Live Fluoroscopic Images Research Articles

MO‐DE‐BRA‐04: Hands‐On Fluoroscopy Safety Training with Real‐Time Patient and Staff Dosimetry

Purpose:Fluoroscopically guided interventions (FGI) are routinely performed across many different hospital departments. However, many involved staff members have minimal training regarding safe and optimal use of fluoroscopy systems. We developed and taught a hands‐on fluoroscopy safety class incorporating real‐time patient and staff dosimetry in order to promote safer and more optimal use of fluoroscopy during FGI.Methods:The hands‐on fluoroscopy safety class is taught in an FGI suite, unique to each department. A patient equivalent phantom is set on the patient table with an ion chamber positioned at the x‐ray beam entrance to the phantom. This provides a surrogate measure of patient entrance dose. Multiple solid state dosimeters (RaySafe i2 dosimetry systemTM) are deployed at different distances from the phantom (0.1, 1, 3 meters), which provide surrogate measures of staff dose. Instructors direct participating clinical staff to operate the fluoroscopy system as they view live fluoroscopic images, patient entrance dose, and staff doses in real‐time. During class, instructors work with clinical staff to investigate how patient entrance dose, staff doses, and image quality are affected by different parameters, including pulse rate, magnification, collimation, beam angulation, imaging mode, system geometry, distance, and shielding.Results:Real‐time dose visualization enables clinical staff to directly see and learn how to optimize their use of their own fluoroscopy system to minimize patient and staff dose, yet maintain sufficient image quality for FGI. As a direct result of the class, multiple hospital departments have implemented changes to their imaging protocols, including reduction of the default fluoroscopy pulse rate and increased use of collimation and lower dose fluoroscopy modes.Conclusion:Hands‐on fluoroscopy safety training substantially benefits from real‐time patient and staff dosimetry incorporated into the class. Real‐time dose display helps clinical staff visualize, internalize, and ultimately utilize the safety techniques learned during the training.RaySafe/Unfors/Fluke lent us a portable version of their RaySafe i2 Dosimetry System for 6 months.

176-05: Low Fluoroscopic Protocol for Ablation of Atrial Fibrillation: Utilization of 3-dimensional Mapping to Facilitate Leadless Post-Transeptal Procedure

Background: Live fluoroscopic imaging continues to be an important tool in atrial fibrillation (AF) ablation. The availability of 3-dimensional (3D) mapping systems, intracardiac ultrasound, and other adjuvant technologies (CARTO-UNIVU and MediGuide) have helped to reduce fluoroscopic exposure in the electrophysiology lab. We report the results of a low-fluoroscopic protocol for ablation of AF that relies primarily on 3D mapping. Methods: 28 consecutive patients referred for AF ablation underwent ablation for AF utilizing a low fluoroscopic protocol. All catheters were placed without the use of fluoroscopy. Right and left atrial anatomy were created using Fast Activation Mapping (FAM) utilizing Biosense Webster's CARTO 4 navigation system. Double transeptal puncture was achieved using a combination of intracardiac ultrasound and limited fluoroscopic imaging. Following transeptal access, lead protection was discontinued and no fluoroscopy was employed for the remainder of the case. In select cases linear ablation, and ablation of the cavo-tricuspid isthmus were performed. Results: Pulmonary venous isolation was achieved in 100% of cases (Table 1). Of the patients in our cohort, 57% were classified as Long Standing Persistent AF. The median fluoroscopic time for this protocol was 1.55 minutes IQR (1.3, 2.2). Median radiation dose was 32 mGy. No complications occurred. Procedural Data for Atrial Fibrillation Ablation Procedures Procedural Data for Atrial Fibrillation Ablation Procedures Conclusions: A low fluoroscopic protocol utilizing primarily CARTO 4's navigation system is achievable and safe. Our protocol results in fluoroscopic times, and radiation exposure are equivalent or superior to previously published protocols Further studies will help to further refine the use of low fluoroscopic protocols in the ablation of atrial fibrillation.

Three-dimensional image fusion of CTA and angiography for real-time guidance during neurointerventional procedures

AimTo evaluate the accuracy of three-dimensional (3D) images from two modalities—CT angiography (CTA) and digital subtraction angiography (DSA). Additionally, to explore the value of using preprocedural CTA for real-time guidance...

