MO‐F‐108‐12: Evaluation of the Planar Ion Chamber and the Cylindrical Diode Arrays for Extracranial Cyberknife Patient Specific QA

M. Lin, I. Veltchev, J. li, R. Price, J. Fan, L. Jin, S. Koren, C. ma

Research output: Contribution to journalArticle

Abstract

Purpose: The robotic‐radiosurgery‐system (Cyberknife) has been increasingly employed for extracranial treatments. The recent development of the MLC‐equipped ‐ Cyberknife emphasizes this application more, especially for larger treatment volumes. This work is aimed to study the feasibility of the ArcCHECK and the MatriXX systems for CyberKnife patient‐specific QA and compare their performance. Methods: Fiducial markers were implanted in both systems to enable image‐based setup. The output factors measured by them were compared with commissioning data. The impact of angular dependency on the Cyberknife measurements and the sensitivity of detecting the translational (1–3mm) and the rotational (1–3 degree) delivery errors were also evaluated for both systems. Single‐beam‐plans, isocentric‐plans and ten extracranial Cyberknife patient plans (PTV 5–136cm3) were measured and compared with calculated QA plans. The plan dose distributions were calculated with Ray‐tracing and the Monte Carlo (MC) method, respectively. The gamma‐passing‐rates with different criteria were evaluated and compared. Results: With the 0.8×0.8 mm2 diodes, the output factors measured with the ArcCHECK compare better with commissioning data. The maximum angular‐correction for a given beam is 8.2% for the MatriXX and 2.4% for the ArcCHECK. Both systems demonstrate a comparable sensitivity of detecting the translational targeting errors while the ArcCHECK is more sensitive to the rotational targeting error. MC calculations are necessary for the ArcCHECK calculations since the Ray‐tracing‐algorithm fails to handle the heterogeneity. For all the studied Cyberknife patient plans, the ArcCHECK system demonstrates 100% (3%/3mm) and >96% (2%/2mm) passing‐rates. In contrast, the MatriXX system demonstrates >92% (3%/3mm) and ∼80% (2%/2mm) passing‐rates and the passing‐rates decrease with PTV/cone sizes. Conclusions: The feasibility of using the ArcCHECK or the MatriXX systems for Cyberknife patient‐specific QA has been demonstrated. The gamma‐passing‐rate is higher for the ArcCHECK system. The custom angular correction is necessary as proven by the improved passing‐rate, especially with the MatriXX system.

Original languageEnglish (US)
Number of pages1
JournalMedical Physics
Volume40
Issue number6
DOIs
StatePublished - Jan 1 2013

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging

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