Computer- and robot-assisted Medical Intervention

Medical robotics includes assistive devices used by the physician in order to make his/her diagnostic or therapeutic practices easier and more efficient. This chapter focuses on such systems. It introduces the general field of Computer-Assisted Medical Interventions, its aims, its different components and describes the place of robots in that context. The evolutions in terms of general design and control paradigms in the development of medical robots are presented and issues specific to that application domain are discussed. A view of existing systems, on-going developments and future trends is given. A case-study is detailed. Other types of robotic help in the medical environment (such as for assisting a handicapped person, for rehabilitation of a patient or for replacement of some damaged/suppressed limbs or organs) are out of the scope of this chapter.Comment: Handbook of Automation, Shimon Nof (Ed.) (2009) 000-00

IGRT and motion management during lung SBRT delivery.

Patient motion can cause misalignment of the tumour and toxicities to the healthy lung tissue during lung stereotactic body radiation therapy (SBRT). Any deviations from the reference setup can miss the target and have acute toxic effects on the patient with consequences onto its quality of life and survival outcomes. Correction for motion, either immediately prior to treatment or intra-treatment, can be realized with image-guided radiation therapy (IGRT) and motion management devices. The use of these techniques has demonstrated the feasibility of integrating complex technology with clinical linear accelerator to provide a higher standard of care for the patients and increase their quality of life

Real-time intrafraction motion monitoring in external beam radiotherapy

© 2019 Institute of Physics and Engineering in Medicine. Radiotherapy (RT) aims to deliver a spatially conformal dose of radiation to tumours while maximizing the dose sparing to healthy tissues. However, the internal patient anatomy is constantly moving due to respiratory, cardiac, gastrointestinal and urinary activity. The long term goal of the RT community to 'see what we treat, as we treat' and to act on this information instantaneously has resulted in rapid technological innovation. Specialized treatment machines, such as robotic or gimbal-steered linear accelerators (linac) with in-room imaging suites, have been developed specifically for real-time treatment adaptation. Additional equipment, such as stereoscopic kilovoltage (kV) imaging, ultrasound transducers and electromagnetic transponders, has been developed for intrafraction motion monitoring on conventional linacs. Magnetic resonance imaging (MRI) has been integrated with cobalt treatment units and more recently with linacs. In addition to hardware innovation, software development has played a substantial role in the development of motion monitoring methods based on respiratory motion surrogates and planar kV or Megavoltage (MV) imaging that is available on standard equipped linacs. In this paper, we review and compare the different intrafraction motion monitoring methods proposed in the literature and demonstrated in real-time on clinical data as well as their possible future developments. We then discuss general considerations on validation and quality assurance for clinical implementation. Besides photon RT, particle therapy is increasingly used to treat moving targets. However, transferring motion monitoring technologies from linacs to particle beam lines presents substantial challenges. Lessons learned from the implementation of real-time intrafraction monitoring for photon RT will be used as a basis to discuss the implementation of these methods for particle RT

Expanding the use of real-time electromagnetic tracking in radiation oncology.

In the past 10 years, techniques to improve radiotherapy delivery, such as intensity-modulated radiation therapy (IMRT), image-guided radiation therapy (IGRT) for both inter- and intrafraction tumor localization, and hypofractionated delivery techniques such as stereotactic body radiation therapy (SBRT), have evolved tremendously. This review article focuses on only one part of that evolution, electromagnetic tracking in radiation therapy. Electromagnetic tracking is still a growing technology in radiation oncology and, as such, the clinical applications are limited, the expense is high, and the reimbursement is insufficient to cover these costs. At the same time, current experience with electromagnetic tracking applied to various clinical tumor sites indicates that the potential benefits of electromagnetic tracking could be significant for patients receiving radiation therapy. Daily use of these tracking systems is minimally invasive and delivers no additional ionizing radiation to the patient, and these systems can provide explicit tumor motion data. Although there are a number of technical and fiscal issues that need to be addressed, electromagnetic tracking systems are expected to play a continued role in improving the precision of radiation delivery

Couch-based motion compensation: modelling, simulation and real-time experiments

Abstract The paper presents a couch-based active motion compensation strategy evaluated in simulation and validated experimentally using both a research and a clinical Elekta Precise Table™. The control strategy combines a Kalman filter to predict the surrogate motion used as a reference by a linear model predictive controller with the control action calculation based on estimated position and velocity feedback provided by an observer as well as predicted couch position and velocity using a linearized state space model. An inversion technique is used to compensate for the dead-zone nonlinearity. New generic couch models are presented and applied to model the Elekta Precise Table™ dynamics and nonlinearities including dead zone. Couch deflection was measured for different manufacturers and found to be up to 25 mm. A feed-forward approach is proposed to compensate for such couch deflection. Simultaneous motion compensation for longitudinal, lateral and vertical motions was evaluated using arbitrary trajectories generated from sensors or loaded from files. Tracking errors were between 0.5 and 2 mm RMS. A dosimetric evaluation of the motion compensation was done using a sinusoidal waveform. No notable differences were observed between films obtained for a fixed- or motion-compensated target. Further dosimetric improvement could be made by combining gating, based on tracking error together with beam on/off time, and PSS compensation.</jats:p

