251 research outputs found
Advanced tracking and image registration techniques for intraoperative radiation therapy
Mención Internacional en el título de doctorIntraoperative electron radiation therapy (IOERT) is a technique used to
deliver radiation to the surgically opened tumor bed without irradiating healthy
tissue. Treatment planning systems and mobile linear accelerators enable
clinicians to optimize the procedure, minimize stress in the operating room (OR)
and avoid transferring the patient to a dedicated radiation room. However,
placement of the radiation collimator over the tumor bed requires a validation
methodology to ensure correct delivery of the dose prescribed in the treatment
planning system. In this dissertation, we address three well-known limitations of
IOERT: applicator positioning over the tumor bed, docking of the mobile linear
accelerator gantry with the applicator and validation of the dose delivery
prescribed. This thesis demonstrates that these limitations can be overcome by
positioning the applicator appropriately with respect to the patient’s anatomy.
The main objective of the study was to assess technological and procedural
alternatives for improvement of IOERT performance and resolution of
problems of uncertainty. Image-to-world registration, multicamera optical
trackers, multimodal imaging techniques and mobile linear accelerator docking
are addressed in the context of IOERT.
IOERT is carried out by a multidisciplinary team in a highly complex
environment that has special tracking needs owing to the characteristics of its
working volume (i.e., large and prone to occlusions), in addition to the requisites
of accuracy. The first part of this dissertation presents the validation of a
commercial multicamera optical tracker in terms of accuracy, sensitivity to
miscalibration, camera occlusions and detection of tools using a feasible surgical
setup. It also proposes an automatic miscalibration detection protocol that
satisfies the IOERT requirements of automaticity and speed. We show that the
multicamera tracker is suitable for IOERT navigation and demonstrate the
feasibility of the miscalibration detection protocol in clinical setups.
Image-to-world registration is one of the main issues during image-guided
applications where the field of interest and/or the number of possible
anatomical localizations is large, such as IOERT. In the second part of this
dissertation, a registration algorithm for image-guided surgery based on lineshaped
fiducials (line-based registration) is proposed and validated. Line-based registration decreases acquisition time during surgery and enables better
registration accuracy than other published algorithms.
In the third part of this dissertation, we integrate a commercial low-cost
ultrasound transducer and a cone beam CT C-arm with an optical tracker for
image-guided interventions to enable surgical navigation and explore image based
registration techniques for both modalities.
In the fourth part of the dissertation, a navigation system based on optical
tracking for the docking of the mobile linear accelerator to the radiation
applicator is assessed. This system improves safety and reduces procedure time.
The system tracks the prescribed collimator location to solve the movements
that the linear accelerator should perform to reach the docking position and
warns the user about potentially unachievable arrangements before the actual
procedure. A software application was implemented to use this system in the
OR, where it was also evaluated to assess the improvement in docking speed.
Finally, in the last part of the dissertation, we present and assess the
installation setup for a navigation system in a dedicated IOERT OR, determine
the steps necessary for the IOERT process, identify workflow limitations and
evaluate the feasibility of the integration of the system in a real OR. The
navigation system safeguards the sterile conditions of the OR, clears the space
available for surgeons and is suitable for any similar dedicated IOERT OR.La Radioterapia Intraoperatoria por electrones (RIO) consiste en la
aplicación de radiación de alta energía directamente sobre el lecho tumoral,
accesible durante la cirugía, evitando radiar los tejidos sanos. Hoy en día, avances
como los sistemas de planificación (TPS) y la aparición de aceleradores lineales
móviles permiten optimizar el procedimiento, minimizar el estrés clínico en el
entorno quirúrgico y evitar el desplazamiento del paciente durante la cirugía a
otra sala para ser radiado. La aplicación de la radiación se realiza mediante un
colimador del haz de radiación (aplicador) que se coloca sobre el lecho tumoral
de forma manual por el oncólogo radioterápico. Sin embargo, para asegurar una
correcta deposición de la dosis prescrita y planificada en el TPS, es necesaria una
adecuada validación de la colocación del colimador. En esta Tesis se abordan
tres limitaciones conocidas del procedimiento RIO: el correcto posicionamiento
del aplicador sobre el lecho tumoral, acoplamiento del acelerador lineal con el
aplicador y validación de la dosis de radiación prescrita. Esta Tesis demuestra
que estas limitaciones pueden ser abordadas mediante el posicionamiento del
aplicador de radiación en relación con la anatomía del paciente.
