Development and feasibility evaluation of an AR-assisted radiotherapy positioning system

Abstract

PurposeThe aim of this study is to develop an augmented reality (AR)–assisted radiotherapy positioning system based on HoloLens 2 and to evaluate the feasibility and accuracy of this method in the clinical environment.MethodsThe obtained simulated computed tomography (CT) images of an “ISO cube”, a cube phantom, and an anthropomorphic phantom were reconstructed into three-dimensional models and imported into the HoloLens 2. On the basis of the Vuforia marker attached to the “ISO cube” placed at the isocentric position of the linear accelerator, the correlation between the virtual and real space was established. First, the optimal conditions to minimize the deviation between virtual and real objects were explored under different conditions with a cube phantom. Then, the anthropomorphic phantom–based positioning was tested under the optimal conditions, and the positioning errors were evaluated with cone-beam CT.ResultsUnder the normal light intensity, the registration and tracking angles are 0°, the distance is 40 cm, and the deviation reached a minimum of 1.4 ± 0.3 mm. The program would not run without light. The hologram drift caused by the light change, camera occlusion, and head movement were 0.9 ± 0.7 mm, 1.0 ± 0.6 mm, and 1.5 ± 0.9 mm, respectively. The anthropomorphic phantom–based positioning errors were 3.1 ± 1.9 mm, 2.4 ± 2.5 mm, and 4.6 ± 2.8 mm in the X (lateral), Y (vertical), and Z (longitudinal) axes, respectively, and the angle deviation of Rtn was 0.26 ± 0.14°.ConclusionThe AR-assisted radiotherapy positioning based on HoloLens 2 is a feasible method with certain advantages, such as intuitive visual guidance, radiation-free position verification, and intelligent interaction. Hardware and software upgrades are expected to further improve accuracy and meet clinicalbrendaannmae requirements.

Feasibility evaluation of radiotherapy positioning system guided by augmented reality and point cloud registration

“…6 Therefore, to meet the accuracy and stability requirements of radiotherapy positioning, we used an HD camera instead of an HMD, which can provide more stable recognition results and also enables AR surveillance. Compared with other studies using AR, 6,21,25 the error of the proposed system is significantly lower, especially the displacement deviations in sub-millimeter, which is comparable to the advanced SGRT. 26 Although the application of PCR has become increasingly extensive in the medical field, [27][28][29] few studies focus on its optimal utilization in radiotherapy.…”

“…However, despite the decreased accuracy observed in free-breathing positioning, the results still fall within the clinically acceptable error range and are higher than those reported in similar studies. 6,21,25 Nevertheless, the decrease in the accuracy highlights the need to minimize the effects of breathing-induced deformation during positioning.To address this,it is necessary to optimize the registration algorithm, such as by incorporating a deformation registration step to correct for breathing errors. In addition to considering the impact of breathing.…”

“…For instance, it will bring more complex workflows to radiotherapy technicians and additional radiation to patients. Most importantly, the positioning error can only be reflected by these technologies at the time of scanning, while real‐time guidance cannot be achieved 6 . By contrast, SGRT can achieve radiation‐free and high‐precision radiotherapy placement.…”

“…However, it is more suitable for applications that do not require high stability and accuracy, including medical AR games, 22 medical teaching tools, 23 simulation experiments, 24 etc., since users can easily get fatigued when using HMD. Additionally, it is difficult to ensure system stability due to the wearer's angle, height, etc., and only relatively steady results can be recorded 6 . Therefore, to meet the accuracy and stability requirements of radiotherapy positioning, we used an HD camera instead of an HMD, which can provide more stable recognition results and also enables AR surveillance.…”

“…Nevertheless, the method had an accuracy error of up to 3.0 ± 1.5 mm, which did not fall within the clinically acceptable error range. A previous study about AR‐assisted radiotherapy positioning systems was only conducted under optimal conditions, and the errors in all directions were above 2 mm, which posed a significant limitation 6 . Results of AR‐assisted radiotherapy positioning in another study showed that the errors of the Y and Z axis were lower than manual positioning, but the errors were still above 2 mm 7 .…”