Advances in real-time thoracic guidance systems

Substantial tissue motion: \u3e1cm) arises in the thoracic/abdominal cavity due to respiration. There are many clinical applications in which localizing tissue with high accuracy: \u3c1mm) is important. Potential applications include radiation therapy, radio frequency ablation, lung/liver biopsies, and brachytherapy seed placement. Recent efforts have made highly accurate sub-mm 3D localization of discrete points available via electromagnetic: EM) position monitoring. Technology from Calypso Medical allows for simultaneous tracking of up to three implanted wireless transponders. Additionally, Medtronic Navigation uses wired electromagnetic tracking to guide surgical tools for image guided surgery: IGS). Utilizing real-time EM position monitoring, a prototype system was developed to guide a therapeutic linear accelerator to follow a moving target: tumor) within the lung/abdomen. In a clinical setting, electromagnetic transponders would be bronchoscopically implanted into the lung of the patient in or near the tumor. These transponders would ax to the lung tissue in a stable manner and allow real-time position knowledge throughout a course of radiation therapy. During each dose of radiation, the beam is either halted when the target is outside of a given threshold, or in a later study the beam follows the target in real-time based on the EM position monitoring. We present quantitative analysis of the accuracy and efficiency of the radiation therapy tumor tracking system. EM tracking shows promise for IGS applications. Tracking the position of the instrument tip allows for minimally invasive intervention and alleviates the trauma associated with conventional surgery. Current clinical IGS implementations are limited to static targets: e.g. craniospinal, neurological, and orthopedic intervention. We present work on the development of a respiratory correlated image guided surgery: RCIGS) system. In the RCIGS system, target positions are modeled via respiratory correlated imaging: 4DCT) coupled with a breathing surrogate representative of the patient\u27s respiratory phase/amplitude. Once the target position is known with respect to the surrogate, intervention can be performed when the target is in the correct location. The RCIGS system consists of imaging techniques and custom developed software to give visual and auditory feedback to the surgeon indicating both the proper location and time for intervention. Presented here are the details of the IGS lung system along with quantitative results of the system accuracy in motion phantom, ex-vivo porcine lung, and human cadaver environments

Intraoperative Navigation Systems for Image-Guided Surgery

Recent technological advancements in medical imaging equipment have resulted in a dramatic improvement of image accuracy, now capable of providing useful information previously not available to clinicians. In the surgical context, intraoperative imaging provides a crucial value for the success of the operation. Many nontrivial scientific and technical problems need to be addressed in order to efficiently exploit the different information sources nowadays available in advanced operating rooms. In particular, it is necessary to provide: (i) accurate tracking of surgical instruments, (ii) real-time matching of images from different modalities, and (iii) reliable guidance toward the surgical target. Satisfying all of these requisites is needed to realize effective intraoperative navigation systems for image-guided surgery. Various solutions have been proposed and successfully tested in the field of image navigation systems in the last ten years; nevertheless several problems still arise in most of the applications regarding precision, usability and capabilities of the existing systems. Identifying and solving these issues represents an urgent scientific challenge. This thesis investigates the current state of the art in the field of intraoperative navigation systems, focusing in particular on the challenges related to efficient and effective usage of ultrasound imaging during surgery. The main contribution of this thesis to the state of the art are related to: Techniques for automatic motion compensation and therapy monitoring applied to a novel ultrasound-guided surgical robotic platform in the context of abdominal tumor thermoablation. Novel image-fusion based navigation systems for ultrasound-guided neurosurgery in the context of brain tumor resection, highlighting their applicability as off-line surgical training instruments. The proposed systems, which were designed and developed in the framework of two international research projects, have been tested in real or simulated surgical scenarios, showing promising results toward their application in clinical practice