El objetivo principal de este trabajo es la evaluación de alternativas
tecnológicas y procedimentales para la mejora de la práctica de la RIO y resolver
los problemas de incertidumbre descritos anteriormente. Concretamente se
revisan en el contexto de la radioterapia intraoperatoria los siguientes temas: el
registro de la imagen y el paciente, sistemas de posicionamiento multicámara,
técnicas de imagen multimodal y el acoplamiento del acelerador lineal móvil.
El entorno complejo y multidisciplinar de la RIO precisa de necesidades
especiales para el empleo de sistemas de posicionamiento como una alta
precisión y un volumen de trabajo grande y propenso a las oclusiones de los
sensores de posición. La primera parte de esta Tesis presenta una exhaustiva
evaluación de un sistema de posicionamiento óptico multicámara comercial.
Estudiamos la precisión del sistema, su sensibilidad a errores cometidos en la
calibración, robustez frente a posibles oclusiones de las cámaras y precisión en
el seguimiento de herramientas en un entorno quirúrgico real. Además,
proponemos un protocolo para la detección automática de errores por calibración que satisface los requisitos de automaticidad y velocidad para la RIO
demostrando la viabilidad del empleo de este sistema para la navegación en RIO.
Uno de los problemas principales de la cirugía guiada por imagen es el
correcto registro de la imagen médica y la anatomía del paciente en el quirófano.
En el caso de la RIO, donde el número de posibles localizaciones anatómicas es
bastante amplio, así como el campo de trabajo es grande se hace necesario
abordar este problema para una correcta navegación. Por ello, en la segunda
parte de esta Tesis, proponemos y validamos un nuevo algoritmo de registro
(LBR) para la cirugía guiada por imagen basado en marcadores lineales. El
método propuesto reduce el tiempo de la adquisición de la posición de los
marcadores durante la cirugía y supera en precisión a otros algoritmos de registro
establecidos y estudiados en la literatura.
En la tercera parte de esta tesis, integramos un transductor de ultrasonido
comercial de bajo coste, un arco en C de rayos X con haz cónico y un sistema
de posicionamiento óptico para intervenciones guiadas por imagen que permite
la navegación quirúrgica y exploramos técnicas de registro de imagen para ambas
modalidades.
En la cuarta parte de esta tesis se evalúa un navegador basado en el sistema
de posicionamiento óptico para el acoplamiento del acelerador lineal móvil con
aplicador de radiación, mejorando la seguridad y reduciendo el tiempo del propio
acoplamiento. El sistema es capaz de localizar el colimador en el espacio y
proporcionar los movimientos que el acelerador lineal debe realizar para alcanzar
la posición de acoplamiento. El sistema propuesto es capaz de advertir al usuario
de aquellos casos donde la posición de acoplamiento sea inalcanzable. El sistema
propuesto de ayuda para el acoplamiento se integró en una aplicación software
que fue evaluada para su uso final en quirófano demostrando su viabilidad y la
reducción de tiempo de acoplamiento mediante su uso.
Por último, presentamos y evaluamos la instalación de un sistema de
navegación en un quirófano RIO dedicado, determinamos las necesidades desde
el punto de vista procedimental, identificamos las limitaciones en el flujo de
trabajo y evaluamos la viabilidad de la integración del sistema en un entorno
quirúrgico real. El sistema propuesto demuestra ser apto para el entorno RIO
manteniendo las condiciones de esterilidad y dejando despejado el campo
quirúrgico además de ser adaptable a cualquier quirófano similar.Programa Oficial de Doctorado en Multimedia y ComunicacionesPresidente: Raúl San José Estépar.- Secretario: María Arrate Muñoz Barrutia.- Vocal: Carlos Ferrer Albiac
Camera Marker Networks for Pose Estimation and Scene Understanding in Construction Automation and Robotics.
The construction industry faces challenges that include high workplace injuries and fatalities, stagnant productivity, and skill shortage. Automation and Robotics in Construction (ARC) has been proposed in the literature as a potential solution that makes machinery easier to collaborate with, facilitates better decision-making, or enables autonomous behavior. However, there are two primary technical challenges in ARC: 1) unstructured and featureless environments; and 2) differences between the as-designed and the as-built. It is therefore impossible to directly replicate conventional automation methods adopted in industries such as manufacturing on construction sites. In particular, two fundamental problems, pose estimation and scene understanding, must be addressed to realize the full potential of ARC.
