Dosimetric accuracy of a cross-calibration coefficient for plane-parallel ionization chamber obtained in low-energy electron beams using various cylindrical dosimeters

• Autorzy: Polaczek-Grelik Kinga , Kawa-Iwanicka Aneta , Michalecki Łukasz

Identyfikatory

DOI

10.2478/pjmpe-2021-0036

• Języki publikacji: EN

Abstrakty

EN

Introduction: The accuracy of the cross-calibration procedure depends on ionization chamber type, both used as reference one and under consideration. Also, the beam energy and phantom medium could influence the precision of cross calibration coefficient, resulting in a systematic error in dose estimation and thus could influence the linac beam output checking. This will result in a systematic mismatch between dose calculated in treatment planning system and delivered to the patient. Material and methods: The usage of FC65-G, CC13 and CC01 thimble reference chambers as well as 6, 9, and 15 MeV electron beams has been analyzed. A plane-parallel PPC05 chamber was calibrated since scarce literature data are available for this dosimeter type. The influence of measurement medium and an effective point of measurement (EPOM) on obtained results are also presented. Results: Dose reconstruction precision of ~0.1% for PPC05 chamber could be obtained when cross-calibration is based on a thimble CC13 chamber. N_d,w,Qcross obtained in beam ≥ 9MeV gives 0.1 – 0.5% precision of dose reconstruction. Without beam quality correction, 15 MeV N_d,w,Qcross is 10% lower than Co-60 N_d,w,0. Various EPOM shifts resulted in up to 0.6% discrepancies in N_d,w,Qcross values. Conclusions: Ionization chamber with small active volume and tissue-equivalent materials supplies more accurate cross-calibration coefficients in the range of 6 – 15 MeV electron beams. In the case of 6 and 9 MeV beams, the exact position of an effective point of measurement is of minor importance. In-water cross-calibration coefficient can be used in a solid medium without loss of dose accuracy.

Słowa kluczowe

EN

cross calibration; low energy electron beams; effective point of measurement; PPC05 ionization chamber; dosimetry in radiotherapy

• Wydawca: Polskie Towarzystwo Fizyki Medycznej ; De Gruyter
• Czasopismo: Polish Journal of Medical Physics and Engineering
• Rocznik: 2021
• Tom: Vol. 27, Iss. 4
• Strony: 303--313
• Opis fizyczny: Bibliogr. 26 poz., rys., tab.

Twórcy

autor

Polaczek-Grelik Kinga

• NU-Med Cancer Diagnosis and Treatment Centre Katowice, Poland

autor

Kawa-Iwanicka Aneta

• NU-Med Cancer Diagnosis and Treatment Centre Katowice, Poland

autor

Michalecki Łukasz

• NU-Med Cancer Diagnosis and Treatment Centre Katowice, Poland

Bibliografia

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