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ABSTRACT: OBJECTIVE: The cardiac workload associated with various types of aortic obstruction was determined using computational fluid dynamic simulations. METHODS: Computed tomography image data were collected from 4 patients with 4 distinct types of aortic arch obstructions and 4 controls. The categorization of arch hypoplasia corresponded to the "A, B, C" nomenclature of arch interruption; a type "D" was added to represent diffuse arch hypoplasia. Measurements of the vessel diameter were compared against the normal measurements to determine the degree of narrowing. Three-dimensional models were created for each patient, and additional models were created for type A and B hypoplasia to represent 25%, 50%, and 75% diameter narrowing. The boundary conditions for the computational simulations were chosen to achieve realistic flow and pressures in the control cases. The simulations were then repeated after changing the boundary conditions to represent a range of cardiac and vascular adaptations. The resulting cardiac workload was compared with the control cases. RESULTS: Of the 4 patients investigated, 1 had aortic coarctation and 3 had aortic hypoplasia. The cardiac workload of the patients with 25% narrowing type A and B hypoplasia was not appreciably different from that of the control. When comparing the different arch obstructions, 75% type A, 50% type B, and 50% type D hypoplasia required a greater workload increase than 75% coarctation. CONCLUSIONS: The present study has determined the hemodynamic significance of aortic arch obstruction using computational simulations to calculate the cardiac workload. These results suggest that all types of hypoplasia pose more of a workload challenge than coarctation with an equivalent degree of narrowing.
The Journal of thoracic and cardiovascular surgery 04/2012; · 3.41 Impact Factor
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ABSTRACT: The quantification of cardiac flow and ventricular volumes is an essential goal of many congenital heart MRI examinations, often requiring acquisition of multiple 2D phase-contrast and bright-blood cine steady-state free precession (SSFP) planes. Scan acquisition, however, is lengthy and highly reliant on an imager who is well-versed in structural heart disease. Although it can also be lengthy, 3D time-resolved (4D) phase-contrast MRI yields global flow patterns and is simpler to perform. We therefore sought to accelerate 4D phase contrast and to determine whether equivalent flow and volume measurements could be extracted.
Four-dimensional phase contrast was modified for higher acceleration with compressed sensing. Custom software was developed to process 4D phase-contrast images. We studied 29 patients referred for congenital cardiac MRI who underwent a routine clinical protocol, including cine short-axis stack SSFP and 2D phase contrast, followed by contrast-enhanced 4D phase contrast. To compare quantitative measurements, Bland-Altman analysis, paired Student t tests, and F tests were used.
Ventricular end-diastolic, end-systolic, and stroke volumes obtained from 4D phase contrast and SSFP were well correlated (ρ = 0.91-0.95; r(2) = 0.83-0.90), with no statistically significant difference. Ejection fractions were well correlated in a subpopulation that underwent higher-resolution compressed-sensing 4D phase contrast (ρ = 0.88; r(2) = 0.77). Four-dimensional phase contrast and 2D phase contrast flow rates were also well correlated (ρ = 0.90; r(2) = 0.82). Excluding ventricles with valvular insufficiency, cardiac outputs derived from outlet valve flow and stroke volumes were more consistent by 4D phase contrast than by 2D phase contrast and SSFP.
Combined parallel imaging and compressed sensing can be applied to 4D phase contrast. With custom software, flow and ventricular volumes may be extracted with comparable accuracy to SSFP and 2D phase contrast. Furthermore, cardiac outputs were more consistent by 4D phase contrast.
