quantification of organ motion with magnetic resonance in carbon ion therapy of the abdominal tumors
PO-2343
Abstract
quantification of organ motion with magnetic resonance in carbon ion therapy of the abdominal tumors
Authors: Luca Anemoni1, Martina Serantoni1, Maria Elena Piazzolla1, Margherita Sofia Cadeo1, Alessandro Vai2, Chiara Paganelli3, Ester Orlandi1, Sara Tampellini1
1National Center for Oncological Hadrontherapy (Fondazione CNAO), Radiotherapy, Pavia, Italy; 2National Center for Oncological Hadrontherapy (Fondazione CNAO), Medical Physics, Pavia, Italy; 3Politecnico di Milano, Elettronica, Informazione e Bioingegneria, Milano, Italy
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Purpose or Objective
Imaging plays a key role in hadrontherapy, being fundamental for the study of breathing motion and its impact on treatment with thermoplastic mask.The objective of the Study is to support the clinical component in the identification of organ motion at the abdominal level both inter and intra fraction,using 4D magnetic resonance imaging,and the contouring of target and organ at risk in order to suggest optimal strategies for customizing treatment.
Material and Methods
A group of 10 patient was considered both for inter-fraction and intra-fraction evaluation.
Inter-fraction evaluation:segmentation of liver,kidney and hepatic dome in VIBE sequence acquired in MRI. The mass center of the planning and revaluation CT has been calculated,the result was compared with the mass center data of the vibe sequences to establish the movement of liver and kidney.
Intra-fraction evaluation:segmentation of liver and right kidney in reconstructed 4DMRI sequence.The phase 1= end Exhale,that is the phase of end exhalation and the phase 5=end-inhale,that is the phase of end inhalation, have been surrounded .The center of mass was calculated by comparing phase 1 and phase 5 data.
Results
The intra-fraction movement,calculated as the difference between EX and IN phase of 4DMRI,is 1.48mm(std 0.67mm)for liver and 1.30mm(std 0.65mm)for kidney.
Similarly,inter-fraction motion,measured on both CT and MRI imaging, and calculated between repeated acquisitions ,is contained on all patients and it is below the maximum voxel of MRI imaging(i.e. 5mm).
Conclusion
The motion compensation technique,based on compression mask,is able to limit intra and inter-fraction motion,providing accurate dose delivery even in abdominal district organs subject to respiratory motion.It is important to remember that we refer to the maximum dimension of the voxel because this is the minimum dimension and therefore the movement that you can solve.