Affiliation:
1. NU-Med Cancer Diagnosis and Treatment Centre Katowice , Poland
Abstract
Abstract
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. Nd,w,Qcross obtained in beam ≥ 9MeV gives 0.1 – 0.5% precision of dose reconstruction.
Without beam quality correction, 15 MeV Nd,w,Qcross is 10% lower than Co-60 Nd,w,0. Various EPOM shifts resulted in up to 0.6% discrepancies in Nd,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.
Reference26 articles.
1. 1. Andreo P, Burns DT, Hohlfeld K, Huq MS, Kanai T, Laitano F, Smyth V, Vynckier S. Absorbed Dose Determination in External Beam Radiotherapy: An International Code of Practice for Dosimetry based on Standards of Absorbed Dose to Water. Vienna: International Atomic Energy Agency. (IAEA TRS-398); 2006.
2. 2. Almond PR, Biggs PJ, Coursey BM, Hanson WF, Huq MS, Nath R, Rogers DWO. AAPM’s TG-51 protocol for clinical reference dosimetry of high-energy photon and electron beams. Med Phys. 1999;26(9):1847-1870. https://doi.org/10.1118/1.59869110.1118/1.598691
3. 3. Thwaites DI, DuSautoy AR, Jordan T, McEwen MR, Nisbet A, Nahum AE, Pitchford WG. The IPEM code of practice for electron dosimetry for radiotherapy beams of initial energy from 4 to25 MeV based on an absorbed dose to water calibration. Phys Med Biol. 2003;48(18):2929-70. https://doi.org/10.1088/0031-9155/48/18/30110.1088/0031-9155/48/18/301
4. 4. Deutches Institut für Normung, Procedures of dosimetry with probe-type detectors for photon and electron radiation - Part 2: ionization chamber dosimetry of high energy photon and electron radiation; 2019. DIN 6800-2:2019-07
5. 5. Gerbi BJ, Antolak JA, Deibel FC, Followill DS, Herman MG, Higgins PD, Huq MS, Mihailidis DN, Yorke ED. Recommendations for clinical electron beam dosimetry: supplement to the recommendations of task group 25. Med Phys. 2009;36(7):3239-79. https://doi.org/10.1118/1.312582010.1118/1.3125820
Cited by
1 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献