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C.(. Shieh



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    MA13 - Modern Technologies and Biological Factors in Radiotherapy (ID 395)

    • Event: WCLC 2016
    • Type: Mini Oral Session
    • Track: Radiotherapy
    • Presentations: 1
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      MA13.01 - Markerless Tumour Tracking during Lung Radiotherapy Using Intrafraction X-Ray Imaging (ID 5533)

      16:00 - 17:30  |  Author(s): C.(. Shieh

      • Abstract
      • Presentation
      • Slides

      Background:
      Lung tumours often exhibit large and unpredictable motion that can severely compromise radiotherapy outcomes. Markerless tumour tracking can enable wide access to motion-adaptive radiotherapy, negating the risks and costs associated with implanting markers. The main barrier to markerless tumour tracking is the inferior tumor visibility on x-ray images due to overlapping anatomic structures. The aim of this study is to develop a markerless tumor tracking method for lung radiotherapy using intrafraction x-ray imaging.

      Methods:
      The markerless tumour tracking method (Figure1a) consists of four steps: (1) Building a tumour and anatomic model from the cone-beam CT (CBCT) acquired prior to treatment, (2) Using the anatomic model to remove the contribution of anatomic structures on intrafraction x-ray images, (3) Locating the tumour on the intrafraction 2D x-ray image via template matching using the tumour model, (4) Determining the tumour 3D position by a Kalman filter. The proposed method was retrospectively validated on (i) 11 CBCT scans from four patients with central tumours, and (ii) a kV fluoroscopic scan during a stereotactic ablative radiotherapy (SABR) treatment from the Light SABR trial (NCT02514512). Tracking errors were estimated using the motions of markers or beacons implanted near the tumours. Figure 1



      Results:
      Markerless tumour tracking successfully tracked tumours in all cases at every imaging angle. The mean 3D tracking error ranged from 1.8-4.1mm for the 11 CBCT scans, and was 3.0mm for the SABR case. Compared with the current standard of care, i.e. a single estimation of tumour position prior to treatment from the pre-treatment CBCT, markerless tumour tracking reduced tumour localization error by 0.9-7.9mm. Tracking errors in the left-right, superior-inferior, and anterior-posterior directions are shown in Figure1b.

      Conclusion:
      A markerless tumour tracking method was developed and shown to improve tumour localization accuracy in 12 lung cancer cases. This method can potentially enable wide access to motion-adaptive radiotherapy.

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    P2.05 - Poster Session with Presenters Present (ID 463)

    • Event: WCLC 2016
    • Type: Poster Presenters Present
    • Track: Radiotherapy
    • Presentations: 1
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      P2.05-043 - Lung Tumour Motion Kilovoltage Intrafraction Monitoring (KIM): First Clinical Results (ID 5538)

      14:30 - 15:45  |  Author(s): C.(. Shieh

      • Abstract

      Background:
      Lung tumour positional uncertainty has been identified as a major issue that deteriorates the efficacy of radiotherapy. The recent development of the Kilovoltage intrafraction monitoring (KIM) which uses widely available gantry-mounted kilovoltage (kV) imager has been applied to prostate motion monitoring. This study reports the first clinical result of KIM for lung cancer radiotherapy with an Elekta machine.

      Methods:
      A locally advanced stage IIIlung cancer patient undergoing conventionally fractionated VMAT was enrolled in an ethics-approved study of KIM. A Gold Anchor fiducial marker (0.4 mm diameter x 20 mm length) was implanted in the tumour near the right hilum (Fig 1, left). kV images were acquired at 5.5 Hz during treatment. Post-treatment, markers were segmented and reconstructed to obtain 3D tumour trajectories. A Microsoft Kinect audio and depth sensing device was also mounted on the couch to get the external respiratory signal. Figure 1 Figure 1. kV image of the Gold Anchor marker (left) and the KIM measured lung tumour 3D motion and the external Kinect signal (right).



      Results:
      Our method was successfully applied for the first KIM lung patient. The fiducial marker was visible on 62.9% of the kV images. The average lung tumour motion (mean ± SD) in superior-inferior (SI), anterior-posterior (AP) left-right (LR), directions were 0.27±7.52, -0.09±3.37, and -0.64±4.55 mm respectively. Seven fractions of lung tumour 3D motion and Kinect external signal were acquired, with the representative result illustrated (Fig 1, right).

      Conclusion:
      This is the first time that KIM has been used for intrafractional tumour motion monitoring during lung cancer radiotherapy, and also the first implementation of KIM on an Elekta imaging platform. This clinical translational research milestone paves the way for the broad implementation of image guidance to facilitate the detection and correction of geometric error for lung radiotherapy, and resultant improved clinical outcomes.