Evaluation of cardiac valvular disease with MR imaging: qualitative and quantitative techniques

Deep Layer Kernel Sparse Representation Network for the Detection of Heart Valve Ailments from the Time-Frequency Representation of PCG Recordings

The heart valve ailments (HVAs) are due to the defects in the valves of the heart and if untreated may cause heart failure, clots, and even sudden cardiac death. Automated early detection of HVAs is necessary in the hospitals for proper diagnosis of pathological cases, to provide timely treatment, and to reduce the mortality rate. The heart valve abnormalities will alter the heart sound and murmurs which can be faithfully captured by phonocardiogram (PCG) recordings. In this paper, a time-frequency based deep layer kernel sparse representation network (DLKSRN) is proposed for the detection of various HVAs using PCG signals. Spline kernel-based Chirplet transform (SCT) is used to evaluate the time-frequency representation of PCG recording, and the features like L1-norm (LN), sample entropy (SEN), and permutation entropy (PEN) are extracted from the different frequency components of the time-frequency representation of PCG recording. The DLKSRN formulated using the hidden layers of extreme learning machine- (ELM-) autoencoders and kernel sparse representation (KSR) is used for the classification of PCG recordings as normal, and pathology cases such as mitral valve prolapse (MVP), mitral regurgitation (MR), aortic stenosis (AS), and mitral stenosis (MS). The proposed approach has been evaluated using PCG recordings from both public and private databases, and the results demonstrated that an average sensitivity of 100%, 97.51%, 99.00%, 98.72%, and 99.13% are obtained for normal, MVP, MR, AS, and MS cases using the hold-out cross-validation (CV) method. The proposed approach is applicable for the Internet of Things- (IoT-) driven smart healthcare system for the accurate detection of HVAs.

Aortic valvular imaging with cardiovascular magnetic resonance: seeking for comprehensiveness

Cardiovascular magnetic resonance (CMR) has an emerging role in aortic valve disease evaluation, becoming an all-in-one technique. CMR evaluation of the anatomy and flow through the aortic valve has a higher reproducibility than echocardiography. Its unique ability of in vivo myocardial tissue characterization, significantly improves the risk stratification and management of patients. In addition, CMR is equivalent to cardiac CT angiography for trans-aortic valvular implantation and surgical aortic valve replacement planning; on the other hand, its role in the evaluation of ventricular function improving and post-treatment complications is undisputed. This review encompasses the existing literature regarding the role of CMR in aortic valve disease, exploring all the aspects of the disease, from diagnosis to prognosis.

The effect of reducing spatial resolution by in-plane partial volume averaging on peak velocity measurements in phase contrast magnetic resonance angiography

BACKGROUND

The aim of this study was to quantify the degree of the effect of in-plane partial volume averaging on recorded peak velocity in phase contrast magnetic resonance angiography (PCMRA).

METHODS

Using cardiac optimized 1.5 Tesla MRI scanners (Siemens Symphony and Avanto), 145 flow measurements (14 anatomical locations; ventricular outlets, aortic valve (AorV), aorta (5 sites), pulmonary arteries (3 sites), pulmonary veins, superior and inferior vena cava)- in 37 subjects (consisting of healthy volunteers, congenital and acquired heart disease patients) were analyzed by Siemens Argus default voxel averaging technique (where peak velocity = mean of highest velocity voxel and four neighbouring voxels) and by single voxel technique (1.3×1.3×5 or 1.7×1.7×5.5 mm³) (where peak velocity = highest velocity voxel only). The effect of scan protocol (breath hold versus free breathing) and scanner type (Siemens Symphony versus Siemens Avanto) were also assessed. Statistical significance was defined as P<0.05.

RESULTS

There was a significant mean increase in peak velocity of 7.1% when single voxel technique was used compared to voxel averaging (P<0.0001). Significant increases in peak velocity were observed by single voxel technique compared to voxel averaging regardless of subject type, anatomical flow location, scanner type and breathing command. Disabling voxel averaging did not affect the volume of flow recorded.

