Patient-specific Anatomy Research Articles

Patient-specific design process and evaluation of a hip prosthesis femoral stem.

There are several commercially available hip implant systems. However, for some cases, custom implant designed based on patient-specific anatomy can offer the patient the best available implant solution. Currently, there is a growing trend toward personalization of medical implants involving additive manufacturing into orthopedic medical implants' manufacturing. This article introduces a systematic design methodology of femoral stem prosthesis based on patient's computer tomography data. Finite element analysis is used to evaluate and compare the micromotion and stress distribution of the customized femoral component and a conventional stem. The proposed customized femoral stem achieved close geometrical fit and fill between femoral canal and stem surfaces. The customized stem demonstrated lower micromotion (peak: 21 μm) than conventional stem (peak: 34 μm). Stress results indicate up to 89% increase in load transfer by conventional stem than custom stem because the higher stiffness of patient-specific femoral stem proximally increases the custom stem shielding in Gruen's zone 7. Moreover, patient-specific femoral stem transfers the load widely in metaphyseal region. The customized femoral stem presented satisfactory results related to primary stability, but compromising proximo-medial load transfer due to increased stem cross-sectional area increased stem stiffness.

Patient-Specific Three-Dimensional Model for a Safe Surgical Pathway in Sacral Chondrosarcoma.

Sacral tumors are amongst the most challenging procedures to treat because of the complex anatomy. This study determined whether patient-specific models change preoperative planning decisions made in preparation for en bloc resection of complex sacral mass surgical procedures. Imaging showed a big encapsulated mass at the S2-3 level involving the neural foramina and obscuring the nerve roots. High-resolution images were acquired and utilized to generate a patient-specific 3D tumor model. The visual and tactile inspection of 3D models allowed the best anatomical understanding, with faster and clearer comprehension of the surgical anatomy. The 3D sacral model was for observation of previously unapparent anatomical details; with this new technology, surgeon can observe their planned surgical intervention, explore the patient-specific anatomy and extension of the tumor, and sharpen their procedure choices. Moreover, multiple planes showed how far the angles on the plane would extend for osteotomy of the sacrum. Another result was identifying correct guides and safe venture landmarks. The study helped to establish safe osteotomy line wherever the nerve roots were retained and enabled osteotomy by preserving bilaterally the S1 and S2 nerve roots for wide excision of wide excision of primary sacral tumor to get adequate bowel and bladder functions. Finally, it helped to determine whether or not the remaining bone in the sacrum is sufficient for spinopelvic stability and needed fixation. It was decided spinopelvic fixation was not necessary for this case. Surgical intervention of sacral tumors varies depending on the tumor, its size, extension, and location. Surgery can have profound risks including unnecessary nerve root resection spinopelvic instability and suboptimal oncological resection. 3D models help to transfer complex anatomical information to clinicians and provide guidance in the preoperative planning stage, for intraoperative navigation and for surgical training purposes.

Predicting image properties in penalized-likelihood reconstructions of flat-panel CBCT.

Model-based iterative reconstruction (MBIR) algorithms such as penalized-likelihood (PL) methods exhibit data-dependent and shift-variant properties. Image quality predictors have been derived to prospectively estimate local noise and spatial resolution, facilitating both system hardware design and tuning of reconstruction methods. However, current MBIR image quality predictors rely on idealized system models, ignoring physical blurring effects and noise correlations found in real systems. In this work, we develop and validate a new set of predictors using a physical system model specific to flat-panel cone-beam CT (FP-CBCT). Physical models appropriate for integration with MBIR analysis are developed and parameterized to represent nonidealities in FP projection data including focal spot blur, scintillator blur, detector aperture effect, and noise correlations. Flat-panel-specific predictors for local spatial resolution and local noise properties in PL reconstructions are developed based on these realistic physical models. Estimation accuracy of conventional (idealized) and FP-specific predictors is investigated and validated against experimental CBCT measurements using specialized phantoms. Validation studies show that flat-panel-specific predictors can accurately estimate the local spatial resolution and noise properties, while conventional predictors show significant deviations in the magnitude and scale of the spatial resolution and local noise. The proposed predictors show accurate estimations over a range of imaging conditions including varying x-ray technique and regularization strength. The conventional spatial resolution prediction is sharper than ground truth. Using conventional spatial resolution predictor, the full width at half maximum (FWHM) of local point spread function (PSF) is underestimated by 0.2 mm. This mismatch is mostly eliminated in FP-specific prediction. The general shape and amplitude of local noise power spectrum (NPS) FP-specific predictions are consistent with measurement, while the conventional predictions underestimated the noise level by 70%. The proposed image quality predictors permit accurate estimation of local spatial resolution and noise properties for PL reconstruction, accounting for dependencies on the system geometry, x-ray technique, and patient-specific anatomy in real FP-CBCT. Such tools enable prospective analysis of image quality for a range of goals including novel system and acquisition design, adaptive and task-driven imaging, and tuning of MBIR for robust and reliable behavior.

