Dosimetric characterization of INTRABEAM® miniature accelerator flat and surface applicators for dermatologic applications

Purpose: This study aims at characterizing the dosimetric behavior of an INTRABEAM(®) miniature accelerator equipped with flat and surface applicators, converting the spherical dose distribution into a flat one.

Methods: Dosimetric characterization was carried out in two steps. Firstly characterization was made in standard conditions for dermatologic applications, which is with the applicator directly on contact with the skin. Secondly, characterization was made in more clinical conditions, such as obliquities and heterogeneities.

Results: Behaviors of flat and surface applicators are different. Dose distribution for surface applicators is uniform at surface, whereas for flat applicator the maximum homogeneity is shown at a particular depth in water. Some results are different from previously published studies due to differences in the X-ray source design. The study showed that in the absence of a perfect contact between the applicator and the skin of the patient, there is a dose distribution spread on the edge of the irradiation field where the contact is not made. Dose loss due to lack of backscatter radiations is significant. By contrast, influence of a denser material behind the measurement point has no significant influence on the dose at this point. Thickness of tissue treated with flat and surface applicators is only a few millimeters, depending on the applicator's size, making these applicators ideal for superficial lesions, compared to high energy electrons and iridium brachytherapy.

Conclusions: The INTRABEAM(®) miniature accelerator equipped with surface applicators is a reliable way of treating superficial cutaneous malignancies.