Preprocedural Computed Tomography Imaging Research Articles

Artificial intelligence–based skeletal muscle estimates and outcomes of EUS-guided treatment of pancreatic fluid collections

Background and AimsSkeletal muscle status may impact clinical outcomes of a variety of pancreatic diseases. Skeletal muscle quality and quantity have not been fully examined in relation to the outcomes of endoscopic ultrasound (EUS)-guided treatment of pancreatic fluid collections (PFCs). MethodsUsing a multi-institutional cohort of 372 patients receiving EUS-guided treatment of PFCs in 2010-2020, we examined the association of skeletal muscle status with adverse outcomes including clinical treatment failure and in-hospital mortality. Utilizing an in-house deep learning-based platform for pre-procedural computed tomography images, we calculated skeletal muscle density (SMD) and skeletal muscle index (SMI, height-adjusted muscle area) as surrogates for muscular quality and quantity, respectively. Multivariable logistic regression analysis was conducted to calculate odds ratios (ORs) for adverse outcomes. ResultsLower-level SMD was associated with higher risks of clinical failure and in-hospital mortality (Ptrend < 0.001). The adjusted OR for clinical failure comparing the extreme quartiles was 3.64 (95% confidence interval, 1.52-8.72). Compared with patients in the top two quartiles, patients in the lowest quartile had an adjusted OR for in-hospital mortality of 12.4 (95% confidence interval, 3.43-44.8). We observed no effect modification by the PFC types on the SMD-outcome relationship (Pinteraction > 0.16). SMD was not associated with the risk of procedure-related adverse events or PFC recurrence. SMI was not associated with adverse outcomes (Ptrend > 0.39). ConclusionsIn patients with endoscopically managed PFCs, SMD, but not SMI, was associated with the risks of clinical failure and in-hospital mortality, supporting the prognostic role of skeletal muscle quality.

Comparison of a High-Pitch Non-ECG-Gated and a Prospective ECG-Gated Protocol for Preprocedural Computed Tomography Imaging Before TAVI/TAVR.

Preprocedural computed tomography (CT) imaging before transcatheter aortic valve implantation/replacement (TAVI/TAVR) requires high diagnostic accuracy without motion artifacts. The aim of this retrospective study is to compare the image quality of a high-pitch non-electrocardiography (ECG)-gated CT protocol used in patients with atrial tachyarrhythmias with a prospectively ECG-gated CT protocol used in patients with sinus rhythm. We retrospectively included 108 patients who underwent preprocedural CT imaging before TAVI/TAVR. 52 patients with sinus rhythm were imaged using a prospectively ECG-gated protocol (Group A), and 56 patients with atrial tachyarrhythmias were imaged using the high-pitch non-ECG-gated protocol (Group B). Image quality was rated subjectively by two experienced radiologists and assessed by objective parameters including radiation dose, image noise, contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR) at the levels of the aortic root and abdominal aorta. Subjective image quality was equally good with both CT protocols, and interrater agreement was substantial in both groups but tended to be higher in Group B at the level of the aortic root (Group A: κw = 0.644, Group B: κw = 0.741). With the high-pitch non-ECG-gated CT protocol, image noise was significantly increased (p = 0.001), whereas the SNR, CNR, and radiation dose were significantly decreased (p = 0.002, p = 0.003, and p < 0.001, respectively) at the level of the aortic root compared to the prospectively ECG-gated CT protocol. The high-pitch non-ECG-gated protocol yields images with similar subjective image quality compared with the prospectively ECG-gated CT protocol and allows motion-free assessment of the aortic root for accurate TAVI/TAVR planning. The high-pitch non-ECG-gated protocol may be used as an alternative for preprocedural CT imaging in patients with atrial tachyarrhythmias. · In patients with atrial tachyarrhythmias, a high-pitch non-ECG-gated CT protocol achieves similar subjective image quality compared to a prospective ECG-gated CT protocol.. · At the level of the aortic root, image noise is significantly increased, whereas SNR and CNR are significantly decreased using the high-pitch non-ECG-gated protocol.. · Radiation dose is reduced by 55 % using the high-pitch non-ECG-gated protocol.. · Shnayien S, Beetz N, Bressem KK et al. Comparison of a High-Pitch Non-ECG-Gated and a Prospective ECG-Gated Protocol for Preprocedural Computed Tomography Imaging Before TAVI/TAVR. Fortschr Röntgenstr 2023; 195: 139 - 147.