Interest of fusion imaging and modern navigation tools with hybrid rooms in endovascular aortic procedures

Because of the emergence of hybrid operating rooms, cone-beam CT scans (CBCT) allow new intraoperative imaging to be produced. Image fusion (3D preoperative CT scan overlaid onto 2D live fluoroscopy image) is the most popular application and makes it possible to navigate throughout the aorta and its branches without having to make use of an additional injection, and allows a reduction to be achieved in the quantity of contrast medium and irradiation required during complex procedures. Planning-oriented software available in hybrid rooms makes it possible to adjust to the patient and the nature of the procedure, the information that is relevant during the operation. CBCT can also be used as a diagnostic tool at the end of a procedure for the detection of endoleaks and could replace routine CT scans made during the first month following the procedure, indirectly contributing again to a reduction of X-ray and contrast agent doses.

Value of C-Arm Cone Beam Computed Tomography Image Fusion in Maximizing the Versatility of Endovascular Robotics

To report our initial experience and highlight the value of using intraoperative C-arm cone beam computed tomography (CT; DynaCT(®)) image fusion guidance along with steerable robotic endovascular catheter navigation to optimize vessel cannulation. Between May 2013 and January 2015, all patients who underwent endovascular procedures using DynaCT image fusion technique along with Hansen Magellan vascular robotic catheter were included in this study. As a part of preoperative planning, relevant vessel landmarks were electronically marked in contrast-enhanced multi-slice computed tomography images and stored. At the beginning of procedure, an intraoperative noncontrast C-arm cone beam CT (syngo DynaCT(®), Siemens Medical Solutions USA Inc.) was acquired in the hybrid suite. Preoperative images were then coregistered to intraoperative DynaCT images using aortic wall calcifications and bone landmarks. Stored landmarks were then overlaid on 2-dimensional (2D) live fluoroscopic images as virtual markers that are updated in real-time with C-arm, table movements and image zoom. Vascular access and robotic catheter (Magellan(®), Hansen Medical) was setup per standard. Vessel cannulation was performed based on electronic virtual markers on live fluoroscopy using robotic catheter. The impact of 3-dimensional (3D) image fusion guidance on robotic vessel cannulation was evaluated retrospectively, by assessing quantitative parameters like number of angiograms acquired before vessel cannulation and qualitative parameters like accuracy of vessel ostium and centerline markers. All 17 vessels were cannulated successfully in 14 patients' attempted using robotic catheter and image fusion guidance. Median vessel diameter at origin was 5.4 mm (range, 2.3-13 mm), whereas 12 of 17 (70.6%) vessels had either calcified and/or stenosed origin from parent vessel. Nine of 17 vessels (52.9 %) were cannulated without any contrast injection. Median number of angiograms required before cannulation was 0 (range, 0-2). On qualitative assessment, 14 of 15 vessels (93.3%) had grade = 1 accuracy (guidewire inside virtual ostial marker). Fourteen of 14 vessels had grade = 1 accuracy (virtual centerlines that matched with the actual vessel trajectory during cannulation). In this small series, the experience of using DynaCT image fusion guidance together with a steerable endovascular robotic catheter indicates that such image fusion strategies can enhance intraoperative 2D fluoroscopy by bringing preoperative 3D information about vascular stenosis and/or calcification, angulation, and take off from main vessel thereby facilitating ultimate vessel cannulation.

Safety and Accuracy of Endovascular Aneurysm Repair Without Pre-operative and Intra-operative Contrast Agent

Severe chronic kidney disease is a major limitation for endovascular aortic aneurysm repair (EVAR). The aim of this study is to assess the safety and accuracy of fusion imaging, when performing EVAR in the absence of pre- and intra-operative contrast agents. From October 2013 to February 2014, every patient requiring EVAR and presenting with severe chronic renal impairment underwent a specific pre-operative imaging assessment, based on a non-enhanced CT scan. Centrelines were manually extracted and key points were placed at the landing zones. In house software makes it possible to artificially enhance the contrast between vascular structures and the surrounding tissue, by increasing the values attributed to the vascular structure voxels (500 Hounsfield units). EVAR was performed in a hybrid room (Zeego, Siemens), and the artificially enhanced CT scan was used for the construction of fusion imaging. The 3D vascular volume, together with the centrelines and key points, was overlaid onto the 2D live fluoroscopic image. Six patients (mean age 77.1 years) were treated by EVAR (5 abdominal aneurysms and 1 thoracic aneurysm), using fusion imaging without a contrast agent. The median pre-operative estimated glomerular filtration rate (eGFR) was 17.5 mL/min/1.73 m2. No contrast was used during the procedure. No intra-operative endoleak was observed on the duplex scan. No deterioration was observed in the eGFR at 1 week (eGFR = 21.7, p = .49), nor at 1 month follow up (eGFR = 21, p = .28). The stent graft positioning error was assessed in terms of the difference between the effective and planned landing zones, measured on pre- and post-operative CT scans. The mean error was 1.3 mm at the proximal landing zone, and 6.5 mm at the distal landing zone. EVAR without the use of pre-operative and intra-operative contrast agents appears to be safe and accurate for patients with severe chronic kidney disease.