Clinical Validation of an Optical Surface Detection System for Stereotactic Radiosurgery with Frameless Immobilization Device in CNS Tumors

Tese de mestrado integrado, Engenharia Biomédica e Biofísica (Radiações em Diagnóstico e Terapia), 2022Stereotactic Radiosurgery (SRS) has been consolidated in recent years as the treatment of choice in selected central nervous system (CNS) tumors. With the introduction of stereotactic approach in clinical practice, accurate immobilization and motion control during treatment becomes fundamental. During SRS treatments, the common practice is to immobilize CNS patients in a cushion molded head support, with specific open-face thermoplastic masks. To verify and correct internal isocenter uncertainties before and during treatment, X-Ray volumetric imaging (XVI) is performed - image guided radiation therapy (IGRT). An alternative to mid‐treatment imaging is optical surface detection (OSD) imaging – a non‐invasive, non‐radiographic form of image guidance – to monitor patient intra-fraction motion. This imaging technique has shown to properly position, accurately monitor, and quantify patient movements throughout the entirety of the treatment – surface guided radiation therapy (SGRT). The aim of this investigation is to test the viability of the implementation of a maskless immobilization approach, using only a vacuum mouthpiece suction system for head fixation in patients with CNS tumors who will undergo SRS treatment under the guidance of an OSD system coupled with 6-Degree of Freedom (6-DOF) robotic couch for submillimeter position correction. This master thesis addresses the five technical performance tests conducted on the Linear Accelerator components – XVI, HexaPOD couch and OSD system in the Radiotherapy Department of Hospital CUF Descobertas. The results obtained lecture the best acquisition orientation to perform image verification; if the HexaPOD couch is correctly calibrated to the XVI radiation isocenter to assure submillimeter corrections; OSD system performance regarding phantom surface detection since some immobilization components can block the signal reading; which coplanar and non-coplanar angles occur most signal inconsistencies due to camera pod occlusion; what is the overall OSD system accuracy and what is the best non-coplanar angle arrangement to perform an SRS treatment with OSD system monitoring

Strategies for Reducing the Impact of Tumour Motion During Helical Tomotherapy

Tumour motion presents a significant limitation for effective radiotherapy of lung cancer, and more specifically for helical tomotherapy. The simultaneous and continuous movements of tomotherapy subsystems (gantry, couch, and binary multi-leaf collimator) can lead to inaccurate dose delivery, when combined with tumour motion. In this thesis, we have investigated the impact of tumour motion and strategies to reduce the resulting dose discrepancies for helical tomotherapy, through computer simulations and film measurements performed in a dynamic body phantom. Three distinctively different types of dose discrepancies have been isolated: dose rounding, dose rippling, and the intensity-modulated radiation therapy (IMRT) asynchronization effect. Each effect was shown to be affected by different combinations of tumour motion and treatment parameters. In clinical practice using a conventional fractionation scheme, the dose rounding effect remains the major concern, which can be compensated by assigning a larger treatment margin around the tumour volume. For hypofractionation schemes, the IMRT asynchronization effect can become an additional concern by introducing dose discrepancies inside the target volume, necessitating the use of a motion management technique. Two new motion management techniques have thus been developed for helical tomotherapy: loose helical tomotherapy with breath-holding and multi-pass respiratory gating. Both methods require the treatment couch to be reset to its starting position to repeat the entire helical treatment, until nearly all planned dose is delivered. For sinusoidal target motion, employing multi-pass respiratory gating was shown to reduce the dose deviation inside the target volume from 14% to 2% for a single fraction, using 4 gated passes. For non-sinusoidal tumour motion causing a dose deviation of 6% within the tumour volume, the required number of passes to keep the dose deviation below 1% was approximately 4 passes for 30 fractions and 5 passes for 3 fractions, demonstrating the feasibility of the multi-pass respiratory gating approach. Clinical implementation of the multi-pass respiratory gating technique would require a number of electronic control and communication modifications to the existing tomotherapy machine, which would lead to significant improvements in the dose distributions delivered for lung tomotherapy treatments – especially for patients exhibiting large tumour motion who are treated with hypofractionation schemes

The impact of technology on the changing practice of lung SBRT

Stereotactic body radiotherapy (SBRT) for lung tumours has been gaining wide acceptance in lung cancer. Here, we review the technological evolution of SBRT delivery in lung cancer, from the first treatments using the stereotactic body frame in the 1990's to modern developments in image guidance and motion management. Finally, we discuss the impact of current technological approaches on the requirements for quality assurance as well as future technological developments