Patient-Specific Computer Simulation to Predict Conduction Disturbance With Current-Generation Self-Expanding Transcatheter Heart Valves

BackgroundPatient-specific computer simulation may predict the development of conduction disturbance following transcatheter aortic valve replacement (TAVR). Validation of the computer simulations with current-generation devices has not been undertaken. MethodsA retrospective study was performed on patients who had undergone TAVR with a current-generation self-expanding transcatheter heart valve (THV). Preprocedural computed tomography imaging was used to create finite element models of the aortic root. Procedural contrast angiography was reviewed, and finite element analysis performed using a matching THV device size and implantation depth. A region of interest corresponding to the atrioventricular bundle and proximal left bundle branch was identified. The percentage of this area (contact pressure index [CPI]) and maximum contact pressure (CPMax) exerted by THV were recorded. Postprocedural electrocardiograms were reviewed, and major conduction disturbance was defined as the development of persistent left bundle branch block or high-degree atrioventricular block. ResultsA total of 80 patients were included in the study. THVs were 23- to 29-mm Evolut PRO (n = 53) and 34-mm Evolut R (n = 27). Major conduction disturbance occurred in 27 patients (33.8%). CPI (28.3 ± 15.8 vs. 15.6 ± 11.2%; p < 0.001) and CPMax (0.51 ± 0.20 vs. 0.36 ± 0.24 MPa; p = 0.008) were higher in patients who developed major conduction disturbance. CPI (area under the receiver operating characteristic curve [AUC], 0.74; 95% CI, 0.63-0.86; p < 0.001) and CPMax (AUC, 0.69; 95% CI, 0.57-0.81; p = 0.006) demonstrated a discriminatory power to predict the development of major conduction disturbance. ConclusionsPatient-specific computer simulation may identify patients at risk for conduction disturbance after TAVR with current-generation self-expanding THVs.

Pre-procedural CT imaging aids neonatal PDA stenting for ductal-dependent pulmonary blood flow with reduction in overall procedural morbidity.

Patent ductus arteriosus stenting for ductal-dependent pulmonary blood flow is a technically challenging neonatal procedure to maintain a stable pulmonary circulation. Pre-procedural computed tomography imaging aids in outlining ductal origin, insertion, size, course and curvature. Computed tomography imaging may add value to procedural outcomes and reduce overall procedural morbidity in neonatal patent ductus arteriosus stenting. We conducted a single centre retrospective chart review of neonates with ductal-dependent pulmonary blood flow who underwent patent ductus arteriosus stenting between January 1, 2014 and June 31, 2020. We compared patients variables between patients who underwent pre-procedural computed tomography imaging to those who did not. A total of 64 patients were referred for patent ductus arteriosus stenting with 33 (52%) obtaining pre-procedural computed tomography imaging. Average age [19 days; range 1-242 days (p = 0.85)] and weight [3.3 kg (range 2.2-6.0 kg; p = 0.19)] was not significantly different between the groups. A diagnosis of pulmonary atresia was made in 42 out of 64 (66%) patients prior to patent ductus arteriosus stenting. The cohort with pre-intervention computed tomography imaging had a significant reduction in the total number of access sites (1.2 versus 1.5; p = 0.03), contrast needed (5.9 versus 8.2 ml/kg; p = 0.008), fluoroscopy (20.7 versus 38.8 minutes; p = 0.02) and procedural time (83.4-128.4 minutes; p = 0.002) for the intervention. There was no significant difference in radiation burden between the groups (p = 0.35). Pre-procedural computed tomography imaging adds value by aiding interventional planning for neonatal patent ductus arteriosus stenting. A statistically significant reduction in the number of access sites, contrast exposure, as well as fluoroscopic and procedural time was noted without significantly increasing the cumulative radiation burden.

Anatomic predictors of recurrence after cryoablation for atrial fibrillation: a computed tomography based composite score.

