A Study of the TPS Based Beam-Matching Concept for Medical Linear Accelerators at a Tertiary Hospital

The flexibility in radiotherapy can be improved if patients can be moved between any one of the department’s medical linear accelerators (LINACs) without the need to change anything in the patient’s treatment plan. For this to be possible, the dosimetric characteristics of the various accelerators must be the same, or nearly the same. The purpose of this work is to describe further and compare measurements and parameters after the initial vendor-recommended beam matching of the five LINACs. Deviations related to dose calculations and to beam matched accelerators may compromise treatment accuracy. The safest and most practical way to ensure that all accelerators are within clinical acceptable accuracy is to include TPS calculations in the LINACs matching evaluation. Treatment planning system (TPS) was used to create three photons plans with different field sizes 3 × 3 cm, 10 × 10 cm and 25 × 25 cm at a depth of 4.5 cm in Perspex. Calculated TPS plans were sent to Mosaiq to be delivered by five LINACs. TPS plans were compared with five LINACs measurements data using Gamma analyses of 2% and 2 mm. The results suggest that for four out of the five LINACs, there was generally good agreement, less than a 2% deviation between the planned dose distribution and the measured dose distribution. However, one specific LINAC named “Asterix” exhibited a deviation of 2.121% from the planned dose. The results show that all of the LINACs’ performance were within the acceptable deviation and delivering radiation dose consistently and accurately.

TLD calibration and absorbed dose measurement in a radiation-induced liver injury model under a linear accelerator

The application of a thermoluminescent detector(TLD) for dose detection at the liver irradiation site in mice under linear accelerator precision radiotherapy and the use of a single high dose to irradiate the mouse liver to construct a biological model of a radiation-induced liver injury(RILD) in mice were to determine the feasibility of constructing a precision radiotherapy model in small animals under a linear accelerator. A 360° arc volumetric rotational intensity-modulated radiotherapy(VMAT) plan with a prescribed dose of 2 Gy was developed for the planned target volume(PTV) at the location of the TLD within solid water to compare the difference between the measured dose of TLD and the assessed parameters in the TPS system. The TLD was implanted in the livers of mice, and VMAT was planned based on TLD to compare the measured and prescribed doses. C57BL/6 J mice were randomly divided into control and 25-Gy radiation groups and were examined daily for changes in body weight. They were euthanized at 3 and 10 weeks after radiation, and the levels of liver serum enzymes such as alanine aminotransferase(ALT), aspartate aminotransferase(AST), and alkaline phosphatase(ALP) were measured to observe any pathological histological changes in the irradiated areas of the mouse liver. The measured values of solid underwater TLD were within ± 3% of the Dmean value of the evaluation parameter in the TPS system. The mice in the 25-Gy radiation group demonstrated pathological signs of radiation-induced liver injury at the site of liver irradiation. The deviation in the measured and prescribed doses of TLD in the mouse liver ranged from-1.5 to 6%;construction of an accurate model of RILD using the VMAT technique under a linear accelerator is feasible.

联影URT-linac506c直线加速器在乳腺癌保乳手术后放疗中的应用价值

目的研究联影URT-linac506c直线加速器在乳腺癌保乳手术后放疗中的应用价值。方法回顾性选择2023年1—12月就诊于河南省人民医院的乳腺癌保乳手术后接受放射治疗的150例患者,随机分为两组,每组75例,对照组接受医科达infinity直线加速器,观察组接受联影URT-linac506c直线加速器。比较两种直线加速器照射误差、计划靶区的剂量参数、心脏、肺部与乳腺的受照剂量、照射反应。结果观察组X轴、Y轴、Z轴以及旋转角度误差均小于对照组(P<0.05)。两组D 1、D 99、D_(mena)剂量差异无统计学意义(P>0.05)。观察组适形指数、均匀性指数低于对照组(P<0.05)。两组心脏V 30、健侧乳腺D_(mena)照射剂量差异无统计学意义(P>0.05);观察组心脏D_(mena)、肺部患侧D_(mena)、V 30、健侧D_(mena)低于对照组(P<0.05)。所有患者均顺利完成放疗,未出现放疗终止的情况。观察组0~2度反应占比高于对照组(P<0.05),3级反应占比低于对照组(P<0.05)。两组4级反应差异无统计学意义(P>0.05)。结论乳腺癌保乳手术后采用联影URT-linac506c直线加速器放疗效果较好,可减小照射误差,降低计划靶区与危机器官的照射剂量,且皮肤照射反应程度较轻。