New Mechatronic Systems for the Diagnosis and Treatment of Cancer

Both two dimensional (2D) and three dimensional (3D) imaging modalities are useful tools for viewing the internal anatomy. Three dimensional imaging techniques are required for accurate targeting of needles. This improves the efficiency and control over the intervention as the high temporal resolution of medical images can be used to validate the location of needle and target in real time. Relying on imaging alone, however, means the intervention is still operator dependent because of the difficulty of controlling the location of the needle within the image. The objective of this thesis is to improve the accuracy and repeatability of needle-based interventions over conventional techniques: both manual and automated techniques. This includes increasing the accuracy and repeatability of these procedures in order to minimize the invasiveness of the procedure. In this thesis, I propose that by combining the remote center of motion concept using spherical linkage components into a passive or semi-automated device, the physician will have a useful tracking and guidance system at their disposal in a package, which is less threatening than a robot to both the patient and physician. This design concept offers both the manipulative transparency of a freehand system, and tremor reduction through scaling currently offered in automated systems. In addressing each objective of this thesis, a number of novel mechanical designs incorporating an remote center of motion architecture with varying degrees of freedom have been presented. Each of these designs can be deployed in a variety of imaging modalities and clinical applications, ranging from preclinical to human interventions, with an accuracy of control in the millimeter to sub-millimeter range

Medical Robotics

The first generation of surgical robots are already being installed in a number of operating rooms around the world. Robotics is being introduced to medicine because it allows for unprecedented control and precision of surgical instruments in minimally invasive procedures. So far, robots have been used to position an endoscope, perform gallbladder surgery and correct gastroesophogeal reflux and heartburn. The ultimate goal of the robotic surgery field is to design a robot that can be used to perform closed-chest, beating-heart surgery. The use of robotics in surgery will expand over the next decades without any doubt. Minimally Invasive Surgery (MIS) is a revolutionary approach in surgery. In MIS, the operation is performed with instruments and viewing equipment inserted into the body through small incisions created by the surgeon, in contrast to open surgery with large incisions. This minimizes surgical trauma and damage to healthy tissue, resulting in shorter patient recovery time. The aim of this book is to provide an overview of the state-of-art, to present new ideas, original results and practical experiences in this expanding area. Nevertheless, many chapters in the book concern advanced research on this growing area. The book provides critical analysis of clinical trials, assessment of the benefits and risks of the application of these technologies. This book is certainly a small sample of the research activity on Medical Robotics going on around the globe as you read it, but it surely covers a good deal of what has been done in the field recently, and as such it works as a valuable source for researchers interested in the involved subjects, whether they are currently “medical roboticists” or not

Enhancement of the UK primary standard for absorbed dose for proton radiotherapy

With the implementation of proton beam therapy; modern radiotherapy treatments have better outcomes than ever before. Likewise, the development of spatially fractionated radiotherapy treatments have shown tremendous potential in pre-clinical studies for improving patient outcomes. Both of these implementation come at the cost of increasing complexity, providing a greater challenge for both routine quality assurance and primary standard dosimetry. Simultaneously, recent advances in the field of silicon radiation detectors offer a possible solution for high resolution real-time monitoring would would increase confidence in the dosimetry. This thesis describes the application of Silicon Strip Detectors (SSD) and Complementary Metal-Oxide Semiconductor (CMOS) devices to X-ray and Proton beam therapies with the intention to develop new methods of quality assurance and a combined system using the NPL Graphite Calorimeter for proton radiotherapy. A combined system using a large-format CMOS is tested in 6 MV X-ray beams at the NPL, verifying the concept and providing a proof of principle. These measurements produced some unexpected results, which required the development of a model of the Calorimeter in COMSOL, a finite-element simulation software package, to study and better understand the internal heat flow. The developed model can use parameterised beam data acquired by an independent silicon detector (whether CMOS or SSD detectors) as a heat source for coupled simulations of delivered beams. After validating against experimental results, the model was subjected to fields of radiation representative of Pencil beam scanning (PBS), providing confidence in the effectiveness of the NPL Graphite Calorimeter in these radiation beams

A method for validating a transperineal ultrasound system for intrafraction monitoring of the prostate during external beam radiotherapy

