Objective. In brachytherapy for gynecological cancers using intracavitary applicators, implant reconstruction is commonly performed using applicator libraries. These libraries contain applicator geometry models as well as dwell position (DP) models defined in respect to the applicator geometry. In this study, we investigate whether an afterloader integrated electromagnetic tracking (EMT) system can be utilized for DP model definition and quality assurance in such applicators. Approach. DPs in four sets of two configurations of the Elekta Venezia Advanced Gynaecological Applicator (22 mm ovoids/40 mm intrauterine (IU) and 26 mm ovoids/70 mm IU) were measured using an afterloader integrated EMT system. Measurements were evaluated for reproducibility and compared against manufacturer-specified (MS) DPs and a computed tomography (CT)-corrected DP model. Main Results. Excellent EMT measurement reproducibility was observed, with values of ⩽0.2 mm for both configurations. The overall reproducibility, including applicator geometry reproducibility, was ⩽0.4 mm for both configurations. Significant discrepancies from the manufacturer’s DP model were observed, with a mean ± sd deviation of 1.13 ± 0.66 mm (22/40) and 1.37 ± 0.63 (26/70), particularly in the IU channel, where MS DPs were not experimentally defined. Discrepancies were reduced to 0.89 ± 0.41 mm (22/40) and 0.81 ± 0.33 mm (26/70) when the CT-corrected DP model was used as baseline, highlighting the need for experimentally defined DP models. The overall uncertainty of single measurements was below the clinically acceptable 2 mm limit. Significance. This study confirms that afterloader integrated EMT can accurately reconstruct source paths in gynecological brachytherapy applicators and supports its incorporation into clinical workflows for improved quality assurance and treatment precision. The importance of EMT for quality assurance was highlighted by measured deviations from manufacturer’s DP model in a clinical relevant part of the IU channel.

BACKGROUND AND PURPOSE: Although MRI-based image guided adaptive brachytherapy (IGABT) for locally advanced cervical cancer (LACC) has resulted in favorable outcomes, it can be logistically complex and time consuming compared to 2D image-based brachytherapy, and both physically and emotionally intensive for patients. This prospective study aims to perform time-action and patient experience analyses during IGABT to guide further improvements. MATERIALS AND METHODS: LACC patients treated with IGABT were included for the time-action (56 patients) and patient experience (29 patients) analyses. Times per treatment step were reported on a standardized form. For the patient experience analysis, a baseline health status was established with the EQ-5D-5L questionnaire and the perceived pain, anxiety and duration for each treatment step were assessed with the NRS-11. RESULTS: The median total procedure time from arrival until discharge was 530 (IQR: 480–565) minutes. Treatment planning (delineation, reconstruction, optimization) required the most time and took 175 (IQR: 145–195) minutes. Highest perceived pain was reported during applicator removal and treatment planning, anxiety during applicator removal, and duration during image acquisition and treatment planning. Perceived pain, anxiety and duration were correlated. Higher pre-treatment pain and anxiety scores were associated with higher perceived pain, anxiety and duration. CONCLUSION: This study highlights the complexity, duration and impact on patient experience of the current IGABT workflow. Patient reported pre-treatment pain and anxiety can help identify patients that may benefit from additional support. Research and implementation of measures aiming at shortening the overall procedure duration, which may include logistical, staffing and technological aspects, should be prioritized.

Purpose. Patient-tailored intracavitary/interstitial (IC/IS) brachytherapy (BT) applicators may increase dose conformity in cervical cancer patients. Current configuration planning methods in these custom applicators rely on manual specification or a small set of (straight) needles. This work introduces and validates a two-stage approach for establishing channel configurations in the 3D printed patient-tailored ARCHITECT applicator. Methods. For each patient, the patient-tailored applicator shape was based on the first BT application with a commercial applicator and integrated connectors to a commercial (Geneva) intrauterine tube and two lunar ring channels. First, a large candidate set was generated of channels that steer the needle to desired poses in the target region and are contained in the applicator. The channels’ centrelines were represented by Bézier curves. Channels running between straight target segments and entry points were optimised and refined to ensure (dynamic) feasibility. Second, channel configurations were selected using geometric coverage optimisation. This workflow was applied to establish patient-tailored geometries for twenty-two patients previously treated using the Venezia applicator. Treatment plans were automatically generated using the in-house developed algorithm BiCycle. Plans for the clinically used configuration, T P clin , and patient-tailored configuration, T P arch , were compared. Results. Channel configurations could be generated in clinically feasible time (median: 2651 s, range 1826-3812 s). All T P arch and T P clin plans were acceptable, but planning aims were more frequently attained with patient-tailored configurations (115/132 versus 100/132 instances). Median CTV_IR D 98 and bladder D 2 c m 3 doses significantly improved ( p < 0.001 and p < 0.01 respectively) in T P arch plans in comparison with T P clin plans, and in approximately half of the patients dosimetric indices improved. Conclusion. Automated patient-tailored BT channel configuration planning for 3D printed applicators is clinically feasible. A treatment planning study showed that all plans met planning limits for the patient-tailored configurations, and in selected cases improved the plan quality in comparison with commercial applicator configurations.

Background: The steep radiation dose gradients in cervical cancer brachytherapy (BT) necessitate a thorough understanding of the behavior of afterloader source cables or needles in the curved channels of (patient-tailored) applicators. Purpose: The purpose of this study is to develop and validate computer models to simulate: (1) BT source positions, and (2) insertion forces of needles in curved applicator channels. The methodology presented can be used to improve the knowledge of instrument behavior in current applicators and aid the development of novel (3D-printed) BT applicators. Methods: For the computer models, BT instruments were discretized in finite elements. Simulations were performed in SPACAR by formulating nodal contact force and motion input models and specifying the instruments’ kinematic and dynamic properties. To evaluate the source cable model, simulated source paths in ring applicators were compared with manufacturer-measured source paths. The impact of discrepancies on the dosimetry was estimated for standard plans. To validate needle models, simulated needle insertion forces in curved channels with varying curvature, torsion, and clearance, were compared with force measurements in dedicated 3D-printed templates. Results: Comparison of simulated with manufacturer-measured source positions showed 0.5–1.2 mm median and <2.0 mm maximum differences, in all but one applicator geometry. The resulting maximum relative dose differences at the lateral surface and at 5 mm depth were 5.5% and 4.7%, respectively. Simulated insertion forces for BT needles in curved channels accurately resembled the forces experimentally obtained by including experimental uncertainties in the simulation. Conclusion: The models developed can accurately predict source positions and insertion forces in BT applicators. Insights from these models can aid novel applicator design with improved motion and force transmission of BT instruments, and contribute to the estimation of overall treatment precision. The methodology presented can be extended to study other applicator geometries, flexible instruments, and afterloading systems.