瓦里安Clinac 21EX直线加速器GFIL连锁的故障分析与维修

本文对本院瓦里安Clinac 21EX直线加速器9年内发生的GFIL连锁故障进行了总结。GFIL连锁故障的发生主要是由冷端Power Supply板、热端小电源板、热端Hot Deck Filament Power supply板、热端backplane板以及机架内Patch Panel板故障引起的。故障发生后,控制台会出现红色GFIL连锁警报,据详细的硬件状态分析故障原因并进行故障排除处理。本文阐述的5种故障类型基本囊括了与GFIL连锁相关的大部分硬件,根据硬件原理指出了快速有效的故障解决办法,为直线加速器维修提供参考。

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。

瓦里安Clinac 23EX医用直线加速器故障维修1例

介绍了瓦里安Clinac 23EX医用直线加速器在开机晨检中出现的FLOW联锁故障,分析了故障产生的原因,提出了具体的故障排除思路与维修方法,为同行维修类似故障提供了参考。

Commissioning of TrueBeamTM Medical Linear Accelerator: Quantitative and Qualitative Dosimetric Analysis and Comparison of Flattening Filter (FF) and Flattening Filter Free (FFF) Beam

Motive of the study is to present quantitative and qualitative analysis and comparison of beam data measurement with FF (flattening filter) and FFF (flattening filter free) beam in a Varian TrueBeamTM Medical Linear Accelerator. Critique of beam characterization and evolution of dosimetric properties for 6 MV, 10 MV, 15 MV FF beam and 6 MVFFF, 10 MVFFF FFF beam has been carried out. We performed the comparison of photon beam data for two standard FF photon energy 6 MV, 10 MV verses 6 MVFFF, and 10 MVFFF FFF beam. Determination and comparison of parameter involved PDD (Percentage depth dose), Depth dose profile, Symmetry, Flatness, Quality index, Relative output factor, Penumbra, Transmission factor, DLG (Dosimetric leaf gap), in addition to degree of Un-flatness and off-axis ratio of FFF beam. Outcomes of presenting study had shown that change of various parameters such as Percentage depth dose curves, Shape of the depth dose profile, Transmission, Value of quality index and significant rise in surface dose for FFF in comparison with FF beam. Differences in the output factor at lower and higher field sizes for FFF beam compared to that of FF beam were found. The maximum output factor deviation between 6 MV and 6 MVFFF was found to be 4.55%, whereas in 10 MV and 10 MVFFF was 5.71%. Beam quality TPR20/10 for FFF beam was found to be lesser in magnitude, 5.42% for 6 MVFFF whereas 4.50% for 10 MVFFF compared to 6 MV and 10 MV FF beam respectively. Jaw transmission and interleaf leakage for FFF beam were found to be lesser than FF beam. Also DLG for FFF beam was found to be lesser in magnitude comparable to that of flattened beam. This study is mainly inclined towards evaluation and comparison of the FF and FFF beam. It has been observed that, the outcome of a commissioning beam data generation fully complies with vendor specification and published literature.

Measurement of the Energy Spectrum of a 6 MV Linear Accelerator Using Compton Scattering Spectroscopy and Monte Carlo-Generated Corrections

