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Evaluation of Leaf Position and Irradiation Accuracy for Two Different Multileaf Collimators Equipped On CyberKnife

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J Suzuki

J Suzuki*, H Takahashi , K Hamajima , M Niwa , Y Ohashi , T Okuda , TOYOTA Memorial Hospital, Toyota, Aichi


SU-I-GPD-T-611 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: A second-generation multileaf collimator (MLC) for the CyberKnife system (InCise 2: 26 leaf pairs, leaf width of 3.85 mm) has been introduced recently. Its leaves are thicker and heavier than those of the first-generation MLC (InCise: 41 leaf pairs, leaf width of 2.5 mm). We evaluated the effect of the heavier leaves on the leaf position accuracy and the irradiation accuracy.

Methods: The leaf position accuracy for the two MLCs was quantitatively evaluated at the home position and at two other positions were gravity effects may become significant, using the Bayouth test with an EBT3 film . Similarly, the picket fence test was carried out as a qualitative evaluation. To assess the irradiation accuracy, an end-to-end test was performed using the MLCs with five different image guidance techniques.

Results: In the Bayouth test, which yields quantitative results in the three directions, the average absolute position error was 0.20 ± 0.10 mm for InCise and 0.08 ± 0.04 mm for InCise 2. Also, no systematic error due to gravity was observed on the MLCs. The qualitative visual analysis performed through the picket fence test clearly showed that InCise 2 generated better match lines than InCiseTM . In end-to-end test, the average irradiation accuracy was 0.50 ± 0.19 mm for InCise and 0.45 ± 0.20 mm for InCise 2.

Conclusion: The leaf position accuracy was improved in InCise 2, even with heavier leaves. However, in terms of the irradiation accuracy, there was no obvious difference between InCise and InCise 2.

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