Thu, 21 Aug 2008 14:18:27 BST CiteULike: tmansi's library [173 articles] http://www.citeulike.org/user/tmansi CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/tmansi/article/2833519 <i>Medical Image Computing and Computer-Assisted Intervention – MICCAI 2001 (2001), pp. 1159-1161.</i><br /><br />Models of the electro-mechanical activity of the cardiac muscle can be very useful in computing stress, strain and action potential fields from three-dimensional image processing. We designed a chemically-controlled constitutive law of cardiac myofibre mechanics, acting on the mesoscopic scale and devoted to be embedded into a macroscopic model. This law ensues from the modelling of the collective behaviour of actin-myosin molecular motors, acting on the nanoscopic scale to convert chemical into mechanical energy. The resulting dynamics of sarcomeres, acting on the microscopic scale, is shown to be consistent with the “sliding filament hypothesis”, which was first introduced by A. F. Huxley [1]. A Biomechanical Model of Muscle Contraction J Bestel F Clément M Sorine doi:10.1007/3-540-45468-3_143 Medical Image Computing and Computer-Assisted Intervention – MICCAI 2001 (2001), pp. 1159-1161. 2008-05-26T11:08:32-00:00 2001 Medical Image Computing and Computer-Assisted Intervention – MICCAI 2001 1159 1161 biomechanics heart http://www.citeulike.org/user/tmansi/article/2825263 <i>Br. Heart J., Vol. 63, No. 1. (1 January 1990), pp. 45-49.</i><br /><br />Ventricular pressure-volume diagrams were obtained from the right ventricle in patients before and after relief of right ventricular pressure load, in patients with volume loaded right ventricles, and from the left ventricle in patients after the Mustard procedure for transposition of the great arteries. The patterns of ejection during pressure development and decline were similar in patients after relief of pressure load and in those with isolated volume load. A right ventricular pressure load, however, reduced ejection during the two "isovolumic" periods, and the overall shape of the pressure-volume loop resembled that of the normal left ventricle. Pressure-volume diagrams obtained from the left ventricle after the Mustard procedure were indistinguishable from the normal right ventricle, which accords with the hypothesis that the normal right ventricular contraction pattern is a consequence of loading conditions rather than a reflection of an intrinsic property of the myocardium. 10.1136/hrt.63.1.45 Changes in the pressure-volume relation of the right ventricle when its loading conditions are modified. AN Redington ML Rigby EA Shinebourne PJ Oldershaw doi:10.1136/hrt.63.1.45 Br. Heart J., Vol. 63, No. 1. (1 January 1990), pp. 45-49. 2008-05-23T12:43:55-00:00 1990 Br. Heart J. 63 1 45 49 heart medical tof http://www.citeulike.org/user/tmansi/article/1016482 <i>Annals of Biomedical Engineering, Vol. 35, No. 1. (January 2007), pp. 1-18.</i> Coupling of a 3D Finite Element Model of Cardiac Ventricular Mechanics to Lumped Systems Models of the Systemic and Pulmonic Circulation Kerckhoffs Roy Neal Maxwell Gu Quan Bassingthwaighte James Omens Jeff Mcculloch Andrew doi:10.1007/s10439-006-9212-7 Annals of Biomedical Engineering, Vol. 35, No. 1. (January 2007), pp. 1-18. 2006-12-27T10:58:57-00:00 2007 Annals of Biomedical Engineering 0090-6964 35 1 1 18 Springer heart model regurgitation http://www.citeulike.org/user/tmansi/article/2804711 <i>Comput. Struct., Vol. 85, No. 11-14. (2007), pp. 988-997.</i> In vivo MRI-based 3D FSI RV/LV models for human right ventricle and patch design for potential computer-aided surgery optimization Chun Yang Dalin Tang Idith Haber Tal Geva Pedro doi:10.1016/j.compstruc.2006.11.008 Comput. Struct., Vol. 85, No. 11-14. (2007), pp. 988-997. 2008-05-16T08:47:35-00:00 2007 Comput. Struct. 0045-7949 85 11-14 988 997 Pergamon Press, Inc. heart model virtual-surgery http://www.citeulike.org/user/tmansi/article/2804695 <i>Complex Medical Engineering, 2007. CME 2007. IEEE/ICME International Conference on (2007), pp. 157-162.</i><br /><br />Right ventricular (RV) dysfunction is a common cause of heart failure in patients with congenital heart defects and often leads to impaired functional capacity and premature death. A novel surgical/modeling procedure is proposed to test the hypotheses that a) patient-specific image-based computational modeling can provide accurate information for assessment of RV function and that b) more aggressive scar removal using computer-aided surgery design with optimized post-operative RV morphology and patch design will lead to improved recovery of RV functions. Cardiac Magnetic Resonance (CMR) Imaging studies were performed in a dedicated MRI suite located in the Department of Cardiology at Children's Hospital Boston to acquire patient-specific ventricle geometry, heart motion, flow velocity, and flow rate for patients needing RV remodeling and pulmonary valve replacement operations before and after scheduled surgeries and healthy volunteers. MRI-based RV/LV combination models with fluid-structure interaction (FSI), RV-LV interaction, and RV-patch interaction were introduced to perform mechanical analysis and assess RV cardiac functions. The patient-specific FSI model (validated by pre-operation data) was used to predict possible outcome of virtual surgeries (i.e., with modified RV morphologies) and good agreement between computational predictions and pre-post operation RV stroke volume and ejection ratio as measured by CMR was found. Patient-Specific Virtual Surgery for Right Ventricle Volume Reduction and Patch Design Using MRI-Based 3D FSI RV/LV/Patch Models Dalin Tang Chun Yang T Geva Del doi:10.1109/ICCME.2007.4381712 Complex Medical Engineering, 2007. CME 2007. IEEE/ICME International Conference on (2007), pp. 157-162. 2008-05-16T08:40:21-00:00 2007 Complex Medical Engineering, 2007. CME 2007. IEEE/ICME International Conference on 157 162 heart model virtual-surgery http://www.citeulike.org/user/tmansi/article/2801504 <i>Seminars in Thoracic and Cardiovascular Surgery: Pediatric Cardiac Surgery Annual, Vol. 9, No. 1. (2006), pp. 29-34.</i><br /><br />With the increasing number of late survivors of repair of tetralogy of Fallot, surgical management of patients with right ventricular (RV) dysfunction and limited exercise capacity has become a more frequent problem. The wide variability in clinical status, extent of RV dilatation, and dysfunction at the time of presentation for surgical intervention has resulted in disparate surgical results after pulmonary valve insertion. With increasing use of magnetic resonance imaging, quantitative measures of RV volumes, function, and pulmonary regurgitant fraction have enabled a more systematic analysis of results. While there is a group of patients that responds favorably to pulmonary valve insertion, there is also a large subgroup that does not; this requires further analysis of the mechanisms responsible. We have developed a surgical approach to this latter group of patients, which incorporates the concepts of ventricular remodeling or restoration developed for the left ventricle following myocardial infarction. Preliminary results indicate that this procedure is equally safe to pulmonary valve insertion alone, and may result in improved RV function. Surgical Management of Right Ventricular Dysfunction Late After Repair of Tetralogy of Fallot: Right Ventricular Remodeling Surgery Del doi:10.1053/j.pcsu.2006.02.007 Seminars in Thoracic and Cardiovascular Surgery: Pediatric Cardiac Surgery Annual, Vol. 9, No. 1. (2006), pp. 29-34. 2008-05-15T12:29:03-00:00 2006 Seminars in Thoracic and Cardiovascular Surgery: Pediatric Cardiac Surgery Annual 9 1 29 34 clinical surgery tof http://www.citeulike.org/user/tmansi/article/2501301 <i>Br. Heart J., Vol. 60, No. 1. (1 July 1988), pp. 57-65.</i><br /><br />Biplane right ventriculograms with simultaneous high fidelity pressure recordings were obtained in 24 patients with tetralogy of Fallot. Twelve patients were studied before repair and 12 were studied 67 (42) months after radical surgical repair without the use of a transannular patch. In the patients who had repair right ventricular end diastolic and end systolic volume indices were higher, and the ejection fraction was lower. Time to peak ventricular filling and the peak rate of ventricular fillings were also lower in this group and there was a significant relation between peak filling rate and ejection fraction. Postoperative pressure-volume loops from nine patients showed an increase in cavity volume during the decline in right ventricular pressure, which indicated pulmonary regurgitation. The mean regurgitant volume for the group correlated with end diastolic volume index, stroke volume index, and peak filling rate, but not with ejection fraction. These data show that both systolic and diastolic abnormalities of right ventricular function are detected in most patients after radical repair of tetralogy of Fallot. The reduction of ejection fraction previously reported in these patients is unrelated to the degree of pulmonary regurgitation and primarily reflects an impairment of contractile function that presumably is related to intraoperative events. 10.1136/hrt.60.1.57 A new technique for the assessment of pulmonary regurgitation and its application to the assessment of right ventricular function before and after repair of tetralogy of Fallot. AN Redington PJ Oldershaw EA Shinebourne ML Rigby doi:10.1136/hrt.60.1.57 Br. Heart J., Vol. 60, No. 1. (1 July 1988), pp. 57-65. 