American Journal of Roentgenology 03/2012; 198(3):W250-9. · 2.78 Impact Factor
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ABSTRACT: Previous clinical studies in pulmonary arterial hypertension (PAH) have concentrated predominantly on distal pulmonary vascular resistance, its contribution to the disease process, and response to therapy. However, it is well known that biomechanical factors such as shear stress have an impact on endothelial health and dysfunction in other parts of the vasculature. This study tested the hypothesis that wall shear stress is reduced in the proximal pulmonary arteries of PAH patients with the belief that reduced shear stress may contribute to pulmonary endothelial cell dysfunction and as a result, PAH progression. A combined MRI and computational fluid dynamics (CFD) approach was used to construct subject-specific pulmonary artery models and quantify flow features and wall shear stress (WSS) in five PAH patients with moderate-to-severe disease and five age- and sex-matched controls. Three-dimensional model reconstruction showed PAH patients have significantly larger main, right, and left pulmonary artery diameters (3.5 ± 0.4 vs. 2.7 ± 0.1 cm, P = 0.01; 2.5 ± 0.4 vs. 1.9 ± 0.2 cm, P = 0.04; and 2.6 ± 0.4 vs. 2.0 ± 0.2 cm, P = 0.01, respectively), and lower cardiac output (3.7 ± 1.2 vs. 5.8 ± 0.6 L/min, P = 0.02.). CFD showed significantly lower time-averaged central pulmonary artery WSS in PAH patients compared to controls (4.3 ± 2.8 vs. 20.5 ± 4.0 dynes/cm(2), P = 0.0004). Distal WSS was not significantly different. A novel method of measuring WSS was utilized to demonstrate for the first time that WSS is altered in some patients with PAH. Using computational modeling in patient-specific models, WSS was found to be significantly lower in the proximal pulmonary arteries of PAH patients compared to controls. Reduced WSS in proximal pulmonary arteries may play a role in the pathogenesis and progression of PAH. This data may serve as a basis for future in vitro studies of, for example, effects of WSS on gene expression.
Pulmonary circulation. 01/2012; 2(4):470-476.
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ABSTRACT: Treatments for coarctation of the aorta (CoA) can alleviate blood pressure (BP) gradients (Δ), but long-term morbidity still exists that can be explained by altered indices of hemodynamics and biomechanics. We introduce a technique to increase our understanding of these indices for CoA under resting and nonresting conditions, quantify their contribution to morbidity, and evaluate treatment options. Patient-specific computational fluid dynamics (CFD) models were created from imaging and BP data for one normal and four CoA patients (moderate native CoA: Δ12 mmHg, severe native CoA: Δ25 mmHg and postoperative end-to-end and end-to-side patients: Δ0 mmHg). Simulations incorporated vessel deformation, downstream vascular resistance and compliance. Indices including cyclic strain, time-averaged wall shear stress (TAWSS), and oscillatory shear index (OSI) were quantified. Simulations replicated resting BP and blood flow data. BP during simulated exercise for the normal patient matched reported values. Greatest exercise-induced increases in systolic BP and mean and peak ΔBP occurred for the moderate native CoA patient (SBP: 115 to 154 mmHg; mean and peak ΔBP: 31 and 73 mmHg). Cyclic strain was elevated proximal to the coarctation for native CoA patients, but reduced throughout the aorta after treatment. A greater percentage of vessels was exposed to subnormal TAWSS or elevated OSI for CoA patients. Local patterns of these indices reported to correlate with atherosclerosis in normal patients were accentuated by CoA. These results apply CFD to a range of CoA patients for the first time and provide the foundation for future progress in this area.
Journal of Biomechanical Engineering 09/2011; 133(9):091008. · 1.90 Impact Factor
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ABSTRACT: Atherosclerotic plaque in the descending thoracic aorta (dAo) is related to altered wall shear stress (WSS) for normal patients. Resection with end-to-end anastomosis (RWEA) is the gold standard for coarctation of the aorta (CoA) repair, but may lead to altered WSS indices that contribute to morbidity.
Computational fluid dynamics (CFD) models were created from imaging and blood pressure data for control subjects and age- and gender-matched CoA patients treated by RWEA (four males, two females, 15 ± 8 years). CFD analysis incorporated downstream vascular resistance and compliance to generate blood flow velocity, time-averaged WSS (TAWSS), and oscillatory shear index (OSI) results. These indices were quantified longitudinally and circumferentially in the dAo, and several visualization methods were used to highlight regions of potential hemodynamic susceptibility.