Purpose: The energy spectrum of a linear accelerator used for dose calculations is determined during beam commissioning by iteratively adjusting the spectrum and comparing calculated and measured percent depth-dose curves. Direct measurement of the energy spectrum using pulse mode detectors is particularly challenging because of the high-energy, high fluence nature of these beams and limitations of the detector systems. This work implements a Compton scattering (CS) spectroscopy setup and presents detector corrections and spectral unfolding techniques to measure the spectrum of a 6 MV linear accelerator using a pulse mode detector. Methods: Spectral measurements were performed using a Varian Clinac 21EX linear accelerator and a high-purity germanium (HPGe) detector. To reduce fluence to the detector, a custom-built lead shield and a CS spectrometry setup were used. The detector was placed at CS angles of 46°, 89°, and 125°. At each of these locations, a detector response function was generated to account for photon interactions within the experimental geometry. Gold’s deconvolution algorithm was used to unfold the energy spectrum. The measured spectra were compared to simulated spectra, which were obtained using an experimentally benchmarked model of the Clinac 21EX in MCNP6. Results: Measurements were acquired and detector response corrections were calculated for all three CS angles. A comparison of spectra for all CS angles showed good agreement with one another. The spectra for all three angles were averaged and showed good agreement with the MCNP6 simulated spectrum, with all points above 400 keV falling within 4%, which was within the uncertainty of the measurement and statistical uncertainty. Conclusions: The measurement of the energy spectrum of a 6 MV linear accelerator using a pulse-mode detector is presented in this work. For accurate spectrum determination, great care must be taken to optimize the detector setup, determine proper corrections, and to unfold the spectrum.

Electromagnetic Oscillations in a Spherical Conducting Cavity with Dielectric Layers. Application to Linear Accelerators

We present an analysis of electromagnetic oscillations in a spherical conducting cavity filled concentrically with either dielectric or vacuum layers. The fields are given analytically, and the resonant frequency is determined numerically. An important special case of a spherical conducting cavity with a smaller dielectric sphere at its center is treated in more detail. By numerically integrating the equations of motion we demonstrate that the transverse electric oscillations in such cavity can be used to accelerate strongly relativistic electrons. The electron’s trajectory is assumed to be nearly tangential to the dielectric sphere. We demonstrate that the interaction of such electrons with the oscillating magnetic field deflects their trajectory from a straight line only slightly. The Q factor of such a resonator only depends on losses in the dielectric. For existing ultra low loss dielectrics, Q can be three orders of magnitude better than obtained in existing cylindrical cavities.

Comparison of two methods for assessing leakage radiation dose around the head of the medical linear accelerators

Objective:The aim of this study was to measure the leakage by two methods with ion chamber and ready packs film,and to investigate the feasibility and the advantages of using two dosimetry methods for assessing leakage radiation around the head of the linear accelerators.Methods:Measurements were performed using a 30 cm3ion chamber;the gantry at 0°,the X-ray head at 0°,the field size at between the central axis and a plane surface at a FSD of 100 as a reference,a series of concentric circles having radii of 50,75,and 100 cm with their common centre at the reference point.The absorbed dose was measured at the reference point,and this would be used as the reference dose.With the diaphragm closed,the measurements were taken along the circumference of the three circles and at 45°intervals.Results:Leakage radiations while the treatment head was in the vertical position varied between 0.016%–0.04%.With the head lying horizontally,leakage radiation was the same order magnitude and varied between 0.02%–0.07%.In the second method,the verification was accomplished by closing the collimator jaws and covering the head of the treatment unit with the ready pack films.The films were marked to permit the determination of their positions on the machine after exposed and processed.With the diaphragm closed,and the ready packs films around the linear accelerator the beam turned on for 2500 cGy(2500 MU).The optical density of these films was measured and compared with this of the reference dose.Leakage radiation varied according to the film positions and the magnitude of leakage was between 0.005%–0.075%.Conclusion:The differences between the values of the leakage radiation levels observed at different measurement points do not only reflect differences in the effective shielding thickness of the head wall,but are also related to differences in the distances between the target and the measurement points.The experimental errors involved in dosimetric measurement also contribute to such differences.