Effective pulmonary vein isolation (PVI) with cryoablation depends on adequate occlusion of pulmonary veins (PV) by the cryoballoon and is therefore likely to be affected by PV and left atrial (LA) anatomical characteristics and variants. Thus, the objective of this study was to investigate the effect of LA and PV anatomy, evaluated by computed tomography (CT), on acute and long-term outcomes of cryoablation for atrial fibrillation (AF). Fifty-eight patients (64.72+9.44years, 60.3% male) undergoing cryoablation for paroxysmal or early persistent AF were included. Pre-procedural CT images were analyzed to evaluate LA dimensions and PV anatomical characteristics. Predictors of recurrence were identified using regression analysis. 60.3% of patients had two PVs on each side with separate ostia, whereas 29.3% and 10.3% had right middle and left common PVs, respectively. The following anatomic characteristics were found to be independent predictors of recurrence: right superior PV ostial max:min diameter ratio > 1.32, left superior PV ostial max:min diameter ratio > 1.2, right superior PV antral circumference > 69.1mm, right inferior PV antral circumference > 61.38mm, right superior PV angle > 22.7°. Using these factors, LA diameter and right middle PV, a scoring model was created for prediction of "unfavorable" LA-PV anatomy (AUC = 0.867, p = 0.000009, score range = 0-7). Score of ≥ 4 predicted need for longer cryoenergy ablation (p = 0.039) and more frequent switch to radiofrequency energy (p = 0.066) to achieve PVI, and had a sensitivity of 83.3% and specificity of 82.5% to predict clinical recurrence. CT-based scoring system is useful to identify "unfavorable" anatomy prior to cryo-PVI, which can result in procedural difficulty and poor outcomes.

Patient-Specific Computer Simulation of Transcatheter Aortic Valve Replacement in Bicuspid Aortic Valve Morphology.

A patient-specific computer simulation of transcatheter aortic valve replacement (TAVR) in tricuspid aortic valve has been developed, which can predict paravalvular regurgitation and conduction disturbance. We wished to validate a patient-specific computer simulation of TAVR in bicuspid aortic valve and to determine whether patient-specific transcatheter heart valve (THV) sizing and positioning might improve clinical outcomes. A retrospective study was performed on TAVR in bicuspid aortic valve patients that had both pre- and postprocedural computed tomography imaging. Preprocedural computed tomography imaging was used to create finite element models of the aortic root. Finite element analysis and computational fluid dynamics was performed. The simulation output was compared with postprocedural computed tomography imaging, cineangiography, echocardiography, and electrocardiograms. For each patient, multiple simulations were performed, to identify an optimal THV size and position for the patient's specific anatomic characteristics. A total of 37 patients were included in the study. The simulations accurately predicted the THV frame deformation (minimum-diameter intraclass correlation coefficient, 0.84; maximum-diameter intraclass correlation coefficient, 0.88; perimeter intraclass correlation coefficient, 0.91; area intraclass correlation coefficient, 0.91), more than mild paravalvular regurgitation (area under the receiver operating characteristic curve, 0.86) and major conduction abnormalities (new left bundle branch block or high-degree atrioventricular block; area under the receiver operating characteristic curve, 0.88). When compared with the implanted THV size and implant depth, optimal patient-specific THV sizing and positioning reduced simulation-predicted paravalvular regurgitation and markers of conduction disturbance. Patient-specific computer simulation of TAVR in bicuspid aortic valve may predict the development of important clinical outcomes, such as paravalvular regurgitation and conduction abnormalities. Patient-specific THV sizing and positioning may improve clinical outcomes of TAVR in bicuspid aortic valve.

Computed Tomography-Determined Muscle Quality Rather Than Muscle Quantity Is a Better Determinant of Prolonged Hospital Length of Stay in Patients Undergoing Transcatheter Aortic Valve Implantation

Computed tomography (CT)-determined skeletal muscle measures have been used for predicting postoperative outcomes in patients undergoing transcatheter aortic valve implantation (TAVI). We investigated the impact of CT-determined muscle quantity (measured as psoas muscle area [PMA] and psoas muscle index [PMI]) and quality (measured as psoas muscle density [PMD]) on hospital length of stay (LOS) after TAVI. We retrospectively identified 182 consecutive patients who underwent TAVI between March 2013 and August 2017 with adequate preprocedural CT imaging. Baseline demographic and clinical data, the Society of Thoracic Surgeons score, the essential frailty toolset (EFT) frailty rating, and precontrast PMD, PMA, and PMI were obtained in all study patients. The primary outcome was prolonged postoperative LOS defined as greater than 14 days. Patients with prolonged LOS had a significantly higher Society of Thoracic Surgeons score (p < 0.001) and significantly lower PMD (p < 0.001) than those with LOS ≤14 days. More patients with prolonged LOS had concomitant peripheral vascular disease (p = 0.001), had undergone percutaneous coronary interventions (p = 0.022), and had an EFT score ≥4 (p < 0.001) compared to those without prolonged LOS. Neither PMA (p = 0.123) nor PMI (p = 0.271) were associated with prolonged LOS. Multivariate analysis identified EFT score ≥4, the presence of peripheral vascular disease, and PMD as independent predictors of prolonged LOS. The precontrast CT-determined muscle quality measurement PMD is a simple and objective predictor of prolonged LOS after TAVI.

