Flash radiotherapy is a kind of radiotherapy method using ultra-high dose rate radiation. Compared with the traditional dose rate radiotherapy, it has unique radiobiological advantages. In this paper, the principle of flash radiotherapy, the process and results of biological experiments are summarized. At the same time, the advantages and challenges of flash radiotherapy are analyzed, and the future clinical application is prospected.
Radiotherapy/methods* ; Radiotherapy Dosage ; Technology

This paper introduces the failure phenomenon, failure analysis, maintenance process and method of SIEMENS PRIMUS linear accelerator.
Particle Accelerators ; Radiotherapy Dosage

PURPOSETo validate that DMPO model for "one step" algorithm can reduce the total MLC segments number, we compare the dosage distribution of "one-step" algorithm with "two-step" algorithm for generating IMRT MLC segments.

METHODSOn the platform of "Pinnacle 8.0h" version radiation treatment planning system developed by Philips, we respectively select one head and neck tumor case, one thorax tumor case and one abdomen tumor case, by means of designing seven fields IMRT planning, then utilized "one-step" algorithm and "two-step" algorithm to optimize and generate IMRT MLC segments, and then calculated dosage distribution, evaluated dosage distribution lines and DVH diagram, in order to compare the two MLC segment groups generated by the two different algorithm.

RESULTFor the three IMRT plans selected by us, the number of MLC segments generated by "two-step" algorithm appear to be larger than "one-step" algorithm but dosage distribution seems to be worse than the latter.

DISCUSSIONFor utilizing the "Pinnacle" plan system to design IMRT plan, "one-step" algorithm with "DMPO" definitely can effectively reduce the number of MLC segments, what's more, the result of dosage distribution seems to be better.

In order to adapt to different target shapes and protect the surrounding normal tissues, the design of two-dimensional electron beam radiotherapy planning requires additional lead blocks. But the Pinnacle treatment planning system can not directly shape the lead block conformity to the size of the beam field given by the doctor. Every time, physicists need to manually drag the lead block to form the required beam field. When meeting a two-dimensional electron beam treatment planning with the same field parameters as before, physicists need to rearrange the field for dose calculation, which greatly reduces the design efficiency of the two-dimensional electron beam treatment planning. In this study, we independently developed a two-dimensional electron beam radiotherapy planning system based on Qt Creator. The system can quickly design a two-dimensional electron beam radiotherapy plan, which reduces the repeated work of physicists.
Electrons ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted

OBJECTIVETo investigate the impact of metal implants with different materials on radiation dose distribution based on film measurement method.

METHODSTitanium plate, titanium intramedullary pin and stainless steel plate were set into phantom and irradiated separately by 6 MV and 15 MV X ray from linear accelerator. Dose distributions derived from different materials metal implants were measured and analyzed by film dosimeter.

RESULTSFor 6 MV X ray, the maximum interface dose increments of titanium plate, titanium intramedullary pin and stainless steel plate were 12.3%, 15.4% and 20.3%. As the radiation energy was increased from 6 MV to 15MV, the maximum interface dose increment of the titanium plate rose from 12.3% to 15.1%, the maximum interface dose increment of the steel plate rose from 20.3% to 30.8%.

CONCLUSIONSMetal implants with different materials have obvious impact on radiation dose distribution. With the increase of the metal atomic number and energy of radiation, the degree of elevated dose also increases. These results suggest that correction of dose distribution is required for radiotherapy of patients with metal implants.

OBJECTIVETo discuss the influence of setup errors on the accuracy of pelvic cancer in IGRT, analysis setup errors and determine the CTV-to-PTV margins.

METHODS60 pelvic cancer patients treated with Varian 23IX, all of them were performed by CBCT before and after-correction three times in the first week and after that once a week. Then, to measure the setup errors at X(left-right), Y(superior-inferior), Z(anterior-posterior) axis and E(coronal), F(sagittal), G(axial) rotation directions.

RESULTS530 scans obtained in all, the setup errors in X, Y, Z, E, F, G were (-0.52 ± 4.18) mm, (0.73 ± 4.86) mm, (-0.36 ± 3.62) mm, (0.14 ± 1.20)degrees, (0.13 ± 1.34)degrees, (0.21 ± 1.73)degrees respectively and were much lower after correction at X, Y, Z axis, besides, CTV-to-PTV margins decrease a lot.

CONCLUSIONThe accuracy of radiotherapy can be highly increased with the use of IGRT in pelvic cancer.

KylinRay-IMRT is the advanced radiotherapy treatment planning module of accurate radiotherapy system (KylinRay) aiming to provide accurate and efficient plan design platform. In this paper the system design, main functions and key technologies of KylinRay-IMRT were introduced. KylinRay-IMRT supports three dimensional conformal radiotherapy (3D-CRT), intensity modulated radiotherapy (IMRT) and many other types of treatment plan design with function modules including patient data management, image registration and fusion, image contouring, image three dimensional reconstruction and visualization, three dimensional conformal radiotherapy planning, intensity modulated radiotherapy planning, plan evaluation and comparison, and report print. KylinRay-IMRT has been tested by the national standard YY/T 0889-2013, the results showed that the performance of KylinRay-IMRT can fully meet the standard requirements.
Humans ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted ; Radiotherapy, Conformal ; Radiotherapy, Intensity-Modulated ; Tomography, X-Ray Computed

In this paper, two new concepts of DR (Dose Repulsion) and DG (Dose Gravitation) are presented with their calculation formulas. For the problem of selecting beam arcs in x-knife radiotherapy Planning system, a mathematics model of constrained optimization has been built. Furthermore, we have produced a feasible project of automatic selecting optimized beam arcs plan using SA (Simulated Annealing) arithmetic based on the distribution of the fields of DR and DG in the reduced phase space.
Algorithms ; Brain Neoplasms ; radiotherapy ; Models, Theoretical ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted ; methods ; Radiotherapy, Conformal ; methods

To investigate the dose effect of isocenter difference during IMRT dose verification with the 2D chamber array. The samples collected from 10 patients were respectively designed for IMRT plans, the isocenter of which was independently defined as P(o), P(x) and P(y). P(o) was fixed on the target center and the other points shifted 8cm from the target center in the orientation of x/y. The PTW729 was used for 2D dose verification in the 3 groups which beams of plans were set to 0 degrees. The γ-analysis passing rates for the whole plan and each beam were gotten using the different standards in the 3 groups, The results showed the mean passing rate of γ-analysis was highest in the P(o) group, and the mean passing rate of the whole plan was better than that of each beam. In addition, it became worse with the increase of dose leakage between the leaves in P(y) group. Therefore, the determination of isocenter has a visible effect for IMRT dose verification of the 2D chamber array, The isocenter of the planning design should be close to the geometric center of target.
Gamma Rays ; Humans ; Radiotherapy Dosage ; Radiotherapy, Intensity-Modulated ; instrumentation ; methods

OBJECTIVETo research the method of dosimetric verification of the intensity modulated radiation therapy (IMRT).

METHODSThe IMRT treatment plans were designed by Eclipse TPS and were implemented in Varian ClinacIX LA with 6MV X-ray. The absolute point doses were measured using a PTW 0.6 cc ion chamber with UNIDOS E dosimeter and the planes dose distributions were measured using PTW 2D-Array ion chamber in the phantom.

RESULTSThe error between the measured dose and calculated dose in the interesting points was less than 3%. The points passed ratio was more than 90% in gamma analysis method (3 mm 13%) about the plane dose distribution verification.

CONCLUSIONThe method of dosimetric verification of IMRT is reliable and efficient in the implementation.