The total dAo area exposed to subnormal TAWSS and OSI was similar between groups, but several statistically significant local differences were revealed. Control subjects experienced left-handed rotating patterns of TAWSS and OSI down the dAo. TAWSS was elevated in CoA patients near the site of residual narrowings and OSI was elevated distally, particularly along the left dAo wall. Differences in WSS indices between groups were negligible more than 5 dAo diameters distal to the aortic arch.
Localized differences in WSS indices within the dAo of CoA patients treated by RWEA suggest that plaque may form in unique locations influenced by the surgical repair. These regions can be visualized in familiar and intuitive ways allowing clinicians to track their contribution to morbidity in longitudinal studies.
Congenital Heart Disease 07/2011; 6(5):432-43. · 0.90 Impact Factor
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ABSTRACT: Contrast-enhanced cardiac MRA suffers from cardiac motion artifacts and often requires a breath-hold.
This work develops and evaluates a blood pool contrast-enhanced combined respiratory- and ECG-triggered MRA method.
An SPGR sequence was modified to enable combined cardiac and respiratory triggering on a 1.5-T scanner. Twenty-three consecutive children referred for pediatric heart disease receiving gadofosveset were recruited in HIPAA-compliant fashion with IRB approval and informed consent. Children underwent standard non-triggered contrast-enhanced MRA with or without suspended respiration. Additionally, a free-breathing-triggered MRA was acquired. Triggered and non-triggered studies were presented in blinded random order independently to two radiologists twice. Anatomical structure delineation was graded for each triggered and non-triggered acquisition and the visual quality on triggered MRA was compared directly to that on non-triggered MRA.
Triggered images received higher scores from each radiologist for all anatomical structures on each of the two reading sessions (Wilcoxon rank sum test, P < 0.05). In direct comparison, triggered images were preferred over non-triggered images for delineating cardiac structures, with most comparisons reaching statistical significance (binomial test, P < 0.05).
Combined cardiac and respiratory triggering, enabled by a blood pool contrast agent, improves delineation of most anatomical structures in pediatric cardiovascular MRA.
Pediatric Radiology 07/2011; 41(12):1536-44. · 1.67 Impact Factor
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ABSTRACT: Cardiovascular flow is commonly assessed with two-dimensional, phase-contrast MRI (2-D PC-MRI). However, scan prescription and acquisition over multiple planes is lengthy, often requires direct physician oversight and has inconsistent results. Time-resolved volumetric PC-MRI (4-D flow) may address these limitations.
We assess the degree of agreement and internal consistency between 2-D and 4-D flow quantification in our clinical population.
Software enabling flow calculation from 4-D flow was developed in Java. With IRB approval and HIPAA compliance, 18 consecutive patients without shunts were identified who underwent both (1) conventional 2-D PC-MRI of the aorta and main pulmonary artery and (2) 4-D flow imaging. Aortic and pulmonary flow rates were assessed with both techniques.
Both methods showed general agreement in flow rates (ρ: 0.87-0.90). Systemic and pulmonary arterial flow rates were well-correlated (ρ: 4-D 0.98-0.99, 2-D 0.93), but more closely matched with 4-D (P < 0.05, Brown-Forsythe). Pulmonary flow rates were lower than systemic rates for 2-D (P < 0.05, two-sample t-test). In a sub-analysis of patients without pulmonary or aortic regurgitation, 2-D showed improved correlation of flow rates while 4-D phase-contrast remained tightly correlated (ρ: 4-D 0.99-1.00, 2-D 0.99).
4-D PC-MRI demonstrates greater consistency than conventional 2-D PC-MRI for flow quantification.