Intracardiac Versus Transesophageal Echocardiographic Guidance for Left Atrial Appendage Occlusion: The LAAO Italian Multicenter Registry

ObjectivesThis study sought to evaluate the feasibility, safety, and efficacy of intracardiac echocardiography (ICE)–guided versus transesophageal echocardiography (TEE)–guided left atrial appendage occlusion (LAAO) by the use of Amplatzer Cardiac Plug or Amulet devices included in a large Italian registry. BackgroundTEE is widely used for LAAO procedure guidance. ICE may be a potential alternative imaging modality in LAAO. MethodsData from 604 LAAO procedures performed in 16 Italian centers were reviewed. ICE-guided LAAO was performed in 187 patients, whereas TEE was used in 417 patients. Procedural success was defined as LAAO without occurrence of pericardial tamponade, stroke, systemic embolism with end organ damage, major bleeding, and device embolization. Stroke, transient ischemic attack, major bleeding, overall and cardiovascular death were analyzed. ResultsCHA2DS2-VASc (congestive heart failure, hypertension, age ≥75 years, diabetes mellitus, prior stroke or transient ischemic attack or thromboembolism, vascular disease, age 65 to 74 years, sex category) and HAS-BLED (hypertension, abnormal renal and liver function, stroke, bleeding, labile international normalized ratio, elderly, drugs or alcohol) scores were similar between the ICE and TEE groups. TEE implied lower procedural (delta 12 min) and fluoroscopy time (delta 5 min) when compared with ICE. Procedural success was similarly high (≥94%) between the TEE and ICE groups with a complication rate of 6.5% for TEE versus 4.2% for ICE (odds ratio: 1.468; 95% confidence interval: 0.681 to 3.166; p = 0.327). At median follow-up of 451 days (interquartile range: 162 to 899 days), the rate of cerebral ischemic events was similar between TEE-guided and ICE-guided procedures. ConclusionsICE-guided LAAO by means of Amplatzer devices may represent a second alternative imaging modality after an appropriate learning curve and bearing in mind that pre-procedural computed tomography imaging is mandatory. When comparing ICE with TEE, TEE remains the gold standard.

Location, variations, and predictors of epicardial fat mapping using multidetector computed tomography to assist epicardial ventricular tachycardia ablation.

A significant number of ventricular tachycardia circuits are located close to the epicardial surface and are amendable to epicardial ablation. Epicardial fat often interferes with substrate mapping and ablation, though little is known regarding the distribution of fat and its fluctuation with the cardiac cycle. We studied 40 patients who underwent a 64-slice multidetector computed tomography in order to describe patterns of epicardial fat distribution, variation during cardiac cycle, and clinical predictors of epicardial fat. Multiplanar reconstructions were analyzed during systole and diastole in six cross-sections. Epicardial fat thickness was measured across multiple wall segments in each view. Epicardial fat was found to be thicker in areas overlying coronary vasculature (7.8 ± 2.6mm vs 3.5 ± 0.9mm, P=0.001), along with the right ventricular wall (3.9 ± 0.8mm vs 2.6 ± 0.6mm, P=0.001) and the ventricular base (6.1 ± 1.7mm vs 4.6 ± 1.6mm, P<0.01). Epicardial fat thickness increased 27% during systole as compared to diastole (4.9 ± 2.7mm vs 6.2 ± 3.0mm, P=0.04). Variation with cardiac cycle was most evident along the right ventricular wall (3.9 ± 0.8mm vs 5.0 ± 1.3mm, P=0.001) and nonvascular areas (P=0.001), especially at the ventricular base (3.7 ± 1.1mm vs 5.3 ± 1.5mm, P=0.001). In multivariate logistic regression, we found that age >50 years (P=0.031) and coronary artery disease (P=0.023) were statistically correlated with epicardial fat >5-mm thickness and body mass index >33 (P=0.052) nearly so. Baseline epicardial fat thickness >5mm is common in areas typically targeted during epicardial ablation and further increases during the cardiac cycle. Simple clinical characteristics can identify patients with >5mm epicardial fat in which preprocedural computed tomography imaging and three-dimensional fat map reconstruction may facilitate epicardial ablation.

