An electromechanical, patient positioning system for head and neck radiotherapy

Abstract

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.

Radiotherapy-Compatible Robotic System for Multi-Landmark Positioning in Head and Neck Cancer Treatments

“…The mechanical positioning accuracy of this system was less than that of other similar robotic applications, such as those presented by Liu 12 or Ostyn 11 . For example, our previously introduced system had a positioning error of 0.4 ± 0.3 mm error, compared to the 0.7 ± 0.3 mm of the system in this work.…”

“…All materials used in the positioning robotic system were carefully selected to minimize the effects of scatter and attenuation during radiotherapy. Based on the similar method from our prior work 11 , we conducted a more rigorous method for prospectively assessing radio-compatibility for any arbitrary material. All components within 40 cm horizontally of the positioning system’s isocenter were constructed by fully using low-Z materials.…”

“…However, previous studies 1,5–10 have demonstrated that these rigid shoulder-to-face-covering masks do not fully mitigate this uncertainty with typical setup errors of 3–5 mm between distant landmarks along the spine of the neck. Recent reports 11–15 show that an accurate positioning in head and neck therapy can be achieved by independent positioning of the head from the rest of the body. However, these mechanical systems have not yet been introduced into regular clinical practice.…”

“…The placement of high-atomic number (Z) materials in the irradiated region can excessively interfere with X-ray setup guidance and therapeutic X-ray delivery. Even though our prior work 11 uses primarily low-Z plastics, this system still includes metallic motors near the treatment region or clinically infeasible locations, which limits the clearance of the linear accelerator gantry.…”

Development of twist‐correction system for radiotherapy of head and neck cancer patients

“…For the systems excluding the 6DoF couch, Dhabaan et al reported that pitch and roll angles can be corrected by mounting the customized device on the top of the treatment couch in the cranial position . Belcher et al and Ostyn et al developed an electromechanical robotic system that can provide precise 6DoF motion trajectories . These systems can correct the rotational position of the patient by themselves; therefore, they might be able to correct the twist with the couch, which has the ability to achieve rotational correction.…”