Evaluation of the painful total knee arthroplasty.

There are a substantial number of patients who continue to complain of pain following total knee arthroplasty (TKA). There are many potential causes of continued pain, and these are broadly categorized into intrinsic and extrinsic sources. When evaluating a patient with a painful TKA, the physician begins with a thorough history and physical examination, along with the appropriate radiographs. Further workup includes laboratory analysis, specifically evaluating the inflammatory markers erythrocyte sedimentation rate and C-reactive protein, along with a synovial fluid aspirate evaluating the white blood cell count with differential and culture. Advanced imaging modalities are sometimes helpful when the diagnosis remains unclear, including stress radiographs, live fluoroscopic imaging, ultrasound, nuclear imaging, and magnetic resonance imaging. Further surgery is not advisable without a clear diagnosis, as this is associated with very poor results. Instead, serial follow-up or a referral to a specialist for a second opinion may be most appropriate.

“Contrast-Less” Stent-Assisted Coiling of an A1 Aneurysm

Iodine-based contrast medium used in diagnostic and therapeutic cerebrovascular imaging may cause renal toxicity, especially in patients with underlying renal impairment. Contrast dilution may impede efforts of the neurointerventionalist to treat intracranial vascular pathology. A 36-year-old man with renal impairment presented with an unruptured A1 segment anterior cerebral artery aneurysm. Previously obtained magnetic resonance angiography was fused with intraoperative noncontrast computed tomography and live 2-dimensional fluoroscopic images. The aneurysm was successfully treated with stent-assisted coil embolization without the use of contrast. Neurointervention without contrast was feasible, and although the presented case is one example, the imaging fusion techniques used in this case can substantially decrease the exposure to contrast and subsequent risk of renal injury during intracranial procedures. Further development of and experience with this technique is needed to improve its safety and efficacy.

E-059 Guiding Sclerotherapy for Deep Lying Lesions using Advanced Angiographic Imaging Applications and MR-Fusion

BackgroundDeep head and neck lesions are challenging to treat using conventional guidance, such as ultrasound (US) and fluoroscopy. High impedance structures prevent the use of US, while fluoroscopy lacks resolution...

CTA with Fluoroscopy Image Fusion Guidance in Endovascular Complex Aortic Aneurysm Repair

To evaluate the effect of intraoperative guidance by means of live fluoroscopy image fusion with computed tomography angiography (CTA) on iodinated contrast material volume, procedure time, and fluoroscopy time in endovascular thoraco-abdominal aortic repair. CTA with fluoroscopy image fusion road-mapping was prospectively evaluated in patients with complex aortic aneurysms who underwent fenestrated and/or branched endovascular repair (FEVAR/BEVAR). Total iodinated contrast material volume, overall procedure time, and fluoroscopy time were compared between the fusion group (n=31) and case controls (n=31). Reasons for potential fusion image inaccuracy were analyzed. Fusion imaging was feasible in all patients. Fusion image road-mapping was used for navigation and positioning of the devices and catheter guidance during access to target vessels. Iodinated contrast material volume and procedure time were significantly lower in the fusion group than in case controls (159mL [95% CI 132-186mL] vs. 199mL [95% CI 170-229mL], p=.037 and 5.2 hours [95% CI 4.5-5.9 hours] vs. 6.3 hours (95% CI 5.4-7.2 hours), p=.022). No significant differences in fluoroscopy time were observed (p=.38). Respiration-related vessel displacement, vessel elongation, and displacement by stiff devices as well as patient movement were identified as reasons for fusion image inaccuracy. Image fusion guidance provides added value in complex endovascular interventions. The technology significantly reduces iodinated contrast material dose and procedure time.