Role of atrial wall thickness in wave-dynamics of atrial fibrillation.

Background/AimsAtrial anatomy and thickness may affect the electrical wave-dynamics of atrial fibrillation (AF). We explored the relationship between left atrial (LA) wall thickness (LAWT) or LA geometry and AF wave-dynamics.MethodsWe included 15 patients with persistent AF (age, 62.3 ± 11.9 years) who underwent AF catheter ablation. We measured the LAWT, LA endocardial curvature, and SD-curvature (surface bumpiness) from preprocedural computed tomography images. We compared those anatomical characteristics with electrophysiologic parameters such as dominant frequency (DF), Shannon entropy (ShEn), or complex fractionated atrial electrogram (CFAE)-cycle length (CL), calculated from intracardiac bipolar electrograms (300–500 points, 5 s), acquired during ablation procedures.Results1. LAWT (excluding fat) varied widely among patients, locations, and types of AF. LAWT was inversely correlated with LA volume (r = -0.565, p = 0.028) and positively correlated with SD-curvature (r = 0.272, p < 0.001). 2. LAWT was positively correlated with ShEn (r = 0.233, p < 0.001) and negatively correlated with CFAE-CL (r = -0.107, p = 0.038). 3. In the multivariate linear regression analyses for AF wave-dynamics parameters, DF (β = -0.29 [95% CI -0.44–-0.14], p < 0.001), ShEn (β = 0.19 [95% CI 0.12–0.25], p < 0.001), and CFAE-CL (β = 7.49 [95% CI 0.65–14.34], p = 0.032) were independently associated with LAWT.ConclusionRegional LAWT is associated with LA structural features, and has significant correlations with the wave-dynamics parameters associated with electrical wavebreaks or rotors in patients with persistent AF.

MR and CT Imaging to Optimize CT-Guided Biopsies in Suspected Spondylodiscitis

The diagnostic value of computed tomography (CT)-guided spinal biopsy in patients with suspected spondylodiscitis is reported inconsistently in the literature. Our aim was to evaluate associations between procedural, clinical, and imaging parameters and the diagnostic yield of CT-guided spinal biopsy. One hundred and two procedures performed in 87 patients with clinically suggested spondylodiscitis were analyzed retrospectively. Preprocedural magnetic resonance (MR) and CT images were evaluated regarding signal alterations, vertebral destruction, and soft-tissue involvement. The position of the biopsy needle in correlation with MR imaging findings was assessed. Patient characteristics and clinical details were noted. Parameters were compared in patients with positive and negative microbiological and histologic results. Following microbiologic and histologic analysis, infectious spondylodiscitis was diagnosed in 29 and 23 biopsies, respectively. Microbiology results were significantly higher in biopsy specimens with central needle positioning within contrast enhancing tissue in correlation with the MR images (36% vs. 7%; P= 0.005). Biopsy specimens positioned in fluid-equivalent hyperintense discs in T2-weighted sequences yielded significantly lower microbiology results (6% vs. 33%; P= 0.036). Purely lytic endplate destruction and mixed vertebral density as shown by CT increased microbiology results (60% vs. 24%; P= 0.028). Previous antibiotic treatment for any cause did not influence microbiology yields significantly (P= 0.232). MR imaging is mandatory to determine the optimal biopsy position. No clinical or imaging parameter could rule out a positive biopsy result and thus omit an unnecessary procedure. Biopsy should not be avoided if antibiotic treatment has previously been administered.

Role of Imaging in Transcatheter Aortic Valve Replacement.

