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Title: Kilovoltage Intrafraction Monitoring for Prostate Intensity Modulated Arc Therapy: First Clinical Results

Abstract

Purpose: Most linear accelerators purchased today are equipped with a gantry-mounted kilovoltage X-ray imager which is typically used for patient imaging prior to therapy. A novel application of the X-ray system is kilovoltage intrafraction monitoring (KIM), in which the 3-dimensional (3D) tumor position is determined during treatment. In this paper, we report on the first use of KIM in a prospective clinical study of prostate cancer patients undergoing intensity modulated arc therapy (IMAT). Methods and Materials: Ten prostate cancer patients with implanted fiducial markers undergoing conventionally fractionated IMAT (RapidArc) were enrolled in an ethics-approved study of KIM. KIM involves acquiring kV images as the gantry rotates around the patient during treatment. Post-treatment, markers in these images were segmented to obtain 2D positions. From the 2D positions, a maximum likelihood estimation of a probability density function was used to obtain 3D prostate trajectories. The trajectories were analyzed to determine the motion type and the percentage of time the prostate was displaced {>=}3, 5, 7, and 10 mm. Independent verification of KIM positional accuracy was performed using kV/MV triangulation. Results: KIM was performed for 268 fractions. Various prostate trajectories were observed (ie, continuous target drift, transient excursion, stable target position, persistent excursion,more » high-frequency excursions, and erratic behavior). For all patients, 3D displacements of {>=}3, 5, 7, and 10 mm were observed 5.6%, 2.2%, 0.7% and 0.4% of the time, respectively. The average systematic accuracy of KIM was measured at 0.46 mm. Conclusions: KIM for prostate IMAT was successfully implemented clinically for the first time. Key advantages of this method are (1) submillimeter accuracy, (2) widespread applicability, and (3) a low barrier to clinical implementation. A disadvantage is that KIM delivers additional imaging dose to the patient.« less

Authors:
 [1];  [2]; ; ;  [3]; ; ;  [4];  [2]
  1. Radiation Physics Laboratory, Sydney Medical School and Institute of Medical Physics, School of Physics, University of Sydney, New South Wales (Australia)
  2. Institute of Medical Physics, School of Physics, University of Sydney, New South Wales (Australia)
  3. Department of Oncology, Aarhus University Hospital, Denmark, and Institute of Clinical Medicine, Aarhus University (Denmark)
  4. Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney, New South Wales (Australia)
Publication Date:
OSTI Identifier:
22149694
Resource Type:
Journal Article
Journal Name:
International Journal of Radiation Oncology, Biology and Physics
Additional Journal Information:
Journal Volume: 84; Journal Issue: 5; Other Information: Copyright (c) 2012 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0360-3016
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; ACCURACY; ETHICAL ASPECTS; MAXIMUM-LIKELIHOOD FIT; MONITORING; NEOPLASMS; PATIENTS; PROBABILITY DENSITY FUNCTIONS; PROSTATE; RADIATION DOSES; RADIOTHERAPY; VERIFICATION; X RADIATION

Citation Formats

Ng, Jin Aun, Institute of Medical Physics, School of Physics, University of Sydney, New South Wales, Booth, Jeremy T., Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney, New South Wales, Poulsen, Per R., Fledelius, Walther, Worm, Esben Schjodt, Eade, Thomas, Hegi, Fiona, Kneebone, Andrew, Kuncic, Zdenka, and Keall, Paul J., E-mail: paul.keall@sydney.edu.au. Kilovoltage Intrafraction Monitoring for Prostate Intensity Modulated Arc Therapy: First Clinical Results. United States: N. p., 2012. Web. doi:10.1016/J.IJROBP.2012.07.2367.
Ng, Jin Aun, Institute of Medical Physics, School of Physics, University of Sydney, New South Wales, Booth, Jeremy T., Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney, New South Wales, Poulsen, Per R., Fledelius, Walther, Worm, Esben Schjodt, Eade, Thomas, Hegi, Fiona, Kneebone, Andrew, Kuncic, Zdenka, & Keall, Paul J., E-mail: paul.keall@sydney.edu.au. Kilovoltage Intrafraction Monitoring for Prostate Intensity Modulated Arc Therapy: First Clinical Results. United States. https://doi.org/10.1016/J.IJROBP.2012.07.2367
Ng, Jin Aun, Institute of Medical Physics, School of Physics, University of Sydney, New South Wales, Booth, Jeremy T., Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney, New South Wales, Poulsen, Per R., Fledelius, Walther, Worm, Esben Schjodt, Eade, Thomas, Hegi, Fiona, Kneebone, Andrew, Kuncic, Zdenka, and Keall, Paul J., E-mail: paul.keall@sydney.edu.au. 2012. "Kilovoltage Intrafraction Monitoring for Prostate Intensity Modulated Arc Therapy: First Clinical Results". United States. https://doi.org/10.1016/J.IJROBP.2012.07.2367.
@article{osti_22149694,
title = {Kilovoltage Intrafraction Monitoring for Prostate Intensity Modulated Arc Therapy: First Clinical Results},
author = {Ng, Jin Aun and Institute of Medical Physics, School of Physics, University of Sydney, New South Wales and Booth, Jeremy T. and Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney, New South Wales and Poulsen, Per R. and Fledelius, Walther and Worm, Esben Schjodt and Eade, Thomas and Hegi, Fiona and Kneebone, Andrew and Kuncic, Zdenka and Keall, Paul J., E-mail: paul.keall@sydney.edu.au},
abstractNote = {Purpose: Most linear accelerators purchased today are equipped with a gantry-mounted kilovoltage X-ray imager which is typically used for patient imaging prior to therapy. A novel application of the X-ray system is kilovoltage intrafraction monitoring (KIM), in which the 3-dimensional (3D) tumor position is determined during treatment. In this paper, we report on the first use of KIM in a prospective clinical study of prostate cancer patients undergoing intensity modulated arc therapy (IMAT). Methods and Materials: Ten prostate cancer patients with implanted fiducial markers undergoing conventionally fractionated IMAT (RapidArc) were enrolled in an ethics-approved study of KIM. KIM involves acquiring kV images as the gantry rotates around the patient during treatment. Post-treatment, markers in these images were segmented to obtain 2D positions. From the 2D positions, a maximum likelihood estimation of a probability density function was used to obtain 3D prostate trajectories. The trajectories were analyzed to determine the motion type and the percentage of time the prostate was displaced {>=}3, 5, 7, and 10 mm. Independent verification of KIM positional accuracy was performed using kV/MV triangulation. Results: KIM was performed for 268 fractions. Various prostate trajectories were observed (ie, continuous target drift, transient excursion, stable target position, persistent excursion, high-frequency excursions, and erratic behavior). For all patients, 3D displacements of {>=}3, 5, 7, and 10 mm were observed 5.6%, 2.2%, 0.7% and 0.4% of the time, respectively. The average systematic accuracy of KIM was measured at 0.46 mm. Conclusions: KIM for prostate IMAT was successfully implemented clinically for the first time. Key advantages of this method are (1) submillimeter accuracy, (2) widespread applicability, and (3) a low barrier to clinical implementation. A disadvantage is that KIM delivers additional imaging dose to the patient.},
doi = {10.1016/J.IJROBP.2012.07.2367},
url = {https://www.osti.gov/biblio/22149694}, journal = {International Journal of Radiation Oncology, Biology and Physics},
issn = {0360-3016},
number = 5,
volume = 84,
place = {United States},
year = {Sat Dec 01 00:00:00 EST 2012},
month = {Sat Dec 01 00:00:00 EST 2012}
}