2008-03-10T15:04:31-00:00 1988 Br. Heart J. 60 1 57 65 heart medical tof http://www.citeulike.org/user/tmansi/article/2497274 <i>Functional Imaging and Modeling of the Heart (2007), pp. 350-360.</i><br /><br />Clinical trials evaluating cardiac resynchronization therapy (CRT) have demonstrated that 30% of patients with heart failure and wide QRS do not respond to CRT (especially patients with myocardial infarcts). We have developed 3D numerical models of failing hearts, with and without chronic infarcts in different regions of the left ventricle. The hearts were coupled to a closed circulation, and the model included effects of the pericardium. The hearts were either paced at the right ventricular apex (RVA) or left ventricular free wall (LVFW). In normal and failing hearts, LV pump function was moderately better for LVFW pacing. In the normal heart model, heterogeneity of ejection strain was similar for RVA and LVFW pacing. However, in the failing heart model, LVFW pacing was associated with 44% less heterogeneity of ejection strain. This may be an important factor in the remodeling process associated with pacing. Effect of Pacing Site and Infarct Location on Regional Mechanics and Global Hemodynamics in a Model Based Study of Heart Failure Roy Kerckhoffs Andrew Mcculloch Jeffrey Omens Lawrence Mulligan doi:10.1007/978-3-540-72907-5_36 Functional Imaging and Modeling of the Heart (2007), pp. 350-360. 2008-03-09T20:52:55-00:00 2007 Functional Imaging and Modeling of the Heart 350 360 electrophysiology heart patient-specific http://www.citeulike.org/user/tmansi/article/2494933 <i>Med Image Anal, Vol. 8, No. 3. (September 2004), pp. 245-254.</i><br /><br />We present a fully automated deformable model technique for myocardium segmentation in 3D MRI. Loss of signal due to blood flow, partial volume effects and significant variation of surface grey value appearance make this a difficult problem. We integrate various sources of prior knowledge learned from annotated image data into a deformable model. Inter-individual shape variation is represented by a statistical point distribution model, and the spatial relationship of the epi- and endocardium is modeled by adapting two coupled triangular surface meshes. To robustly accommodate variation of grey value appearance around the myocardiac surface, a prior parametric spatially varying feature model is established by classification of grey value surface profiles. Quantitative validation of 121 3D MRI datasets in end-diastolic (end-systolic) phase demonstrates accuracy and robustness, with 2.45 mm (2.84 mm) mean deviation from manual segmentation. Automated segmentation of the left ventricle in cardiac MRI. MR Kaus J von Berg J Weese W Niessen V Pekar doi:10.1016/j.media.2004.06.015 Med Image Anal, Vol. 8, No. 3. (September 2004), pp. 245-254. 2008-03-09T11:12:26-00:00 2004 Med Image Anal 1361-8415 8 3 245 254 heart lv segmentation http://www.citeulike.org/user/tmansi/article/2491331 <i>Medical Image Computing and Computer-Assisted Intervention — MICCAI 2002 (2002), pp. 642-650.</i><br /><br />We propose a novel method for fully automated segmentation and tracking of the myocardium and left and right ventricles (LV and RV) using 4D MR images. The method uses non-rigid registration to elastically deform a cardiac atlas built automatically from 14 normal subjects. The registration yields robust performance and is particularly suitable for processing a sequence of 3D images in a cardiac cycle. Transformations are calculated to obtain the deformations between images in a sequence. The registration algorithm aligns the cardiac atlas to a subject specific atlas of the sequence generated with the transformations. The method relates images spatially and temporally and is suitable for measuring regional motion and deformation, as well as for labelling and tracking specific regions of the heart. In this work experiments for the registration, segmentation and tracking of a cardiac cycle are presented on nine MRI data sets. Validation against manual segmentations and computation of the correlation between manual and automatic tracking and segmentation on 141 3D volumes were calculated. Results show that the procedure can accurately track the left ventricle (r=0.99), myocardium (r=0.98) and right ventricle (r=0.96). Results for segmentation are also obtained for left ventricle (r=0.92), myocardium (r=0.82) and right ventricle (r=0.90). Atlas-Based Segmentation and Tracking of 3D Cardiac MR Images Using Non-rigid Registration M Lorenzo-Valdés G Sanchez-Ortiz R Mohiaddin D Rueckert doi:10.1007/3-540-45786-0_79 Medical Image Computing and Computer-Assisted Intervention — MICCAI 2002 (2002), pp. 642-650. 2008-03-08T22:55:47-00:00 2002 Medical Image Computing and Computer-Assisted Intervention — MICCAI 2002 642 650 heart registration segmentation tracking http://www.citeulike.org/user/tmansi/article/2491317 <i>Prog Biophys Mol Biol, Vol. 69, No. 2-3. (1998), pp. 153-155.</i> Computational biology of the heart: from structure to function. A McCulloch J Bassingthwaighte P Hunter D Noble Prog Biophys Mol Biol, Vol. 69, No. 2-3. (1998), pp. 153-155. 2008-03-08T22:49:25-00:00 1998 Prog Biophys Mol Biol 0079-6107 69 2-3 153 155 electromechanical heart http://www.citeulike.org/user/tmansi/article/244099 <i>Annu Rev Biomed Eng, Vol. 5 (2003), pp. 147-177.</i><br /><br />Computational models of the electrical and mechanical function of the heart are reviewed. These models attempt to explain the integrated function of the heart in terms of ventricular anatomy, the structure and material properties of myocardial tissue, the membrane ion channels, and calcium handling and myofilament mechanics of cardiac myocytes. The models have established the computational framework for linking the structure and function of cardiac cells and tissue to the integrated behavior of the intact heart, but many more aspects of physiological function, including metabolic and signal transduction pathways, need to be included before significant progress can be made in understanding many disease processes. Modeling total heart function. PJ Hunter AJ Pullan BH Smaill doi:10.1146/annurev.bioeng.5.040202.121537 Annu Rev Biomed Eng, Vol. 5 (2003), pp. 147-177. 2005-07-03T15:21:07-00:00 2003 Annu Rev Biomed Eng 1523-9829 5 147 177 electromechanical heart http://www.citeulike.org/user/tmansi/article/2491270 <i>Heart, Vol. 76, No. 3. (September 1996), pp. 280-286.</i><br /><br />BACKGROUND: Little attention has been paid to the architecture of the muscle fibres of the ventricular walls in congenitally malformed hearts. In this study the gross pattern of myocardial fibres in normal hearts was compared with that in cases of tetralogy of Fallot. METHODS AND RESULTS: After morphological examination nine specimens with tetralogy were dissected to study the ventricular myoarchitecture. Changes were found in the shape of the malformed ventricles. The ventricular walls were arranged in layers in all hearts. Superficial and deep layers were present in both ventricles, with the superficial layer showing a more oblique orientation in the specimens with tetralogy than in normal hearts. Modifications of muscle fibre that were related to the type of malformation were seen in the deep layer. A middle layer was present in the left ventricles of normal hearts and specimens with tetralogy: this showed a horizontal orientation in both groups. In contrast, a middle layer was found in the right ventricle only in specimens showing tetralogy. CONCLUSIONS: The malformed hearts showed modifications in ventricular shape, in the arrangement of muscle in the right ventricle, and in the overall myoarchitecture. These changes could well be the consequence of the same agent (or agents) that caused the structural defect. Ventricular myoarchitecture in tetralogy of Fallot. D Sanchez-Quintana RH Anderson SY Ho Heart, Vol. 76, No. 3. (September 1996), pp. 280-286. 2008-03-08T22:25:15-00:00 1996 Heart 1355-6037 76 3 280 286 anatomy fibre tof http://www.citeulike.org/user/tmansi/article/2491252 <i>Am J Physiol Heart Circ Physiol, Vol. 280, No. 5. (1 May 2001), pp. H2222-2229.</i><br /><br />Cardiac myofibers are organized into laminar sheets about four cells thick. Recently, it has been suggested that these layers coincide with the plane of maximum shear during systole. In general, there are two such planes, which are oriented at +/-45degrees to the main principal strain axes. These planes do not necessarily contain the fiber axis. In the present study, we explicitly added the constraint that the sheet planes should also contain the muscle fiber axis. In a mathematical analysis of previously measured three-dimensional transmural systolic strain distributions in six dogs, we computed the planes of maximum shear, adding the latter constraint by using the also-measured muscle fiber axis. Generally, for such planes two solutions were found, suggesting that two populations of sheet orientation may exist. The angles at which the predicted sheets intersected transmural tissue slices, cut along left ventricular short- or long-axis planes, were strikingly similar to experimentally measured values. In conclusion, sheets coincide with planes of maximum systolic shear subject to the constraint that the muscle fiber axis is contained in this plane. Sheet orientation is not a unique function of the transmural location but occurs in two distinct populations. Relating myocardial laminar architecture to shear strain and muscle fiber orientation T Arts KD Costa JW Covell AD Mcculloch Am J Physiol Heart Circ Physiol, Vol. 280, No. 5. (1 May 2001), pp. H2222-2229. 