The Contribution of the RTNORM EU Consortium to the Update of the k_Q,Q0 Factors for the International Dosimetry Code of Practice IAEA TRS 398

The International Atomic Energy Agency (IAEA) issued the TRS-398 radiation dosimetry Code of Practice (CoP) in 2000, which is the de facto norm for radiotherapy dosimetry and is used on a worldwide basis. One of the essential contributions of the TRS 398 CoP is the ability to correct a radiation dosimeter response for differences between beam qualities, which relate to the energy distribution of the radiation fields, at the calibration laboratory (Q0) and the beam qualities at the hospitals (Q). These corrections are called beam quality correction factors and are known as k_Q,Q0 (or k_Q, for short, when the Q₀ quality is that of radiation emitted from ⁶⁰Co sources). The datasets of the TRS 398 were prepared in the mid-1990s and include values of k_Q factors that were calculated for clinical radiotherapy beams over the entire range of beam modalities that were available at that time. Many technological advances have resulted since the first publication of the TRS 398: new models of ionization chambers, new radiation beam modalities (e.g. flattening filter free beams) and new recommendations [2] have emerged. Accordingly, the IAEA has recently issued two calls for new k_Q datasets, a first call aimed at experimental determinations, and a second call for Monte Carlo-calculated k_Q factors.