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  4. The First Prospective Implementation of Markerless Lung Tumor Tracking On a Standard Linear Accelerator

The First Prospective Implementation of Markerless Lung Tumor Tracking On a Standard Linear Accelerator

M Mueller1*, R Zolfaghari1, A Briggs2, H Furtado3, J Booth2 , P Keall1 , D Nguyen1 , R O'Brien1 , C Shieh1 , (1) ACRF Image X Institute, Sydney, Australia, (2) Royal North Shore Hospital, Sydney, Australia, (3) Medical University of Vienna, Austria

Presentations

(Sunday, 7/14/2019) 2:00 PM - 3:00 PM

Room: 225BCD

Purpose: The ability to track tumor motion without implanted markers on a standard linac will enable wide access to adaptive radiotherapy. This study presents the first prospective implementation of markerless tumor tracking (MTT) on a standard linac and its quality assurance (QA) procedure.

Methods: A QA procedure following the AAPM TG147 report was developed to measure static and dynamic localization accuracy and latency. A CIRS lung phantom was attached to the HexaMotion platform to emulate 3D motion from seven static and five dynamic motion traces that en-compass different types of lung tumor motion. For MTT a patient specific model was built from 4D treatment planning data. On the treatment day, a pre-treatment imaging arc was acquired to update for daily motion information. KV-projections were acquired during VMAT-treatment delivery. The model was exploited to find the projected tumor and an extended Kalman filter was used to infer the 3D tumor position. MTT was implemented in the VMAT-treatment workflow using only clinical imaging protocols. The linac was operated in clinical mode, while a frame-grabber-software transmitted kV-projections to a dedicated laptop. The performance was accelerated using a GPU and the OpenCV package.

Results: The prospective evaluation was successful. The mean tracking error was left-right (LR): 0.5±0.2mm, superior-inferior (SI): -0.7±0.2mm and anterior-posterior (AP): -0.0±0.3mm for the static localization test, and LR: -0.2±1.5mm, SI: -0.5±0.7mm and AP: -0.3±0.9mm for the dynamic localization test. The computational latency for each kV-projection was 108±8ms.

Conclusion: This study presents the first implementation of MTT on a standard linac. A QA procedure was developed to benchmark tracking accuracy and precision. This study paves the way for the first clinical use of MTT on a standard linac, which has the potential to enable real-time adaptive radiotherapy for a large population of cancer patients. Ethics have been submitted for related clinical trials.

Keywords

Target Localization, Treatment Techniques, Image-guided Therapy

Taxonomy

IM/TH- RT X-ray Imaging: General (most aspects)

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