CONCLUSIONS

Reducing spatial resolution by the use of voxel averaging produces a significant underestimation of peak velocity. While this is of itself not surprising this is the first report to quantify the size of the effect. When PCMRA is used to assess peak velocity recording pixel averaging should be disabled.

Cardiac MR Imaging in the Evaluation of Rheumatic Valvular Heart Diseases

INTRODUCTION

Rheumatic heart disease is the most common cause of valvular heart disease throughout the world. Echocardiography is the dominant imaging investigation in the assessment of cardiac valvular disease and the role of Magnetic Resonance Imaging (MRI) is so far limited. However, due to rapid improvements in the cardiac MRI technology in past few years, this non invasive technique is gaining interest in the examination of cardiac valves.

AIM

Our study was undertaken to define the role of MRI in the evaluation of Rheumatic valvular heart disease and to compare the role of MRI with transthoracic echocardiography with regard to quantity of stenosis and volume regurgitation.

MATERIALS AND METHODS

ECG gated Cardiac MRI was performed with a 1.5-Tesla system (MAGNETOM SYMPHONY- Model 2005) using basic cardiac software (Argus viewer) by a phased-array multicoil on 50 subjects who were known cases of Rheumatic valvular heart disease. A chest radiograph and echocardiography were done in all patients before MR examination. Informed consent was taken from all patients.

RESULTS

Mitral stenosis either as an isolated valvular abnormality or in combination with other valvular abnormalities constituted the major bulk of Rheumatic valvular heart disease in our study population. The average ejection fraction by ECHO is 64.94±7.11 and by MRI 67.52±7.84. The average mitral valve area by ECHO is 1.79±0.43 cm(2) and by MRI 1.82±0.47 cm(2). The average aortic valve area by ECHO is 1.10±0.21 cm(2) and by MRI 1.12±0.25 cm(2). The Coefficient of Correlation (r) is 0.82 for ejection fraction, 0.98 for mitral valve area and 0.92 for aortic valve area which means a strong positive association between the results by ECHO and MRI. In all instances, the p-value is <0.00001, suggesting that the test is highly significant.

CONCLUSION

In our study echocardiography was found to be the gold standard for the diagnosis of Rheumatic valvular heart disease and the role of MRI remained only complimentary to Echocardiography. However with advanced cardiac software, more advanced techniques, and faster imaging sequences, MRI may become a valuable procedure for investigation and follow-up of patients with valvular heart disease.

Imaging of the aortic valve with MRI and CT angiography

The aortic valve may be affected by a wide range of congenital and acquired diseases. Echocardiography is the main non-invasive imaging technique for assessing patho-anatomical alterations of the aortic valve and adjacent structures and in many cases is sufficient to establish a diagnosis and/or guide treatment decisions. Recent technological advances in magnetic resonance imaging (MRI) and multidetector computed tomography (MDCT) have enabled these techniques to play a complimentary role in certain clinical scenarios and as such can be useful problem-solving tools. Radiologists should be familiar with the indications, advantages, and limitations of MRI and MDCT in order to advise and direct an appropriate imaging strategy depending upon the clinical scenario. This article reviews the role of MRI and MDCT angiography for assessment of the aortic valve including relevant anatomy, scan acquisition protocols, and post-processing methods. An approach to interpretation and the key imaging features of commonly encountered aortic valvular diseases are discussed.

The past, present and future of minimally invasive therapy in endovascular interventions: a review and speculative outlook

Cardiovascular disease is a leading cause of death in all developed countries. In response to this need, endovascular management techniques have been developed across a large range of medical specialties. Minimally invasive percutaneous interventions were initially complex and challenging, but with the continued development of equipment and expertise their use has become routine in many fields. With routine use, it has become important to establish the safety and efficacy of endovascular treatments against the respective "gold standard" procedures, especially in light of their initial intended use for the management of patients at unacceptably high risk for standard therapy only. Such evaluation has to take into account the variety and diversity of devices and techniques, as well as the effects of operator dependability. Endovascular techniques are increasingly recognised as valid alternative management options for a variety of conditions, and it is anticipated that the current trend towards minimally invasive techniques will continue in the future, with moves towards increasingly complex endovascular techniques and hybrid interventions.

