RESUMEN
An electromagnetic-based tracking and navigation system was evaluated for interventional radiology. The electromagnetic tracking system (CAPPA IRAD EMT, CASinnovations, Erlangen, Germany) was used for real-time monitoring of punctures of the lumbar facet joints and intervertebral disks in a spine phantom, three pig cadavers and three anaesthesized pigs. Therefore, pre-interventional computed tomography (CT) datasets were transferred to the navigation system and puncture trajectories were planned. A coaxial needle was advanced along the trajectories while the position of the needle tip was monitored in real time. After puncture tracts were marked with pieces of wire another CT examination was performed and distances between wires and anatomical targets were measured. Performing punctures of the facet joints mean needle positioning errors were 0.4 +/- 0.8 mm in the spine phantom, 2.8 +/- 2.1 mm ex vivo and 3.0 +/- 2.0 mm in vivo with mean length of the puncture tract of 54.0 +/- 10.4 mm (phantom), 51.6 +/- 12.6 mm (ex vivo) and 50.9 +/- 17.6 mm (in vivo). At first attempt, intervertebral discs were successfully punctured in 15/15 in the phantom study, in 12/15 in the ex-vivo study and 14/15 in the in-vivo study, respectively. Immobilization of the patient and optimal positioning of the field generator are essential to achieve a high accuracy of needle placement in a clinical CT setting.
Asunto(s)
Radiografía Intervencional/métodos , Radiología Intervencionista/métodos , Columna Vertebral/diagnóstico por imagen , Tomografía Computarizada por Rayos X/métodos , Animales , Diagnóstico por Imagen/métodos , Campos Electromagnéticos , Diseño de Equipo , Fantasmas de Imagen , Radiografía Intervencional/instrumentación , Radiología Intervencionista/instrumentación , Reproducibilidad de los Resultados , Columna Vertebral/patología , Cirugía Asistida por Computador/métodos , PorcinosRESUMEN
The aim of this study was to prospectively evaluate the needle visualization and placement error and use of an electromagnetic field-based tracking navigation device for puncture procedures based on C-arm CT (CACT) images. A commercially available navigation device was mounted on an angiographic X-ray system setup for CACT. After the target was defined, needle placement was performed under real-time visualization of the virtual needle in CACT images. The final, real needle position was assessed by CACT. Punctures were performed in phantoms (n = 76) and in twelve patients (eight biopsies, three drainages, one injection). Procedure times, system error, user error and total error were assessed. In phantoms, mean total error was 2.3 +/- 0.9 mm, user error was 1.4 +/- 0.8 mm and system error was 1.7 +/- 0.8 mm. In the patient study, the targeted puncture was successful in all twelve cases. The mean total error was 5.4 mm +/- 1.9 mm (maximum 8.1 mm), user error was 3.7 +/- 1.7 mm, system error was 3.2 +/- 1.4 mm and mean skin-to-target time was less than 1 min. The navigation device relying on CACT was accurate in terms of needle visualization and useful for needle placement under both experimental and clinical conditions. For more complex procedures, electromagnetic field-based tracking guidance might be of help in facilitating the puncture and reducing both the puncture risk and procedure time.
Asunto(s)
Electrónica/instrumentación , Punciones/instrumentación , Radiografía Intervencional/instrumentación , Tomografía Computarizada por Rayos X/instrumentación , Campos Electromagnéticos , Fenómenos Electromagnéticos , Diseño de Equipo , Análisis de Falla de Equipo , Humanos , Fantasmas de Imagen , Punciones/métodos , Radiografía Intervencional/métodos , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Tomografía Computarizada por Rayos X/métodosRESUMEN
Rate-responsive pacing based on the atrio-ventricular conduction time is a promising therapy for restoring physiological heart rate control in chronotropic incompetent patients. This paper compares four different algorithms. Three of them had been formulated as patents, but no real test or application has been reported up to now. The fourth was recently published by the authors of this paper. There the steps involved in the development process were stationary and dynamic system identification, control system design and a pilot study with patients. The data obtained were used to formulate a simulation model of the cardiac system by means of which the other algorithms were tested. Test criteria were stability, the attenuation of disturbances and the response time to changes of the exercise rate. None of the three patents worked when being strictly implemented as described. The problems encountered were instability, unusable parameterisations and some questionable adaptation mechanisms. In a redesign we tried to improve the patents, but only in one case would the results obtained justify real use. In the other cases the variability of the pacing frequency was intolerably high.
Asunto(s)
Estimulación Cardíaca Artificial/métodos , Frecuencia Cardíaca , Ventrículos Cardíacos/patología , Algoritmos , Gasto Cardíaco , Fenómenos Fisiológicos Cardiovasculares , Sistema de Conducción Cardíaco , Humanos , Modelos Cardiovasculares , Modelos Químicos , Marcapaso Artificial , TiempoRESUMEN
In order to achieve diagnostically useful CT (computed tomography) images of the moving heart, the standard image reconstruction has to be modified to a phase-correlated reconstruction, which considers the motion phase of the heart and generates a quasi-static image in one defined motion phase. For that purpose a synchronization signal is needed, typically a concurrent ECG recording. Commonly, the reconstruction phase is adapted by the user to the patient-specific heart motion to improve the image quality and thus the diagnostic value. The purpose of our work is to automatically identify the optimal reconstruction phase for cardiac CT imaging with respect to motion artifacts. We provide a solution for a patient- and heart rate-independent detection of the optimal phase in the cardiac cycle which shows a minimum of cardiac movement. We validated our method by the correlation with the reconstruction phase selected visually on the basis of ECG-triggering and used for the medical diagnosis. The mean difference between both reconstruction phases was 12.5% with respect to a whole cardiac motion cycle indicating a high correlation. Additionally, reconstructed cardiac images are shown which confirm the results expressed by the correlation measurement and in some cases even indicating an improvement using the proposed method.
Asunto(s)
Algoritmos , Artefactos , Electrocardiografía/métodos , Corazón/diagnóstico por imagen , Interpretación de Imagen Asistida por Computador/métodos , Almacenamiento y Recuperación de la Información/métodos , Movimiento , Tomografía Computarizada por Rayos X/métodos , Inteligencia Artificial , Humanos , Aumento de la Imagen/métodos , Reconocimiento de Normas Patrones Automatizadas/métodos , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
The purpose of our project was to develop a novel navigation system for interventional radiology. Fields of application are minimally invasive percutaneous interventions performed under local anaesthesia. In order to reduce unintentional patient movements we used a patient vacuum immobilization device. Together with the vacuum fixation and a newly developed reference frame we achieved a fully automatic patient-to-image registration independent from the tracking system. The combination of the software and a novel designed needle holder allows for an adjustment of the needle within a few seconds. The complete system is adapted to the requirements of the radiologist and to the clinical work-flow. For evaluation of the navigation system we performed a phantom study with a perspex phantom and achieved an average needle positioning accuracy of less than 0.7 mm.