Hello, my name is Dante Capaldi and here I'll be summarizing our work on developing a tungsten filled 3D printed lung block manufacturing workflow for total body irradiation. Though there's been recent developments in VMAT-TBI techniques, a recent survey published by the Children's Oncology Group revealed that the majority of TBI treatments still rely on traditional AP-PA or lateral techniques which require the manufacturing of lung blocks to shield and protect the lungs. The process of manufacturing lung blocks has traditionally used Cerrobend, which although relatively easy to use is known to contain toxic materials. Furthermore, the antiquated process of manufacturing lung blocks requires significant clinical resources and labor which ultimately limits the reproducibility and accuracy. Therefore, the objective of our study was to develop a more modern approach for generating lung blocks using 3D printing and tungsten BBs. This approach aims to improve accuracy and eliminate toxic material from clinical use. Currently, the Cerrobend block manufacturing workflow involves a significant amount of manual labor. This process includes printing and tracing lung contours onto Styrofoam, which are then cut and used as molds for pouring Cerrobend. Once the Cerrobend hardens, the blocks are then cleaned to remove any sharp edges. Alternatively, the proposed approach significantly reduces the need for manual labor and cost by employing a more digital approach, which also eliminates the need for Cerrobend. In this process, DICOM RT plan files are exported from the TPS and read in by an in-house Matlab script, which automatically generates 3D shells and caps of the lung blocks. The shells and caps are then printed and filled with tungsten BBs. Qualitatively, EPID images of the Cerrobend and 3D printed blocks are displayed along with the line profiles through the blocks. These profiles were utilized to conduct spatial comparisons between the full- width-half-max measurements from the block profiles and the plan dimensions within the TPS which are indicated here by vertical lines and the line profile plots. Quantitatively moving left to right, both ion chamber and EPID dosimetry indicated that transmission measurements through the blocks dropped by more than 50% where the 3D printed blocks attenuated to be more than the Cerrobend blocks. On average, the difference of the profiles between the TPS and the 3D printed blocks was significantly lower than that of the Cerrobend blocks. And lastly, the coefficient of variation within the central 80% of the full-width-half-max of the line profiles was significantly higher than the 3D printed blocks compared to the Cerrobend blocks. In summary, we developed and implemented a 3D printed Tungsten filled workflow for constructing TBI lung blocks, offering an alternative to the traditional Cerrobend block workflow used in clinics. Our comparison between the proposed approach and the current clinical workflow using Cerrobend revealed that the difference between the TPS defined size of the lung blocks and the 3D printed blocks was significantly less than that observed with the Cerrobend blocks and that the dosimetric measurements through the blocks demonstrated that they effectively reduce the beam by more than 50%. Ultimately, this workflow enables the production of clinically accurate lung blocks with minimal effort and facilitates the elimination of toxic material from the radiotherapy workflow.