2008-03-08T22:17:21-00:00 2001 Am J Physiol Heart Circ Physiol 280 5 H2222 2229 fibre heart http://www.citeulike.org/user/tmansi/article/2483535 <i>Circulation, Vol. 112, No. 8. (23 August 2005), pp. 1189-1197.</i><br /><br />Background Right ventricular outflow tract (RVOT) reconstruction with valved conduits in infancy and childhood leads to reintervention for pulmonary regurgitation and stenosis in later life. Methods and Results Patients with pulmonary regurgitation with or without stenosis after repair of congenital heart disease had percutaneous pulmonary valve implantation (PPVI). Mortality, hemodynamic improvement, freedom from explantation, and subjective and objective changes in exercise tolerance were end points. PPVI was performed successfully in 58 patients, 32 male, with a median age of 16 years and median weight of 56 kg. The majority had a variant of tetralogy of Fallot (n=36), or transposition of the great arteries, ventricular septal defect with pulmonary stenosis (n=8). The right ventricular (RV) pressure (64.4+/-17.2 to 50.4+/-14 mm Hg, P<0.001), RVOT gradient (33+/-24.6 to 19.5+/-15.3, P<0.001), and pulmonary regurgitation (PR) (grade 2 of greater before, none greater than grade 2 after, P<0.001) decreased significantly after PPVI. MRI showed significant reduction in PR fraction (21+/-13% versus 3+/-4%, P<0.001) and in RV end-diastolic volume (EDV) (94+/-28 versus 82+/-24 mL middle dot beat1 middle dot m2, P<0.001) and a significant increase in left ventricular EDV (64+/-12 versus 71+/-13 mL middle dot beat1 middle dot m2, P=0.005) and effective RV stroke volume (37+/-7 versus 42+/-9 mL middle dot beat1 middle dot m2, P=0.006) in 28 patients (age 19+/-8 years). A further 16 subjects, on metabolic exercise testing, showed significant improvement in [V]O2max (26+/-7 versus 29+/-6 mL middle dot kg1 middle dot min1, P<0.001). There was no mortality. Conclusions PPVI is feasible at low risk, with quantifiable improvement in MRI-defined ventricular parameters and pulmonary regurgitation, and results in subjective and objective improvement in exercise capacity. 10.1161/CIRCULATIONAHA.104.523266 Percutaneous Pulmonary Valve Implantation in Humans: Results in 59 Consecutive Patients Sachin Khambadkone Louise Coats Andrew Taylor Younes Boudjemline Graham Derrick Victor Tsang Jeffrey Cooper Vivek Muthurangu Sanjeet Hegde Reza Razavi Denis Pellerin John Deanfield Philipp Bonhoeffer doi:10.1161/CIRCULATIONAHA.104.523266 Circulation, Vol. 112, No. 8. (23 August 2005), pp. 1189-1197. 2008-03-07T11:00:09-00:00 2005 Circulation 112 8 1189 1197 no-tag http://www.citeulike.org/user/tmansi/article/2483521 <i>The American Journal of Cardiology, Vol. 95, No. 6. (15 March 2005), pp. 779-782.</i><br /><br />The timing of pulmonary valve replacement in adult patients with repaired tetralogy of Fallot remains controversial. A magnetic resonance imaging study in 17 adult patients with repaired tetralogy of Fallot reveals a statistically significant decrease in right ventricular (RV) volume (RV end-diastolic volume 163 +/- 34 to 107 +/- 26 ml/m2, p <0.001; RV end-systolic volume 109 +/- 27 to 69 +/- 22 ml/m2, p <0.001) at a mean follow-up of 21 months after pulmonary valve replacement; whereas RV systolic function remained unchanged (mean RV ejection fraction 32 +/- 7% to 34 +/- 10%, p = 0.12). In no patients with a RV end-diastolic volume >170 ml/m2 or a RV end-systolic volume >85 ml/m2 before pulmonary valve replacement were RV volumes "normalized" after surgery. Optimal timing for pulmonary valve replacement in adults after tetralogy of Fallot repair Judith Therrien Yves Provost Naeem Merchant William Williams Jack Colman Gary Webb doi:10.1016/j.amjcard.2004.11.037 The American Journal of Cardiology, Vol. 95, No. 6. (15 March 2005), pp. 779-782. 2008-03-07T10:57:26-00:00 2005 The American Journal of Cardiology 95 6 779 782 no-tag http://www.citeulike.org/user/tmansi/article/2483324 <i>Circulation, Vol. 92, No. 2. (15 July 1995), pp. 231-237.</i><br /><br />Background Life-threatening ventricular arrhythmia and sudden death remain serious late complications after tetralogy of Fallot repair. Nevertheless, there remains no clear way of predicting which patients are at risk. Methods and Results The study population included a total of 178 adult survivors (mean follow-up, 21.4 years) of tetralogy of Fallot repair who were currently attending our clinic. Mechanoelectrical relations were sought in 41 of the patients (mean follow-up, 23.6 years) who were operated on by one surgeon and who were prospectively studied with a 12-lead ECG, chest radiography, and two-dimensional and Doppler echocardiography. Nine patients (mean follow-up, 17 years) from the total group of 178 were identified as having had sustained ventricular tachycardia (8 with near-miss sudden death), and their ECGs, Holter monitor readings, electrophysiological studies, and chest radiographs were reviewed. The case notes of an additional 4 patients with postoperative sudden cardiac death also were available for review. QRS duration in the 41 patients in whom mechanoelectrical interaction was sought ranged between 90 and 200 milliseconds and correlated with cardiothoracic ratio (CTR) on chest radiography (r=.64, P<.001) and with right ventricular size on echocardiography (r=.43, P<.02). Twenty of the 41 patients had restrictive right ventricular Doppler physiology (reduced ventricular compliance) with mean QRS duration of 129.3+/-20 milliseconds and mean CTR of 0.51+/-0.03. The remaining 21 patients with no evidence of right ventricular restriction had prolonged QRS duration of 157.5+/-13.2 milliseconds (P<.001) and CTR of 0.55+/-0.04 (P<.04) compared with the restrictive. In the 9 patients with ventricular tachycardia, the QRS duration ranged from 180 to 230 milliseconds (mean, 198.9+/-17.6 milliseconds), and the CTR ranged from 0.54 to 0.9 (mean, 0.67+/-0.12) (P<.0001 and P<.01, respectively, compared with patients without life-threatening arrhythmias). All patients with documented sustained ventricular tachycardia and the 4 patients with sudden death had a QRS duration of [>=]180 milliseconds (100% sensitivity). Conclusions Chronic right ventricular volume overload after tetralogy of Fallot repair is related to diastolic function and correlates with QRS prolongation. The risk of symptomatic arrhythmia is high when marked right ventricular enlargement and QRS prolongation develop. A QRS duration on the resting ECG of [>=]180 milliseconds is the most sensitive predictor of life-threatening ventricular arrhythmias yet described. Mechanoelectrical Interaction in Tetralogy of Fallot : QRS Prolongation Relates to Right Ventricular Size and Predicts Malignant Ventricular Arrhythmias and Sudden Death Michael Gatzoulis Jan Till Jane Somerville Andrew Redington Circulation, Vol. 92, No. 2. (15 July 1995), pp. 231-237. 2008-03-07T10:49:10-00:00 1995 Circulation 92 2 231 237 no-tag http://www.citeulike.org/user/tmansi/article/2483309 <i>J Am Coll Cardiol, Vol. 36, No. 5. (1 November 2000), pp. 1670-1675.</i><br /><br />OBJECTIVES The purpose of this study is to evaluate right ventricular (RV) volume and function after pulmonary valve replacement (PVR) and to address the issue of optimal surgical timing in these patients. BACKGROUND Chronic pulmonary regurgitation (PR) following repair of tetralogy of Fallot (TOF) leads to RV dilation and an increased incidence of sudden cardiac death in adult patients. METHODS We studied 25 consecutive adult patients who underwent PVR for significant PR late after repair of TOF. Radionuclide angiography was performed in all at a mean of 8.2 months (+/- 8 months) before PVR and repeated at a mean of 28.0 months (+/- 22.8 months) after the operation. Right ventricular (RV) end-systolic volume (RVESV), RV end-diastolic volume (RVEDV) and RV ejection fraction (RVEF) were measured. RESULTS Mean RVEDV, RVESV and RVEF remained unchanged after PVR (227.1 ml versus 214.9 ml, p = 0.74; 157.4 ml versus 155.4 ml, p = 0.94; 35.6% versus 34.7%, p = 0.78, respectively). Of the 10 patients with RVEF [≥] 0.40 before PVR, 5 patients (50%) maintained a RVEF [≥] 0.40 following PVR, whereas only 2 out of 15 patients (13%) with pre-operative values <0.40 reached an RVEF [≥] 0.40 postoperatively (p < 0.001). CONCLUSIONS Right ventricular recovery following PVR for chronic significant pulmonary regurgitation after repair of TOF may be compromised in the adult population. In order to maintain adequate RV contractility, pulmonary valve implant in these patients should be considered before RV function deteriorates. Pulmonary valve replacement in adults late after repair of tetralogy of Fallot: are we operating too late? Judith Therrien Samuel Siu Peter Mclaughlin Peter Liu William Williams Gary Webb J Am Coll Cardiol, Vol. 36, No. 5. (1 November 2000), pp. 1670-1675. 2008-03-07T10:44:48-00:00 2000 J Am Coll Cardiol 36 5 1670 1675 no-tag http://www.citeulike.org/user/tmansi/article/2483296 <i>Pediatric Cardiology, Vol. 24, No. 3. (18 May 2003), pp. 195-221.