Introduction: The Clarity Autoscan 40 transperineal ultrasound (TPUS) system (Eiekta, Sweden) for prostate motion management employs a vertically-oriented 20 ultrasound array that is continuously swept mechanically to repeatedly produce 30 images containing the prostate [1]. The target position relative to a pre-fraction reference scan is determined multiple times per second. Other investigators have studied the tracking accuracy of the system using displacements of ~1 0 mm from the initial normalisation point typical to a clinical treatment [1-4]. The primary aim of this work was to utilise clinically available equipment to compare the target positions reported by the Clarity Autoscan system to known target positions over the full imaging volume. A scanning dosimetry water tank was used, however refraction in the 20 mm PMMA wall of the tank presented a significant complication. The potential variation in target dose due to intervention based on the Clarity prostate motion management was also investigated. Method: A prostate analogue was mounted to the scanning mechanism of a MP3-XS scanning water tank "' (PTW, Germany). The Clarity probe was positioned externally against the wall of the scanning tank in the treatment orientation. The scanning mechanism was programmed to make in-plane, cross-plane and diagonal 'profiles' in the horizontal plane ranging approximately ±30 mm from the isocentre. Seven sets of these four 'profiles' were acquired between ±30 mm in the vertical direction yielding data throughout a 60 cm-sided cube centred on the isocentre. A bi-layer 30 refraction correction algorithm was derived to account for refraction caused by differences between the speed of sound in both PMMA and water from the speed of sound in soft tissue assumed by the Clarity system. The prostate analogue was then replaced with a Farmer-type ionisation chamber and monitored by the Clarity system during beam delivery. Programmed movements of the chamber triggered manual or automatic suspension of the beam and the resulting measured doses compared. Results: Without refraction correction the maximum difference in the reported positions from the programmed positions was 9.3 mm and the mean(±SD) difference was 4.0±1.8 mm. Refraction correction reduced this to a maximum of 3.4 mm, and a mean(±SD) of 1.0±0.5 mm. The worst results were at the peripheries of the imaged volume and near the transducer where the Clarity system had difficulty maintaining tracking due to narrowing of the swept imaging volume. At the lateral (left-right) and vertical (anterior-posterior) extremities, the prostate analogue images were visibly distorted which may have affected the accuracy of the Clarity centroid position calculation. There was no significant difference in measured dose between manual and automatic beam suspension in a 10x10 cm2 field when the target moved along the beam axis. Furthermore, there was only a minimal difference in measured dose to the centre of the 'prostate' between intervention and no intervention when the 'prostate' was programmed to move ±20 mm along the beam axis during a 180 MU 1 Ox1 0 cm2 field beam. However, it was found that there was a delay of 5.4±0.9 s between threshold crossing and beam suspension which could become significant at higher dose rates. Conclusions: The target positions reported by the Elekta Clarity Autoscan system can be validated using a programmable scanning water tank by employing a refraction correction if care is taken in the initial positioning of the transducer. Further improvement might be achieved by using a smaller target analogue and associated volume to reduce the effect of the refraction-induced distortion on the Clarity centroid calculation. Intervention following detected prostate motion along the beam axis will have minimal effect on the dose to the centre of the prostate; however, motion in any direction will compromise target coverage and dose minimisation to healthy tissue.Thesis (MPhil) -- University of Adelaide, School of Physical Sciences, 201

A Platform for Robot-Assisted Intracardiac Catheter Navigation

Steerable catheters are routinely deployed in the treatment of cardiac arrhythmias. During invasive electrophysiology studies, the catheter handle is manipulated by an interventionalist to guide the catheter's distal section toward endocardium for pacing and ablation. Catheter manipulation requires dexterity and experience, and exposes the interventionalist to ionizing radiation. Through the course of this research, a platform was developed to assist and enhance the navigation of the catheter inside the cardiac chambers. This robotic platform replaces the interventionalist's hand in catheter manipulation and provides the option to force the catheter tip in arbitrary directions using a 3D input device or to automatically navigate the catheter to desired positions within a cardiac chamber by commanding the software to do so. To accomplish catheter navigation, the catheter was modeled as a continuum manipulator, and utilizing robot kinematics, catheter tip position control was designed and implemented. An electromagnetic tracking system was utilized to measure the position and orientation of two key points in catheter model, for position feedback to the control system. A software platform was developed to implement the navigation and control strategies and to interface with the robot, the 3D input device and the tracking system. The catheter modeling was validated through in-vitro experiments with a static phantom, and in-vivo experiments on three live swines. The feasibility of automatic navigation was also veri ed by navigating to three landmarks in the beating heart of swine subjects, and comparing their performance with that of an experienced interventionalist using quasi biplane fluoroscopy. The platform realizes automatic, assisted, and motorized navigation under the interventionalist's control, thus reducing the dependence of successful navigation on the dexterity and manipulation skills of the interventionalist, and providing a means to reduce the exposure to X-ray radiation. Upon further development, the platform could be adopted for human deployment