Calculation and Analysis of Small-Field Dosimetric Correction Factors (K) for IBA CC01 and CC04 Chambers in Elekta Versa HD 6 MV FFF and 10 MV FFF Beams

Abstract

Author(s): Mohamed Ouali Alami*, EL Mehdi AL IBRAHMI, Ouafae CHFIK, EL Mahjoub CHAKIR, Khalid EL OUARDY, Yassine HERRASSI, Khalid NABAOUI and Otmane Allaoui

Accurate dosimetry in very small radiation fields is crucial for advanced radiotherapy techniques like stereotactic radiosurgery (SRS) and intensitymodulated radiotherapy (IMRT). However, small fields pose unique measurement challenges due to loss of charged-particle equilibrium and detector volume effects [1][2]. In this study, we measured field output factors for 1×1 cm² to 5×5 cm² fields in 6 MV and 10 MV flattening-filter-free (FFF) photon beams from an Elekta Versa HD linear accelerator. Two small ionization chambers, IBA CC01 (0.01 cm³) and CC04 (0.04 cm³), were used. We compared measured doses to Golden Beam Data (GBD) reference values and derived output correction factors k (the ratio of calculated-to-measured output). Results show that both chambers require modest corrections (generally 1–2%) for the smallest fields. These findings align with international recommendations for small-field dosimetry [1] and underscore the importance of applying detector-specific corrections. Clinically, using the appropriate k factors improves the agreement between planned and delivered dose in small fields, thereby enhancing treatment accuracy and patient safety.

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