MRI-driven design of customised 3D printed gynaecological brachytherapy applicators with curved needle channels

Abstract

BackgroundBrachytherapy involves placement of radioactive sources inside or near the tumour. For gynaecological cancer, recent developments, including 3D imaging and image-guided adaptive brachytherapy, have improved treatment quality and outcomes. However, for large or complex tumours, target coverage and local control with commercially available applicators remain suboptimal. Moreover, side effects are frequent and impact on quality of life. This signifies that brachytherapy treatment conformity can improve. Therefore, the aim of this study is to develop 3D printed personalised brachytherapy applicators with a custom vaginal topography and guided needle source channels, based on the patients’ anatomy.MethodsCustomised applicators were derived from MRI data of two gynaecological cancer patients. Needle channels were planned by the Radiation Oncologist during image segmentation. Applicators contained multi-curved channels for 6F needles (ProGuide, Elekta) and were manufactured using a digital light processing-based 3D printer. Needle channel radius constraints were measured by analysing needle insertion forces in a 3D printed template, and imposed on the designs.ResultsTwo customised needle applicators are presented. Interstitial needle channels have tapered ends to increase needle protrusion angle accuracy. Additional structures were included to serve as anchor points in MR images for applicator and needle modelling and reconstruction during treatment planning. An insertion force analysis yielded a radius constraint of 35 mm to minimise the risk on needle jamming or buckling. For radii larger than 50 mm, no differences in insertion forces were found.ConclusionA novel method to design and produce vaginal topography-based 3D prints for personalised brachytherapy applicators, derived from patient MRI data, is presented. The applicators include curved needle channels that can be used for intracavitary and guided interstitial needle placement. Further spatial optimisation of brachytherapy source channels to the patient anatomy is expected to increase brachytherapy conformity and outcome.

Design and evaluation of 3D printable patient‐specific applicators for gynecologic HDR brachytherapy

“…The initial CT scan of the patient with the water‐equivalent applicator is obtained for OARs and target contouring as well as for developing a plan in a clinical treatment planning system. The geometry of the applicator could either be based on a generic cylinder or could be entirely patient specific, based on imaging of inserted packing material 8,12,13,34,35 . Source dwell times and positions as well as contoured CT data would then be used for shielding design, which could be evaluated with applicator modelling in the planning system as well as MC simulation.…”

A single-institution review of image-guided brachytherapy for vaginal malignancies using customized molded applicators and interstitial needles

“…Nilsson et al used a two-part putty [55]. However, further work is warranted investigating the use of 3D printing in the treatment of vaginal malignancies [56,57].…”

Efficacy and safety of a 3D-printed applicator for vaginal brachytherapy in patients with central pelvic-recurrent cervical cancer after primary hysterectomy

“…While Laan et al . designed an MRIcompatible 3D-printed applicator with curved needle channels suitable for large tumors ( 35 ), we used reusable, readily available, CT-compatible, and more economical straight metal needles.…”