</i><br /><br />To analyze complex and noncomplex cardiac malformations regarding prevalence and in relation to demographic variables, we pooled data on infants (age 1 year or younger) with congenital cardiovascular defects from three large birth defect registries in California, Sweden, and France. Altogether, 12,932 infants had one or more congenital heart defects out of 4.4 million live births and stillbirths. The registries in Sweden and France obtained data through reporting from various sources; in California, medical records were reviewed. As expected, definitions and ascertained conditions differed among each of the registries. The total rates for severe defects were similar (1.43 per 1,000), but differed for specific defects. Clear differences in epidemiological characteristics existed for specific defects; for example, severe cardiac defects sex ratios were significantly high for hypoplastic left heart syndrome, d-transposition of great vessels, double outlet right ventricle, total anoralous pulmonary venous return, tetralogy of Fallot, and significantly low for pulmonary atresia without ventricular septal defect and endocardial cushion defect. Few defects were similar for several epidemiological characteristics, but, for example, the combination of ventricular and atrial septal defects appeared equivalent with endocardial cushion defect under some circumstances, yet behaved differently with regard to associated noncardiovascular defects. The Epidemiology of Cardiovascular Defects, Part I: A Study Based on Data from Three Large Registries of Congenital Malformations P Pradat C Francannet JA Harris E Robert doi:10.1007/s00246-002-9401-6 Pediatric Cardiology, Vol. 24, No. 3. (18 May 2003), pp. 195-221. 2008-03-07T10:41:09-00:00 2003 Pediatric Cardiology 24 3 195 221 no-tag http://www.citeulike.org/user/tmansi/article/763143 <i>Can J Cardiol, Vol. 14, No. 1. (January 1998), pp. 123-134.</i><br /><br />The guinea-pig ventricular cell model, originally developed by Noble et al in 1991, has been greatly extended to include accumulation and depletion of calcium in a diadic space between the sarcolemma and the sarcoplasmic reticulum where, according to contempory understanding, the majority of calcium-induced calcium release is triggered. The calcium in this space is also assumed to play the major role in calcium-induced inactivation of the calcium current. Delayed potassium current equations have been developed to include the rapid (IKr) and slow (IKs) components of the delayed rectifier current based on the data of of Heath and Terrar, along with data from Sanguinetti and Jurkiewicz. Length- and tension-dependent changes in mechanical and electrophysiological processes have been incorporated as described recently by Kohl et al. Drug receptor interactions have started to be developed, using the sodium channel as the first target. The new model has been tested against experimental data on action potential clamp, and on force-interval and duration-interval relations; it has been found to reliably reproduce experimental observations. Improved guinea-pig ventricular cell model incorporating a diadic space, IKr and IKs, and length- and tension-dependent processes. D Noble A Varghese P Kohl P Noble Can J Cardiol, Vol. 14, No. 1. (January 1998), pp. 123-134. 2006-07-18T14:59:44-00:00 1998 Can J Cardiol 0828-282X 14 1 123 134 electrophysiology heart http://www.citeulike.org/user/tmansi/article/2482605 <i>Chaos, Solitons & Fractals, Vol. 7, No. 3. (March 1996), pp. 293-301.</i><br /><br />We modified the FitzHugh-Nagumo model of an excitable medium so that it describes adequately the dymanics of pulse propagation in the canine myocardium. The modified model is simple enough to be used for intensive 3-dimensional (3D) computations of the whole heart. It simulates the pulse shape and the restitution property of the canine myocardium with good precision. A simple two-variable model of cardiac excitation Rubin Aliev Alexander Panfilov doi:10.1016/0960-0779(95)00089-5 Chaos, Solitons & Fractals, Vol. 7, No. 3. (March 1996), pp. 293-301. 2008-03-07T09:23:01-00:00 1996 Chaos, Solitons & Fractals 7 3 293 301 electrophysiology heart http://www.citeulike.org/user/tmansi/article/2482583 <i>Journal of Mathematical Biology, Vol. 28, No. 2. (1 February 1990), pp. 121-176.</i><br /><br />In this paper we present a macroscopic model of the excitation process in the myocardium. The composite and anisotropic structure of the cardiac tissue is represented by a bidomain, i.e. a set of two coupled anisotropic media. The model is characterized by a non linear system of two partial differential equations of parabolic and elliptic type. A singular perturbation analysis is carried out to investigate the cardiac potential field and the structure of the moving excitation wavefront. As a consequence the cardiac current sources are approximated by an oblique dipole layer structure and the motion of the wavefront is described by eikonal equations. Finally numerical simulations are carried out in order to analyze some complex phenomena related to the spreading of the wavefront, like the front-front or front-wall collision. The results yielded by the excitation model and the eikonal equations are compared. Wavefront propagation in an activation model of the anisotropic cardiac tissue: asymptotic analysis and numerical simulations Colli L Guerri S Rovida doi:10.1007/BF00163143 Journal of Mathematical Biology, Vol. 28, No. 2. (1 February 1990), pp. 121-176. 2008-03-07T09:12:31-00:00 1990 Journal of Mathematical Biology 28 2 121 176 eikonal electrophysiology heart http://www.citeulike.org/user/tmansi/article/2464028 <i>Computer Vision, 2007. ICCV 2007. IEEE 11th International Conference on (2007), pp. 1-8.</i><br /><br />Multi-chamber heart segmentation is a prerequisite for global quantification of the cardiac function. The complexity of cardiac anatomy, poor contrast, noise or motion artifacts makes this segmentation problem a challenging task. In this paper, we present an efficient, robust, and fully automatic segmentation method for 3D cardiac computed tomography (CT) volumes. Our approach is based on recent advances in learning discriminative object models and we exploit a large database of annotated CT volumes. We formulate the segmentation as a two step learning problem: anatomical structure localization and boundary delineation. A novel algorithm, Marginal Space Learning (MSL), is introduced to solve the 9-dimensional similarity search problem for localizing the heart chambers. MSL reduces the number of testing hypotheses by about six orders of magnitude. We also propose to use steerable image features, which incorporate the orientation and scale information into the distribution of sampling points, thus avoiding the time-consuming volume data rotation operations. After determining the similarity transformation of the heart chambers, we estimate the 3D shape through learning-based boundary delineation. Extensive experiments on multi-chamber heart segmentation demonstrate the efficiency and robustness of the proposed approach, comparing favorably to the state-of-the-art. This is the first study reporting stable results on a large cardiac CT dataset with 323 volumes. In addition, we achieve a speed of less than eight seconds for automatic segmentation of all four chambers. Fast Automatic Heart Chamber Segmentation from 3D CT Data Using Marginal Space Learning and Steerable Features Yefeng Zheng Adrian Barbu Bogdan Georgescu Michael Scheuering Dorin Comaniciu doi:10.1109/ICCV.2007.4408925 Computer Vision, 2007. ICCV 2007. IEEE 11th International Conference on (2007), pp. 1-8. 2008-03-04T12:04:08-00:00 2007 Computer Vision, 2007. ICCV 2007. IEEE 11th International Conference on 1 8 segmentation http://www.citeulike.org/user/tmansi/article/2457494 <i>IEEE Trans Med Imaging, Vol. 20, No. 11. (November 2001), pp. 1131-1139.</i><br /><br />We address the problem of applying spatial transformations (or "image warps") to diffusion tensor magnetic resonance images. The orientational information that these images contain must be handled appropriately when they are transformed spatially during image registration. We present solutions for global transformations of three-dimensional images up to 12-parameter affine complexity and indicate how our methods can be extended for higher order transformations. Several approaches are presented and tested using synthetic data. One method, the preservation of principal direction algorithm, which takes into account shearing, stretching and rigid rotation, is shown to be the most effective. Additional registration experiments are performed on human brain data obtained from a single subject, whose head was imaged in three different orientations within the scanner. All of our methods improve the consistency between registered and target images over naïve warping algorithms. Spatial transformations of diffusion tensor magnetic resonance images. DC Alexander C Pierpaoli PJ Basser JC Gee IEEE Trans Med Imaging, Vol. 20, No. 11. (November 2001), pp. 1131-1139. 2008-03-02T14:52:10-00:00 2001 IEEE Trans Med Imaging 0278-0062 20 11 1131 1139 dti http://www.citeulike.org/user/tmansi/article/2299230 <i>Medical Imaging, IEEE Transactions on, Vol. 26, No. 9. (2007), pp. 1136-1153.