Purpose: To facilitate the clinical use of 3D printed bolus (3DPB) with accurate placement during setup based on projected isocenter and bolus orientation and with a new clinical workflow to allow a coherent link between radiotherapy planners, machine-shop engineers, and therapists.
Methods: An Eclipse plugin program to export 3DP_Bolus.stl file with 3DPB structure and ISO-points.txt file containing 3 key-point coordinates, including the projected isocenter and two points that are 1cm away from the isocenter in the X1 and Y2 directions (Varian jaw definition) to the external surface of the 3DPB. A special ARIA carepath with patient treatment information and bolus labeling instruction was created to pass the 3DPB task from planners, to machine-shop, and to therapists. Based on the ISO-points.txt file, three 2mm-diameter hemispheres were created and merged with the 3DP-bolus.stl file before printing. Machine-shop staff labeled it with a crosshair at the isocenter, writing 4 orientation labels and patient ID, and shipping it to a specified treatment room. 3DPB was placed after the initial patient setup by aligning the room lasers with the crosshair. Seven patients were used in this clinical 3DPB test, including 4 breast electronic-boost, 2 nasal, and 1 extremity cases.
Results: The 3DPB labeling is accurate for 7 patients’ cases by visually checking the isocenter locations and bolus orientation against the plans. Bolus placement with laser alignment is taken seconds and taped down to secure its position. It provides a conformal shape to the skin without distorting the local anatomy. The new clinical workflow ensures necessary handshakes between clinical staff.
Conclusion: This study has demonstrated that the new tool for printing and labeling 3DPB is accurate, facilitating bolus placement and that the new clinical workflow helps to ensure a reliable custom bolus production for treatment. This procedure is ready to be implemented in our hospitals.
3D, Beam Hardening, Radiation Therapy