Catheter interventions for congenital heart disease with less and less radiation

Evelina London Children’s Hospital, Department of Paediatric Cardiology, Westminster Bridge Road, London, SE1 7EH, UK Percutaneous intervention for congenital heart disease (CHD) has been established as a core treatment modality since Rashkind pioneered balloon septostomy for neonates with transposition of the great arteries [1]. Since then, cardiac catheterization has progressed from mainly being a diagnostic procedure to interventions in the majority of cases, especially as a large amount of diagnostic information can be obtained with imaging modalities, such as echocardiography, computed tomography and MRI. Catheter interventions for CHD (as well as for coronary disease) are traditionally performed under f luoroscopic guidance using radiation. Especially in pediatric practice, any use of radiation carries the potential risk of DNA damage and the development of malignancy years to decades after the procedure [2,3]. Hence, the ‘as low as reasonably achievable’ principle has been introduced, and efforts have been made to minimize the dose used for common interventions [4]. This can be facilitated by detailed visualization of complex anatomy with imaging modalities, such as MRI, prior to intervention. Such preprocedural planning allows preselection of the angulations needed for interventional angiography, hence decreasing procedure time and minimizing contrast and radiation load [5]. Echocardiography and angiography do not always correlate well, as shown for neonatal aortic valves [6]. Hence, in these cases, angiography as the gold standard to determine balloon size cannot be replaced by echocardiography. Image fusion is a technique in which preexisting MRI or computed tomography images are overlaid on the live fluoroscopic images and are used as a ‘road map’ to guide catheter interventions (i.e., in coarctation of the aorta) [7].

Simultaneous Tracking of Catheters and Guidewires: Comparison to Standard Fluoroscopic Guidance for Arterial Cannulation

The purpose of this in vitro study was to clinically assess the feasibility of a three-dimensional (3D) electromagnetic (EM) navigator, including sensorized catheters and guidewires, to determine any reduction in radiation dose and contrast medium injection. The study was performed using a navigator prototype developed at the EndoCAS center. The system includes catheters and guidewires simultaneously tracked with an EM localizer (Aurora, Northern Digital, Waterloo, Canada). Tests were performed on a commercial abdominal aortic aneurysm model. Fifteen operators were asked to cannulate renal arteries using the conventional fluoroscopic guidance and the EM navigator without fluoroscopic support. Each trial was video-recorded and analyzed for timing and success of completing the cannulation task by two blinded and independent observers. Performances were also qualitatively evaluated using the Imperial College Endovascular Cannulation Scoring Tool (IC3ST). Moreover, a questionnaire was administered to participants to evaluate the navigator potentialities. Quantitative analysis results show no significant difference between the fluoroscopic and EM guidance regarding the total procedure time (median 2.36 minutes [interquartile range {IQR} = 1.26-4.7) vs. 2.95 min [IQR = 1.35-5.38], respectively; p = .93); number of total hits with catheter/guidewire tip to vessels wall (median 5.50 [IQR = 2.00-10.00] vs. 3.50 [IQR = 2.50-7.00], respectively; p = .65); and number of attempts at cannulation (median 4.0 [IQR = 2.00-5.00] vs. 4.0 [IQR = 2.00-5.00], respectively; p = .72]. Moreover, there was no significant difference between the IC3ST score obtained using the EM navigator and the traditional method (average 22.37 [STD = 7.95] vs. 21.58 [STD = 6.86]; p = .92). Finally, questionnaire results indicate a general agreement concerning the navigator usefulness, which clearly shows the positions of instruments inside the 3D model of the patient's anatomy. Participants also agreed that the navigator can reduce the amount of contrast media delivered to the patient, as well as fluoroscopy time. This work provides proof of concept that simultaneous EM navigation of guidewires and catheters is feasible without the use of live fluoroscopic images.