Transcatheter aortic valve replacement (TAVR) has emerged as an effective treatment alternative in patients with severe aortic stenosis (AS) who are deemed surgically high-risk or ineligible for surgery. Pre-procedural imaging, in particular computed tomography (CT), plays an integral part in the planning and performance of TAVR and is crucial for a successful treatment. Novel technological advances in CT include high-pitch, low kV acquisitions, and iterative reconstruction resulting in high image quality at substantially reduced scan duration, contrast volume, and radiation exposure. Given the high spatial and temporal resolution of the acquisitions, CT angiography provides critical information on the eligibility for the peripheral vascular access, aortic root assessment, as well as the aortic annulus measurements, including the coronary ostia and concomitant cardiac pathology. Pre-procedural CT imaging is key for appropriate device size selection to minimize peri-procedural complications and optimize procedural success. In this article, we review the current state of imaging in the pre-interventional setting of TAVR with a special emphasis on CT.

Transcatheter embolotherapy with N-butyl cyanoacrylate for ectopic varices.

To address technical feasibility and clinical outcome of transcatheter embolotherapy with N-butyl cyanoacrylate (NBCA) for bleeding ectopic varices. The institutional review board approved this retrospective study and waived informed consent. From January 2004 to June 2013, a total of 12 consecutive patients received transcatheter embolotherapy using NBCA for bleeding ectopic varices in our institute. Clinical and radiologic features of the endovascular procedures were comprehensively reviewed. Preprocedural computed tomography images revealed ectopic varices in the jejunum (n = 7), stoma (n = 2), rectum (n = 2), and duodenum (n = 1). The 12 procedures consisted of solitary embolotherapy (n = 8) and embolotherapy with portal decompression (main portal vein stenting in 3, transjugular intrahepatic portosystemic shunt in 1). With regard to vascular access, percutaneous transhepatic access (n = 7), transsplenic access (n = 4), and transjugular intrahepatic portosystemic shunt tract (n = 1) were used. There was no failure in either the embolotherapy or the vascular accesses (technical success rate, 100 %). Two patients died within 1 month from the procedure from preexisting fatal medical conditions. Only one patient, with a large varix that had been partially embolized by using coils and NBCA, underwent rebleeding 5.5 months after the procedure. The patient was retreated with NBCA and did not undergo any bleeding afterward for a follow-up period of 2.5 months. The remaining nine patients did not experience rebleeding during the follow-up periods (range 1.5-33.2 months). Transcatheter embolotherapy using NBCA can be a useful option for bleeding ectopic varices.

Computed Tomographic Imaging of Transcatheter Aortic Valve Replacement for Prediction and Prevention of Procedural Complications

Senile calcific aortic stenosis (AS) is the most common acquired valvular heart disease with an increasing prevalence attributable to an aging population. Survival is poor in patients with severe or critical AS, chiefly after the onset of symptomology that primarily includes angina, dyspnea, or syncope. On the onset of symptoms, mortality occurs at very high rates during the ensuing 2 to 3 years.1 Until recently, surgical aortic valve replacement represented the sole therapy that definitive reduced mortality and morbidity in patients with severe symptomatic AS, with medical therapy generally ineffective of these patients. Given the advanced age commonly associated with severe AS, a high proportion of these patients are denied surgical intervention because of multiple comorbidities and excessively high surgical risk.2 Recently, transcatheter aortic valve replacement (TAVR) has emerged as a novel disruptive technology that serves an alternative therapy to surgical AVR and has been shown to be an effective therapy in nonoperable and high-risk patients with severe symptomatic AS.3,4 TAVR was first described in humans by Cribier et al in 20025 by a transvenous approach delivered in an antegrade fashion. This technique requires a transseptal puncture and passage of the aortic stent valve across the mitral valve to the aortic position. Subsequently, array of alternative transvascular approaches have arisen, including transfemoral, transaortic, trans-subclavian, and aortic methods. Of these, the retrograde transarterial approach through the femoral artery, developed by Webb et al,6 has been the commonly used approach, with >60 000 such procedures performed worldwide to date. To date, the global experience with TAVR as documented in both single and multicenter registries as well as through multicenter trials have shown good clinical outcomes with improvement in hemodynamic and clinical status, establishing TAVR to be a feasible alternative therapy to traditional surgical aortic valve …

Electromagnetic Tracking for Registration and Navigation in Endovascular Aneurysm Repair: A Phantom Study

