In modern radiotherapy there has been an escalation in the use of small static fields (<3×3 cm^2), this raises dosimetric problems for the medical physicist which are not always easy to be managed. These problems are mostly due to the loss of lateral charged particle equilibrium in the beam axis, which prevents Spencer-Attix theory to be applied, and thus reference conditions to be realized. Dosimetry of small fields is therefore generally performed basing on the comparison of the responses of different detector types, without knowing their behavior in conditions of no lateral charge equilibrium.
IAEA Technical Reports Series 483 (Dosimetry of small static fields used in external Beam Radiotherapy) provides detailed information about issues concerning small field dosimetry and a standardized guidance supported by formulas and tables derived from an extensive literature search. This allows a sufficiently accurate dosimetry, including the determination of uncertainties.
Despite the undoubted need of such a document, it has probably generated in the authors a non-optimal caution in addressing some issues, like problems related to the use of microDiamons and scintillator detectors, or ionization chambers orientation during the measurements of the output factors of very small fields. Therefore, while recognizing the importance of the large amount of data and information to which the user will be able to access thanks to this document, the author recommends using it critically, considering also the many recently published scientific articles, and those which will be published in the next future.