Cardiac Magnetic Resonance Imaging of Mechanical Cavopulmonary Assistance

Mechanical circulatory support (MCS) options are limited for patients with dysfunctional single ventricle physiology. To address this unmet clinical need, we are developing an axial-flow blood pump to provide mechanical assistance to the cavopulmonary circulation. In this study, we investigate the use of high-resolution cardiac magnetic resonance imaging (MRI) to visualize the complex fluid flow conditions of mechanical circulatory assist in two patient-specific Fontan anatomies. A three-bladed axial-flow impeller coupled to a supportive cage with a four-bladed diffuser was positioned in the inferior vena cava (IVC) of each Fontan anatomy. Cardiac magnetic resonance (CMR) imaging and power efficiency studies were conducted at physiologic relevant parameters with cardiac outputs of 2, 3, and 4 L/min with impeller rotational speeds of 2000 and 4000 rpm. The axial-flow impeller was able to generate improved flow in the total cavopulmonary connection (TCPC). The higher rotational speed was able to redistribute flow in the TCPC anastomosis aiding in removing stagnant blood. No retrograde flow was observed or measured in the superior vena cava (SVC). As an extension of the CMR data, a scalar stress analysis was performed on both models and found a maximum scalar stress of approximately 42 Pa for both patient anatomies. The power efficiency experiments demonstrated a maximum energy gain of 8.6 mW for TCPC Anatomy 1 and 12.58 mW for TCPC Anatomy 2 for a flow rate of 4 L/min and at 4000 rpm. These findings support the continued development of axial blood pumps for mechanical cavopulmonary assist.

Design of lymphedema ultrasound phantom with 3D-printed patient-specific subcutaneous anatomy: A-mode analysis approach for early diagnosis

The secondary lymphedema is mostly caused due to injury of lymphatic system during cancer treatment and its psychological and cosmetic issues are very critical for patients since it can cause severe thickening and swelling of lesions, mostly upper and lower limbs. Therefore, early diagnosis of the secondary lymphedema is more important to treat the symptoms in advance. The amplitude-mode (A-mode) ultrasound is suggested as an early diagnostic modality because it is relatively more cost-effective, portable, and easy to use than other previous diagnostic modalities. In order to see features of the A-mode ultrasound forearly diagnosis of lymphedema, ultrasound lymphedema phantoms were designed and fabricated with patient-specific subcutaneous honeycomb structures at the sub-stages of the international society of lymphedema (ISL) stage II and gelatin- or gelatin-salt based phantom materials. The patent-specific honeycomb structures were segmented from computed tomography (CT) venography images using various image process technologies and printed using a three dimensional (3D) printer for which its printing material shows similar acoustic impedance range with human subcutaneous tissues. The lymphedema phantoms showed similar subcutaneous anatomical features to those of patient's imagesin brightness mode (B-mode) ultrasound examination, and acoustic information originated from the stage-specific honeycomb structures was well represented in A-mode ultrasound examination. In particular, the A-mode wave form well represented stage-specific honeycomb information even with higher impedance value of fibrous fat region. Such stage-specific wave form information of A-mode ultrasound for the corresponding stage-specific lymphedema phantoms at the ISL stage II can be useful for further development of an A-mode ultrasound applications for early diagnosis of the secondary lymphedema.

