Research On Methods And Criterion Of Quality Assurance (QA) For Excimer Laser

According to an incomplete statistics, medical excimer lasers had been bought in hundreds of hospitals and applied to clinical surgery widely in China. So much difference were in status of these medical excimer lasers and a complete Quality Assurance (QA) system to evaluate and classify the performances of excimer lasers , especially some second-hand laser equipments, were needed. No matter what kind of excimer lasers, first-hand or second-hand, performances were different depends on the Situation of maintenance and use of equipments. It would be difficult to evaluate the performance of excimer lasers if we had not methods and criterion of QA system. Sometimes it could affect the impact of surgery and get the postoperative visual acuity worse in patients with such kind of surgery, also led to a decline in treatment, even a serious medical incidents and irreparable damage to hospitals and patients, as well as surgeons.The main purpose of this study was to ensure the proper parameters in application of QA of excimer laser, and to draw the range of parameters for QA through experiments on the reference of the manufacturer's quality control methods.In this paper, research idea and content was: By the analysis to principle of excimer laser and experiments on SCAN-195 high-frequency small spot excimer laser, which was more representative of current use and produced by PDI Inc. the United States, explored the proposed performance parameters and test methods of excimer laser. In accordance with this approach, divided into different performance of excimer laser and different measured part, which are the laser cavity, the optical transmission, and the end of operator side, 20 groups of data were got through the experiments. Comparing the results with performance of excimer laser, looked for the parameters which could mark the status of excimer laser equipment performance. And through discussion, determine the parameters and QA standards of excimer laser.Through experiments and discussions, the main parameters which can mark the performance of excimer laser include: 1) The pump voltage of laser cavity;2) The energy loss ratio of transmission in optical path;3) The stability of laser pulsing continuously;4) The E_p peak energy of laser pulse in operation end.Through statistical analysis the experimental data of the excimer laser, put forward parameters standards of QA:1) If the pump cavity voltage V≤13.07kv, and compared with the data of two weeks ago,△V≤0.06kv, then it could be determined that the status of laser cavity perform superior. If V≤15.50kv, and compared with the data of two weeks ago,△V≤0.372kv may determine the performance of resonant cavity to meet the clinical needs.2) When the energy loss ratio of transmission in optical path,η≤74.43%, the optical path could be considered that it had excellent transmission ability for the laser pulses, and the optical coating of the lens was in a better state; whenη≤77.70% then the optical path could be considered that the optical path transmission could meet the clinical needs.3) The stability of laser pulsing continuously, expressed by T,≤3.06 means that the stability of laser cavity show excellent status, and T≤6.18 means that the stability of laser cavity just meet the clinical needs.4) In detection of the E_p, peak energy of laser pulse in operator end, F means the pulse number when the laser pulses ablate and pass through 0.6μm reflective polyester film. If F<10, that means laser pulses were with perfect ablation ability, if F≤1 that means ablation ability of laser pulses meet the clinical needs.Because of the differences within model and structure of excimer laser, this article didn't draw parameters criterion with universal significance fully. However, due to a variety of small spot, high-frequency excimer laser working principle was similar, the QA methods and parameters criterion proposed in this study were portability. As the limit of experimental conditions, subject of this article was only SCAN-195 excimer laser. Enough detections on a variety of models excimer laser and summaries of the parameters data via experiments, was the most important condition to build a complete QA system of excimer laser with universal significance fully.