</i><br /><br /><para> This paper presents a method for 3-D deformation recovery of the left ventricular (LV) wall from anatomical cine magnetic resonance imaging (MRI). The method is based on a deformable model that is incompressible, a desired property since the myocardium has been shown to be nearly incompressible. The LV wall needs to be segmented in an initial frame after which the method automatically determines the deformation everywhere in the LV wall throughout the cardiac cycle. Two studies were conducted to validate the method. In the first study, the deformation recovered from a 3-D anatomical cine MRI of a healthy volunteer was compared against the manual segmentation of the LV wall and against the corresponding 3-D tagged cine MRI. The average volume agreement between the model and the manual segmentation had a false positive rate of 3%, false negative rate of 3%, and true positive rate of 93%. The average distance between the model and manually determined intersections of perpendicular tag planes was 1.6 mm (1.1 pixel). Another set of 3-D anatomical and tagged MRI scans was taken of the same volunteer four months later. The method was applied to the second set and the recovered deformation was very similar to the one obtained from the first set. In the second study, the method was applied to 3-D anatomical cine MRI scans of three patients with ventricular dyssynchrony and three age-matched healthy volunteers. The LV wall deformations recovered for the three normals agreed well and the recovered strains were similar to those reported by other researchers for normal subjects. Strains and displacements of the three patients were clearly smaller than those of the three normals indicating reduced cardiac function. The deformation recovered for the three normals and the three patients was validated against manual segmentation and corresponding tag cine MRI scans and the agreement was similar to that of the first validation study. </para> Left Ventricular Deformation Recovery From Cine MRI Using an Incompressible Model A Bistoquet J Oshinski O Skrinjar doi:10.1109/TMI.2007.903693 Medical Imaging, IEEE Transactions on, Vol. 26, No. 9. (2007), pp. 1136-1153. 2008-01-28T19:06:30-00:00 2007 Medical Imaging, IEEE Transactions on 26 9 1136 1153 heart incompressibility segmentation http://www.citeulike.org/user/tmansi/article/2299223 <i>Medical Image Computing and Computer-Assisted Intervention – MICCAI 2007 (2007), pp. 94-101.</i><br /><br />Surgeons need a robust interventional system capable of providing reliable, real-time information regarding the position and orientation of the surgical targets and tools to compensate for the lack of direct vision and to enhance manipulation of intracardiac targets during minimally-invasive, off-pump cardiac interventions. In this paper, we describe a novel method for creating dynamic, pre-operative, subject-specific cardiac models containing the surgical targets and surrounding anatomy, and how they are used to augment the intra-operative virtual environment for guidance of valvular interventions. The accuracy of these pre-operative models was established by comparing the target registration error between the mitral valve annulus characterized in the pre-operative images and their equivalent structures manually extracted from 3D US data. On average, the mitral valve annulus was extracted with a 3.1 mm error across all cardiac phases. In addition, we also propose a method for registering the pre-operative models into the intra-operative virtual environment. Towards Subject-Specific Models of the Dynamic Heart for Image-Guided Mitral Valve Surgery Cristian Linte Marcin Wierzbicki John Moore Stephen Little Gérard Guiraudon Terry Peters doi:10.1007/978-3-540-75759-7_12 Medical Image Computing and Computer-Assisted Intervention – MICCAI 2007 (2007), pp. 94-101. 2008-01-28T19:04:29-00:00 2007 Medical Image Computing and Computer-Assisted Intervention – MICCAI 2007 94 101 guided-surgery heart segmentation http://www.citeulike.org/user/tmansi/article/2299219 <i>Functional Imaging and Modeling of the Heart (2005), pp. 1-11.</i><br /><br />Multi–slice computed tomography image series are a valuable source of information to extract shape and motion parameters of the heart. We present a method how to segment and label all main chambers (both ventricles and atria) and connected vessels (arteries and main vein trunks) from such images and to track their movement over the cardiac cycle. A framework is presented to construct a multi–surface triangular model enclosing all blood–filled cavities and the main myocardium as well as to adapt this model to unseen images, and to propagate it from phase to phase. While model construction still requires a reasonable amount of user interaction, adaptation is mostly automated, and propagation works fully automatically. The adaptation method by deformable surface models requires a set of landmarks to be manually located for one of the cardiac phases for model initialisation. Multi-surface Cardiac Modelling, Segmentation, and Tracking Jens von Berg Cristian Lorenz doi:10.1007/11494621_1 Functional Imaging and Modeling of the Heart (2005), pp. 1-11. 2008-01-28T19:02:06-00:00 2005 Functional Imaging and Modeling of the Heart 1 11 heart segmentation http://www.citeulike.org/user/tmansi/article/2299215 <i>Medical Image Analysis, Vol. 8, No. 3. (September 2004), pp. 255-265.</i><br /><br />In this paper an automatic atlas-based segmentation algorithm for 4D cardiac MR images is proposed. The algorithm is based on the 4D extension of the expectation maximisation (EM) algorithm. The EM algorithm uses a 4D probabilistic cardiac atlas to estimate the initial model parameters and to integrate a priori information into the classification process. The probabilistic cardiac atlas has been constructed from the manual segmentations of 3D cardiac image sequences of 14 healthy volunteers. It provides space and time-varying probability maps for the left and right ventricles, the myocardium, and background structures such as the liver, stomach, lungs and skin. In addition to using the probabilistic cardiac atlas as a priori information, the segmentation algorithm incorporates spatial and temporal contextual information by using 4D Markov Random Fields. After the classification, the largest connected component of each structure is extracted using a global connectivity filter which improves the results significantly, especially for the myocardium. Validation against manual segmentations and computation of the correlation between manual and automatic segmentation on 249 3D volumes were calculated. We used the 'leave one out' test where the image set to be segmented was not used in the construction of its corresponding atlas. Results show that the procedure can successfully segment the left ventricle (LV) (r=0.96), myocardium (r=0.92) and right ventricle (r=0.92). In addition, 4D images from 10 patients with hypertrophic cardiomyopathy were also manually and automatically segmented yielding a good correlation in the volumes of the LV (r=0.93) and myocardium (0.94) when the atlas constructed with volunteers is blurred. Segmentation of 4D cardiac MR images using a probabilistic atlas and the EM algorithm Maria Lorenzo-Valdes Gerardo Sanchez-Ortiz Andrew Elkington Raad Mohiaddin Daniel Rueckert doi:10.1016/j.media.2004.06.005 Medical Image Analysis, Vol. 8, No. 3. (September 2004), pp. 255-265. 2008-01-28T18:59:45-00:00 2004 Medical Image Analysis 8 3 255 265 heart segmentation http://www.citeulike.org/user/tmansi/article/2299213 <i>Medical Image Computing and Computer-Assisted Intervention – MICCAI 2007 (2007), pp. 402-410.</i><br /><br />We present a fully automatic segmentation algorithm for the whole heart (four chambers, left ventricular myocardium and trunks of the aorta, the pulmonary artery and the pulmonary veins) in cardiac MR image volumes with nearly isotropic voxel resolution, based on shape-constrained deformable models. After automatic model initialization and reorientation to the cardiac axes, we apply a multi-stage adaptation scheme with progressively increasing degrees of freedom. Particular attention is paid to the calibration of the MR image intensities. Detailed evaluation results for the various anatomical heart regions are presented on a database of 42 patients. On calibrated images, we obtain an average segmentation error of 0.76mm. Automatic Whole Heart Segmentation in Static Magnetic Resonance Image Volumes Jochen Peters Olivier Ecabert Carsten Meyer Hauke Schramm Reinhard Kneser Alexandra Groth Jürgen Weese doi:10.1007/978-3-540-75759-7_49 Medical Image Computing and Computer-Assisted Intervention – MICCAI 2007 (2007), pp. 402-410. 2008-01-28T18:58:15-00:00 2007 Medical Image Computing and Computer-Assisted Intervention – MICCAI 2007 402 410 heart segmentation http://www.citeulike.org/user/tmansi/article/2299203 <i>Medical Image Computing and Computer-Assisted Intervention – MICCAI 2007 (2007), pp. 44-51.</i><br /><br />Real-time three-dimensional (RT3D) echocardiography is a new imaging modality that presents the unique opportunity to visualize the complex three-dimensional (3 -D) shape and the motion of left ventricle (LV) in vivo. To take advantage of this opportunity, automatic segmentation of LV myocardium is essential. While there are a variety of efforts on the segmentation of LV endocardial (ENDO) boundaries, the segmentation of epicardial (EPI) boundaries is still problematic. In this paper, we present a new approach of coupled-surfaces propagation to address this problem. Our method is motivated by the idea that the volume of the myocardium is close to being constant during a cardiac cycle and takes this tight coupling as an important constraint. We employ two surfaces, each driven by the image-derived information that takes into account the ultrasound physics by modeling speckle using shifted Rayleigh distribution while maintaining the coupling. By evolving two surfaces simultaneously, the final representation of myocardium is thus achieved. Results from 328 sets of RT3D echocardiographic data are evaluated against the outlines of three observers. We show that the results from automatic segmentation are comparable to those from manual segmentation. Segmentation of Myocardial Volumes from Real-Time 3D Echocardiography Using an Incompressibility Constraint Yun Zhu Xenophon Papademetris Albert Sinusas James Duncan doi:10.1007/978-3-540-75757-3_6 Medical Image Computing and Computer-Assisted Intervention – MICCAI 2007 (2007), pp. 44-51. 