A new method to statistically describe microcatheter tip position in patient-specific aneurysm models

Background and purposeEvidence on how to select microcatheters to facilitate aneurysm catheterization during coil embolization is sparse. We developed a new method to define microcatheter tip location inside a patient-specific...

Pre-procedural fit-testing of TAVR valves using parametric modeling and 3D printing

BackgroundSuccessful transcatheter aortic valve replacement (TAVR) requires an understanding of how a prosthetic valve will interact with a patient's anatomy in advance of surgical deployment. To improve this understanding, we developed a benchtop workflow that allows for testing of physical interactions between prosthetic valves and patient-specific aortic root anatomy, including calcified leaflets, prior to actual prosthetic valve placement. MethodsThis was a retrospective study of 30 patients who underwent TAVR at a single high volume center. By design, the dataset contained 15 patients with a successful annular seal (defined by an absence of paravalvular leaks) and 15 patients with a sub-optimal seal (presence of paravalvular leaks) on post-procedure transthoracic echocardiogram (TTE). Patients received either a balloon-expandable (Edwards Sapien or Sapien XT, n = 15), or a self-expanding (Medtronic CoreValve or Core Evolut, n = 14, St. Jude Portico, n = 1) valve. Pre-procedural computed tomography (CT) angiograms, parametric geometry modeling, and multi-material 3D printing were utilized to create flexible aortic root physical models, including displaceable calcified valve leaflets. A 3D printed adjustable sizing device was then positioned in the aortic root models and sequentially opened to larger valve sizes, progressively flattening the calcified leaflets against the aortic wall. Optimal valve size and fit were determined by visual inspection and quantitative pressure mapping of interactions between the sizer and models. ResultsBenchtop-predicted “best fit” valve size showed a statistically significant correlation with gold standard CT measurements of the average annulus diameter (n = 30, p < 0.0001 Wilcoxon matched-pairs signed rank test). Adequateness of seal (presence or absence of paravalvular leak) was correctly predicted in 11/15 (73.3%) patients who received a balloon-expandable valve, and in 9/15 (60%) patients who received a self-expanding valve. Pressure testing provided a physical map of areas with an inadequate seal; these corresponded to areas of paravalvular leak documented by post-procedural transthoracic echocardiography. ConclusionWe present and demonstrate the potential of a workflow for determining optimal prosthetic valve size that accounts for aortic annular dimensions as well as the active displacement of calcified valve leaflets during prosthetic valve deployment. The workflow's open source framework offers a platform for providing predictive insights into the design and testing of future prosthetic valves.

Low-cost physiological simulation system for endovascular treatment of aneurysms

Abstract Minimally invasive procedures are more and more becoming the standard treatment for many surgical procedures such as the treatment of cerebral aneurysms. In an endovascular procedure the aneurysm is filled with flexible platinum coils leading to embolization and blocking the blood flow in the aneurysm. This established treatment needs high skills and experience on the surgeon. In order to practice and plan a specific procedure or test a new device, a realistic simulation environment is needed. Modern 3D printing technology allows the fabrication of patient specific models incorporating the exact geometry of the pathological anatomy. This article describes the development of a low-cost physiological simulation system for the training of the endovascular treatment of aneurysms. In order to practice the procedure in a realistic scenario, a 3D printed model of the aneurysm is embedded in a fluidic simulation s ystem. In addition to the patient-specific anatomy of the aneurysm a pulsatile water flow is generated, which emulates the influence of blood flow on the behaviour of catheters and coils during deployment. The system consist of a controllable pump circuit generating a pulsatile flow which can be regulated automatically and additionally controlled externally by the user. For a suitable representation, a display which graphically represents the sensor data and settings is employed. The components were compactly integrated in a small case allowing for easy deployment in training workshops. The simulation setup was successfully tested in prospective patient specific treatment planning and workshops for students.

