Radiation and Cancer Physics

SS 15 - Physics 3 - Treatment Planning

108 - Automated High-Dose-Rate Surface Brachytherapy Treatment Planning for Complex Head and Neck Cases With 3D-Printable Masks

Monday, October 22
4:25 PM - 4:35 PM
Location: Room 006

Automated High-Dose-Rate Surface Brachytherapy Treatment Planning for Complex Head and Neck Cases With 3D-Printable Masks
C. V. Guthier1, D. A. O'Farrell1, M. S. Bhagwat1, P. M. Devlin1, R. A. Cormack1, and I. Buzurovic2; 1Department of Radiation Oncology, Brigham and Women’s Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, 2Department of Radiation Oncology, Dana-Farber Cancer Institute/Brigham and Women's Hospital, Boston, MA

Purpose/Objective(s): High-dose-rate brachytherapy with custom surface molds are used to treat malignant skin diseases. In preparation for the treatment for head and neck cases (HN) the radiation oncologist marks the outline of the target area with radiopaque wires and the physicist fabricates a thermoplastic mask with flexible multi-channel surface applicators attached. Based on a planning CT with the mask on catheter are manually digitized followed by semi-automated planning. Building the mask and catheter digitization are time intensive manual processes. To improve the process and increase the quality of plans we introduce a fully automated approach that optimizes dwell-positions and dwell-times and replaces manual catheter digitization and manufacturing of the mask by introducing a 3D printable mask that functions as an applicator holder.

Materials/Methods: The automated planning uses mask free CT images to contour body, CTV, PTV and potential OARs. The in-house developed planning system virtually places the applicator on the body structure in a way that the number of potential dwell-positions on the CTV is maximized and trajectory constraints, i.e. maximum curvature the source can travel, are met. Dwell-times are optimized using constrained least-square optimization. Dwell-positions and connected catheter trajectories define the topology of the applicator hold/mask from which a 3D printable file is automatically generated. The retrospective IRB approved study used 5 head and neck cases covering the range of typical clinical cases. For each of the patient treatment plans and masks were automatically generated and compared with the clinical plans

Results: All automatically generated plans were clinically acceptable. Processing of the structures and catheter placement and dwell-time optimization took from 9.9s to 81.9s, depending on the complexity of the case. The number of used catheters in the study ranged from 10 to 27 with 76 to 445 dwell-positions. Generating the printable mask file took up to 10 minutes and print time was adjusted to take less than 12 hours for a complex mask. By design, the generated plans always meet organs at risk constraints. Compared to the clinical plans it further provided a significant increase of the D90, which was found to be (90.6±2.3)%.

Conclusion: The proposed methodology allowed fully automated treatment planning for complex HN skin cases. The achieved plan quality is comparable or improved in comparison to the clinically used. The 3D printable applicator holder/mask ties the treatment plan to its topology and guarantees highly conformal and reproducible plans. Since manual channel digitization and manufacturing of the mask can be omitted, the presented approach can potentially reduce the planning time and thus save several hours of clinical time per patient.

Author Disclosure: C.V. Guthier: None. D.A. O'Farrell: None. P.M. Devlin: None. R.A. Cormack: Honoraria; American Association of Physicists in Medicine, American Brachytherapy Society, ASTRO. Travel Expenses; American Association of Physicists in Medicine, American Brachytherapy Society. Board Member; New England Chapter of AAPM.

Christian Guthier, PhD, MS

Disclosure:
Employment
Dana-Farber/Brigham and Women's Cancer Center HMS: Postdoctoral Research Fellow: Employee

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