This dissertation proposes a pose estimation and scene understanding framework that addresses the identified research gaps by exploiting cameras, markers, and planar structures to mitigate the identified technical challenges. A fast plane extraction algorithm is developed for efficient modeling and understanding of built environments. A marker registration algorithm is designed for robust, accurate, cost-efficient, and rapidly reconfigurable pose estimation in unstructured and featureless environments. Camera marker networks are then established for unified and systematic design, estimation, and uncertainty analysis in larger scale applications.
The proposed algorithms' efficiency has been validated through comprehensive experiments. Specifically, the speed, accuracy and robustness of the fast plane extraction and the marker registration have been demonstrated to be superior to existing state-of-the-art algorithms. These algorithms have also been implemented in two groups of ARC applications to demonstrate the proposed framework's effectiveness, wherein the applications themselves have significant social and economic value. The first group is related to in-situ robotic machinery, including an autonomous manipulator for assembling digital architecture designs on construction sites to help improve productivity and quality; and an intelligent guidance and monitoring system for articulated machinery such as excavators to help improve safety. The second group emphasizes human-machine interaction to make ARC more effective, including a mobile Building Information Modeling and way-finding platform with discrete location recognition to increase indoor facility management efficiency; and a 3D scanning and modeling solution for rapid and cost-efficient dimension checking and concise as-built modeling.PHDCivil EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/113481/1/cforrest_1.pd
Image-based registration methods for quantification and compensation of prostate motion during trans-rectal ultrasound (TRUS)-guided biopsy
Prostate biopsy is the clinical standard for cancer diagnosis and is typically performed under two-dimensional (2D) transrectal ultrasound (TRUS) for needle guidance. Unfortunately, most early stage prostate cancers are not visible on ultrasound and the procedure suffers from high false negative rates due to the lack of visible targets. Fusion of pre-biopsy MRI to 3D TRUS for targeted biopsy could improve cancer detection rates and volume of tumor sampled. In MRI-TRUS fusion biopsy systems, patient or prostate motion during the procedure causes misalignments in the MR targets mapped to the live 2D TRUS images, limiting the targeting accuracy of the biopsy system.
In order to sample smallest clinically significant tumours of 0.5 cm3with 95% confidence, the root mean square (RMS) error of the biopsy system needs to be
The target misalignments due to intermittent prostate motion during the procedure can be compensated by registering the live 2D TRUS images acquired during the biopsy procedure to the pre-acquired baseline 3D TRUS image. The registration must be performed both accurately and quickly in order to be useful during the clinical procedure. We developed an intensity-based 2D-3D rigid registration algorithm and validated it by calculating the target registration error (TRE) using manually identified fiducials within the prostate. We discuss two different approaches that can be used to improve the robustness of this registration to meet the clinical requirements. Firstly, we evaluated the impact of intra-procedural 3D TRUS imaging on motion compensation accuracy since the limited anatomical context available in live 2D TRUS images could limit the robustness of the 2D-3D registration. The results indicated that TRE improved when intra-procedural 3D TRUS images were used in registration, with larger improvements in the base and apex regions as compared with the mid-gland region. Secondly, we developed and evaluated a registration algorithm whose optimization is based on learned prostate motion characteristics. Compared to our initial approach, the updated optimization improved the robustness during 2D-3D registration by reducing the number of registrations with a TRE \u3e 5 mm from 9.2% to 1.2% with an overall RMS TRE of 2.3 mm.