CT and MR imaging of the aortic valve: radiologic-pathologic correlation

Valvular disease is estimated to account for as many as 20% of cardiac surgical procedures performed in the United States. It may be congenital in origin or secondary to another disease process. One congenital anomaly, bicuspid aortic valve, is associated with increased incidence of stenosis, regurgitation, endocarditis, and aneurysmal dilatation of the aorta. A bicuspid valve has two cusps instead of the normal three; resultant fusion or poor excursion of the valve leaflets may lead to aortic stenosis, the presence of which is signaled by dephasing jets on magnetic resonance (MR) images. Surgery is generally recommended for patients with severe stenosis who are symptomatic or who have significant ventricular dysfunction; transcatheter aortic valve implantation (TAVI) is an emerging therapeutic option for patients who are not eligible for surgical treatment. Computed tomography (CT) is an essential component of preoperative planning for TAVI; it is used to determine the aortic root dimensions, severity of peripheral vascular disease, and status of the coronary arteries. Aortic regurgitation, which is caused by incompetent closure of the aortic valve, likewise leads to the appearance of jets on MR images. The severity of regurgitation is graded on the basis of valvular morphologic parameters; qualitative assessment of dephasing jets at Doppler ultrasonography; or measurements of the regurgitant fraction, volume, and orifice area. Mild regurgitation is managed conservatively, whereas severe or symptomatic regurgitation usually leads to valve replacement surgery, especially in the presence of substantial left ventricular enlargement or dysfunction. Bacterial endocarditis, although less common than aortic stenosis and regurgitation, is associated with substantial morbidity and mortality. Electrocardiographically gated CT reliably demonstrates infectious vegetations and benign excrescences of 1 cm or more on the valve surface, allowing the assessment of any embolic complications.

Towards real-time cardiovascular magnetic resonance guided transarterial CoreValve implantation: in vivo evaluation in swine

BACKGROUND

Real-time cardiovascular magnetic resonance (rtCMR) is considered attractive for guiding TAVI. Owing to an unlimited scan plane orientation and an unsurpassed soft-tissue contrast with simultaneous device visualization, rtCMR is presumed to allow safe device navigation and to offer optimal orientation for precise axial positioning. We sought to evaluate the preclinical feasibility of rtCMR-guided transarterial aortic valve implatation (TAVI) using the nitinol-based Medtronic CoreValve bioprosthesis.

METHODS

rtCMR-guided transfemoral (n = 2) and transsubclavian (n = 6) TAVI was performed in 8 swine using the original CoreValve prosthesis and a modified, CMR-compatible delivery catheter without ferromagnetic components.

RESULTS

rtCMR using TrueFISP sequences provided reliable imaging guidance during TAVI, which was successful in 6 swine. One transfemoral attempt failed due to unsuccessful aortic arch passage and one pericardial tamponade with subsequent death occurred as a result of ventricular perforation by the device tip due to an operating error, this complication being detected without delay by rtCMR. rtCMR allowed for a detailed, simultaneous visualization of the delivery system with the mounted stent-valve and the surrounding anatomy, resulting in improved visualization during navigation through the vasculature, passage of the aortic valve, and during placement and deployment of the stent-valve. Post-interventional success could be confirmed using ECG-triggered time-resolved cine-TrueFISP and flow-sensitive phase-contrast sequences. Intended valve position was confirmed by ex-vivo histology.

CONCLUSIONS

Our study shows that rtCMR-guided TAVI using the commercial CoreValve prosthesis in conjunction with a modified delivery system is feasible in swine, allowing improved procedural guidance including immediate detection of complications and direct functional assessment with reduction of radiation and omission of contrast media.