Pediatric Radiology 01/2011; 41(6):711-20. · 1.67 Impact Factor
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ABSTRACT: The biomechanical forces associated with blood flow have been shown to play a role in pulmonary vascular cell health and disease. Therefore, the quantification of human pulmonary artery hemodynamic conditions under resting and exercise states can be useful in investigating the physiology of disease development and treatment outcomes. In this study, a combined magnetic resonance imaging and computational fluid dynamics approach was used to quantify pulsatile flow fields, wall shear stress (WSS), oscillations in WSS (OSI), and energy efficiency in six subject-specific models of the human pulmonary vasculature with high spatial and temporal resolution. Averaging over all subjects, WSS was found to increase from 19.8±4.0 to 51.8±6.7 dynes/cm2, and OSI was found to decrease from 0.094±0.016 to 0.081±0.015 in the proximal pulmonary arteries between rest and exercise conditions (p<0.05). These findings demonstrate the localized, biomechanical effects of exercise. Furthermore, an average decrease of 10% in energy efficiency was noted between rest and exercise. These data indicate the amount of energy dissipation that typically occurs with exercise and may be useful in future surgical planning applications.
Annals of biomedical engineering 01/2011; 39(1):347-58. · 2.41 Impact Factor
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ABSTRACT: Moderate to severe hereditary spherocytosis (HS) is treated with splenectomy. However, total splenectomy leads to decreased immunologic function with the risk of overwhelming postsplenectomy sepsis. Splenic preservation is postulated as a method to avoid this potentially fatal complication. Although mainly performed through laparotomy, we report our experience with a laparoscopic approach to partial splenectomy for HS.
A retrospective review was conducted on 9 laparoscopic partial splenectomies performed for HS at our institution. Follow-up was from 1 to 3.5 years. Data included preoperative and postoperative hemoglobin, absolute reticulocyte count, splenic size, operative time, complications, and length of stay.
All patients successfully underwent laparoscopic partial splenectomy with a radiologically determined upper-pole remnant of 10% to 30% and preservation of the blood supply through the upper short gastric arteries. The mean preoperative spleen length was 13 cm. Mean hospital stay was 3.6 days (range, 1-6 days). There was 1 intraoperative complication (a small bowel tear during spleen extraction) and 2 minor postoperative complications (ileus and wound infection). One patient underwent completion total splenectomy 2 years after partial splenectomy.
Laparoscopic partial splenectomy is a feasible and effective procedure that addresses the hematologic consequences of HS while retaining a portion of functional spleen, in addition to conferring the advantages of laparoscopy.
Journal of Pediatric Surgery 08/2010; 45(8):1682-6. · 1.45 Impact Factor
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ABSTRACT: To compare generalized autocalibrating partially parallel acquisitions (GRAPPA), modified sensitivity encoding (mSENSE), and SENSE in phase-contrast magnetic resonance imaging (PC-MRI) applications.
Aliasing of the torso can occur in PC-MRI applications. If the data are further undersampled for parallel imaging, SENSE can be problematic in correctly unaliasing signals due to coil sensitivity maps that do not match that of the aliased volume. Here, a method for estimating coil sensitivities in flow applications is described. Normal volunteers (n = 5) were scanned on a 1.5 T MRI scanner and underwent PC-MRI scans using GRAPPA, mSENSE, SENSE, and conventional PC-MRI acquisitions. Peak velocity and flow through the aorta and pulmonary artery were evaluated.
Bland-Altman statistics for flow in the aorta and pulmonary artery acquired with mSENSE and GRAPPA methods (R = 2 and R = 3 cases) have comparable mean differences to flow acquired with conventional PC-MRI. GRAPPA and mSENSE PC-MRI have more robust measurements than SENSE when there is aliasing artifact caused by insufficient coil sensitivity maps. For peak velocity, there are no considerable differences among the mSENSE, GRAPPA, and SENSE reconstructions and are comparable to conventional PC-MRI.
Flow measurements of images reconstructed with autocalibration techniques have comparable agreement with conventional PC-MRI and provide robust measurements in the presence of wraparound.
