Purpose: To explore 3D printing for rapid prototyping of thin-slab low-Z/density ionization chamber arrays viable for specialized QA tasks.
Methods: We designed and fabricated thin-slab ionization chamber arrays as well as a large area parallel plane ion-chamber using an off-the-shelf 3D printer (Luzbotâ„¢). Conductive and insulating components were made of conductive PLA (cPLA) and of ABS, respectively. The constituent elements were assembled in a LEGOTM-like fashion to decrease potential 3D printing artifacts in the final product. We characterized the detector responses using a Varian TrueBeam linac in isocentric setup at 5cm depth in solid water phantom. We measured the current-voltage (IV) curves, the response to different energy beam lines (2.5 MV, 6 MV, 6 MV-FFF) for various dose rates and MUs, and compared them to the responses of a commercial Exradin A12 ionization chamber. We measured off-axis-ratio (OAR) for several small field static and dynamic MLC field sizes (0.5-3cm) and compared them to water tank data measured with stereotactic PTW diode.
Results: We characterized the capabilities of the 3D printer for rapid prototyping of detector arrays with sub-mm features. Cubic and cylindrical shapes of the chambers were printed down to 4mmX4mmX4mm volumes. IV curves for the arrays showed some polarity effect due to the design. Dose and dose rate dependence for the parallel plate and the array compared well with the A12 chamber. OAR measured with the array were comparable to dose profiles obtained from water tank diode data after accounting for the size of the array chambers.
Conclusion: Rapid prototyping of ion chambers by means of low-cost 3D printing is feasible with few limitations in the design and spatial accuracy of the printed details. Despite these limitations, it is a viable solution for fabrication of arrays with a few mm spatial resolution for customized QA tasks (e.g. linac QA).