The impact of implantation depth of the Lotus™ valve on mechanical stress in close proximity to the bundle of His.

It has been proposed that inappropriate positioning of transcatheter aortic valves (TAVs) is associated with procedural complications and decreased device durability. Second-generation TAVs allow for repositioning giving greater control over the final deployment position. However, the impact of positioning on the tissue surrounding these devices needs to be better understood, in particular for the interleaflet triangle in which the conductance system (bundle of His) resides. In this study, we investigate the impact of implantation depth on the frame-tissue interaction for a next-generation repositionable Lotus™ valve. For this purpose, a computational model simulating deployment of the Lotus valve frame into a calcified patient-specific aortic root geometry was generated to predict aortic root stress and frame eccentricity at three different deployment depths. The results of this study predicted that positioning of the Lotus valve had an influence on the stresses in the aortic sinus and frame eccentricity. An analysis of levels of stress arising in the vicinity of the bundle of His, as a function of implantation depth, was conducted, and it was found that, for the specific patient anatomy studied, although the sub-annular position showed reduced peak stress in the aortic sinus, this implantation position showed the highest stress in the area of greatest risks of conductance interference. In contrast, while a supra-annular position increased the peak arterial stress, this implantation position resulted in lower stress in the interleaflet triangle and thus might reduce the risk of conductance interference. These results provide pre-operative information that can inform clinical decision-making regarding TAVI positioning.

Journey of the glenoid in anatomic total shoulder replacement.

Anatomic total shoulder arthroplasty (TSR) has been shown to generate good to excellent results for patients with osteoarthritis and a functioning rotator cuff. Many studies have reported that the glenoid component loosening and failure remain the most common long-term complication of total shoulder arthroplasty. The approach to glenoid component is critical because a surgeon should consider patient-specific anatomy, preserving bone stock and joint line restoration, for a good and durable shoulder function. Over the years, different glenoid design and materials have been tried in various configurations. These include cemented polyethylene, uncemented metal-backed and hybrid implants. Although advances in biomechanics, design and tribology have improved our understanding of the glenoid, the journey of the glenoid component in anatomic total shoulder arthroplasty has not yet reached its final destination. This article attempts to describe the evolution of the glenoid component in anatomic TSR and current practice.

Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters: P59. X-ray vision: the performance of a technology that allows clinicians to see spinal X-rays superimposed on a patient's back

BACKGROUND CONTEXT Clinicians of all disciplines learn to visualize internal anatomy to enhance diagnostic accuracy and reduce iatrogenic injury. Unfortunately, the performance of this skill is poor. To address this issue, our team developed technology that superimposes diagnostic images on to a patient's skin while minimizing distortion caused by patient topography. The result is that clinicians can immediately visualize their patient's underlying anatomy while freeing their hands to conduct clinical procedures such as palpation, injections or even surgery. PURPOSE In this project, we assess the accuracy and reliability of a holographic projection system with respect to representing underlying anatomy. STUDY DESIGN/SETTING Experimental system compared to criterion reference. PATIENT SAMPLE Ten (10) males (76.9%, mean age 42, age range 31–58) and 3 females (23.1%, mean age 41.6, age range 27–68) were enrolled in the study. OUTCOME MEASURES The projected location of any spinous process was judged to be accurate or “on target” if its location was within known spinous dimensions for that specific level. METHODS Thirteen participants were enrolled in the study, each having a pre-existing anteroposterior lumbar radiograph. Each participant's image was uploaded into a goggle system which when worn, allowed the operator to view the radiograph superimposed on the participant's back. The projected image was topographically corrected using depth information obtained by the goggles then aligned via existing anatomic landmarks. Using this superimposed image, vertebral levels were identified and validated against spinous process locations obtained by ultrasound. This process was repeated 1-5days later. The projection of each vertebra was deemed to be “on-target” if it fell within the known dimensions of the spinous process for that specific vertebral level. RESULTS The projection system created on-target projections with respect to individual vertebral levels 74% of the time with no significant difference seen between testing sessions. The average agreement for all vertebral levels between testing sessions was 75%. CONCLUSIONS The projection system tested here shows promise as a unique technology to assist clinicians in locating internal anatomy. While there are presently many sources of error including those from the device (resolution), viewer (inaccurate marking and placement) X-ray (magnification) and patient (when using generic images), we anticipate these errors can be mitigated, if not corrected, in future studies to provide an accurate and reliable way for clinicians to visualize patient-specific anatomy while allowing their hands to move freely.