Journal of Magnetic Resonance Imaging 04/2010; 31(4):1004-14. · 2.70 Impact Factor
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ABSTRACT: Whether congenital or acquired, timely recognition and management of disease is imperative, as hemodynamic alterations in blood flow, tissue perfusion, and cellular oxygenation can have profound effects on organ function, growth and development, and quality of life for the pediatric patient. Ensuring safe computed tomographic angiography (CTA) practice and "gentle" pediatric imaging requires the cardiovascular imager to have sound understanding of CTA advantages, limitations, and appropriate indications as well as strong working knowledge of acquisition principles and image post processing. From this vantage point, CTA can be used as a useful adjunct along with the other modalities. This article presents a summary of dose reduction CTA methodologies along with techniques the authors have employed in clinical practice to achieve low-dose and ultralow-dose exposure in pediatric CTA. CTA technical principles are discussed with an emphasis on the low-dose methodologies and safe contrast medium delivery strategies. Recommended parameters for currently available multidetector-row computed tomography scanners are summarized alongside recommended radiation and contrast medium parameters. In the second part of the article an overview of pediatric CTA clinical applications is presented, illustrating low-dose and ultra-low dose techniques, with an emphasis on the specific protocols.
Radiologic Clinics of North America 03/2010; 48(2):439-67, x. · 2.59 Impact Factor
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ABSTRACT: Despite an abundance of prior Fontan simulation articles, there have been relatively few clinical advances that are a direct result of computational methods. We address a few key limitations of previous Fontan simulations as a step towards increasing clinical relevance. Previous simulations have been limited in scope because they have primarily focused on a single energy loss parameter. We present a multi-parameter approach to Fontan modeling that establishes a platform for clinical decision making and comprehensive evaluation of proposed interventions.
Time-dependent, 3-D blood flow simulations were performed on six patient-specific Fontan models. Key modeling advances include detailed pulmonary anatomy, catheterization-derived pressures, and MRI-derived flow with respiration. The following performance parameters were used to rank patients at rest and simulated exercise from best to worst performing: energy efficiency, inferior and superior vena cava (IVC, SVC) pressures, wall shear stress, and IVC flow distribution.
Simulated pressures were well matched to catheterization data, but low Fontan pressure did not correlate with high efficiency. Efficiency varied from 74% to 96% at rest, and from 63% to 91% with exercise. Distribution of IVC flow ranged from 88%/12% (LPA/RPA) to 53%/47%. A "transcatheter" virtual intervention demonstrates the utility of computation in evaluating interventional strategies, and is shown to result in increased energy efficiency.
A multiparameter approach demonstrates that each parameter results in a different ranking of Fontan performance. Ranking patients using energy efficiency does not correlate with the ranking using other parameters of presumed clinical importance. As such, current simulation methods that evaluate energy dissipation alone are not sufficient for a comprehensive evaluation of new Fontan designs.
Congenital Heart Disease 03/2010; 5(2):104-17. · 0.90 Impact Factor
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ABSTRACT: The objective of this work is to evaluate the hemodynamic performance of a new Y-graft modification of the extracardiac conduit Fontan operation. The performance of the Y-graft design is compared to two designs used in current practice: a t-junction connection of the venae cavae and an offset between the inferior and superior venae cavae.
The proposed design replaces the current tube grafts used to connect the inferior vena cava to the pulmonary arteries with a Y-shaped graft. Y-graft hemodynamics were evaluated at rest and during exercise with a patient-specific model from magnetic resonance imaging data together with computational fluid dynamics. Four clinically motivated performance measures were examined: Fontan pressures, energy efficiency, inferior vena cava flow distribution, and wall shear stress. Two variants of the Y-graft were evaluated: an "off-the-shelf" graft with 9-mm branches and an "area-preserving" graft with 12-mm branches.
