Commissioning of an Integrated Platform for Time-Resolved Treatment Delivery in Scanned Ion Beam Therapy by Means of Optical Motion Monitoring

Abstract

The integrated use of optical technologies for patient monitoring is addressed in the framework of time-resolved treatment delivery for scanned ion beam therapy. A software application has been designed to provide the therapy control system (TCS) with a continuous geometrical feedback by processing the external surrogates tridimensional data, detected in real-time via optical tracking. Conventional procedures for phase-based respiratory phase detection were implemented, as well as the interface to patient specific correlation models, in order to estimate internal tumor motion from surface markers. In this paper, particular attention is dedicated to the quantification of time delays resulting from system integration and its compensation by means of polynomial interpolation in the time domain. Dedicated tests to assess the separate delay contributions due to optical signal processing, digital data transfer to the TCS and passive beam energy modulation actuation have been performed. We report the system technological commissioning activities reporting dose distribution errors in a phantom study, where the treatment of a lung lesion was simulated, with both lateral and range beam position compensation. The zero-delay systems integration with a specific active scanning delivery machine was achieved by tuning the amount of time prediction applied to lateral (14.61 ± 0.98 ms) and depth (34.1 ± 6.29 ms) beam position correction signals, featuring sub-millimeter accuracy in forward estimation. Direct optical target observation and motion phase (MPh) based tumor motion discretization strategies were tested, resulting in −0.3(2.3)% and −1.2(9.3)% median (IQR) percentual relative dose difference with respect to static irradiation, respectively. Results confirm the technical feasibility of the implemented strategy towards 4D treatment delivery, with negligible percentual dose deviations with respect to static irradiation.

Target position reproducibility in left‐breast irradiation with deep inspiration breath‐hold using multiple optical surface control points

“…(b), the optical tracking system is composed by three IR cameras rigidly fixed to the ceiling of the treatment room and provides the 3D reconstruction of fiducials in the isocentric reference system with millimetric accuracy at 100 Hz frame rate. As described in details in previous works, the isocentric calibration of the optical tracking system is based on the BrainLab (BrainLAB AG, Feldkirchen, Germany) phantom, which is fitted with a known geometric configuration of passive fiducials. The phantom is manually aligned to the isocentric room lasers to find the mapping between the optical cameras reference system and the isocentric room reference frame.…”

The National Centre for Oncological Hadrontherapy (CNAO): Status and perspectives

“…Real-time tumour tracking based on external surrogates has been tested as future clinical implementation, allowing full motion compensation at any respiratory phase [46]. Experimental data acquired during the tumour tracking sessions performed at GSI over the years 2011e2012 have been assessed in order to support strategies for tumour tracking in particle therapy [47,48]. Two internaleexternal correlation models for internal target position estimation from external surrogates have been implemented and tested: a state space model (SSM) and an artificial neural network (ANN).…”

Optical eye tracking system for real‐time noninvasive tumor localization in external beam radiotherapy

“…The execution time of the different eye tracking functions was assessed on the videos acquired during tests on healthy subjects. Dedicated test were performed to quantify the ETS delays contributions due to video cameras image acquisition, USB data transfer and image processing following the approach proposed by Fattori et al 32 A custom-made electronic board featuring four IR LEDs and a 16-1 demultiplexer (HEF4514B, Philips Semiconductors, The Netherlands) was connected to the PC through a data acquisition (DAQ) device (NI USB-6211, National Instruments). The ETS monitored the IR emission of LEDs while DAQ provided digital inputs to switch on IR LEDs following a regular pattern.…”