Program Information
Ultrasound Guided Radiation Therapy of the Canine Urinary Bladder Using a Custom Designed Image Guidance Platform
J Sick, MS1*, N Rancilio, DVM2 , S Blake1 , H Heng, DVM, MVS, MS2 , J Poulson, DVM, PhD1,2 , D Knapp, DVM, MS2 , K Stantz, PhD1 , (1) School of Health Sciences, Purdue University, West Lafayette, Indiana, (2) College of Veterinary Medicine, Purdue University, West Lafayette, Indiana
Presentations
PO-BPC-Exhibit Hall-5 (Saturday, March 7, 2015) Room: Exhibit Hall
Purpose: Radiation therapy (RT) for the treatment of transitional cell carcinoma (TCC) is technically difficult due to potentially large interfraction variations in bladder size, shape and position. The goal of this research is to develop real-time image-guided radiotherapy techniques based on ultrasound instrumentation and methods. The proposed design is to combine US and photoacoustic (PA) molecular imaging in a single system that can be positioned on the radiation therapy treatment couch.
Methods: We constructed the platform and calibrated it to the coordinate system of the linear accelerator couch. This was done by assembling the platform and recording the couch position at each discrete position. The positions were saved to a graphical user interface (GUI) in MATLABTM. The GUI was used to predict where the couch should be positioned to ensure the end of the radial arm was positioned at isocenter. Prior to simulation CT, subjects were imaged via US and positions of the transducer recorded with the same set-up as during CT acquisition. IMRT treatment plans were developed to a bladder PTV with 1cm margins.
Results: The highly conformal IMRT plans show the necessity for strict patient positioning guidelines. The mechanical motion error of the platform was determined to be within the precision of the treatment couch (vrt =0.158±1.08mm, lng=0.205±0.73mm, lat=0.16±1.09mm). CT and US images were co-registered in Oncentra™. Use of platform for patient positioning is still under evaluation.
Conclusion: Next generation designs are currently in production. Improvements will include micron movements in the longitudinal direction and radial arm in addition to a water bolus intended to decouple the transducer-patient interface. IMRT plans are highly conformal and lead to greater probability of geographic miss. Our system is an alternative to radiographic methods of image guidance that we will test in a clinical trial of spontaneously occurring TCC in dogs.
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