Program Information
Patient Specific Fluoroscopic Skin Dose Maps From Volume Rendered CT Images
M DeLorenzo*, K Yang , X Li , B Liu , Massachusetts General Hospital, Boston, MA
Presentations
SU-E-702-4 (Sunday, July 30, 2017) 1:00 PM - 1:55 PM Room: 702
Purpose: To accurately calculate patient specific skin dose maps for fluoroscopy guided interventional (FGI) procedures.
Methods: ImageJ was used to read and render a CT scan volume of an anthropomorphic body phantom (CIRS ATOM) in three dimensions. Mask matrices identified the tissue and skin voxels of the CT volume. A virtual support table was created, whose dimensions matched an interventional table in our department, and was automatically positioned at the surface of the patient skin. Radiation event parameter files were created to store the x-ray field size, orientation, beam quality and the reference point air kerma. The files also contained the table coordinates and angles with respect to the rotation isocenter of the gantry for a specific radiation event. Radiation beams were rendered as pyramids and were rotated and translated according to the specified beam file geometry description. Vector geometry determined voxels within a given beam and dose calculations were performed using the reference point air kerma, inverse square correction, backscatter factor, f-factor and measured table transmission factor tables.
Results: X-ray field size and orientation, as well as table location, incline, swing and cradle angles were successfully used to position beams with respect to the virtual patient. The dose was mapped to color, allowing visualization of skin dose for an arbitrary number of x-ray beams.
Conclusion: A graphical user interface (GUI) was developed to calculate absorbed dose to skin voxels of an anthropomorphic phantom based on three dimensional modeling from CT volumes. This software is easily extended to real patients with available three dimensional image data to estimate patient specific fluoroscopic skin dose. Further testing and experimental validation is in progress to determine the accuracy of the generated skin dose maps.
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