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Purpose: To evaluate the accuracy of needle placement using a three-dimensional (3D) augmented reality (AR) protractor on smartphones (AR Puncture)., Materials and Methods: An AR protractor that can be rotated in three directions against the CT plane with angle guidance lines for smartphones was developed. The protractor center can be adjusted to an entry point by manually moving the smartphone with the protractor center fixed at the center of the screen (Fix-On-Screen) or by image tracking with a printed QR code placed at an entry point (QR-Tracking). Needle placement was performed by viewing a target line in the tangent direction with the Bull's eye method. The needle placement errors placed by four operators in six out-of-plane directions in a phantom using a smartphone (iPhone XR, Apple, Cupertino, CA, USA) were compared with two registration methods., Results: No significant difference in the average needle placement error was observed between the Fix-On-Screen and QR-Tracking methods (5.6 ± 1.7 mm vs. 6.1 ± 2.9 mm, p = 0.475). The average procedural time of the Fix-On-Screen method was shorter than that of the QR-Tracking method (71.0 ± 23.9 s vs. 98.4 ± 59.5 s, p = 0.042)., Conclusion: The accuracies of out-of-plane needle placements using the 3D AR protractor with the two registration methods were equally high, with short procedure times. In clinical use, the Fix-On-Screen registration method would be more convenient because no additional markers are required., (© 2023. Springer Science+Business Media, LLC, part of Springer Nature and the Cardiovascular and Interventional Radiological Society of Europe (CIRSE).)

Purpose: This study aims to introduce a new handheld device application for noncontact and real-time measurements of the angle of a biopsy needle using augmented reality (AR) image tracking technology. Furthermore, this study discusses the methods used to optimize the related coordinate design for computed tomography (CT)-guided biopsy procedures., Methods: An in-house noncontact angle measurement application was developed using AR platform software. This application tracks the position and direction of a printed texture located on the handle of a biopsy needle. The needle direction was factorized into two directions: tilting or rolling. Tilting was defined following the tilting of the CT gantry so that rolling would match the angle measured in CT images. In this study, CT-guided tumor biopsies were performed using a conventional guiding method with a protractor. The true value of needle rolling was measured by CT imaging and was then compared to the rolling measurement provided by the application developed in the current study using a mobile phone., Results: This study enrolled 18 cases of tumor biopsy (five renal tumors, five lung tumors, four retroperitoneal tumors, one soft tissue tumor, one thyroid tumor, one mesentery tumor, and one bone tumor). The measurement accuracy was - 0.2°, which was the average difference between AR and CT, and the measurement precision was 2.0°, which was the standard deviation of the difference between AR and CT measurements. The coefficient of determination (R 2 ) was 0.996., Conclusion: The noncontact needle measurement software using AR technology is sufficiently reliable for use in clinical settings. A real-time display of the needle angle that also shows the direction of the CT gantry is expected to enable a simple biopsy needle navigation., (© 2022. CARS.)

Purpose: To develop and assess the accuracy of a mixed reality (MR) needle guidance application on smartglasses., Materials and Methods: An MR needle guidance application on HoloLens2, without pre-procedural CT image reconstruction or import by manually matching the spatial and MR coordinate systems, was developed. First, the accuracy of the target locations in the image overlay at 63 points arranged on a 45 × 35 × 21 cm box and needle angles from 0° to 80°, placed using the MR application, was verified. The needle placement errors from 12 different entry points in a phantom by seven operators (four physicians and three non-physicians) were compared using a linear mixed model between the MR guidance and conventional methods using protractors., Results: The average errors of the target locations and needle angles placed using the MR application were 5.9 ± 2.6 mm and 2.3 ± 1.7°, respectively. The average needle insertion error using the MR guidance was slightly smaller compared to that using the conventional method (8.4 ± 4.0 mm vs. 9.6 ± 5.1 mm, p = 0.091), particularly in the out-of-plane approach (9.6 ± 3.5 mm vs. 12.3 ± 4.6 mm, p = 0.003). The procedural time was longer with MR guidance than with the conventional method (412 ± 134 s vs. 219 ± 66 s, p < 0.001)., Conclusion: MR needle guidance without pre-procedural CT image import is feasible when matching coordinate systems, and the accuracy of needle insertion is slightly better than that of the conventional method., (© 2021. Springer Science+Business Media, LLC, part of Springer Nature and the Cardiovascular and Interventional Radiological Society of Europe (CIRSE).)