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Through repaired the RF driver momentary oscillation stop of Varian 2300CD linear accelerator, systematically and comprehensively expounds the three state machine mode of control system and the in-machine fault monitoring mechanism involved in maintainability of Varian high energy accelerator. It proposes an improved solution to bring RF driver output into interlock system, by doing so it can avoid the control computer breakdown and improve maintainability.
Subject(s)
Particle Accelerators , Reference StandardsABSTRACT
Objective:To analyze and compare the dose monitoring and control systems of two types of medical linear accelerator systematically from the view of mechanical and electrical engineering, and establish the method of the quality assurance of the dosimetry system and the solution in the routine maintenance.Methods: To systematically compare and analyze the system of dose monitoring and control for two types of linear accelerators (Precise Elekta and C-series of Varian Medical Systems) from twofold aspects that included machine physics and electric engineering of medical linear accelerators.Results:The monitoring system that took ionization chamber as center was established between connotation of machine physics and concrete realization of electromechanical engineering, and explained the difference and similarity between open type and sealed type of ionization chamber, and the theory that Precise series needn't be serviced by PFN.Conclusion: Based on the analysis of ionization chambers structure of medical linear accelerators on the principle of quality assurance system, proposed dosimetric testing and adjustment method, and provide reference for the establishment of quality assurance system and technical procedures of the maintenance engineering.
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Objective:To explore the process of maintenance management for large medical equipment, and the structure design and core connotation of the maintenance management software of them.Methods: Medical linear accelerator of Precise series of Elekta company was combined to achieve the objective. From the aim of designing normal operation rate to start, the failure mode and effects analysis (FMEA) was operated to analyze the maintenance strategies and maintenance manners which were established on the basis of PDCA(Plan, Do, Check, Action) cycle and the analysis mode of SWOT (Strength, Weakness, Opportunity, Threat), and it could achieve the aim of normal operation rate.Results: Through explored the connotation of maintenance management and the preliminary framework of the software of maintenance management, the detail and process of maintenance management that based on personalized accelerator of process control were established, and the element factors of software of maintenance management of accelerator also was established at the same time.Conclusion: The effective maintenance management of large medical equipment is based on informatization process management of process control, and the element factor of management software need personalized customization. On the other hand, failure mode and degradation mechanism of equipment were the basis for personalized customization, and the creation has practical value.
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Objective Toexploreinfluencingfactorsoftheulinastatin(UTI)onmyocardialprotection.Methods 120casesofa-cute myocardial infarction(AMI) patients were given UTI at the base of conventional treatment for heart failure like thrombolysis , resistance to shock .The patients were divided into group A (within 12 hours) and group B (after 12 hours) ,and than each group was divided into subdivision small dose (250 kU) ,medium dose (500 kU) ,large dose (1 000 kU) groups .The patients were re-ceived echocardiogram examination ,determination of left ventricular contraction end-diastolic diameter(LVESD ,LVEDD) testing , left ventricular ejection fraction(LVEF) testing ,each stroke output(SV) ,peak concentration of creatine kinase isoenzyme(CK-MB) after treated for one week .Results Compared with the small dose and after 12 hours groups ,large dose and within 12 hours group caused an increase of cardiac function and density loss of CK-MB peak concentration (P<0 .05) .Conclusion The same cause of myocardial injury ,dose and administration timing will affect the clinical efficacy of UTI .
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Simplified dose calculation model with high computation efficiency is often used to generate the dose matrices for beamlets in the inverse planning of the intensity modulate radiation therapy. It is likely that this simplification could degrade the quality of the final treatment plans. This paper is aimed at testing the influence of such simplification in dose calculations of beamlets and accordingly proposing methods to avoid severe degradation of the plans. Two simulation instances were adopted. The primary dose calculation model without involvment of scattering effect was used to generate the dose matrices of beamlets. The differential convolution superposition dose calculation model that well accounts for scattering effect was used to calculate the final dose distributions for given intensity profiles. It is found that the simplification in dose matrices of beamlets degrades the dose levels in the edge area of the targets, however, the degradation could be diminished or even avoided by adding a suitable margin around the targets or by using the multiple-shifted-beamlet-matrices (MSBM) method that was proposed in our previous paper.
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Humans , Radiometry , Methods , Radiotherapy Dosage , Radiotherapy Planning, Computer-Assisted , Methods , Radiotherapy, Conformal , Methods , Scattering, RadiationABSTRACT
Conformal radiation therapy using multi-leaf collimator (MLC) is considered as a conventional technology in the hospital nowadays. However the stepped leaf edge caused by the finite width of the leaves could influence the conformality that could be achievable. In this paper, the effect produced by rotating the collimator angle on the conformality was investigated. A method, in which multiple MLC fields of various rotation angles are applied, has been proposed to have the targets be more uniformly irradiated and thus to eliminate the cold spots on the targets and hot spots in normal tissues. By simulation, it has been shown that the multiple MLC field method can eliminate the stepped leaf edges and improve the conformality significantly, moreover, the PTV can receive a more uniform delivery with cold spot eliminated.
Subject(s)
Humans , Radiometry , Methods , Radiotherapy Dosage , Radiotherapy Planning, Computer-Assisted , Methods , Radiotherapy, Conformal , MethodsABSTRACT
Objective To research the validity of PET/CT in clinic for detecting lung cancer. Method There were 20 subjects who may have lung cancer according to the result form other detecting way, including 15 males and 5 females with an average age from 54 to 86. Results Malignant lesions were found in 15 cases and benign lesions in 5 cases. Discussion The examination of chest with PET/CT is suit for early diagnosis of lung cancer. The number of patient of false postive and false negative is decreased by controlling some factor.
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Objective To evaluate the value of Bolus chase technology for angiography of lower extremity. Methods 12 cases with diabetes foot or leg pain were examined with Bolus chase technology. Results Low extremity artery thrombosis was found in 12 cases. Conclusion Bolus chase technology is better than standard DSA in the display of lower extremity vessel.
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Objective To study the clinical application of Multi-slice spiral CT angiography (MSCTA) in renal arterial stenosis. Methods 36 patients clinically suspected of renovascular hypertension were examined by 16 slice or 64 slice spiral CT angiography. After scanning , three dimensional reconstruction of the blood vessels were operated. 28 cases were detected diseases of renal vessels and perivascular, and then compared with DSA. Results In the 36 cases, MSCTA showed 19 renal areterial stenosis, 3 adrenal gland neoplasms, 2 adrenal hyperplasia, 1 polycystic kidney disease. In 19 cases with MSCTA , there were 2 double renal areterial stenosis and 2 renal areterial anatomical variants. DSA showed 21 renal areterial stenosis with various degree, the accordant rate of MSCTA and DSA exceeded 90%. Conclusion MSCTA play an important role in clinical application in diagnosis of renal arterial stenosis.
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Objective To evaluate the clinical application value of MR/DSA- 3D fusion software. Method Fusion imaging was made with fusion software after performing MR and DSA examinations on nine cerebrovascular diseases sufferers. Results The fusion image of six sufferers could display the exact part having pathological changes to cerebral vessel and specify the relationship between the tissue of pathological changes and cerebral vessel, offering a scientific basis for clinics and the fusion images of three sufferers were not ideal. Conclusion MRDSA-3D fusion software can provide image with high diagnostic accuracy and treatment precision.