WE‐E‐108‐09: An Investigation of the Feasibility of Rodentmorphic 3D Dosimeters for Verification of Precision Micro‐Irradiator Treatment

Abstract

Purpose: To evaluate the feasibility of novel rodentmorphic 3D dosimeters for comprehensive high‐resolution verification of the treatment accuracy of a state‐of‐the‐art micro‐irradiator equipped with on‐line cone‐beam‐CT guidance. Methods: Anatomically accurate 3D dosimeter molds were created in a two step procedure. First, rodents were CT scanned and the structures of interest contoured (e.g. body and spine). These contours were then exported for input to a 3D printer, to generate positive dosimeter molds. The rat body dosimeter was made of regular water‐equivalent PRESAGE, while the spine was made from high‐Z PRESAGE with an effective atomic‐number close to bone. Evaluation of the dosimeters involved (i) establishing the feasibility of manufacture and accurate positioning of heterogenous inserts, (ii) verification of accurate dose‐readout by optical‐CT, and (iii) verification of sufficient bony/soft‐tissue contrast for representative CBCT IGRT positioning. Simulated rat prostate treatments were delivered with dose of 16Gy given by 4 2.5cm diameter circular fields. Results: High resolution (0.5mm isotropic) 3D dosimetry data was acquired in rodentmorphic dosimeters both with and without the high‐Z spinal insert. The spinal insert was visible under kV radiographs and CBCT, demonstrating the feasibility of IGRT positioning. Pronounced edge artifacts were observed near the flat undersurface of the rat, and near regions of sharp curvature. Further artifacts were observed in some regions near the spinal insert caused by bubbles trapped during manufacture. New manufacturing procedures utilizing the flexibility of 3D printing to precisely customize contours in non‐critical regions have improved on both of these limitations. Conclusion: This work demonstrates promising feasibility for anatomically accurate 3D rodentmorphic dosimeters compatible with very high resolution 3D dosimetry. The ability to create such dosimeters is an important step forward in enabling accurate verification of complex micro‐irradiator treatments in the pre‐clinical setting. NIH Grant No. R01 CA 100835