ObjectiveTo assess the feasibility of using an electromagnetic tracking for both registration and navigation in endovascular aneurysm repair. Materials and methodsA registration process was implemented to align computed tomography (CT) data and electromagnetic tracking data. Two abdominal aortic aneurysm (AAA) phantoms were used, a rigid plastic AAA model (phantom A) and a soft silicon AAA model (phantom B). A pre-procedural CT volume was acquired for each phantom. Intra-operative simulation was performed by placing each phantom in the magnetic field of the tracking device. Using a modified electromagnetic catheter, a set of three-dimensional positions was acquired in the phantom's aortic lumen. Pre-procedural CT images and intra-procedural tracked positions were registered. Four reference points were used to calculate the registration accuracy of phantom A. Three surgeons simulated catheterisation of the left renal artery with phantom B using only image-guided procedure software. ResultsThe mean registration error was 1.3 mm (range 0.88–1.89). The median time for left renal catheterisation was 22 s (range 15–59). ConclusionRegistration of CT data and electromagnetic tracking data is feasible using catheter positions in the aorto-iliac structure as landmark. This navigation system could reduce X-ray exposure time and the use of contrast medium injections.

Reconstructing and Registering Three‐Dimensional Rotational Angiogram of Left Atrium during Ablation of Atrial Fibrillation

Three-dimensional (3D) image of left atrium (LA) can greatly facilitate ablation of atrial fibrillation (AF). Reconstructing method using computed tomography (CT) has certain limitations. The 3D image of LA can be intraprocedurally reconstructed by a rotational angiography technique. Forty-six patients undergoing AF ablation were included in this study. Preprocedural CT imaging and intraprocedural reconstructing 3D rotational angiogram (3DRA) of LA were performed in all the patients. Rapid ventricular pacing (RVP, 300 ms) was used to inhibit the drainage of atrium. During RVP, contrast medium was injected into the LA, and rotational angiography was performed. The 3DRA was reconstructed and was registered with the live fluoroscopy. The 3DRA was evaluated in comparison to the CT image. In the navigation of the registered 3DRA, the ablation of AF was performed. Forty-four 3DRAs (95.7%) were successfully reconstructed and registered with the live fluoroscopy. The LA anatomy was delineated in the 3DRA in comparison to a CT image. AF ablation was successfully performed in the 44 patients in the navigation of the registered 3DRA. There were good correlations in the PV ostial diameter and the LA volume as assessed by 3DRA in comparison to a CT image (r>=0.87). The radiation exposure in rotational angiography was substantially less than that in CT scanning (2.7+/-0.9 mSv vs. 24.9+/-3.1 mSv, P<0.001). It is feasible to reconstruct and register the 3DRA with live fluoroscopy using the RVP method during the ablation of AF.

FPGA-Accelerated Deformable Image Registration for Improved Target-Delineation During CT-Guided Interventions

Minimally invasive image-guided interventions (IGIs) are time and cost efficient, minimize unintended damage to healthy tissue, and lead to faster patient recovery. With the advent of multislice computed tomography (CT), many IGIs are now being performed under volumetric CT guidance. Registering pre-and intraprocedural images for improved intraprocedural target delineation is a fundamental need in the IGI workflow. Earlier approaches to meet this need primarily employed rigid body approximation, which may not be valid because of nonrigid tissue misalignment between these images. Intensity-based automatic deformable registration is a promising option to correct for this misalignment; however, the long execution times of these algorithms have prevented their use in clinical workflow. This article presents a field-programmable gate array-based architecture for accelerated implementation of mutual information (Ml)-based deformable registration. The reported implementation reduces the execution time of MI-based deformable registration from hours to a few minutes. This work also demonstrates successful registration of abdominal intraprocedural noncontrast CT (iCT) images with preprocedural contrast-enhanced CT (preCT) and positron emission tomography (PET) images using the reported solution. The registration accuracy for this application was evaluated using 5 iCT-preCT and 5 iCT-PET image pairs. The registration accuracy of the hardware implementation is comparable with that achieved using a software implementation and is on the order of a few millimeters. This registration accuracy, coupled with the execution speed and compact implementation of the reported solution, makes it suitable for integration in the IGI-workflow.