2008-01-28T18:53:06-00:00 2007 Medical Image Computing and Computer-Assisted Intervention – MICCAI 2007 44 51 echography heart segmentation http://www.citeulike.org/user/tmansi/article/1961159 <i>Medical Image Computing and Computer-Assisted Intervention – MICCAI 2005 (2005), pp. 375-382.</i><br /><br />Focal cortical dysplasia (FCD), a malformation of cortical development, is an important cause of medically intractable epilepsy. FCD lesions are difficult to distinguish from non-lesional cortex and their delineation on MRI is a challenging task. This paper presents a method to segment FCD lesions on T1-weighted MRI, based on a 3D deformable model, implemented using the level set framework. The deformable model is driven by three MRI features: cortical thickness, relative intensity and gradient. These features correspond to the visual characteristics of FCD and allow to differentiate lesions from normal tissues. The proposed method was tested on 18 patients with FCD and its performance was quantitatively evaluated by comparison with the manual tracings of two trained raters. The validation showed that the similarity between the level set segmentation and the manual labels is similar to the agreement between the two human raters. This new approach may become a useful tool for the presurgical evaluation of patients with intractable epilepsy. Segmentation of Focal Cortical Dysplasia Lesions Using a Feature-Based Level Set O Colliot T Mansi N Bernasconi V Naessens D Klironomos A Bernasconi doi:10.1007/11566465_47 Medical Image Computing and Computer-Assisted Intervention – MICCAI 2005 (2005), pp. 375-382. 2007-11-22T20:14:19-00:00 2005 Medical Image Computing and Computer-Assisted Intervention – MICCAI 2005 375 382 epilepsy fcd level-set segmentation http://www.citeulike.org/user/tmansi/article/1943292 <i>Biomedical Imaging: Nano to Macro, 2006. 3rd IEEE International Symposium on (2006), pp. 323-326.</i><br /><br />Focal cortical dysplasia (FCD), a malformation of cortical development, is an important cause of intractable epilepsy. On magnetic resonance images (MRI), FCD lesions are difficult to distinguish from healthy cortex and defining their spatial extent is challenging. We previously introduced a method to segment FCD lesions on MRI, relying on a 3D deformable model driven by MR features of FCD. In the present paper, we propose to improve our approach by adding a second evolution step which expands the result towards the cortical boundaries. A quantitative evaluation was performed in 18 FCD patients by comparison with manually traced lesion labels. The proposed approach achieved a strong agreement with the manual labels and substantially improved the results obtained with our previous method. Improved segmentation of focal cortical dysplasia lesions on MRI using expansion towards cortical boundaries O Colliot T Mansi P Besson N Bernasconi A Bernasconi Biomedical Imaging: Nano to Macro, 2006. 3rd IEEE International Symposium on (2006), pp. 323-326. 2007-11-20T13:15:49-00:00 2006 Biomedical Imaging: Nano to Macro, 2006. 3rd IEEE International Symposium on 323 326 epilepsy fcd level-set segmentation http://www.citeulike.org/user/tmansi/article/1943282 <i>NeuroImage, Vol. 32, No. 4. (1 October 2006), pp. 1621-1630.</i><br /><br />Focal cortical dysplasia (FCD) is the most frequent malformation of cortical development in patients with medically intractable epilepsy. On MRI, FCD lesions are not easily differentiable from the normal cortex and defining their spatial extent is challenging. In this paper, we introduce a method to segment FCD lesions on T1-weighted MRI. It relies on two successive three-dimensional deformable models, whose evolutions are based on the level set framework. The first deformable model is driven by probability maps obtained from three MRI features: cortical thickness, relative intensity and gradient. These features correspond to the visual characteristics of FCD and allow discriminating lesions and normal tissues. In a second stage, the previous result is expanded towards the underlying and overlying cortical boundaries, throughout the whole cortical section. The method was quantitatively evaluated by comparison with manually traced labels in 18 patients with FCD. The automated segmentations achieved a strong agreement with the manuals labels, demonstrating the applicability of the method to assist the delineation of FCD lesions on MRI. This new approach may become a useful tool for the presurgical evaluation of patients with intractable epilepsy related to cortical dysplasia. Segmentation of focal cortical dysplasia lesions on MRI using level set evolution O Colliot T Mansi N Bernasconi V Naessens D Klironomos A Bernasconi doi:10.1016/j.neuroimage.2006.04.225 NeuroImage, Vol. 32, No. 4. (1 October 2006), pp. 1621-1630. 2007-11-20T13:09:42-00:00 2006 NeuroImage 32 4 1621 1630 epilepsy fcd level-set segmentation http://www.citeulike.org/user/tmansi/article/1856388 <i>J Am Coll Cardiol, Vol. 45, No. 12. (21 June 2005), pp. 2034-2041.</i><br /><br />OBJECTIVES: We sought to examine the accuracy/consistency of a novel ultrasound speckle tracking imaging (STI) method for left ventricular torsion (LVtor) measurement in comparison with tagged magnetic resonance imaging (MRI) (a time-domain method similar to STI) and Doppler tissue imaging (DTI) (a velocity-based approach). BACKGROUND: Left ventricular torsion from helically oriented myofibers is a key parameter of cardiac performance but is difficult to measure. Ultrasound STI is potentially suitable for measurement of angular motion because of its angle-independence. METHODS: We acquired basal and apical short-axis left ventricular (LV) images in 15 patients to estimate LVtor by STI and compare it with tagged MRI and DTI. Left ventricular torsion was defined as the net difference of LV rotation at the basal and apical planes. For the STI analysis, we used high-frame (104 +/- 12 frames/s) second harmonic two-dimensional images. RESULTS: Data on 13 of 15 patients were usable for STI analysis, and LVtor profile estimated by STI strongly correlated with those by tagged MRI (y = 0.95x + 0.19, r = 0.93, p < 0.0001, analyzed by repeated-measures regression models). The STI torsional velocity profile also correlated well with that by the DTI method (y = 0.79x + 2.4, r = 0.76, p < 0.0001, by repeated-measures regression models) with acceptable bias. CONCLUSIONS: The STI estimation of LVtor is concordant with those analyzed by tagged MRI (data derived from tissue displacement) and also showed good agreement with those by DTI (data derived from tissue velocity). Ultrasound STI is a promising new method to assess LV torsional deformation and may make the assessment more available in clinical and research cardiology. 10.1016/j.jacc.2005.02.082 Measurement of Ventricular Torsion by Two-Dimensional Ultrasound Speckle Tracking Imaging Yuichi Notomi Peter Lysyansky Randolph Setser Takahiro Shiota Zoran Popovic Maureen Martin-Miklovic Joan Weaver Stephanie Oryszak Neil Greenberg Richard White James Thomas doi:10.1016/j.jacc.2005.02.082 J Am Coll Cardiol, Vol. 45, No. 12. (21 June 2005), pp. 2034-2041. 2007-11-02T14:23:06-00:00 2005 J Am Coll Cardiol 45 12 2034 2041 echography heart lv sti torsion http://www.citeulike.org/user/tmansi/article/1856356 <i>Circulation, Vol. 110, No. 19. (9 November 2004), pp. 3093-3099.</i><br /><br />Background-- Objective, quantitative, segmental noninvasive/bedside measurement of cardiac motion is highly desirable in cardiovascular medicine, but current technology suffers from significant drawbacks, such as subjectivity of conventional echocardiographic reading, angle dependence of tissue Doppler measurements, radiation exposure by computer tomography, and infrastructure requirements in MRI. We hypothesized that computer vision technology could represent a powerful new paradigm for quantification in echocardiography. Methods and Results-- We present multiscale motion mapping, a novel computer vision technology that is based on mathematical image processing and that exploits echocardiographic information in a fashion similar to the human visual system. It allows Doppler- and border-independent determination of motion and deformation in echocardiograms at arbitrary locations. Correctness of the measurements was documented in synthetic echocardiograms and phantom experiments. Exploratory case studies demonstrated its usefulness in a series of complex motion analyses that included abnormal septal motion and analysis of myocardial twisting. Clinical applicability was shown in a consecutive series of echocardiograms, in which good feasibility, good correlation with expert rating, and good intraobserver and interobserver concordance were documented. Separate assessment of 2D displacement and deformation at the same location was successfully applied to elucidate paradoxical septal motion, a common clinical problem. Conclusions-- This is the first clinical report of multiscale motion mapping, a novel approach to echocardiographic motion quantification. For the first time, full 2D echocardiographic assessment of both motion and deformation is shown to be feasible. Overcoming current limitations, this computer vision-based technique opens a new door to objective analysis of complex heart motion. 