ABSTRACT
Aim: The purpose of this study is to measure radiation leakage of Siemens Primus Plus and Siemens Artiste linear accelerators in electron mode and to compare the leakage level with that recommended by the International Electrotechnical Commission (IEC) standard. Materials and Methods: In this assessment, Siemens Primus Plus linear accelerator with 10 cm × 10 cm, 15 cm × 15 cm, and 25 cm × 25 cm applicators was used. The radiation leakage in lateral and vertical directions was measured for Siemens Primus Plus and Siemens Artiste linear accelerators. Results: Data derived from radiation leakage measurement for Siemens Primus Plus and Siemens Artiste linear accelerators in lateral direction from the field edge and in vertical direction from the applicator were reported. The radiation leakage data were then compared with the IEC standard to evaluate in-air field leakage. Conclusion: Comparing the radiation leakage level from fields with the IEC standard for two applicators, the maximum that was occurred for 12 MeV electron beam and applicator size of 10 cm × 10 cm in Siemens Artiste linear accelerator was 2.3%, which is less than the IEC's recommended limit of 10%. It is concluded that the leakage amount is much less than the specified limit and that both of the linear accelerators have high level of safety. Considering the measurement stage, it also needs to be noted that the beam angle affected the radiation leakage level from field edge, and in 25° angle, it is higher than in 0° angle. Comparing radiation leakage from the right side of the field for the two linear accelerators, the amount of leakage for Siemens Primus Plus linear accelerator is more than Siemens Artiste linear accelerator
ABSTRACT
Objective To study the effects of using jaw tracking technique with Smart LMC algorithm on the absorbing dose of planning target volume (PTV) and organs at risk (OARs) in dynamic intensity-modulated radiation therapy (IMRT) for nasopharyngeal carcinoma (NPC).Methods Field fluencies of 10 cases of NPC patients were optimized using DVO algorithm on Eclipse TPS (11.0),and according to the same optimal fluence,MLC operation files were calculated using jaw tracking technique and jaw fixing technique respectively,dose distribution was calculated with AAA algorithm and jaw tracking IMRT plan (JT-IMRT) and jaw fixing IMRT plan (JF-IMRT) were generated respectively.Collimators' position at the plan implementation was observed,and the total number of plans' monitor units (MU),the dose of PTV,the absorb dose of OARs,and the actual fluence verification pass rate were compared.Results The collimators' opening gap distances in 166 control points of the JT-IMRT reduced in both X and Y directions in the field,compared to that of the JF-IMRT.Total number of the JT-IMRT's MU increased by 3.59％-11.63％.There was no statistical significant difference between the doses of the PTV.Statistical significance was found in the differences between maximum dose (Dmax) of brainstem,spinal cord,crystal,optic nerve,the mean dose (Dmean) and D50％ of parotid and their decreased values after therapy (t=5.70-8.66,P＜0.05).The actual fluence verification pass rate of the JT-IMRT was higher than that of the JF-IMRT.There was a significant difference between the results (t=5.18,P＜0.05).Conclusions The JT-IMRT plan of the smart LMC algorithm is more tolerant to the radiation leakage between inter-and intra-leaf.The dose of OARs is lower,while the dose calculation precision and the verification pass rate are higher,the actual radiation dose is more accurate and reliable.Therefore it is more suitable for clinical applications.