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Int J Radiat Oncol Biol Phys. 2010 Nov 1;78(3):904-11. doi: 10.1016/j.ijrobp.2009.12.068. Epub 2010 Jun 25.

A failure detection strategy for intrafraction prostate motion monitoring with on-board imagers for fixed-gantry IMRT.

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  • 1Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA, USA.

Abstract

PURPOSE:

To develop methods to monitor prostate intrafraction motion during fixed-gantry intensity-modulated radiotherapy using MV treatment beam imaging together with minimal kV imaging for a failure detection strategy that ensures prompt detection when target displacement exceeds a preset threshold.

METHODS AND MATERIALS:

Real-time two-dimensional (2D) marker position in the MV image plane was obtained by analyzing cine-MV images. The marker's in-line movement, and thus its time-varying three-dimensional (3D) position, was estimated by combining the 2D projection data with a previously established correlative relationship between the directional components of prostate motion. A confirmation request for more accurate localization using MV-kV triangulation was triggered when the estimated prostate displacement based on the cine-MV data was greater than 3 mm. An interventional action alert followed on positive MV-kV confirmation. To demonstrate the feasibility and accuracy of the proposed method, simulation studies of conventional-fraction intensity-modulated radiotherapy sessions were done using 536 Calypso-measured prostate trajectories from 17 radiotherapy patients.

RESULTS:

A technique for intrafraction prostate motion management has been developed. The technique, using "freely available" cine-MV images and minimum on-board kV imaging (on average 2.5 images/fraction), successfully limited 3D prostate movement to within a range of 3 mm relative to the MV beam for 99.4% of the total treatment time. On average, only approximately one intervention/fraction was needed to achieve this level of accuracy.

CONCLUSION:

Instead of seeking to accurately and continuously localize the prostate target as existing motion tracking systems do, the present technique effectively uses cine-MV data to provide a clinically valuable way to minimize kV usage, while maintaining high targeting accuracy.

Copyright © 2010 Elsevier Inc. All rights reserved.

PMID:
20579818
[PubMed - indexed for MEDLINE]
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