Aria record and verify system

The Calypso system has previously been described in detail.10, 17 For this study, three Calypso beacon transponders were inserted into a radiolucent foam cylinder representing the prostate gland. The transponders were positioned in the shape of an equilateral triangle with side length approximately 3 cm, in accordance with the manufacturer's recommendations. The foam cylinder was subsequently placed inside an anthropomorphic pelvic phantom (CIRS pelvic phantom) (Fig. 1). The phantom was scanned on a Siemens SOMATOM Emotion CT scanner (Siemens Medical Systems, Forchheim, Germany) with 1 mm slices.
Images were transferred to Varian's Eclipse™ treatment planning system (Version 11.0.42) (Varian Medical Systems, Palo Alto, California). Following standard planning procedures for Calypso patients, a treatment plan was created with the isocenter at the center of mass of the transponders. CBCT and orthogonal kV setup fields were added to the plan, to allow radiographic acquisition at the linear accelerator. Standard departmental procedures were used to transfer the treatment plan and associated imaging fields to Varian's Aria record and verify system (Version 13.6) and the Calypso tracking station (Version 3.0).

To evaluate and compare the various techniques described above, all available imaging and treatment plan information from each completed treatment fraction was exported from the Ethos Treatment Planning System and imported into the Aria Record and Verify System (Varian Medical Systems, Palo Alto, CA). This included the original reference treatment plan and structure set, along with the CBCT, synthetic CT, and structure set generated during each treatment fraction. All data was available whether or not the adapted plan had been clinically delivered to the patient. In the Aria Image Registration workspace, each fraction's synthetic CT was registered twice to the simulation CT, once using 3DOF (translations only) and once using 6DOF (translations and rotations). These registrations were conducted manually with the qualitative goal of maximizing the overlap of the clinical target volumes contours (CTVs) as depicted on the two image sets.

In our department, all plans are calculated using the Varian Eclipse TPS (version 10.0; Varian, Palo Alto, CA) with the analytical anisotropic algorithm (AAA). The data presented in this study were obtained using a Varian Clinac 2100 CD equipped with a Millennium 120 leaf MLC and a PortalVision aS500 imager (Varian, Palo Alto, CA). All IMRT plans consisted of fixed field arrangements using a dynamic delivery technique (sliding window). All measurements described in this work were performed in clinical mode at nominal dose rates of 300 and 600 MU/min. The IMRT plans used in this study were delivered using the Aria record and verify system (version 10; Varian).