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      Spatial and rotational quality assurance of 6DOF patient tracking systems : Spatial and rotational quality assurance of 6DOF

      , , ,
      Medical Physics
      Wiley

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          Abstract

          <div class="section"> <a class="named-anchor" id="d482568e145"> <!-- named anchor --> </a> <h5 class="section-title" id="d482568e146">Purpose:</h5> <p id="d482568e148">External tracking systems used for patient positioning and motion monitoring during radiotherapy are now capable of detecting both translations and rotations. In this work, the authors develop a novel technique to evaluate the 6 degree of freedom 6(DOF) (translations and rotations) performance of external motion tracking systems. The authors apply this methodology to an infrared marker tracking system and two 3D optical surface mapping systems in a common tumor 6DOF workspace. </p> </div><div class="section"> <a class="named-anchor" id="d482568e150"> <!-- named anchor --> </a> <h5 class="section-title" id="d482568e151">Methods:</h5> <p id="d482568e153">An in-house designed and built 6DOF parallel kinematics robotic motion phantom was used to perform motions with sub-millimeter and subdegree accuracy in a 6DOF workspace. An infrared marker tracking system was first used to validate a calibration algorithm which associates the motion phantom coordinate frame to the camera frame. The 6DOF positions of the mobile robotic system in this space were then tracked and recorded independently by an optical surface tracking system after a cranial phantom was rigidly fixed to the moveable platform of the robotic stage. The calibration methodology was first employed, followed by a comprehensive 6DOF trajectory evaluation, which spanned a full range of positions and orientations in a 20 × 20 × 16 mm and 5° × 5° × 5° workspace. The intended input motions were compared to the calibrated 6DOF measured points. </p> </div><div class="section"> <a class="named-anchor" id="d482568e155"> <!-- named anchor --> </a> <h5 class="section-title" id="d482568e156">Results:</h5> <p id="d482568e158">The technique found the accuracy of the infrared (IR) marker tracking system to have maximal root-mean square error (RMSE) values of 0.18, 0.25, 0.07 mm, 0.05°, 0.05°, and 0.09° in left–right (LR), superior–inferior (SI), anterior–posterior (AP), pitch, roll, and yaw, respectively, comparing the intended 6DOF position and the measured position by the IR camera. Similarly, the 6DOF RSME discrepancy for the HD optical surface tracker yielded maximal values of 0.46, 0.60, 0.54 mm, 0.06°, 0.11°, and 0.08° in LR, SI, AP, pitch, roll, and yaw, respectively, over the same 6DOF evaluative workspace. An earlier generation 3D optical surface tracking unit was observed to have worse tracking capabilities than both the IR camera unit and the newer 3D surface tracking system with maximal RMSE of 0.69, 0.74, 0.47 mm, 0.28°, 0.19°, and 0.18°, in LR, SI, AP, pitch, roll, and yaw, respectively, in the same 6DOF evaluation space. </p> </div><div class="section"> <a class="named-anchor" id="d482568e160"> <!-- named anchor --> </a> <h5 class="section-title" id="d482568e161">Conclusions:</h5> <p id="d482568e163">The proposed technique was found to be effective at evaluating the performance of 6DOF patient tracking systems. All observed optical tracking systems were found to exhibit tracking capabilities at the sub-millimeter and subdegree level within a 6DOF workspace. </p> </div>

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          A solution for the best rotation to relate two sets of vectors

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            Target localization and real-time tracking using the Calypso 4D localization system in patients with localized prostate cancer.

            The Calypso 4D Localization System is being developed to provide accurate, precise, objective, and continuous target localization during radiotherapy. This study involves the first human use of the system, to evaluate the localization accuracy of this technique compared with radiographic localization and to assess its ability to obtain real-time prostate-motion information. Three transponders were implanted in each of 20 patients. Eleven eligible patients of the 20 patients participated in a study arm that compared radiographic triangulated transponder locations to electromagnetically recorded transponder locations. Transponders were tracked for 8-min periods. The implantations were all successful, with no major complications. Intertransponder distances were largely stable. Comparison of the patient localization on the basis of transponder locations as per the Calypso system with the radiographic transponder localization showed an average (+/-SD) 3D difference of 1.5 +/- 0.9 mm. Upon tracking during 8 min, 2 of the 11 patients showed significant organ motion (>1 cm), with some motion lasting longer that 1 min. Calypso transponders can be used as magnetic intraprostatic fiducials. Clinical evaluation of this novel 4D nonionizing electromagnetic localization system with transponders indicates a comparable localization accuracy to isocenter, (within 2 mm) compared with X-ray localization.
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              Physical aspects of a real-time tumor-tracking system for gated radiotherapy

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                Author and article information

                Journal
                Medical Physics
                Med. Phys.
                Wiley
                00942405
                June 2016
                May 11 2016
                May 11 2016
                : 43
                : 6Part1
                : 2785-2793
                Article
                10.1118/1.4948506
                4866954
                27277026
                cb0e9076-4091-463a-98b8-0415254a19a4
                © 2016

                http://doi.wiley.com/10.1002/tdm_license_1

                http://onlinelibrary.wiley.com/termsAndConditions

                http://doi.wiley.com/10.1002/tdm_license_1.1

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