Journal Article

DKFZ-2023-01745

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Leaf-individual calibration for a double stack multileaf collimator in photon radiotherapy.

Rippke, C. ; Renkamp, C. K. ; Attieh, C. ; Schlüter, F. ; Buchele, C. ; Debus, J.DKFZ* ; Alber, M. ; Klüter, S.

2023
Elsevier Science Amsterdam [u. a.]

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Please use a persistent id in citations: doi:10.1016/j.phro.2023.100477

Abstract: In online adaptive stereotactic body radiotherapy treatments, linear accelerator delivery accuracy is essential. Recently introduced double stack multileaf collimators (MLCs) have new facets in their calibration. We established a radiation-based leaf-individual calibration (LIMCA) method for double stack MLCs.MLC leaf positions were evaluated from four cardinal angles with test patterns at measurement positions throughout the radiation field on EBT3 radiochromic film for each single stack. The accuracy of the method and repeatability of the results were assessed. The effect of MLC positioning errors was characterized for a measured output factor curve and a clinical patient plan.All positions in the motor step - position calibration file were optimized in the established LIMCA method. The resulting double stack mean accuracy for all angles was 0.2 ± 0.1 mm for X1 (left bank) and 0.2 ± 0.2 mm for X2 (right bank). The accuracy of the leaf position evaluation was 0.2 mm (95% confidence level). The MLC calibration remained stable over four months. Small MLC leaf position errors (e.g. 1.2 mm field size reduction) resulted in important dose errors (-5.8 %) for small quadratic fields of 0.83 × 0.83 cm2. Single stack position accuracy was essential for highly modulated treatment plans.LIMCA is a new double stack MLC calibration method that increases treatment accuracy from four angles and for all moving leaves.

Keyword(s): Adaptive radiotherapy ; Image guided radiotherapy ; MR-Linac ; MR-guided radiotherapy ; Multileaf collimator ; Photon radiotherapy ; Quality assurance ; Quality control ; Small field dosimetry

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Contributing Institute(s):

1. E050 KKE Strahlentherapie (E050)
2. DKTK HD zentral (HD01)

Research Program(s):

1. 315 - Bildgebung und Radioonkologie (POF4-315) (POF4-315)

Appears in the scientific report 2023

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Database coverage:
; ; Article Processing Charges ; Clarivate Analytics Master Journal List ; DOAJ Seal ; Emerging Sources Citation Index ; Fees ; IF < 5 ; JCR ; PubMed Central ; SCOPUS ; Web of Science Core Collection

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