting coil to steer proton bunches with all energy,a fast beam scanner using radio-frequency(RF)deflectors,and a fast low-level RF system.All relevant principles and conceptual proposals are presented herein.

Strip line beam position monitor for HLS LINAC

The parameters of beam transverse positions at HLS 200 MeV LINAC are very important to injection ef-ficiency. We have designed a new non-interceptive strip line beam position monitor (BPM) as a substitution for the original interceptive fluorescent target. This paper gives out the theoretical analysis and bench test result of the strip line BPM. The BPM has a characteristic impedance of (50±5)?, a reflection coefficient of less than –4 dB, a band-width of 400 MHz, a coupling coefficient of less than -15 dB, and a sensitivity of 1.16 dB/mm. Additionally, the strip line BPM has a good linearity.

What Do We Mean When We Talk about the Linac Isocenter?

Purpose: The isocenter of a medical linac system is a frequently used concept in clinical practice. However, so far not all the isocenters are rigorously defined. This work is intended as an attempt of deriving consistent and operable isocenter definitions. Methods: The isocenter definition is based on a fundamental concept, the axis of rotation of a rigid body. The axis of rotation is determined using the trajectory of any point on a plane that intersects the rigid body. A point on the axis of rotation is found through the minimal bounding sphere of the trajectory when the rigid body makes a full rotation. The essential mathematical tool of the isocenter definition system is three-dimensional coordinate transformation. Results: The axes of rotation of the linac collimator, gantry, and couch are established first. The linac mechanical isocenter (linac isocenter) is defined as the center of a circle that best fits the trajectory of a select linac X-ray source position. The axis of rotation and the minimal bounding sphere are cornerstones for the rotation isocenters of the collimator, gantry and couch. The definition of radiation isocenter incorporates a surrogate of the useful beam axis. Conclusions: A framework of isocenter definitions for medical linacs is presented in this manuscript. Consistent meanings of the mechanical and radiation isocenters can be achieved using this approach.

Fabrication and cold test of prototype of spatially periodic radio frequency quadrupole focusing linac

A 325 MHz aluminum prototype of a spatially periodic RF quadrupole focusing linac was developed at the Institute of Modern Physics,Chinese Academy of Sciences,as a promising candidate for the front end of a high-current linac.It consists of an alternating series of crossbar H-type drift tubes and RF quadrupole sections.Owing to its special geometry,cavity fabrication is a major hurdle for its engineering development and application.In this paper,we report the detailed mechanical design of this structure and describe its fabrication process,including machining,assembly,and inspection.The field distribution was measured by the bead-pull technique.The results show that the field errors of both the accelerating and focusing fields are within an acceptable range.A tuning scheme for this new structure is proposed and verified.The cold test process and results are presented in detail.The development of this prototype provides valuable guidance for the application of the spatially periodic RF quadrupole structure.

Phase control system for SSRF linac

The design of phase control system in Shanghai Synchrotron Radiation Facility (SSRF) linac is presented in this paper. And digital phase detecting algorithm, the key for phase control system, is fully described. The testing results for phase control system in 100MeV linac are discussed in detail.

Commissioning experiences with the spoke-based CW superconducting proton linac

The 10-MeV Accelerator-Driven Subcritical(ADS)system Injector-I test stand at the Institute of High Energy Physics(IHEP)is a testing facility dedicated to demonstrating the feasibility of the spoke-based super-conducting(SC)linear accelerator(linac)for the ADS project in China.The injector adopted a four-vane copper structure radio frequency quadrupole(RFQ)with an output energy of 3.2 MeV and an SC section accommodating 14 β_(g)=0.12 single spoke cavities,14 SC solenoids,and 14 cold beam position monitors(BPMs).A 10-MeV pulsed beam with a beam current of 10 mA and a 2-mA continuous wave(CW)beam were successfully shooting through.The commissioning results confirmed the feasibility of using a 325-MHz spoke-type cavity for accelerating the proton beam in the low β and medium β sections.This paper describes the results achieved,the difficulties encountered,and the experiences obtained during commissioning.

The waveguide system of the HLS 800 MeV Linac

To upgrade Hefei Light Source(HLS) Linac, eight accelerating units have been constructed to realize fullenergy injection of the storage ring. Each of the units consists of two 3-m accelerators driven by one klystron.The input cavity detuning method was developed to measure and correct the phase length of the RF power distribution waveguide system. The design of the waveguide network and the principles of the detuning method are presented in this paper. After correction, the phase error between the waveguide of the two accelerators was less than ±0.5?, and the maximum electron energy of Linac reached 805 MeV, which is very near the theoretical maximum value of 810 MeV. These results demonstrate that the calibration of the waveguide was successful.

Velocity bunching for the linac of Shanghai Deep UV FEL facility

High brightness electron beam is one of the main goals of the research and development effort in RF photo-injectors.Compared with the normally used magnetic chicane,an alternative scheme,commonly known as 'velocity bunching',has been proposed as a tool to compress electron beam pulses in modern high brightness photo-injector sources.This paper presents numerical optimization systematically and the first attempt to demonstrate the velocity bunching scheme on SDUV-FEL linac experimentally.The relationship between the degree of bunching and the off-crest phase of the accelerating structure is explored experimentally.Velocity bunching operating mode illustrates flexible performances with an intrinsic machine jitter,which agrees well with the theoretical prediction.

BEPCII Injector Linac Upgrade and Beam Instabilities

The upgrade project of the Beijing Electron Positron Collider （BEPCII） and its injector linac is working well. The linac upgrade aims at a higher injection rate of 5OmA/min into the storage ring, which requires an injected beam with low emittance, low energy spread and high beam orbit and energy stabilities. This goal is finally reached recently by upgrading the linac components and by dealing with rich and practical beam physics, which are described in this study.