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Real-Time Ultrasound Monitoring with Speckle Tracking in Abdominal Stereotactic Body Radiation Therapy

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L Su

L Su1*, T O'Shea2 , S K Ng1 , Y Zhang1 , I Iordachita3 , J Wong1 , E Harris2 , J Bamber2 , H T Sen4 , P Kazanzides4 , M Lediju Bell4 , K Ding1 , (1) Department of Radiation Oncology, Johns Hopkins University, Baltimore, MD, (2) Joint Department of Physics, Institute of Cancer Research, Sutton, London SM2 5NG, UK,(3) Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD, (4) Department of Computer Science, Johns Hopkins University, Baltimore, MD


TH-EF-BRB-9 (Thursday, July 16, 2015) 1:00 PM - 2:50 PM Room: Ballroom B

Ultrasound is ideal for real-time monitoring with high soft tissue contrast, non-ionization, portability, and cost effectiveness. No studies have investigated clinical feasibility of real-time ultrasound monitoring for abdominal stereotactic body radiation therapy (SBRT) under active breath control (ABC). We are able to monitor target motion using 4D ultrasound and speckle tracking.

An arm-bridge system (ABS) was designed to allow clinician to freely move and lock ultrasound probe. A ceiling mounted infrared camera was calibrated to track probe position using an reflector on the probe. An abdominal ultrasound phantom was secured on a programmable respiratory motion platform to simulate the 20 second expiration and inspiration phases of the ABC with 10 mm inferior translation for 6 cycles. The probe was coupled to the phantom using gel. 4D ultrasound B-mode images were simultaneously acquired at each breath-hold for monitoring. A 3D normalized cross-correlation template matching algorithm was developed to track speckle and feature Point-of-interest (POI) motion at shallow, medium and deep positions in B-mode images. The reproducibility of breath-hold was evaluated by comparing speckle tracking and motion platform position as a function of ROI size.

During the repeated respiration movement, the probe position variation was minimal (< 0.5 mm at all time in all directions). For target motion monitoring, ultrasound speckle tracking showed high reproducibility (0.005±0.005 mm AP and 0.01±0.01 mm SI for all ROIs, and 0.03±0.02 mm RL for the shallow and medium ROI). For the deep speckle ROI, the RL error was 0.04±0.04 mm likely due to reduced resolution with depth. Deep ROI showed increased RL tracking accuracy with increased ROI size.

Our ABS was able to maintain fixed probe position during the respiration movement with high fidelity. Ultrasound speckle tracking was able to precisely determine the motion over repeated breath-hold for real time monitoring.

Funding Support, Disclosures, and Conflict of Interest: This work is supported by NIT grant R01CA161613.

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