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Multiple Clinical Implementations of Real-Time 3D IGRT On Standard-Equipped Cancer Radiotherapy Systems: The Tipping Point for the Era of Real-Time Radiotherapy?

P Keall1*, D Nguyen1 , R O'Brien1 , P Zhang2 , L Happersett2 , J Bertholet3 , P Poulsen4 , (1) University of Sydney, Camperdown, NSW, (2) Memorial Sloan-Kettering Cancer Center, New York, NY, (3) Institute of Cancer Research and Royal Marsden NHS Foundation, London, (4) Aarhus University Hospital, Aarhus


(Tuesday, 7/31/2018) 9:30 AM - 10:00 AM

Room: Exhibit Hall | Forum 9

Purpose: Until now, real-time 3D image guided radiotherapy (IGRT) has been the domain of boutique cancer radiotherapy systems. However, this paradigm is changing. Real-time 3D IGRT using widely available standard equipped cancer radiotherapy systems has been clinically implemented in three novel ways by three groups over three continents. This study will describe and assess the impact of these real-time 3D IGRT implementations.

Methods: After over a decade of theoretical and pre-clinical development, three groups have clinically implemented three novel real-time 3D IGRT solutions on standard-equipped linear accelerators. These technologies encompass kilovoltage, combined megavoltage-kilovoltage and combined kilovoltage-optical imaging. The cancer sites treated span prostate and liver tumors where respiratory motion is present. For each method the 3D-measured motion during treatment is reported. Post-treatment, dose reconstruction is used to assess the treatment quality in the presence of motion with and without real-time 3D IGRT. The geometric accuracy was quantified through phantom experiments.

Results: All three real-time 3D IGRT methods were successfully clinically implemented with over 200 prostate and liver cancer patients treated to date. Systematic target position shifts were observed during treatment using all three methods. Dose reconstruction demonstrated that the delivered dose is closer to the planned dose with real-time 3D IGRT compared to without real-time 3D IGRT. In addition, compromised target dose coverage and variable normal tissue doses were found without real-time 3D IGRT. The geometric accuracy results with real-time 3D IGRT had a mean error of <0.5mm and a standard deviation of less than 1.1mm.

Conclusion: Multiple clinical implementations of real-time 3D IGRT on standard-equipped cancer radiotherapy systems have been recently demonstrated. These in-house solutions provide a pathway for the broader adoption of methods to make radiotherapy more accurate, impacting tumor and normal tissue dose, margins and ultimately patient outcomes.

Funding Support, Disclosures, and Conflict of Interest: Grants from the National Cancer Institute, Cancer Australia, Australian Government NHMRC and Varian Medical Systems. Two authors have a kV imaging-related patent licensed to Varian Medical Systems and Leo Cancer Care by Stanford University.


Image-guided Therapy, Linear Accelerator, X Rays


IM/TH- RT X-ray Imaging: combined KV/MV imaging

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