Multimodality 3D‐roadmap for cardiovascular interventions in congenital heart disease—A single‐center, retrospective analysis of 78 cases

Modern fluoroscopic angiography systems permit rendering of three-dimensional volumetric data sets using rotational angiography (3D-RA). Along with magnetic resonance imaging (MRI) or multi-detector-row computed tomography (MDCT) data sets, they can be fused with live fluoroscopy images for roadmapping during therapeutic procedures, but the value of multimodality fused data sets has not been clarified. In a pediatric cardiac catheterization laboratory, we analyzed 78 interventional cardiovascular procedures in which 3D models of 3D-RA, MRI, or MDCT were used for 3D-guidance. Accuracy of 2D-3D registration as well as overall procedural benefit was independently rated by two pediatric interventionalists. Fluoroscopy time, radiation dose, and contrast dye consumption were evaluated and, grouping a subgroup analysis, the parameters were compared between patients who underwent stenting of aortic coarctation with and without 3D-roadmapping. 3D-guiding was used in 78 cases, 75 of these cases were with accurate 2D-3D registration. 3D-roadmapping was rated superior to conventional biplane imaging in 74 cases. 3D-guidance was used in 64 cases to define the ideal C-arm angulation and in 60 cases for accurate device positioning. Median dose-area product in the total investigation was 706.3 μGym(2) (104.8-7249.7 μGym(2) ), 3.3 ml/kg (0.9-13.7 ml/kg) of contrast dye was used, and total fluoroscopy time was 14.5 min (2.9-68.1 min). Fluoroscopy time for 3D-guided stenting of aortic coarctation is significantly lower (8.35 versus 10.2 min; P = 0.04). 3D-image fusion with live fluoroscopy can be applied successfully in catheter-based interventions of congenital heart disease. 3D-guidance facilitates catheter manipulations and interventions, allows preselection of ideal projection angles, reduces fluoroscopic time and the number of control angiographies.

Integration of cardiac and respiratory motion into MRI roadmaps fused with x‐ray

Volumetric roadmaps overlaid on live x-ray fluoroscopy may be used to enhance image guidance during interventional procedures. These roadmaps are often static and do not reflect cardiac or respiratory motion. In this work, the authors present a method for integrating cardiac and respiratory motion into magnetic resonance imaging (MRI)-derived roadmaps to fuse with live x-ray fluoroscopy images, and this method was tested in large animals. Real-time MR images were used to capture cardiac and respiratory motion. Nonrigid registration was used to calculate motion fields to deform a reference end-expiration, end-diastolic image to different cardiac and respiratory phases. These motion fields were fit to separate affine motion models for the aorta and proximal right coronary artery. Under x-ray fluoroscopy, an image-based navigator and ECG signal were used as inputs to deform the roadmap for live overlay. The in vivo accuracy of motion correction was measured in four swine as the ventilator tidal volume was varied. Motion correction reduced the root-mean-square error between the roadmaps and manually drawn centerlines, even under high tidal volume conditions. For the aorta, the error was reduced from 2.4 ± 1.5 mm to 2.2 ± 1.5 mm (p < 0.05). For the proximal right coronary artery, the error was reduced from 8.8 ± 16.2 mm to 4.3 ± 5.2 mm (p < 0.001). Using real-time MRI and an affine motion model it is feasible to incorporate physiological cardiac and respiratory motion into MRI-derived roadmaps to provide enhanced image guidance for interventional procedures. A method has been presented for creating dynamic 3D roadmaps that incorporate cardiac and respiratory motion. These roadmaps can be overlaid on live X-ray fluoroscopy to enhance image guidance for cardiac interventions.

O-014 A new application of MRI fusion in angiographic percutaneous intervention for pediatric orbital lesions

Introduction/PurposeMRI fusion is a recently developed image targeting technique that volumetrically overlays an MRI sequence onto a live fluoroscopic image updated in real time. The ability to utilize the superior...

Validation of 3D multimodality roadmapping in interventional neuroradiology

Three-dimensional multimodality roadmapping is entering clinical routine utilization for neuro-vascular treatment. Its purpose is to navigate intra-arterial and intra-venous endovascular devices through complex vascular anatomy by fusing pre-operative computed tomography (CT) or magnetic resonance (MR) with the live fluoroscopy image. The fused image presents the real-time position of the intra-vascular devices together with the patient's 3D vascular morphology and its soft-tissue context. This paper investigates the effectiveness, accuracy, robustness and computation times of the described methods in order to assess their suitability for the intended clinical purpose: accurate interventional navigation. The mutual information-based 3D–3D registration proved to be of sub-voxel accuracy and yielded an average registration error of 0.515 mm and the live machine-based 2D–3D registration delivered an average error of less than 0.2 mm. The capture range of the image-based 3D–3D registration was investigated to characterize its robustness, and yielded an extent of 35 mm and 25° for >80% of the datasets for registration of 3D rotational angiography (3DRA) with CT, and 15 mm and 20° for >80% of the datasets for registration of 3DRA with MR data. The image-based 3D–3D registration could be computed within 8 s, while applying the machine-based 2D–3D registration only took 1.5 µs, which makes them very suitable for interventional use.

