In cancer treatment with radiation, accurate patient setup is critical for proper dose delivery. Improper arrangement can lead to disease recurrence, permanent organ damage, or lack of disease control. While current immobilization equipment often helps for patient positioning, manual adjustment is required, involving iterative, time-consuming steps. Here, we present an electromechanical robotic system for improving patient setup in radiotherapy, specifically targeting head and neck cancer. This positioning system offers six degrees of freedom for a variety of applications in radiation oncology. An analytical calculation of inverse kinematics serves as fundamental criteria to design the system. Computational mechanical modeling and experimental study of radiotherapy compatibility and x-ray-based imaging demonstrates the device feasibility and reliability to be used in radiotherapy. An absolute positioning accuracy test in a clinical treatment room supports the clinical feasibility of the system.

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The selection of posture between supine and prone induces changes in the characteristics of respiratory patterns in lung cancer patients. We characterize these differences, as well as introduce two new metrics to describe the quality of amplitude-based gating. The stability of the following metrics were measured for 134 supine-and-prone-paired individual breathing sessions from 22 patients: amplitude, period, inhale-to-exhale period ratio, and location of end-of-exhale and end-of-inhale peaks. A new normalization characteristic of typical amplitude was introduced for comparing patients based on external surrogates. This metric was used to characterize the baseline drift and to compare the overall gating efficiency between different amplitude-based gating parameters in a new proposed metric called the gating efficiency index. While the choice of supine or prone posture had negligible impact on the overall duty cycle or gating efficiency, some metrics showed greater difference, especially with prone showing reduced variability in period, inhale-to-exhale period ratio, amplitude, and relative amplitude of end-of-exhale. Therefore, the breathing pattern resulting from prone positioning was found to be more favorable due to less intrafraction variation. The gating efficiency index was used to quantitatively show that narrow amplitude gating windows near end-of-exhale have the best balance of decreased motion variability within gating while maintaining the longest duty cycle.

Purpose Since the publication of the AAPM TG128 report for the quality assurance (QA) of prostate brachytherapy ultrasound systems, no commercially available phantoms have been developed which satisfy all of the task group recommendations. Current solid phantoms require a separate user‐implemented setup using a container with liquid medium to evaluate the alignment between the needle template and the electronic grid, a test of geometric accuracy with critical implications in dosimetric quality. Utilizing a 3D printer, we constructed a cost‐effective, liquid‐based phantom that provides a complete TG128 solution which improves the efficiency of brachytherapy ultrasound QA. Methods The TG128 report was used to guide the design process of the liquid‐based phantom. The needle template and electronic grid alignment setup served as the foundation with specific components developed to integrate all remaining tests. Water was chosen as the liquid medium, with speed of sound adjusted to 1,540 m/s via salinity per the task group recommendations. The proof of concept was evaluated by comparing the time stamps labeled on QA images between the liquid‐based phantom and a commercially available one for both a new and experienced user. Results A TG128 QA trial run demonstrated that all recommended tests can be completed with the single phantom setup. Evaluation of the time data revealed a total QA duration of 45 min (average of two trials) with the liquid‐based phantom, compared to 70 and 90 min with the commercial phantom for a new and experienced user. Conclusions The liquid‐based phantom is specifically designed to satisfy the recommendations of the TG128 report. The incorporation of 3D printing allows simple design modifications to adapt the phantom on‐the‐fly if needed. The resulting product improves the efficiency of brachytherapy ultrasound QA by eliminating the need for multiple phantom setups.