The methods developed in this work were intended to improve the needle targeting accuracy of 3D TRUS-guided biopsy systems. The successful integration of the techniques into current 3D TRUS-guided systems could improve the overall cancer detection rate during the biopsy and help to achieve earlier diagnosis and fewer repeat biopsy procedures in prostate cancer diagnosis
Advances in navigation and intraoperative imaging for intraoperative electron radiotherapy
Mención Internacional en el título de doctorEsta tesis se enmarca dentro del campo de la radioterapia y trata específicamente sobre
la radioterapia intraoperatoria (RIO) con electrones. Esta técnica combina la resección
quirúrgica de un tumor y la radiación terapéutica directamente aplicada sobre el lecho
tumoral post-resección o sobre el tumor no resecado. El haz de electrones de alta
energía es colimado y conducido por un aplicador específico acoplado a un acelerador
lineal. La planificación de la RIO con electrones es compleja debido a las
modificaciones geométricas y anatómicas producidas por la retracción de estructuras y
la eliminación de tejidos cancerosos durante la cirugía. Actualmente, no se dispone del
escenario real en este tipo de tratamientos (por ejemplo, la posición/orientación del
aplicador respecto a la anatomía del paciente o las irregularidades en la superficie
irradiada), sólo de una estimación grosso modo del tratamiento real administrado al
paciente. Las imágenes intraoperatorias del escenario real durante el tratamiento
(concretamente imágenes de tomografía axial computarizada [TAC]) serían útiles no
sólo para la planificación intraoperatoria, sino también para registrar y evaluar el
tratamiento administrado al paciente. Esta información es esencial en estudios
prospectivos.
En esta tesis se evaluó en primer lugar la viabilidad de un sistema de seguimiento
óptico de varias cámaras para obtener la posición/orientación del aplicador en los
escenarios de RIO con electrones. Los resultados mostraron un error de posición del
aplicador inferior a 2 mm (error medio del centro del bisel) y un error de orientación
menor de 2º (error medio del eje del bisel y del eje longitudinal del aplicador). Estos
valores están dentro del rango propuesto por el Grupo de Trabajo 147 (encargo del
Comité de Terapia y del Subcomité para la Mejora de la Garantía de Calidad y
Resultados de la Asociación Americana de Físicos en Medicina [AAPM] para estudiar
en radioterapia externa la exactitud de la localización con métodos no radiográficos,
como los sistemas infrarrojos). Una limitación importante de la solución propuesta es
que el aplicador se superpone a la imagen preoperatoria del paciente. Una imagen intraoperatoria proporcionaría información anatómica actualizada y permitiría estimar
la distribución tridimensional de la dosis.
El segundo estudio específico de esta tesis evaluó la viabilidad de adquirir con un TAC
simulador imágenes TAC intraoperatorias de escenarios reales de RIO con electrones.
No hubo complicaciones en la fase de transporte del paciente utilizando la camilla y su
acople para el transporte, o con la adquisición de imágenes TAC intraoperatorias en la
sala del TAC simulador. Los estudios intraoperatorios adquiridos se utilizaron para
evaluar la mejora obtenida en la estimación de la distribución de dosis en comparación
con la obtenida a partir de imágenes TAC preoperatorias, identificando el factor
dominante en esas estimaciones (la región de aire y las irregularidades en la superficie,
no las heterogeneidades de los tejidos).
Por último, el tercer estudio específico se centró en la evaluación de varias tecnologías
TAC de kilovoltaje, aparte del TAC simulador, para adquirir imágenes intraoperatorias
con las que estimar la distribución de la dosis en RIO con electrones. Estos dispositivos
serían necesarios en el caso de disponer de aceleradores lineales portátiles en el
quirófano ya que no se aprobaría mover al paciente a la sala del TAC simulador. Los
resultados con un maniquí abdominal mostraron que un TAC portátil (BodyTom) e
incluso un acelerador lineal con un TAC de haz de cónico (TrueBeam) serían
adecuados para este propósito.This thesis is framed within the field of radiotherapy, specifically intraoperative
electron radiotherapy (IOERT). This technique combines surgical resection of a tumour
and therapeutic radiation directly applied to a post-resection tumour bed or to an
unresected tumour. The high-energy electron beam is collimated and conducted by a
specific applicator docked to a linear accelerator (LINAC). Dosimetry planning for
IOERT is challenging owing to the geometrical and anatomical modifications produced
by the retraction of structures and removal of cancerous tissues during the surgery. No
data of the actual IOERT 3D scenario is available (for example, the applicator pose in
relation to the patient’s anatomy or the irregularities in the irradiated surface) and
consequently only a rough approximation of the actual IOERT treatment administered
to the patient can be estimated. Intraoperative computed tomography (CT) images of
the actual scenario during the treatment would be useful not only for intraoperative
planning but also for registering and evaluating the treatment administered to the
patient. This information is essential for prospective trials.