Energy efficiency of the 12-mm Y-graft was higher than all other models at rest and during exercise, and the reduction in efficiency from rest to exercise was improved by 38%. Both Y-graft designs reduced superior vena cava pressures during exercise by as much as 5 mm Hg. The Y-graft more equally distributed the inferior vena cava flow to both lungs, whereas the offset design skewed 70% of the flow to the left lung. The 12-mm graft resulted in slightly larger regions of low wall shear stress than other models; however, minimum shear stress values were similar.
The area-preserving 12-mm Y-graft is a promising modification of the Fontan procedure that should be clinically evaluated. Further work is needed to correlate our performance metrics with clinical outcomes, including exercise intolerance, incidence of protein-losing enteropathy, and thrombus formation.
The Journal of thoracic and cardiovascular surgery 03/2009; 137(2):394-403.e2. · 3.41 Impact Factor
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ABSTRACT: Congenital heart defects with a single functional ventricle, such as hypoplastic left heart syndrome and tricuspid atresia, require a staged surgical approach to separate the systemic and pulmonary circulations. Ultimately, the venous or pulmonary side of the heart is bypassed by directly connecting the vena cava to the pulmonary arteries with a modified t-shaped junction. The Fontan procedure (total cavopulmonary connection, TCPC) completes this process of separation. To date, computational fluid dynamics (CFD) simulations in this low pressure, passive flow, intrathoracic system have neglected the presumed important effects of respiration on physiology and higher "stress" states such as with exercise have never been considered. We hypothesize that incorporating effects of respiration and exercise would provide more realistic estimates of TCPC performance. Time-dependent, 3D blood flow simulations are performed by a custom finite element solver for two patient-specific Fontan models with a novel respiration model, developed to generate physiologic time-varying flow conditions. Blood flow features, pressure, and energy efficiency are analyzed at rest and with increasing flow rates to simulate exercise conditions. The simulations produce realistic pressure and flow data, comparable to that measured by catheterization and echocardiography, and demonstrate substantial increases in energy dissipation (i.e. decreased performance) with exercise and respiration due to increasing intensity of small scale vortices in the flow. As would be expected, these changes are highly dependent on patient-specific anatomy and Fontan geometry. We propose that respiration and exercise should be incorporated into TCPC CFD simulations to provide increasingly realistic evaluations of TCPC performance.
Annals of Biomedical Engineering 03/2007; 35(2):250-63. · 2.37 Impact Factor
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ABSTRACT: Phase-contrast (PC) magnetic resonance imaging (MRI) technique has important clinical applications in blood flow quantification and pressure gradient estimation by velocity measurement. Parallel imaging using sensitivity encoding (SENSE) may substantially reduce scan time. We demonstrate the utility of PC-MRI measurements accelerated by SENSE under clinical conditions.
Accuracy and repeatability of a SENSE-PC implementation was evaluated by comparison with a commercial PC sequence with five normal volunteers. Twenty-six patients were then scanned with SENSE-PC at reduction factors (R = 1, 2, and 3). Blood flow and peak velocity were measured in the aorta and pulmonary trunk in 16 patients and peak velocity was measured at the coarctation of 10 patients. Quantitative flow, shunt ratio, and peak velocity measurements obtained with different reduction factors were compared using correlation, linear regression, and Bland-Altman statistics. All studies were approved by an Institutional Review Board, and informed consent was acquired from all subjects.
The correlation coefficients for all comparisons were >0.962 and with high statistical significance (P < .01). Linear regression slopes ranged between 0.96 and 1.11 for flow and 0.88 to 1.05 for peak velocity. For flow, the Bland-Altman statistics yielded a total mean difference ranging from -0.02 to 0.05) L/minute with 2 standard of deviation limits ranging from -0.52 to 0.75 L/minute. For peak velocity, the total mean difference ranged from -0.10 to -0.004) milliseconds with 2-SD limits ranging from -0.062 to 0.46 milliseconds. R = 3 to R = 1 comparisons had greater 2-SD limits than R = 2 to R = 1 comparisons.
SENSE PC-MRI measurements for flow and pressure gradient estimation were comparable to conventional PC-MRI.