Establishment and validation of a method for cell irradiation in 96-well and 6-well plates using a linear accelerator

To establish and validate a method for cell irradiation in 96-well and 6-well plates using a linear accelerator, three irradiation methods(G0 B0 F40,G0 B1.5 F40, and G180 B1.5 F40) were designed to irradiate cell culture plasticware simulated with RW3 slab phantom and polystyrene. The difference between the actual physical measured dose and the preset dose was compared among the three methods under the preparatory conditions of 2, 4, 6, 8, and 10 Gy. MDA-MB-231 cells were analyzed by using a cell proliferation assay and a clonogenic assay to verify the difference between the three cell irradiation methods on cell radiosensitivity. For each preset dose, the difference between the actual measured dose and the preset dose was the lowest for Method G0 B1.5 F40, the second lowest for Method G180 B1.5 F40, and the maximum for Method GOB0 F40. The ranges of the differences were-0.28 to 0.02%,-2.17 to-1.80%, and-4.92 to-4.55%, and 0.31 to-0.12%,-3.42 to-2.86%, and-7.31 to-6.92%,respectively, for 96-well and 6-well plates. The cell culture experiments proved that Method G0 B1.5 F40 was an accurate, effective, simple, and practical irradiation method. The most accurate and effective cell irradiation method should always be used, as it will reduce dose differences and instability factors and provide improved accuracy and comparability for laboratories researching cellular radiosensitivity.

Performance of an electron linear accelerator for the first photoneutron source in China

A compact 15.0-MeV, 1.5-kW electron linear accelerator(LINAC) was successfully constructed to provide an electron beam for the first photoneutron source at the Shanghai Institute of Applied Physics, Shanghai,China. This LINAC consists of five main parts: a thermal cathode grid-controlled electron gun, a pre-buncher, a variable-phase-velocity buncher, a light-speed accelerating structure, and a high-power transportation beamline. A digital feedforward radio frequency compensator is adopted to reduce the energy spread caused by the transient beam loading effect. Furthermore, a real-time electron gun emission feedback algorithm is used to keep the beam stable. After months of efforts, all the beam parameters successfully met the requirements of the facility. In this paper, the beam commissioning process and performance of the LINAC are presented.

Dose Validation of Physical Wedged Asymmetric Fields in Artiste Linear Accelerator

Aim: The purpose of this study was to make a comparison between measured and calculated physical wedge dose distributions using the superposition algorithm. Settings and Design: The accurate determination of absorbed dose is important radiotherapy because of the relatively steep sigmoidal dose response curves for both tumor control and normal-tissue damage. Materials and Methods: High-energy photons (6 and 10 MV) from Artiste Treatment System Linear Accelerator Machine, available at Alexandria Ayadi Al-Mostakbal Oncology Center, were used. Results and Discussion: The results showed that the difference between measured and calculated wedged isodose curves depends on field size, beam energy, and the angle of the used wedge. Conclusion: The results showed that the presence of a wedge alters the primary and scattered components generated by a linear accelerator and causes beam hardening in 6 and 10 MV. The beam hardening increased as the wedge angle increased.

A Quality Assurance Approach for Linear Accelerator Mechanical Isocenters with Portal Images

Purpose: With usually a millimeter-level PTV margin, stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT) pose a stringent requirement on the isocentricity of the Linac. This requirement is partly fulfilled by routine isocenter quality assurance (QA) test to verify the size and location of the isocenter. The current common QA methods such as spoke shot were developed before SBRT/SRS became popular and when IGRT was largely absent and hence have their limitations. In this work, we describe an isocenter QA approach based on portal imaging to provide the community with a superior alternative. Methods: The proposed approach utilizes a BrainLab ball bearing (BB) phantom in conjunction with an electronic portal imaging devices (EPID) imager. The BB phantom was first aligned with a calibrated room laser system. Portal images were then acquired using 6 MV beam with a 2 × 2 cm2 open field and a 15 mm cone on a Varian TrueBeam STx machine. The gantry, collimator, and table were rotated separately at selected angles to acquire a series of portal images in order to determine the isocenter of each rotating system. The location and diameter of these isocenters were determined by calculating the relative displacement of either BB or open field edge between the acquired EPID images. The demonstration of the reproducibility and robustness of this EPID-based approach was carried out by repeating measurements 10 times independently for each rotating system and simulating clinical scenarios of asymmetric jaws and misalignment of BB phantom, respectively. Results: For our TrueBeam STx machine, the isocenter diameter derived from open-field EPID images was roughly 0.15 mm, 0.18 mm, 0.49 mm for the collimator, table, and gantry, respectively. For the collimator and gantry, images taken with the cone gave considerably smaller isocenter diameter. Results remained almost unchanged despite the presence of simulated BB misalignment and asymmetric jaws error, and between independent measurements. Isocenter location and diameter derived from images obtained at a limited number of angles (≤11) were adequately accurate to represent those derived from images of densely sampled angles. Conclusions: An EPID-based isocenter QA approach is described and demonstrated to be accurate, robust, and reproducible. This approach provides a superior alternative to conventional isocenter QA methods with no additional cost. It can be implemented with convenience for any linear accelerator with an EPID imager.