View-Synchronized Robotic Image-Guided Therapy for Atrial Fibrillation Ablation

A robotic catheter navigation system has been developed that provides a significant degree of freedom of catheter movement. This study examines the feasibility of synchronizing this robotic navigation system with electroanatomic mapping and 3-dimensional computed tomography imaging to perform view-synchronized left atrial (LA) ablation. This study consisted of a porcine experimental validation phase (9 animals) and a clinical feasibility phase (9 atrial fibrillation patients). Preprocedural computed tomography images were reconstructed to provide 3-dimensional surface models of the LA pulmonary veins and aorta. Aortic electroanatomic mapping was performed manually, followed by registration with the corresponding computed tomography aorta image using custom software. The mapping catheter was remotely manipulated with the robotic navigation system within the registered computed tomography image of the LA pulmonary veins. The point-to-surface error between the LA electroanatomic mapping data and the computed tomography image was 2.1+/-0.7 and 1.6+/-0.1 mm in the preclinical and clinical studies, respectively. The catheter was remotely navigated into all pulmonary veins, the LA appendage, and circumferentially along the mitral valve annulus. In 7 of 9 animals, circumferential radiofrequency ablation lesions were applied periostially to ablate 11 pulmonary veins. In patients, all of the pulmonary veins were remotely electrically isolated in an extraostial fashion. Adjunctive ablation included superior vena cava isolation in 6 patients, cavotricuspid isthmus ablation in 5 patients, and ablation of sites of complex fractionated activity and atypical LA flutters in 3 patients. This study demonstrates the safety and feasibility of an emerging paradigm for atrial fibrillation ablation involving the confluence of 3 technologies: 3-dimensional imaging, electroanatomic mapping, and remote robotic navigation.

Computed Tomography‐Fluoroscopy Image Integration‐Guided Catheter Ablation of Atrial Fibrillation

This study examines the feasibility of atrial fibrillation (AF) ablation using registered three-dimensional computed tomography (CT) images of the left atrium with fluoroscopy. A total of 50 consecutive patients with symptomatic AF refractory to medical therapy (32 paroxysmal, 18 persistent, age 55 +/- 10 years) were randomized to undergo a catheter-based AF ablation procedure with or without the CT-fluoroscopy guidance system. All patients underwent preprocedural contrast-enhanced CT imaging and segmentation of the left atrium. For the CT-fluoroscopy group, circumferential lesions encompassing the pulmonary vein (PV) antrum and linear lesions along the roof of the left atrium between the superior PVs and the mitral isthmus were created on the CT image, which was registered with real-time fluoroscopy. The registered images were then used to navigate the ablation catheters to the sites of planned ablation. After the ablation sites were completed, any remaining PV potentials were isolated with electrophysiological guidance. In the control patients, the same technique was performed without using the CT-fluoro guidance system. CT scans were accurately registered to fluoroscopic images with minimal manual correction. Operators could navigate catheters on the registered images to preplanned, extraostial sites for ablation. CT-fluoroscopy guidance decreased procedure duration and fluoro times (P < 0.05). At a mean follow-up of 9 +/- 2 months, 21 patients (84%) in the CT-fluoro guidance group and 16 patients (64%) in the control group have had no recurrence of AF. CT-fluoroscopic-guided left atrial ablation is feasible and allows appropriate catheter manipulation in the left atrium.

Failure of aneurysm sac shrinkage after endovascular repair; the effect of mural calcification

To evaluate the effect of abdominal aortic aneurysm wall calcification on subsequent sac shrinkage after endovascular repair. Seventy-three patients underwent endovascular aneurysm repair. The degree of sac wall calcification on pre-procedural computed tomography (CT) examination was graded from 1 to 4 according to the degree of circumferential involvement. On follow-up CT imaging, the maximum transverse diameter (MTD) of the sac was recorded, as well as the presence or absence of endoleak. In those patients with a non-shrinking aneurysm, but no CT evidence of endoleak, contrast-enhanced ultrasound (USS) was performed. Any patient with an endoleak, however diagnosed, was excluded from the study. Kruskal-Wallis and Spearman's rank correlation coefficient testing was applied to compare the degree of calcification and change in MTD. Sixty-three pre-procedural CT images were available for calcification grading. Six of this group had endoleaks resulting in 57 sets of data being available for the study. A reduction in MTD occurred in 68.25% of these patients by 1 year post-procedure. Our figures show aortic calcification is inversely associated with MTD reduction at 6 months (p = 0.01), 1 year (p = 0.05) and 2 years (p = 0.05). This study indicates that the degree of aortic wall calcification is significant in predicting MTD reduction post-endovascular repair. The possible mechanisms and implications of this are discussed.