In this thesis, the feasibility of using a multi-camera optical tracking system to obtain
the applicator pose in IOERT scenarios was firstly assessed. Results showed that the
accuracy of the applicator pose was below 2 mm in position (mean error of the bevel
centre) and 2º in orientation (mean error of the bevel axis and the longitudinal axis),
which are within the acceptable range proposed in the recommendation of Task Group
147 (commissioned by the Therapy Committee and the Quality Assurance and
Outcomes Improvement Subcommittee of the American Association of Physicists in
Medicine [AAPM] to study the localization accuracy with non-radiographic methods
such as infrared systems in external beam radiation therapy). An important limitation
of this solution is that the actual pose of applicator is superimposed on a patient’s
preoperative image. An intraoperative image would provide updated anatomical
information and would allow estimating the 3D dose distribution.
The second specific study of this thesis evaluated the feasibility of acquiring
intraoperative CT images with a CT simulator in real IOERT scenarios. There were no
complications in the whole procedure related to the transport step using the subtable
and its stretcher or the acquisition of intraoperative CT images in the CT simulator
room. The acquired intraoperative studies were used to evaluate the improvement
achieved in the dose distribution estimation when compared to that obtained from
preoperative CT images, identifying the dominant factor in those estimations (air gap
and the surface irregularities, not tissue heterogeneities).
Finally, the last specific study focused on assessing several kilovoltage (kV) CT
technologies other than CT simulators to acquire intraoperative images for estimating
IOERT dose distribution. That would be necessary when a mobile electron LINAC was
available in the operating room as transferring the patient to the CT simulator room
could not be approved. Our results with an abdominal phantom revealed that a portable
CT (BodyTom) and even a LINAC with on-board kV cone-beam CT (TrueBeam)
would be suitable for this purpose.Programa Oficial de Doctorado en Multimedia y ComunicacionesPresidente: Joaquín López Herráiz.- Secretario: María Arrate Muñoz Barrutia.- Vocal: Óscar Acosta Tamay
Intraoperative Endoscopic Augmented Reality in Third Ventriculostomy
In neurosurgery, as a result of the brain-shift, the preoperative patient models used as a intraoperative reference change. A meaningful use of the preoperative virtual models during the operation requires for a model update. The NEAR project, Neuroendoscopy towards Augmented Reality, describes a new camera calibration model for high distorted lenses and introduces the concept of active endoscopes endowed with with navigation, camera calibration, augmented reality and triangulation modules
Accurate 3D-reconstruction and -navigation for high-precision minimal-invasive interventions
The current lateral skull base surgery is largely invasive since it requires wide exposure and direct visualization of anatomical landmarks to avoid damaging critical structures. A multi-port approach aiming to reduce such invasiveness has been recently investigated. Thereby three canals are drilled from the skull surface to the surgical region of interest: the first canal for the instrument, the second for the endoscope, and the third for material removal or an additional instrument. The transition to minimal invasive approaches in the lateral skull base surgery requires sub-millimeter accuracy and high outcome predictability, which results in high requirements for the image acquisition as well as for the navigation.
Computed tomography (CT) is a non-invasive imaging technique allowing the visualization of the internal patient organs. Planning optimal drill channels based on patient-specific models requires high-accurate three-dimensional (3D) CT images. This thesis focuses on the reconstruction of high quality CT volumes. Therefore, two conventional imaging systems are investigated: spiral CT scanners and C-arm cone-beam CT (CBCT) systems. Spiral CT scanners acquire volumes with typically anisotropic resolution, i.e. the voxel spacing in the slice-selection-direction is larger than the in-the-plane spacing. A new super-resolution reconstruction approach is proposed to recover images with high isotropic resolution from two orthogonal low-resolution CT volumes.
C-arm CBCT systems offers CT-like 3D imaging capabilities while being appropriate for interventional suites. A main drawback of these systems is the commonly encountered CT artifacts due to several limitations in the imaging system, such as the mechanical inaccuracies. This thesis contributes new methods to enhance the CBCT reconstruction quality by addressing two main reconstruction artifacts: the misalignment artifacts caused by mechanical inaccuracies, and the metal-artifacts caused by the presence of metal objects in the scanned region.
CBCT scanners are appropriate for intra-operative image-guided navigation. For instance, they can be used to control the drill process based on intra-operatively acquired 2D fluoroscopic images. For a successful navigation, accurate estimate of C-arm pose relative to the patient anatomy and the associated surgical plan is required. A new algorithm has been developed to fulfill this task with high-precision. The performance of the introduced methods is demonstrated on simulated and real data
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