Phase-contrast MRI and applications in congenital heart disease

A review of phase-contrast magnetic resonance imaging techniques, with specific application to congenital heart disease, is presented. Theory, pitfalls, advantages, and specific examples of multiple, well-described congenital heart disease presentations are discussed.

MR Imaging of Nonischemic Cardiomyopathy

Cardiac magnetic resonance (CMR) imaging plays an important role in the distinction between ischemic and nonischemic cardiomyopathy. It does so principally by its excellent soft-tissue contrast and its ability to detect scar tissue. The distribution of scar tissue not only allows the diagnosis of coronary artery disease in a failing heart but also the type of nonischemic cardiomyopathy. The incorporation of CMR imaging early in the diagnostic cascade of a patient with heart failure of unknown cause can potentially avoid a cardiac catheterization.

Haemodynamic evaluation of aortic regurgitation after transcatheter aortic valve implantation using cardiovascular magnetic resonance

AIMS

Echocardiography may underestimate the degree of paravalvular aortic regurgitation (AR) after transcatheter aortic valve implantation (TAVI) using the Medtronic CoreValve bioprosthesis due to inherent limitations of ultrasound imaging in the evaluation of implanted cardiac prostheses. We aimed to evaluate the accuracy and feasibility of cardiovascular magnetic resonance (CMR) in quantifying regurgitant volume (RV) and regurgitant fraction (RF) in patients treated with this bioprosthesis for severe calcific aortic stenosis, and to compare the results with echocardiography and aortography.

METHODS AND RESULTS

This study included 16 patients with a mean age of 78.7 years (eight women, eight men) who underwent successful TAVI using Medtronic CoreValve bioprosthesis. AR was evaluated by CMR, echocardiography, and aortography. Angiography was performed immediately after valve implantation. CMR and echocardiography were performed four weeks after valve implantation. There was a highly significant correlation between the CMR-derived and the angiographically-estimated degree of AR (r=0.86, p<0.001). On the other hand, there was only a limited correlation between CMR and echocardiography (r=0.374, p=0.15) as well as angiography and echocardiography (r=0.319, p=0.23) regarding the degree of AR. The weighted kappa for agreement between echocardiography and angiography was 0.14, for agreement between echocardiography and CMR 0.20, and for agreement between angiography and CMR 0.72. Echocardiography underestimated AR by one degree compared to CMR in five patients and 2 degrees in two patients; in six of these, the degree of AR obtained by CMR was similar to angiography.

CONCLUSIONS

In patients undergoing TAVI, comparisons between purely quantitative measurements of AR by CMR and qualitative assessment by angiography showed better correlations than those with echocardiography. This suggests that echocardiography may underestimate the degree of AR and CMR in these circumstances has a great potential in reliably measuring the severity of AR in a quantitative manner.

Cardiac MRI in Congenital Heart Disease - Our Experience

A significant recent advance that has occurred world over in the continuously evolving field of Magnetic Resonance Imaging (MRI) practice is the introduction of Cardiac applications. Cardiac MRI has moved to the centre stage of clinical management strategy by non-invasively imaging the structure as well as function of the heart. It has a wide range of specific applications such as delineation of morphological anatomy, quantification of flow and pressure across cardiac valve dysfunction, evaluation of myocardial function, assessment of infarcts, mapping coronary arteries and so on. Evaluation of congenital heart disease (CHD) is an important application of Cardiac MRI since the morphological details of chambers, septum, defects and anomalous connections are depicted accurately. Besides, flow information across valves, chambers, outflow tracts and shunts are also provided. This article describes our experience in the use of cardiac MRI in congenital heart disease.

