Cross-validation of physical dose measurements and Monte Carlo simulations for the dose distribution characteristics of abutted fields between X-rays and electron beams according to electron shielding block’s manufacturing method

Abstract

The purpose of this study was to examine the dose distribution characteristics of abutted fields of X-rays and electron beams on the basis of the electron shielding block’s manufacturing method and apply those characteristics clinically in order to provide the benefits of dosimetry. To achieve this, we created electron shielding blocks by using two different methods: the existing method, without considering the electron beam’s spreading (straight block), and a modified method, which takes this phenomenon into consideration (divergence block). Further, we cross-validated the physical dose measurements and the Monte Carlo simulations in terms of the nominal energies of the X-rays and the electron beams, the field size, and the measurement depth. As a result, compared to the straight block, the divergence block was found to reduce the overdose regions (hot spot) that occur at the field border between the X-rays and the electron beams and to increase the underdose regions (cold spot) that occur near abutted fields. Therefore, the divergence block showed a uniform dose distribution characteristic, providing a dosimetric benefit. In particular, this dosimetric benefit was maximized at the effective treatment depth (80% depth; maximum: 8.36% for the abutted field, maximum: 7.64% for the dose fluctuation region). Therefore, clinical application of shielding blocks, which provide dosimetric benefits at abutted fields by considering the phenomenon of electron-beam spreading, should be seriously considered to increase the accuracy of the prescription dose.