ESTRO 2021 Abstract Book

S1450

ESTRO 2021

Conclusion CNERGY Check provides safety and reduces the number of incidents in delivery of radiation therapy by detecting and preventing errors associated with manual preparation and delivery of radiation therapy.

PO-1725 Phantom study of Cyberknife Synchrony cardiac treatments with a single fiducial marker C. Piccolo 1 , S. Vigorito 1 , E. Rondi 1 , G. Piperno 2 , A.M. Ferrari 2 , M. Pepa 2 , E. Conte 3 , V. Catto 4 , D. Andreini 3,5 , C. Carbucicchio 4 , B.A. Jereczek-Fossa 6,7 , F. Cattani 8 1 IEO European Institute of Oncology IRCCS, Unit of Medical Physics, Milan, Italy; 2 IEO European Institute of Oncology IRCCS, Division of Radiotherapy, Milan, Italy; 3 Centro Cardiologico Monzino, IRCCS, Cardiovascular Computed Tomography and Radiology Unit, Milan, Italy; 4 Centro Cardiologico Monzino, IRCCS, Department of Clinical Electrophysiology and Pacing, Milan, Italy; 5 University of Milan, Department of Clinical Sciences and Community Health, Milan, Italy; 6 IEO European Institute of Oncology, IRCCS, Division of Radiotherapy, Milan, Italy; 7 University of Milan, Department of Oncology and Hemato-oncology, Milan, Italy; 8 IEO European Institute of Oncology, IRCCS, Unit of Medical Physics, Milan, Italy Purpose or Objective This work was developed within the STRA-MI-VT (STereotactic RadioAblation by Multimodal Imaging for Ventricular Tachycardia) study (phase Ib/II, open-label study, NCT04066517). Its aim was to study the feasibility of a Cyberknife treatment on a cardiac lesion by tracking a single marker, represented by the defibrillator catheter present in the heart of the patients. These ones are sub-optimal tracking conditions, that allows the system to follow only the translations of the lesion, losing information on its possible rotations. In particular, the residual movement of the lesion during the tracking was studied, residual planning margins were found and the dosimetric accuracy of the treatment was checked. Materials and Methods A homogeneous water-equivalent phantom (EasyCube phantom, Sun Nuclear Co, Florida, USA), with the defibrillator catheter inside, was used as a surrogate for the heart. This phantom was placed on the ExacTrac Gating Phantom (BrainLAB AG, Feldkirken, Germany), that can translate it following respiratory profiles. Several rotations were simulated by physically rotating the phantom on the platform. A virtual lesion was identified inside the phantom and the residual displacement of this lesion during the tracking was studied. The residual planning margins were obtained by computing the displacements between the unrotated volume and the rotated volume. Two treatment plans were compared, prescribing on the unrotated volume and on the envelope of the unrotated and the rotated volumes. Their dosimetric accuracy was verified by gamma analysis with gafchromic films. Results The residual margin to be considered for planning is greater increasing the distance between the catheter to be tracked and the lesion. In particular, the margin is 3 mm when the catheter is inside the lesion and reaches 5 mm when the distance is 5 cm. The lesion dose coverage is reduced by 3.8% (IQR 2.5% - 4.7%) when the dose is prescribed on the unrotated volume only. All treatment plans are dosimetrically accurate and gamma analysis results with 3% 3 mm tolerance level are greater than 94%. Conclusion Tracking with a single marker is feasible considering adequate residual planning margins. The treatment volumes are reduced comparing with the treatment without tracking. These volumes could be further reduced by using additional markers, for example by placing them on the patient's skin. In this sense, studies on anthropomorphic phantom are ongoing.

PO-1726 Automated transfer of couch coordinates from TPS to R&V system using DICOM to improve patient safety M. Breuers 1 , G. Hilgers 1 , T. Nuver 1 , E. van der Wal 2 , K. Pasma 2