S128
Brachytherapy - Physics
ESTRO 2026
and Skin (HNS) GEC-ESTRO Working Group critical review of recommendations regarding prescription depth, bolus thickness and maximum dose in skin superficial brachytherapy with flaps and customized moulds. Radiother Oncol, 175, 122–132.[2] Delishaj D, Rembielak A, et al. (2016). Non-melanoma skin cancer treated with high-dose-rate brachytherapy: a review of literature. J Contemp Brachytherapy, 8(6), 533–540.[3] Poltorak M, Banatkiewicz P, et al. (2024). Brachytherapy and 3D printing for skin cancer: A review paper. J Contemp Brachytherapy, 16(2), 156– 169. Automated needle reconstruction in HDR prostate brachytherapy via a commercially compatible 3D- printed TRUS sleeve with integrated EM tracking sensors Holly Frank 1 , Andrew J Moyo 2 , Dalton Griner 1 , Kelli A Anderson 1 , Jonathan M Morris 3 , Brad J Stish 1 , Jessica Wilson 1 , Mark R Waddle 1 , Chris L Deufel 1 1 Radiation Oncology, Mayo Clinic, Rochester, USA. 2 Anatomic Modeling Unit, Mayo Clinic, Rochester, USA. 3 Radiology, Mayo Clinic, Rochester, USA Mini-Oral 2509 Purpose/Objective: Electromagnetic (EM) tracking has been shown to improve the quality and efficiency of ultrasound-based HDR prostate brachytherapy1 by using tracking technology to perform the digital reconstruction of needle locations for treatment planning. This work integrates electromagnetic tracking sensors within a 3D-printed transrectal ultrasound (TRUS) sleeve. The sleeve was engineered to be compatible with a commercially available ultrasound probe and stepper to enable clinical adoption. Material/Methods: A commercially available TRUS probe (E14CL4b, B&K Medical, Burlington, MA) was digitally scanned and CAD software was used to create a conformal 3D printed sleeve manufactured using independently verified biocompatible sterilizable material, Biomed Durable Resin (Formlabs, Somerville, MA), within a point of care manufacturing facility at our institution. The sleeve design included channels for EM tracking sensors and ‘snap-on’ mounting features for reproducible positioning with respect to the TRUS probe. EM tracking sensors were located at the apex of the probe in the plane of the TRUS axial image array to minimize EM distortion effects and mounting uncertainties. Multiple sleeves were printed and evaluated for their consistency in sensor insertion and sleeve mounting. Sleeve-to-DICOM image calibrations were performed independently for 8 sleeves in a water tank phantom using 7 needles distributed over
column generation approach was used to generate catheter trajectories while also providing an optimality gap for comparisons. Constraints ensure that the catheters do not intersect, and there are additional constraints on the catheter trajectories, including e.g. restrictions on curvature. The maximum number of catheters can be specified by the user. Results: For both scenarios, we obtain treatment plans in which the dose to the target and the organs of interest adhere to the prescribed dose guidance. See Figure 1 for an illustration of target coverage for scenario (i) and Figure 2 for an illustration of scenario (ii).
Figure 1: The aim is to cover the target with a uniform dose.
Figure 2: The 100%-isodose line should cover the margins, after the non-radical surgery, and it is enough to have a lower dose in the middle of the target. Conclusion: Automated catheter placement and treatment planning for 3D-printed scalp applicators is feasible and produces clinically acceptable dose distributions, reducing manual workload and enabling complex target shapes. Keywords: treatment planning, 3D-printed applicators References: [1] Gonzalez-Perez V, Rembielak A, et al. (2022). H&N
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