Academic Radiology 03/2007; 14(3):258-69. · 1.69 Impact Factor
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Circulation 07/2006; 113(22):e842-3. · 14.74 Impact Factor
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Circulation 06/2006; 113(21):e778-9. · 14.74 Impact Factor
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ABSTRACT: The objective of this study was to evaluate the accuracy and efficiency of primary interpretation of thoracic MDCT using coronal reformations as compared with transverse images.
Fifty patients (18 females, 32 males; age range, 15-93 years; mean age, 63.6 years) underwent 4-MDCT of the chest (detector width, 1 mm; beam pitch, 1.5). Contrast material was administered in 20 of the 50 patients. Coronal and transverse sections were reformatted into 5-mm-thick sections at 3.5-mm intervals. All available image and clinical data consensually reviewed by two thoracic radiologists served as the reference standard. Subsequently, three other thoracic radiologists independently evaluated reformatted coronal and transverse images at two separate review sessions. Each image set was assessed in 58 categories for abnormalities of the lungs, mediastinum, pleura, chest wall, diaphragm, abdomen, and skeleton. Interpretation times and number of images assessed were recorded. Sensitivity, specificity, and interobserver concordance were calculated. Differences in mean sensitivities and specificities were evaluated with Wilcoxon's signed rank test.
The most common findings identified were pulmonary nodules (n = 73, transverse images; n = 72, coronal images) and emphysema (n = 45, transverse; n = 40, coronal). The mean detection sensitivity of all lesions was significantly (p = 0.001) lower on coronal (44% +/- 26% [SD]) than on transverse (51% +/- 22%) images, whereas the mean detection specificity was significantly (p = 0.005) higher (96% +/- 5% vs 95% +/- 6%, respectively). Reporting findings for significantly (p < 0.001) fewer coronal images (mean, 63.0 +/- 4.6 images) than transverse images (mean, 91.9 +/- 8.8 images) took significantly (p = 0.025) longer (mean, 263 +/- 56 sec vs 238 +/- 45 sec, respectively).
Primary interpretation of thoracic MDCT is less sensitive and more time-consuming using 5-mm-thick coronal reformations as compared with transverse images.
American Journal of Roentgenology 12/2005; 185(6):1500-8. · 2.78 Impact Factor
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ABSTRACT: Multi-detector-row computed tomography (MDCT) enables rapid, noninvasive, high-resolution, and three-dimensional imaging of pediatric vascular diseases. In this paper, we explore the adaptation of the MDCT angiographic principles to pediatric patients for vascular diseases of the abdomen, pelvis, and extremities. Special emphasis is placed on the practical aspects of how to perform these studies. Optimizations of scan parameters, contrast medium usage, radiation dose, and three-dimensional image processing are discussed in detail. We provide practical guidance on how to choose between MR angiography and CT angiography. Finally, we review important pediatric vascular diseases, categorized into traumatic injuries, inherited vascular diseases, congenital vascular diseases, vasculitides, and surgical planning and assessment. In each category, we discuss how CT angiography can be tailored to maximize its clinical benefits.
Pediatric Radiology 02/2005; 35(1):40-53. · 1.67 Impact Factor
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ABSTRACT: Tagging with balanced steady-state free-precession (SSFP) magnetic resonance (MR) imaging by using a steady-state storage scheme for myocardial motion analysis was evaluated. Signal-to-noise ratio (SNR), blood-tissue contrast, and tag persistence in volunteers and phantoms showed improved performance of SSFP imaging with tagging compared with that of radiofrequency spoiled gradient-echo (SPGR) MR imaging with tagging. Choice of flip angle with SSFP imaging involved a trade-off among SNR, blood-tissue contrast, and tag persistence. Increased SNR and tag persistence can be achieved simultaneously with SSFP imaging compared with SPGR tagging methods. As a result, the proposed technique may be useful for analysis of diastolic ventricular function.
Radiology 04/2004; 230(3):852-61. · 5.73 Impact Factor
