ESTRO 2021 Abstract Book

S663

ESTRO 2021

PD-0828 Low-cost optical surface capture as CT replacement in 3D printed radiotherapy surface mould creation M. Bolt 1 , K. Wells 2 , J. Willsmore 3 1 Royal Surrey, Medical Physics, Guildford, United Kingdom; 2 University of Surrey, Centre for Vision, Speech and Signal Processing, Guildford, United Kingdom; 3 University of Surrey, Physics, Guildford, United Kingdom Purpose or Objective 3D printing offers an attractive solution for the production of surface moulds for external beam radiotherapy and brachytherapy treatments. Standard practice requires the patient to have a CT image acquisition so that the Treatment Planning System (TPS) can be used for design of the mould or bolus and subsequent treatment planning. In many cases depth of treatment is constant across the treatment surface and the CT serves only to provide the surface contour. The availability of relatively low cost, non-ionising 3D surface capture devices opens up the possibility of obtaining the surface contour without the use, or dose, of CT. This work assesses the workflow feasibility of taking a low-cost surface scan and processing into a DICOM image set for use in a clinical treatment planning system and production of a 3D printed surface mould. Materials and Methods A low-cost surface capture device [1] was used to acquire 3D surface scans of the head section of the RANDO anthropomorphic phantom and repeated once per day for 3 consecutive days. The resulting surface captures were compared to one another and to the surface of a CT scan of the phantom that was taken as the gold standard. A schematic of each step of the process is given in Figure 1. To achieve the required conversion from STL to DICOM, 3DSlicer software [2] was used to convert to a binary filled image and a python script used to convert to the desired HU values. The 3 surface captures taken on different days were compared using GOM Inspect Suite [3]. Each of the points along planes separated by 2.5mm were compared and the absolute differences between them measured. The DICOM files created using 3DSlicer were imported into the Eclipse TPS V15.6 and registered to the original CT scan based on an automatic rigid registration around the VOI. The VOI volumes of each DICOM model were measured based on the TPS surface contour. Bolus was designed in the TPS to be 1cm uniform thickness and included contours over the nose. This bolus structure was exported as an STL file using an in-house script and printed on a LULZBOT TAZ6 3D printer to demonstrate proof-of-concept of the approach.