10.1161/01.CIR.0000146899.05499.72 Multiscale Motion Mapping: A Novel Computer Vision Technique for Quantitative, Objective Echocardiographic Motion Measurement Independent of Doppler: First Clinical Description and Validation Michael Suhling Christian Jansen Muthuvel Arigovindan Peter Buser Stephan Marsch Michael Unser Patrick Hunziker doi:10.1161/01.CIR.0000146899.05499.72 Circulation, Vol. 110, No. 19. (9 November 2004), pp. 3093-3099. 2007-11-02T14:12:27-00:00 2004 Circulation 110 19 3093 3099 echography heart sti torsion http://www.citeulike.org/user/tmansi/article/1705200 <i>Am J Physiol Heart Circ Physiol, Vol. 289, No. 3. (1 September 2005), pp. H1301-1306.</i><br /><br />Pulmonary hypertensive disease is assessed by quantification of pulmonary vascular resistance. Pulmonary total arterial compliance is also an indicator of pulmonary hypertensive disease. However, because of difficulties in measuring compliance, it is rarely used. We describe a method of measuring pulmonary arterial compliance utilizing magnetic resonance (MR) flow data and invasive pressure measurements. Seventeen patients with suspected pulmonary hypertension or congenital heart disease requiring preoperative assessment underwent MR-guided cardiac catheterization. Invasive manometry was used to measure pulmonary arterial pressure, and phase-contrast MR was used to measure flow at baseline and at 20 ppm nitric oxide (NO). Total arterial compliance was calculated using the pulse pressure method (parameter optimization of the 2-element windkessel model) and the ratio of stroke volume to pulse pressure. There was good agreement between the two estimates of compliance (r = 0.98, P < 0.001). However, there was a systematic bias between the ratio of stroke volume to pulse pressure and the pulse pressure method (bias = 61%, upper level of agreement = 84%, lower level of agreement = 38%). In response to 20 ppm NO, there was a statistically significant fall in resistance, systolic pressure, and pulse pressure. In seven patients, total arterial compliance increased >10% in response to 20 ppm NO. As a population, the increase did not reach statistical significance. There was an inverse relation between compliance and resistance (r = 0.89, P < 0.001) and between compliance and mean pulmonary arterial pressure (r = 0.72, P < 0.001). We have demonstrated the feasibility of quantifying total arterial compliance using an MR method. 10.1152/ajpheart.00957.2004 Measurement of total pulmonary arterial compliance using invasive pressure monitoring and MR flow quantification during MR-guided cardiac catheterization Vivek Muthurangu David Atkinson Maxime Sermesant Marc Miquel Sanjeet Hegde Robert Johnson Rado Andriantsimiavona Andrew Taylor Edward Baker Robert Tulloh Derek Hill Reza Razavi doi:10.1152/ajpheart.00957.2004 Am J Physiol Heart Circ Physiol, Vol. 289, No. 3. (1 September 2005), pp. H1301-1306. 2007-09-28T14:53:56-00:00 2005 Am J Physiol Heart Circ Physiol 289 3 H1301 1306 heart modelling windkessel http://www.citeulike.org/user/tmansi/article/1704991 <i>Am J Physiol Heart Circ Physiol, Vol. 276, No. 1. (1 January 1999), pp. H81-88.</i><br /><br />In earlier studies we found that the three-element windkessel, although an almost perfect load for isolated heart studies, does not lead to accurate estimates of total arterial compliance. To overcome this problem, we introduce an inertial term in parallel with the characteristic impedance. In seven dogs we found that ascending aortic pressure could be predicted better from aortic flow by using the four-element windkessel than by using the three-element windkessel: the root-mean-square errors and the Akaike information criterion and Schwarz criterion were smaller for the four-element windkessel. The three-element windkessel overestimated total arterial compliance compared with the values derived from the area and the pulse pressure method (P = 0.0047, paired t-test), whereas the four-element windkessel compliance estimates were not different (P = 0.81). The characteristic impedance was underestimated using the three-element windkessel, whereas the four-element windkessel estimation differed marginally from the averaged impedance modulus at high frequencies (P = 0.0017 and 0.031, respectively). When applied to the human, the four-element windkessel also was more accurate in these same aspects. Using a distributed model of the systemic arterial tree, we found that the inertial term results from the proper summation of all local inertial terms, and we call it total arterial inertance. We conclude that the fourelement windkessel, with all its elements having a hemodynamic meaning, is superior to the three-element windkessel as a lumped-parameter model of the entire systemic tree or as a model for parameter estimation of vascular properties. Total arterial inertance as the fourth element of the windkessel model Nikos Stergiopulos Berend Westerhof Nico Westerhof Am J Physiol Heart Circ Physiol, Vol. 276, No. 1. (1 January 1999), pp. H81-88. 2007-09-28T13:05:18-00:00 1999 Am J Physiol Heart Circ Physiol 276 1 H81 88 heart modelling windkessel http://www.citeulike.org/user/tmansi/article/1438220 <i>Computers & Structures, Vol. 85, No. 11-14. ( 2007), pp. 784-795.</i><br /><br />A new mesh movement algorithm for unstructured grids is developed which is based on interpolating displacements of the boundary nodes to the whole mesh with radial basis functions (RBF's). A small system of equations, only involving the boundary nodes, has to be solved and no grid-connectivity information is needed. The method can handle large mesh deformations caused by translations, rotations and deformations, both for 2D and 3D meshes. However, the performance depends on the used RBF. The best accuracy and robustness with the highest efficiency are obtained with a C2 continuous RBF with compact support, closely followed by the thin plate spline. The deformed meshes are suitable for flow computations as is shown by performing calculations around a NACA-0012 airfoil. Mesh deformation based on radial basis function interpolation A de Boer MS van der Schoot H Bijl Computers & Structures, Vol. 85, No. 11-14. ( 2007), pp. 784-795. 2007-07-05T18:30:31-00:00 2007 Computers & Structures 85 11-14 784 795 geometric implicit rbf http://www.citeulike.org/user/tmansi/article/1669512 <i>Functional Imaging and Modeling of the Heart (2007), pp. 383-392.</i><br /><br />Rhythm disturbances and mechanical function suppression proper to the acute heart failure in the case of cardiomyocyte calcium overload are simulated in a mathematical model of cardiomyocyte electromechanical activity. Particular attention is paid to the overload caused by diminished activity of the Na + - K +  pump. It is shown in the framework of the model that myocardium mechanics may promote arrhythmias in these conditions. In particular, cooperative influence of the attached crossbridges on the calciumtroponin kinetics is shown to contribute to the initiation of spontaneous action potentials. Numerical experiments showed that the recovery of the normal Na + - K +  pump activity during the heart failure attack did not always led to the normal electromechanical function recovery in the failed cardiomyocyte. Alternative approaches were suggested in the model and compared to each other for recovery of the myocardium electrical and mechanical performance in the simulated case of the acute heart failure. Mathematical Modeling of Electromechanical Function Disturbances and Recovery in Calcium-Overloaded Cardiomyocytes Leonid Katsnelson Tatiana Sulman Olga Solovyova Vladimir Markhasin doi:10.1007/978-3-540-72907-5_39 Functional Imaging and Modeling of the Heart (2007), pp. 383-392. 2007-09-18T14:42:26-00:00 2007 Functional Imaging and Modeling of the Heart 383 392 arrythmia electromechanical heart modelling myocyte http://www.citeulike.org/user/tmansi/article/1607380 <i>(1995)</i><br /><br />. This paper gives an introduction to certain techniques for the construction of geometric objects from scattered data. Special emphasis is put on interpolation methods using compactly supported radial basis functions. x1. Introduction We assume a sample of multivariate scattered data to be given as a set X = fx 1 ; : : : ; xN g of N pairwise distinct points x 1 ; : : : ; xN in IR d , called centers, together with N points y 1 ; : : : ; yN in IR D . An interpolating curve, surface, or... Creating surfaces from scattered data using radial basis functions R Schaback (1995) 2007-08-30T14:40:05-00:00 1995 implicit variational http://www.citeulike.org/user/tmansi/article/1593532 <i>Cardiovascular Engineering: An International Journal, Vol. 7, No. 2. (June 2007), pp. 81-88.</i> Cardiovascular Simulation Toolbox Sheffer Liron Santamore William Barnea Ofer doi:10.1007/s10558-007-9030-z Cardiovascular Engineering: An International Journal, Vol. 7, No. 2. (June 2007), pp. 81-88. 2007-08-26T01:57:14-00:00 2007 Cardiovascular Engineering: An International Journal 1567-8822 7 2 81 88 Springer cardiovascular matlab http://www.citeulike.org/user/tmansi/article/1572409 <i>Shape Modeling and Applications, SMI 2001 International Conference on. (2001), pp. 89-98.