(Saturday, 4/7/2018) 10:30 AM - 12:30 PM
Room: Marquis Ballroom 5-8
Purpose: AAPM TG128 raises several challenges with current phantom designs used for brachytherapy ultrasound QA. No single phantom satisfies all of the recommended tests, requiring an additional setup which impedes clinical workflow. Image quality for solid phantoms is highly dependent on setup precision and is susceptible to measurement uncertainties, poor reproducibility, and sudden loss of image quality due to poor surface contact. To address these challenges, we design a novel liquid-based phantom with customizable 3D printed components for fully integrated TG128 compatibility.
Methods: The phantom consists of four components assembled within a rectangular, plastic container. The components incorporate clinical instruments such as implant needles and templates, which are used to fix the geometric relationship of the probe and phantom to reduce uncertainties and improve measurement reproducibility. Water was chosen as the liquid medium, with speed of sound adjusted to 1540 m/s via salinity. To evaluate the performance of this phantom, we conduct a timed TG128 QA compared to the standard method for a new and experienced user.
Results: Including setup and measurement, QA was completed within 45 minutes using the liquid-based phantom, compared to 70 minutes for an experienced user and 90 minutes for a new user with the standard method. The large reduction in time was primarily due to the use of liquid medium, which eliminates the challenge of surface contact encountered with solid phantoms.
Conclusion: A novel brachytherapy ultrasound QA phantom is designed to satisfy all TG128 recommendations. The choice of liquid medium improves the efficiency and reproducibility of QA measurements. Other accommodations are made to reduce the effect of setup uncertainties. The components are 3D printed and customizable to adapt to clinic specific needs. Eliminating the challenges and uncertainties improves characterization ultrasound performance and allows for delivery of ultrasound guided brachytherapy with high confidence.
Funding Support, Disclosures, and Conflict of Interest: An invention disclosure has been submitted and the phantom is in the process of being patented.
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