Image-Guided Transapical Aortic Valve Implantation Sensorless Tracking of Stenotic Valve Landmarks in Live Fluoroscopic Images

Aortic valve stenosis is one of the most frequently acquired valvular heart diseases, accounting for almost 70% of valvular cardiac surgery. Transapical transcatheter aortic valve implantation has recently become a suitable minimally invasive technique for high-risk and elderly patients with severe aortic stenosis. In this article, we aim to automatically define a target area of valve implantation, namely, the area between the coronary ostia and the lowest points of two aortic valve cusps. Therefore, we present a new image-based tracking method of these aortic landmarks to assist in the placement of aortic valve prosthesis under live 2D fluoroscopy guidance. We propose a rigid intensity-based image registration technique for tracking valve landmarks in 2D fluoroscopic image sequences, based on a real-time alignment of a contrast image including the initialized manual valve landmarks to each image of sequence. The contrast image is automatically detected to visualize aortic valve features when the aortic root is filled with a contrast agent. Our registration-based tracking method has been retrospectively applied to 10 fluoroscopic image sequences from routine transapical aortic valve implantation procedures. Most of all tested fluoroscopic images showed a successful tracking of valve landmarks, especially for the images without contrast agent injections. A new intraoperative image-based method has been developed for tracking aortic valve landmarks in live 2D fluoroscopic images to assist transapical aortic valve implantations and to increase the overall safety of surgery as well.

152 Real-time cardiac MR anatomy and dyssynchrony overlay to guide left ventricular lead placement in CRT

<h3>Introduction</h3> Optimal left ventricular (LV) lead placement via the coronary sinus (CS) is a critical factor in defining response to cardiac resynchronisation therapy (CRT). Using novel semi-automated image acquisition, segmentation, overlay and registration software we set out to guide lead placement by avoiding scar and targeting the region of the LV with the latest mechanical activation. <h3>Methods</h3> 17 patients underwent cardiac magnetic resonance (CMR) scans. 3D whole heart images were segmented to produce high fidelity anatomical models of the cardiac chambers and coronary veins. 2, 3, 4 chamber and short axis cine images were processed using Tomtec software to give a 16 segment time volume-dyssynchrony map. In patients with myocardial scar the late gadolinium enhancement images were manually segmented and registered to the anatomical model along with the dyssynchrony map. The 3 latest mechanically activated segments with &lt;50% scar were identified and this information was overlaid at CRT implant on to live fluoroscopic images using a prototype version of the Philips EP Navigator software. Subsequently, the x-ray C-arm and table could be moved freely while automatically maintaining a registered roadmap. We used a high fidelity pressure wire to assess the acute haemodynamic response to pacing in different regions of the overlaid 16 segment model. All dP/dt measurements were compared to baseline AAI or VVI (for those patients in AF) pacing at 5–10 beats/min above intrinsic rate. <h3>Results</h3> 15 of the 17 patients underwent successful placement of a LV pacing lead via the CS with satisfactory pacing parameters and no phrenic nerve stimulation at implant. The mean time from insertion of the CS guide catheter into the venous sheath to successful cannulation of the CS was 1.3±1.0 min. In 2 patients we were unable to place a LV lead successfully in any branch of the CS. We paced in at least one of our 3 target segments in 11 patients. 67% of patients were responders as defined by a 10% increase in +dP/dt over baseline. The mean change in +dP/dt for the best lead position vs baseline+dP/dt was 15.9±11.3% for DDDLV pacing. This compares to a mean change in+dP/dt of 14.9±12.3% when the CMR dyssynchrony-map defined target region was paced DDDLV. The region of best+dP/dt response was postero-lateral, lateral or posterior in all cases. <h3>Conclusion</h3> We have shown it is feasible to acquire, overlay and accurately register cardiac MR data on to fluoroscopic images at the time of CRT implant. Our data suggest that it is also possible to identify and place the LV lead in at least one target region in most patients. This appears to give close to the best acute haemodynamic response that can be achieved in any branch of the CS. The initial results of this pilot study suggest that a MR dyssynchrony guided approach to LV lead placement may allow ideal LV lead positioning (Abstract 152 figures 1 and 2).