Direct Measurement of Medical Linear Accelerator Electron Beam Width at Scattering Foil Position

Purpose: The aim of this study was to develop a method for the direct measurement of electron beam width and distribution at the scattering foil on the carrousel in a medical linear accelerator gantry head, which differs from an existing indirect method for measuring the focal spot size using a camera or metallic slit located outside the gantry head. Methods: The electron beam emitted by the linear accelerator was used to irradiate radiochromic film mounted on the scattering foil on the carrousel, which was not used for clinical treatment. The electron beam width at the scattering foil position was then evaluated using the full width at half maximum of the Gaussian distribution approximated from each one dimensional distribution of the irradiated radiochromic film. Results: The electron beam width at the scattering foil position was found to be 3.1 to 6.4 mm in the crossline direction and 2.8 to 5.5 mm in the inline direction with electron energy of 4 to 16 MeV. The two-dimensional distribution of the electron beam was therefore elliptical or distorted in shape, not circular. Conclusions: Direct measurement of the electron beam width at the scattering foil in the carrousel of a medical linear accelerator is possible, though the use of lower sensitivity film in addition to indirect methods is expected to bring about better results. However, as this method does not allow for direct measurement of the incident angle of the accelerated electron beam, further improvements and refinements are still needed.

Discussion of 90°stopband in low-energy superconducting linear accelerators

Superconducting linear accelerators(SCL)have a high acceleration gradient and are capable of operating in a high-duty factor mode.For high-power and high-intensity SCL,the design of beam dynamics generally follows the principle that the zero-current periodic phase advance(σ0)of each degree of freedom is less than 90°to avoid envelope instability caused by space charge.However,this principle is obtained under the condition of a completely periodic focusing channel,and it is ambiguous for pseudoperiodic structures,such as linear accelerators.Although transverse beam dynamics without acceleration have been studied by other researchers,it appears that there are some connections between pure 2D and 3D beam dynamics.Based on these two points,five focusing schemes for the solenoid and quadrupole doublet channels were designed to simulate the beam behavior with non-constantσ0.Among them,the four schemes follow the characteristics of variation in the zero-current longitudinal phase advance(σ0l)under a constant acceleration gradient and synchronous phase.The zero-current transverse phase advance(σ0t)is consistent withσ0l,based on the equipartition requirement.The initialσ0twas set to 120°,110°,100°,and 90°,and was then gradually decreased to approximately 40°at the end of the channel.The last scheme maintains the maximumσ0tof88°by reducing the acceleration gradient of the corresponding cavities,until the point at whichσ0tequals88°with a normal gradient.Using the stopbands obtained from the linearized envelope equations and multiparticle particle-in-cell(PIC)simulations,the transport properties of both continuous and 3D-bunched beams with the acceleration of the five focusing schemes were studied.It was found that for a CW beam,when tune depression>0.7,σ0tcan break through 90°when the beams were transported in both solenoid and quadrupole doublet periodic focusing channels.When tune depression<0.7,the conclusions were different.For the solenoid focusing system,σ0tcan partially break through 90°,and the beam quality is not significantly affected.For the quadrupole doublet focusing system,a partial breakthrough of 90°has a greater impact on the beam quality.The same conclusions were obtained for a bunched beam with acceleration.

