Beam size limit for pencil minibeam radiotherapy determined from side effects in an in-vivo mouse ear model
Matthias Sammer, Katharina Teiluf, Stefanie Girst, Christoph Greubel, Judith Reindl, Katarina Ilicic, Dietrich W. M. Walsh, Michaela Aichler, Axel Walch, Stephanie E. Combs, Jan J. Wilkens, Günther Dollinger, Thomas E. Schmid
In a recent study, a German research team used SARRP to assess the potential side effects of certain spatially fractionated sub-millimeter radiotherapy beams. Spatial fractionation involves the use of “a pattern of sub-millimeter beams (minibeams)” to deliver radiation with the goal of minimizing side effects and sparing healthy surrounding tissue.
Within this study, a radiotherapy grid pattern called a “pencil beam” was applied to mice ears in varying beam diameters and doses. The study determined that a mouse ear receiving “a high dose (up to 60 Gy) irradiation with a single pencil beam in sizes of up to and including 1 mm” sustained no visible swelling or skin damage. Furthermore, while an increase in beam sizes beyond 1mm did correspond to adverse side effects, researchers saw only a gradual increase in these reactions—as opposed to a sharp increase—which demonstrates that spatial fractionation may play a key role in safeguarding healthy tissue even when leveraged beyond the preferred minibeam range.
The value of SARRP:
Researchers needed a mechanism by which to administer pencil beam radiotherapy to a highly specific area on the mouse ear. Needless to say, extreme accuracy was essential to targeting the appropriate spot each time, on each mouse, in order to ascertain the response to treatment with each varying beam size. Researchers crafted a holding device for the mice that could function within the SARRP, so they were able to properly position the ear to receive radiation in the targeted pattern and location. By enabling a fully functional and accurate pre-clinical environment in which to conduct minibeam radiotherapy studies, SARRP is helping scientists determine best practices for delivering maximally effective cancer radiation treatments with minimal side effects.[:]