Robust automatic rigid registration of MRI and X‐ray using external fiducial markers for XFM‐guided interventional procedures

In X-ray fused with MRI, previously gathered roadmap MRI volume images are overlaid on live X-ray fluoroscopy images to help guide the clinician during an interventional procedure. The incorporation of MRI data allows for the visualization of soft tissue that is poorly visualized under X-ray. The widespread clinical use of this technique will require fully automating as many components as possible. While previous use of this method has required time-consuming manual intervention to register the two modalities, in this article, the authors present a fully automatic rigid-body registration method. External fiducial markers that are visible under these two complimentary imaging modalities were used to register the X-ray images with the roadmap MR images. The method has three components: (a) The identification of the 3D locations of the markers from a full 3D MR volume, (b) the identification of the 3D locations of the markers from a small number of 2D X-ray fluoroscopy images, and (c) finding the rigid-body transformation that registers the two point sets in the two modalities. For part (a), the localization of the markers from MR data, the MR volume image was thresholded, connected voxels were segmented and labeled, and the centroids of the connected components were computed. For part (b), the X-ray projection images, produced by an image intensifier, were first corrected for distortions. Binary mask images of the markers were created from the distortion-corrected X-ray projection images by applying edge detection, pattern recognition, and image morphological operations. The markers were localized in the X-ray frame using an iterative backprojection-based method which segments voxels in the volume of interest, discards false positives based on the previously computed edge-detected projections, and calculates the locations of the true markers as the centroids of the clusters of voxels that remain. For part (c), a variant of the iterative closest point method was used to find correspondences between and register the two sets of points computed from MR and X-ray data. This knowledge of the correspondence between the two point sets was used to refine, first, the X-ray marker localization and then the total rigid-body registration between modalities. The rigid-body registration was used to overlay the roadmap MR image onto the X-ray fluoroscopy projections. In 35 separate experiments, the markers were correctly registered to each other in 100% of the cases. When half the number of X-ray projections was used (10 X-ray projections instead of 20), the markers were correctly registered in all 35 experiments. The method was also successful in all 35 experiments when the number of markers was (retrospectively) halved (from 16 to 8). The target registration error was computed in a phantom experiment to be less than 2.4 mm. In two in vivo experiments, targets (interventional devices with pointlike metallic structures) inside the heart were successfully registered between the two modalities. The method presented can be used to automatically register a roadmap MR image to X-ray fluoroscopy using fiducial markers and as few as ten X-ray projections.

Advanced Image Fusion to Overlay Coronary Sinus Anatomy with Real‐Time Fluoroscopy to Facilitate Left Ventricular Lead Implantation in CRT

Failure rate for left ventricular (LV) lead implantation in cardiac resynchronization therapy (CRT) is up to 12%. The use of segmentation tools, advanced image registration software, and high-fidelity images from computerized tomography (CT) and cardiac magnetic resonance (CMR) of the coronary sinus (CS) can guide LV lead implantation. We evaluated the feasibility of advanced image registration onto live fluoroscopic images to allow successful LV lead placement. Twelve patients (11 male, 59 ± 16.8 years) undergoing CRT had three-dimensional (3D) whole-heart imaging (six CT, six CMR). Eight patients had at least one previously failed LV lead implant. Using segmentation software, anatomical models of the cardiac chambers, CS, and its branches were overlaid onto the live fluoroscopy using a prototype version of the Philips EP Navigator software to guide lead implantation. We achieved high-fidelity segmentations of cardiac chambers, coronary vein anatomy, and accurate registration between the 3D anatomical models and the live fluoroscopy in all 12 patients confirmed by balloon occlusion angiography. The CS was cannulated successfully in every patient and in 11, an LV lead was implanted successfully. (One patient had no acceptable lead values due to extensive myocardial scar). Using overlaid 3D segmentations of the CS and cardiac chambers, it is feasible to guide CRT implantation in real time by fusing advanced imaging and fluoroscopy. This enabled successful CRT in a group of patients with previously failed implants. This technology has the potential to facilitate CRT and improve implant success.