Use of a 2-Dimensional Ionization Chamber Array to Measure Head Leakage of a Varian Truebeam^®Linear Accelerator

The purpose of this work is to evaluate the use of a two-dimensional (2D) planar ion chamber array to characterize leakage radiation from the head of the linear accelerator. Ion chamber arrays provide a benefit over a singular ion chamber measurement as they allow for the measurement of a larger area in order to isolate the point of maximum leakage dose and the small size of each individual ion chamber minimizes volume-averaging effects. A Varian Truebeam® undergoing acceptance testing was used for all measurements. The gantry was wrapped in Portal Pack for Localization (PPL) radiographic film in order to isolate the location of maximum leakage. A calibration curve was developed and used to determine dose-to-film. An Ion Chamber Profiler (IC Profiler™) manufactured by Sun Nuclear Corporation was used to confirm measurements by the PPL film. All measurements were normalized to leakage at 100 cm from the target relative to the central axis. Three points were investigated with the IC Profiler, including the top of the gantry, the Varian logo, and the side of the gantry. For the three locations, respectively, the PPL film and the IC profiler were measured 0.142% and 0.131%, 0.036% and 0.030%, and 0.014% and 0.019%. The good agreement between the PPL film and the IC Profiler provides confidence in the use of a more efficient and accurate ion chamber array for head leakage measurements.

An experimental inter-comparison of radiotherapic dosimetric delivery to assess X-Ray linear accelerator output characteristics

The dosimetric inter-comparison studies carry pertinent significance to ensure uniform radiation dose delivery for clinical trials. This paper investigates the comparative performance analysis of an X-ray high power linear accelerator per- formed by the International Dosimetry Survey Mission and Institute of Nuclear Medicine ＆ Oncology （INMOL）, Lahore. The measurements were made using cylindrical ionization chambers based on the International Atomic Energy Agency （IAEA） TRS-398 protocol for absorbed dose-to-water dosimetric standards, and the percentage deviation was found to be between 0.5 % - 1%. The dosimetric analysis concerning linear X-ray accelerator output performed by INMOL, Lahore was found to be in good agreement with the results of IAEA Dosimtery Survey Mission.

Monte Carlo Modeling and Verification of 6 MV Linear Accelerator

Purpose: To model the ELEKTA COMPACT accelerator head by using EGSnrc/BEAMnrc/DOSXYZnrc and to validatethe simulation according to the depth-dose and lateral profiles of different radiation fields measured by the water phantom. Methods: IBA Blue Water Phantom2 and CC13 Ionization Chamber were used to measure the depth-dose curves at 10 cm × 10 cm field and profile curves at 10 cm depth underwater. In BEAMnrc, the main components of accelerator head and the initial electron beam are established based on the specifications file, and the phase space file containing the photon beam information is generated. In DOXYZnrc, phase space files were used to irradiate a homogeneous water phantom of the same size as the IBA water phantom, and the simulated percentage depth dose curves and lateral profiles were outputted. The accuracy of the model was evaluated by mean square error (MSE) compared with the measured data. PDD curves are used to determine the energy of the initial electron beam. Dose profile curves are used to adjust the flattening filter. The penumbra on lateral profiles is used to adjust the full-width half-maximum (FWHM) of the electron source. Result: The electron energy of 5.8 MeV was considered the best match after comparing the PDD curves of 5.6 - 6.2 MeV electron beams. The flattening filter can only be adjusted by trial. In the final result, the maximum fluctuation of profile curve within 80% of the maximum field size is less than 3%, which meets the requirements of field flatness. The optimum FWHM for different fields is not consistent due to the Transmission penumbra. But a match can be approached by adjusting the FWHM every 10 cm field size.

6-48 Design of the LLRF System for Electron Linear Accelerator

Institute of Modern Physics (IMP) is planning to construct an Electron Linear Accelerator for the research of high energy electron radiography, which consists of a thermionic RF Gun, photo cathode RF Gun, low energy beam transport line, SLAC TW acceleration tube and imaging terminal. In order to meet the demand of high energy density physics, the energy of electron beam must be up to 100 MeV. Table 1 summarizes the primary parameters of the Electron Linear Accelerator.