WP5 3D-US therapy delivery and monitoring
The aim of WP5 is to develop a list of technical constraints for a Focused Ultrasound Surgery (FUS) source adapted to a robotic system, including issues such as weight, size and the need for safe, effective ultrasonic coupling. Based on these technical constraints, IGT will build a new FUS source for robotic deployment.
Furthermore, it is important to integrate the 2D imaging probe confocally within the FUS transducer casing to monitor treatment and the acoustic path to the target. Another important step related to WP6 is to demonstrate the monitoring of therapeutic FUS using the combination of the US probe integrated with the new FUS source and the second US probe capable of independent motion.
An on-line adjustment strategy of robot positioning using image-based motion detection will be implemented to lock the system on target, to track and follow the organ motion and to treat the complete targeted volume without dead time. The ultrasonic coupling mechanisms will be tested to ensure that they allow robotic motion to track physiological/intentional/spontaneous tissue motion. Therapy monitoring protocols for both static and, more importantly, dynamic situations, including complex multi-focal lesions for complete tumor ablation will also be tested within this WP.
DESCRIPTION OF WORK
T5.1 FUS source design and realization - IGT will design the FUS delivery system, including the driving electronics, the ultrasound transducer, based on the following requirements:
- compatibility with the robot mechanical characteristics;
- ability to deliver the focused ultrasound to the entire targeted volume (tumor painting) using mechanical displacement and/or electronic steering of the ultrasound beam (phased array operation);
- ability to maintain an adequate acoustic path for the ultrasound between the transducer and the target at all time, including during transducer motions;
- inclusion of a confocal ultrasonography imaging probe in the FUS transducer casing;
- synchronization between robot motion and FUS emission.
There are currently no standard FUS systems. The 3 existing CE-marked systems have custom made transducers and driving electronics which are adapted to the target organs of the devices (Insightec, Uterine fibroma; EDAP, prostate cancer; Philips, Uterine fibroma). The FUTURA project requires a customized design to provide the real time control of the ultrasound beam emission required for target tracking in the case of moving organs and a versatile transducer which can reach organs a various depth in the body. The transducer will be designed as an annular array in order to enable changing the focal distance through electronic steering of the ultrasound beam. The transducer will also have a central opening to accommodate an ultrasound probe for imaging that will be confocal with the high intensity focused ultrasound beam. IGT has a long experience in the design, the acoustic optimization and realization of phased array ultrasound transducers and their driving electronics. IGT will build a prototype system, sized for human interventions and suitable for experiment on
cadavers or large animals to develop and demonstrate the thermal monitoring and control mechanisms based on ultrasonography imaging. The system will enable the execution of complex, synchronized trajectories of the FUS focal spot through combination of robot controlled transducer motion and electronic steering of the ultrasound beam. In the test implementation, the FUS system will enable steering of the ultrasound beam along the propagation axis only, so as to change dynamically the focal depth of the FUS.
T5.2 Therapy monitoring and control - The therapy is monitored in real time through two US probes. The first probe is positioned coaxially with the FUS transducer to image the ultrasound beam path and the focal point and the second probe will be positioned independently via a second robot arm in such a way as to provide images of the target region and possibly using different image processing to assess the thermal lesion size and location. The locations and orientations of both imaging probes will be registered and a composite, co-registered image set will be displayed for the clinician. The display will also show as an overlay, possibly on previously acquired 3D CT or MRI images used in the treatment planning phase, the parts of the target volume that have been already treated and the remaining ablation steps to achieve complete destruction of the tumor. The 3D-US images from the second US probe will be also used to track the organ motion and to direct the FUS transducer robot arm to follow the tumor. Within this Task, tests will be carried out to demonstrate the effectiveness of system on pre-clinical static and dynamic tissue platforms, including target tracking and target painting.
T5.3 On-line adjustment of robot position - Using image based motion detection, the system will be able to lock on its target and follow the organ motion in order to treat the complete targeted volume without dead times. Images from the coaxial ultrasonography probe and from 3D probe will be processed and will return information on target position and therapy advancement. This information will be continuously converted by custom-made algorithms into inputs for the robotic platform, mainly in terms of position and orientation of the end-effectors. Optimal distance to the skin and adequate acoustic path to the target will be maintained, in order to satisfy safety and reliability requirements as well as therapeutic effectiveness.