Fixation Techniques in Revision TKA with Poor Bone Conditions. Bone, Cement, Stem, Sleeve, or Cone?

Recent registry data predict a significant increase in revision surgery in TKA, which is often associated with severe bony defects. Stable and correct implant fixation remains a challenge. The prerequisite for long-term and reproducible results is the selection of the correct reconstruction and fixation strategy, taking into account the existing bone defect as well as the patient-specific anatomy.

A novel computational framework to predict patient-specific hemodynamics after TEVAR: Integration of structural and fluid-dynamics analysis by image elaboration

Although Thoracic EndoVascular Aortic Repair (TEVAR) is a consolidated procedure to treat thoracic aortic diseases, it still has relevant complications mainly related to suboptimal wall apposition of the stent-graft, impairing the post-operative hemodynamics and the clinical outcomes. Accurate stent-graft sizing and patient selection are the key aspects to minimize drawbacks. Unfortunately, current TEVAR planning is only based on geometrical measurements performed on static images, completely neglecting the biomechanical interplay between the stent-graft and the aorta. Despite an extensive literature dealing with bioengineering simulation of endovascular implants, studies on the prediction of the post-TEVAR hemodynamics based on both pre-operative patient-specific aortic anatomy and stent-graft mechanical features are still missing.The present study aims at providing a realistic and robust computational framework to support TEVAR planning in the clinical practice by predicting the post-operative hemodynamics given a selected stent-graft model and pre-operative medical images of the aorta to be treated. A novel approach based on a distance image aimed at transforming the result of the structural analysis of stent-graft deployment in a volume mesh suitable for a computational study of the post-TEVAR hemodynamics is presented. The study discusses two clinical cases as illustrative examples of the framework application and, for one of the two cases, a comparison of the predicted hemodynamics with a simulation based on real post-operative images is shown.Such a comparison proves that the proposed computational framework is able to capture the main hemodynamic aspects related to the stent-graft implant. In particular, the use of simulations has confirmed the unsuitability for the endovascular repair of one of the two patients due to the short proximal landing zone, leading to a high risk of the so-called bird-beak.The proposed computational framework is shown to be a useful tool to support planning of elective TEVAR, especially in those borderline cases when the sole geometrical analysis of static images is not exhaustive.

Analysis of adverse effects of stimulation during DBS surgery by patient-specific FEM simulations.

Deep brain stimulation (DBS) represents today a well-established treatment for movement disorders. Nevertheless the exact mechanism of action of DBS remains incompletely known. During surgery, numerous stimulation tests are frequently performed in order to evaluate therapeutic and adverse effects before choosing the optimal implantation site for the DBS lead. Anatomical structures responsible for the induced adverse effects have been investigated previously, but only based on stimulation data obtained with the implanted DBS lead. The present study introduces a methodology to identify these anatomical structures during intraoperative stimulation tests based on patient-specific electric field simulations and visualization on the patient specific anatomy. The application to 4 patients undergoing DBS surgery and presenting dysarthria, paresthesia or pyramidal effects shows the different anatomical structures, which might be responsible for the adverse effects. Several of the identified structures have been previously described in the literature. To draw any statistically significant conclusions, the methodology has to be applied to further patients. Together with the visualization of the therapeutic effects, this new approach could assist the neurosurgeons in the future in choosing the optimal implant position.

Image-Based Computational Fluid Dynamic Analysis for Surgical Planning of Sequential Grafts in Coronary Artery Bypass Grafting.

