Résumé
Objective To explore the effect of DAVID system on the beam dosimetry of ELEKTA Synergy accelerator. Methods Three-dimensional water phantom system was used to measure the values of percentage depth dose (PDD) in different fields,gun-trarget(G-T)in different fields and depths as well off-axis ratio(OAR)at left-right(L-R)direction when the accelerator was equipped with DAVID system or not. Results DAVID system had no effects on PDD and OAR, while influenced the absorbed dose so that the ray was attenuated by 7%.Conclusion The field parameters have not to be modified for the planning system when using DAVID system,but the dose correction has to be performed according to ray transmission factors.
Résumé
<p><b>OBJECTIVE</b>To explore the effect on the iso-center and OAR and PDD of the MV class X-ray coming from the linac when we use the glass mirror to replace an imported one.</p><p><b>METHOD</b>Data collected by using a film and 3D water phantom OAR and PDD measuring methods based on the different conditions. Comparison and analysis of the effect levels for different thickness and material mirrors are made.</p><p><b>RESULT</b>The PDD max error of the 4 mm general glass mirror is 6%.When the 8MV X-ray 720 Gy irradiation is given, the light field appears a dual cross lines and has darker brightness. The PDD max error of the 1.5 mm quartz glass mirror is less than 1%. When it accepts the equal radiation dose, the light field iso-center and OAR and field brightness are agreed well with clinical demands.</p><p><b>CONCLUSION</b>Our practice shows that the 4 mm general glass mirror can't suffer the MV class X-ray irradiation but the thin quartz glass mirror can. So the thin quartz glass mirror can be used for the linac.</p>