</i><br /><br />Describes algebraic methods for creating implicit surfaces using linear combinations of radial basis interpolants to form complex models from scattered surface points. Shapes with arbitrary topology are easily represented without the usual interpolation or aliasing errors arising from discrete sampling. These methods were first applied to implicit surfaces by V.V. Savchenko, et al. (1995) and later developed independently by G. Turk and J.F. O'Brien (1998) as a means of performing shape interpolation. Earlier approaches were limited as a modeling mechanism because of the order of the computational complexity involved. We explore and extend these implicit interpolating methods to make them suitable for systems of large numbers of scattered surface points by using compactly supported radial basis interpolants. The use of compactly supported elements generates a sparse solution space, reducing the computational complexity and making the technique practical for large models. The local nature of compactly supported radial basis functions permits the use of computational techniques and data structures such as k-d trees for spatial subdivision, promoting fast solvers and methods to divide and conquer many of the subproblems associated with these methods. Moreover, the representation of complex models permits the exploration of diverse surface geometry. This reduction in computational complexity enables the application of these methods to the study of the shape properties of large, complex shapes Interpolating implicit surfaces from scattered surface data using compactly supported radial basis functions BS Morse TS Yoo P Rheingans DT Chen KR Subramanian Shape Modeling and Applications, SMI 2001 International Conference on. (2001), pp. 89-98. 2007-08-17T11:54:26-00:00 2001 Shape Modeling and Applications, SMI 2001 International Conference on. 89 98 computer-graphics implicit modelling variational http://www.citeulike.org/user/tmansi/article/1454360 <i>(2005)</i> Shape transformation using variational implicit functions Greg Turk James O'Brien doi:10.1145/1198555.1198639 (2005) 2007-07-13T14:08:40-00:00 2005 ACM Press computer-graphics implicit modelling variational http://www.citeulike.org/user/tmansi/article/1569803 <i>Comput. Vis. Image Underst., Vol. 77, No. 9. (February 2000), pp. 192-210.</i> Average brain models: a convergence study Alexandre Guimond Jean Meunier Jean-Philippe Thirion Comput. Vis. Image Underst., Vol. 77, No. 9. (February 2000), pp. 192-210. 2007-08-16T17:22:30-00:00 2000 Comput. Vis. Image Underst. 1077-3142 77 9 192 210 Elsevier Science Inc. average-model brain registration http://www.citeulike.org/user/tmansi/article/1560255 <i>(2005)</i> Anatomic modeling from unstructured samples using variational implicit surfaces Terry Yoo Bryan Morse KR Subramanian Penny Rheingans Michael Ackerman doi:10.1145/1198555.1198654 (2005) 2007-08-14T13:00:49-00:00 2005 ACM Press anatomical-model blood-vessels implicit variational http://www.citeulike.org/user/tmansi/article/1454363 <i>(2005)</i> Modelling with implicit surfaces that interpolate Greg Turk James O'Brien doi:10.1145/1198555.1198640 (2005) 2007-07-13T14:09:48-00:00 2005 ACM Press implicit modelling http://www.citeulike.org/user/tmansi/article/1153176 <i>: Medical Image Computing and Computer-Assisted Intervention - MICCAI 2003 (2003), pp. 440-450.</i> Segmentation of 4D Cardiac MR Images Using a Probabilistic Atlas and the EM Algorithm M Lorenzo-Valdã©s GI Sanchez-Ortiz R Mohiaddin D Rueckert : Medical Image Computing and Computer-Assisted Intervention - MICCAI 2003 (2003), pp. 440-450. 2007-03-10T21:57:53-00:00 2003 : Medical Image Computing and Computer-Assisted Intervention - MICCAI 2003 440 450 atlas heart segmentation http://www.citeulike.org/user/tmansi/article/504049 <i>Medical Image Analysis, Vol. 10, No. 2. (April 2006), pp. 286-303.</i><br /><br />A new technique (SPASM) based on a 3D-ASM is presented for automatic segmentation of cardiac MRI image data sets consisting of multiple planes with arbitrary orientations, and with large undersampled regions. Model landmark positions are updated in a two-stage iterative process. First, landmark positions close to intersections with images are updated. Second, the update information is propagated to the regions without image information, such that new locations for the whole set of the model landmarks are obtained. Feature point detection is performed by a fuzzy inference system, based on fuzzy C-means clustering. Model parameters were optimized on a computer cluster and the computational load distributed by grid computing. SPASM was applied to image data sets with an increasing sparsity (from 2 to 11 slices) comprising images with different orientations and stemming from different MRI acquisition protocols.Segmentation outcomes and calculated volumes were compared to manual segmentation on a dense short-axis data configuration in a 3D manner. For all data configurations, (sub-)pixel accuracy was achieved. Performance differences between data configurations were significantly different (p < 0.05) for SA data sets with less than 6 slices, but not clinically relevant (volume differences < 4 ml). Comparison to results from other 3D model-based methods showed that SPASM performs comparable to or better than these other methods, but SPASM uses considerably less image data. Sensitivity to initial model placement proved to be limited within a range of position perturbations of approximately 20 mm in all directions. SPASM: A 3D-ASM for segmentation of sparse and arbitrarily oriented cardiac MRI data Hans van Assen Mikhail Danilouchkine Alejandro Frangi Sebastian Ordas Jos Westenberg Johan Reiber Boudewijn Lelieveldt doi:10.1016/j.media.2005.12.001 Medical Image Analysis, Vol. 10, No. 2. (April 2006), pp. 286-303. 2006-02-13T13:20:18-00:00 2006 Medical Image Analysis 10 2 286 303 asm heart segmentation shape-modelling sparse-data http://www.citeulike.org/user/tmansi/article/1524162 <i>Functional Imaging and Modeling of the Heart (2007), pp. 340-349.</i><br /><br />Long term responses of the heart to e.g. infarction or surgical intervention are related to response of the tissue to changes in the mechanical environment. The tissue response is likely to involve (local) change of mass. Implementation of the associated inhomogeneous change in volume for a complex geometry is cumbersome. In the present study, we propose a computational framework for finite volumetric growth. The local stimulus for growth is determined from a simulation of beat to beat cardiac mechanics, assuming the tissue to be incompressible. The related local volumetric growth is translated in a global change of cardiac shape through a simulation of long term cardiac mechanics, assuming the tissue to be compressible. We illustrate the model by simulating growth in response to a deviation of end-diastolic sarcomeric strain from a set optimal value assumed to be preferred by the tissue. Inhomogeneity in the stimulus was reduced after inhomogeneous growth of up to 25%. The transmural redistribution of mass due to growth was found to alter an initially unphysiological linear transmural course in myofiber orientations to a more physiological course. We conclude that the model enables simulation of locally inhomogeneous growth in a realistic left ventricular geometry. Constitutive Modeling of Cardiac Tissue Growth Wilco Kroon Tammo Delhaas Theo Arts Peter Bovendeerd doi:10.1007/978-3-540-72907-5_35 Functional Imaging and Modeling of the Heart (2007), pp. 340-349. 2007-07-31T07:28:35-00:00 2007 Functional Imaging and Modeling of the Heart 340 349 anatomical-model heart tissue-growth http://www.citeulike.org/user/tmansi/article/1477479 <i>Computer Vision, 1998. Sixth International Conference on (1998), pp. 427-432.</i><br /><br />In this paper, we introduce a novel geometric shape modeling scheme which allows for representation, of global and local shape characteristics of an object. Geometric models are traditionally well suited for representing global shapes but not the local details. However, in this paper we propose a powerful geometric shape modeling scheme which allows for the representation of global shapes with local detail and permits model shaping as well as topological changes via physics-based control. The proposed modeling scheme consists of representing shapes by pedal curves and surfaces-pedal curves/surfaces are the loci of the foot of perpendiculars to the tangents of a fixed curve/surface from a fixed point called the pedal point. By varying the location of the pedal point, one can synthesize a large class of shapes which exhibit both local and global deformations. We introduce physics-based control for shaping these geometric models by letting the pedal point vary and use a dynamic spline to represent the position of this varying pedal point. The model dubbed as a “snake pedal” allows for interactive manipulation via forces applied to the snake. We demonstrate the applicability of this modeling scheme via examples of shape synthesis and shape estimation from real image data Snake pedals: geometric models with physics-based control BC Vemuri Y Guo Computer Vision, 1998. Sixth International Conference on (1998), pp. 427-432. 2007-07-24T20:49:36-00:00 1998 Computer Vision, 1998. Sixth International Conference on 427 432 geometric pedal-curves shape-modelling