Coronary bypass grafting (CABG) is a surgical procedure for anastomosing small grafts to the coronary vessels. The bypass graft bridges the occluded or diseased coronary artery, allowing sufficient blood flow to deliver oxygen and nutrients to the heart muscles. Patient-specific (PS) anatomy obtained from coronary computed tomography angiography (CCTA) was used to generate a 3D aorto-coronary model (pre-surgery). Additionally, three more models with idealized grafts (individual and sequential grafts), were created using Boolean operations to represent post-surgery configuration. Fractional flow reserve (FFR) and wall shear stress (WSS) were estimated from the computational fluid dynamics (CFD). The pre-surgical FFR values for all the three left coronary arteries were significant (FFR<.80). The flow was restored (FFR>0.80) distal to stenosis in all the three post- surgical idealized graft models. Peak WSS values of 468, 336 and 295 dynes/cm2 were observed at the toe of the individual end-to-side anastomosis for the three graft models. More importantly, low WSS (< 100 dynes/cm2) prevails at the heel and the walls opposite to the anastomosis in the sequential graft models. The prevailing low WSS at the heel and the wall bed opposite to anastomosis, in a sequential graft model, reduces restenosis rates and promotes a uniform hemodynamic environment for a better long-term patency of the graft. PS- CFD simulations based on CCTA can be helpful in assessing the hemodynamic parameters of graft models for optimal surgical planning.

Patient-Specific Parameters Associated with Traction Stiffness in Primary and Revision Hip Arthroscopy

Objectives:To quantify the force of traction required for adequate distraction of the hip during arthroscopy and explore the relationship between hip joint stiffness and patient-specific demographics, flexibility, and anatomy.Methods:101 primary arthroscopy patients (61 females) and 23 patients undergoing revision arthroscopy for capsular repair (all female) were prospectively enrolled. A load cell attached to the traction boot continuously measured traction force. Fluoroscopy images were obtained before and after traction to measure joint displacement. The stiffness coefficient was calculated as the force of traction divided by joint displacement. Primary patients were analyzed in a univariable regression model and re-analyzed separately by gender. Variables significant at p<0.05 were included in a multivariable regression model. Stiffness was compared between female primary and revision patients using independent t-tests.Results:For primary arthroscopy, instantaneous peak force averaged 80 ± 18 kgf, after which the force required to maintain distraction decreased to 57 ± 13 kgf. In univariable regression analysis, gender, alpha angle, hamstring flexibility and Beighton hypermobility score were each correlated to stiffness. However, gender was the only significant variable in the multivariable regression model. Intragender analysis demonstrated increased hamstring flexibility correlated with decreased stiffness in males and higher Beighton scores correlated with decreased stiffness in females. Stiffness was significantly less in the revision cases than the primary cases (p=0.006).Conclusion:A substantial force is required to achieve and maintain hip distraction, with males requiring higher forces. Males with increased hamstring flexibility and females with higher Beighton scores are less stiff than their same gender counterparts. Patients indicated for revision capsule repair were less stiff, supporting the importance of the hip capsule on hip stability. These data may be used to identify patients with microinstability and patients where specific focus on capsular repair and/or plication may be warranted.

Numerical simulation of thermal water delivery in the human nasal cavity

This work describes an extensive numerical investigation of thermal water delivery for the treatment of inflammatory disorders in the human nasal cavity. The numerical simulation of the multiphase air-droplets flow is based upon the Large Eddy Simulation (LES) technique, with droplets of thermal water described via a Lagrangian approach. Droplet deposition is studied for different sizes of water droplets, corresponding to two different thermal treatments, i.e. aerosol and inhalation. Numerical simulations are conducted on a patient-specific anatomy, employing two different grid sizes, under steady inspiration at two breathing intensities.The results are compared with published in vivo and in vitro data. The effectiveness of the various thermal treatments is then assessed qualitatively and quantitatively, by a detailed analysis of the deposition patterns of the droplets. Discretization effects on the deposition dynamics are addressed. The level of detail of the present work, together with the accuracy afforded by the LES approach, leads to an improved understanding of how the mixture of air-water droplets is distributed within the nose and the paranasal sinuses.

Advanced Technical Considerations for Implanting the t-Branch Off-the-Shelf Multibranched Stent-Graft to Treat Thoracoabdominal Aneurysms

Purpose: To demonstrate different techniques and device modifications that can expand the anatomic suitability of the off-the-shelf multibranched t-Branch for treatment of thoracoabdominal aortic aneurysm. Technique: The t-Branch device is not customized for specific patient anatomy, and the most frequent limitations to its use are an inadequate sealing zone and renal artery anatomy. Experience with this device has prompted the development of several techniques that can be employed to maximize the suitability of this stent-graft. Advice is offered on modification of the device to minimize the risk of paraplegia or better match patient anatomy. Maneuvers are explained to ease delivery through tortuous anatomy or existing stent-grafts, catheterize visceral target vessels, select a bridging stent, reduce ischemia time in the limbs, and alter the configuration of the branches. Conclusion: Employing adjunctive maneuvers can increase the anatomic suitability of the t-Branch; in our experience, these techniques have increased the applicability to more than 80% of all elective and urgent thoracoabdominal aortic aneurysm cases.

Transfer Learning From Simulations on a Reference Anatomy for ECGI in Personalized Cardiac Resynchronization Therapy.

Noninvasive cardiac electrophysiology (EP) model personalisation has raised interest for instance in the scope of predicting EP cardiac resynchronization therapy (CRT) response. However, the restricted clinical applicability of current methods is due in particular to the limitation to simple situations and the important computational cost. We propose in this manuscript an approach to tackle these two issues. First, we analyze more complex propagation patterns (multiple onsets and scar tissue) using relevance vector regression and shape dimensionality reduction on a large simulated database. Second, this learning is performed offline on a reference anatomy and transferred onto patient-specific anatomies in order to achieve fast personalized predictions online. We evaluated our method on a dataset composed of 20 dyssynchrony patients with a total of 120 different cardiac cycles. The comparison with a commercially available electrocardiographic imaging (ECGI) method shows a good identification of the cardiac activation pattern. From the cardiac parameters estimated in sinus rhythm, we predicted five different paced patterns for each patient. The comparison with the body surface potential mappings (BSPM) measured during pacing and the ECGI method indicates a good predictive power. We showed that learning offline from a large simulated database on a reference anatomy was able to capture the main cardiac EP characteristics from noninvasive measurements for fast patient-specific predictions. The fast CRT pacing predictions are a step forward to a noninvasive CRT patient selection and therapy optimisation, to help clinicians in these difficult tasks.

Patient-Specific Simulated Dynamics After Total Knee Arthroplasty Correlate With Patient-Reported Outcomes

BackgroundComponent alignment variation following total knee arthroplasty (TKA) does not fully explain the instance of long-term postoperative pain. Joint dynamics following TKA vary with component alignment and patient-specific musculoskeletal anatomy. Computational simulations allow joint dynamics outcomes to be studied across populations. This study aims to determine if simulated postoperative TKA joint dynamics correlate with patient-reported outcomes. MethodsLandmarking and 3D registration of implants was performed on 96 segmented postoperative computed tomography scans of TKAs. A cadaver rig–validated platform for generating patient-specific simulation of deep knee bend kinematics was run for each patient. Resultant dynamic outcomes were correlated with a 12-month postoperative Knee Injury and Osteoarthritis Outcome Score (KOOS). A Classification and Regression Tree (CART) was used for determining nonlinear relationships. ResultsNonlinear relationships between the KOOS pain score and rollback and dynamic coronal alignment were found to be significant. Combining a dynamic coronal angular change from extension to full flexion between 0° and 4° varus (long leg axis) and measured rollback of no more than 6 mm without rollforward formed a “kinematic safe zone” of outcomes in which the postoperative KOOS score is 10.5 points higher (P = .013). ConclusionThe study showed statistically significant correlations between kinematic factors in a simulation of postoperative TKA and postoperative KOOS scores. The presence of a dynamic safe zone in the data suggests a potential optimal target for any given individual patient's joint dynamics and the opportunity to preoperatively determine a patient-specific alignment target to achieve those joint dynamics.