Towards real-time cardiovascular magnetic resonance-guided transarterial aortic valve implantation: in vitro evaluation and modification of existing devices

BACKGROUND

Cardiovascular magnetic resonance (CMR) is considered an attractive alternative for guiding transarterial aortic valve implantation (TAVI) featuring unlimited scan plane orientation and unsurpassed soft-tissue contrast with simultaneous device visualization. We sought to evaluate the CMR characteristics of both currently commercially available transcatheter heart valves (Edwards SAPIEN™, Medtronic CoreValve®) including their dedicated delivery devices and of a custom-built, CMR-compatible delivery device for the Medtronic CoreValve® prosthesis as an initial step towards real-time CMR-guided TAVI.

METHODS

The devices were systematically examined in phantom models on a 1.5-Tesla scanner using high-resolution T1-weighted 3D FLASH, real-time TrueFISP and flow-sensitive phase-contrast sequences. Images were analyzed for device visualization quality, device-related susceptibility artifacts, and radiofrequency signal shielding.

RESULTS

CMR revealed major susceptibility artifacts for the two commercial delivery devices caused by considerable metal braiding and precluding in vivo application. The stainless steel-based Edwards SAPIEN™ prosthesis was also regarded not suitable for CMR-guided TAVI due to susceptibility artifacts exceeding the valve's dimensions and hindering an exact placement. In contrast, the nitinol-based Medtronic CoreValve® prosthesis was excellently visualized with delineation even of small details and, thus, regarded suitable for CMR-guided TAVI, particularly since reengineering of its delivery device toward CMR-compatibility resulted in artifact elimination and excellent visualization during catheter movement and valve deployment on real-time TrueFISP imaging. Reliable flow measurements could be performed for both stent-valves after deployment using phase-contrast sequences.

CONCLUSIONS

The present study shows that the Medtronic CoreValve® prosthesis is potentially suited for real-time CMR-guided placement in vivo after suggested design modifications of the delivery system.

Computed tomography evaluation of cardiac valves: a review

Electrocardiograph (ECG)-gated cardiac computed tomography (CT) angiography has great potential for the evaluation of the cardiac valves, with excellent image quality. The evidence-based, established clinical role of ECG-gated CT coronary angiography provides additional valuable information about valve morphology and function. A wide range of valve pathology, including congenital and acquired conditions, infectious endocarditis, and complications of valve replacement, can be assessed by cardiac CT imaging. Despite recent advances in CT technology, echocardiography remains the gold standard for noninvasive cardiac valve evaluation. Nevertheless, important clinical information about the valves can be obtained with coronary CT angiography examinations. Thus cardiac valve morphology and function should be routinely assessed and reported on coronary CT angiography examinations.

CT angiography of the cardiac valves: normal, diseased, and postoperative appearances

Although echocardiography remains the principal imaging technique for assessment of the cardiac valves, contrast material-enhanced electrocardiographically gated computed tomographic (CT) angiography is proving to be an increasingly valuable complementary modality in this setting. CT angiography allows excellent visualization of the morphologic features and function of the normal valves, as well as of a wide range of valve diseases, including congenital and acquired diseases, infectious endocarditis, and complications of valve replacement. The number, thickness, and opening and closing of the valve leaflets, as well as the presence of valve calcification, can be directly observed. CT angiography also permits simultaneous assessment of the valves and coronary arteries, which may prove valuable in presurgical planning. Unlike echocardiography and magnetic resonance imaging, however, CT angiography requires ionizing radiation and does not provide a direct measure of the valvular pressure gradient. Nevertheless, with further development of related imaging techniques, CT angiography can be expected to play an increasingly important role in the evaluation of the cardiac valves. Supplemental material available at http://radiographics.rsna.org/cgi/content/full/29/5/1393/DC1.

Qualitative echocardiographic assessment of aortic valve regurgitation with quantitative cardiac magnetic resonance: a comparative study

This study examined the correlation of echocardiography (ECHO) and Cardiac Magnetic Resonance (CMR) in the assessment of aortic valve regurgitation (AR) in children and young adults with congenital heart disease. We hypothesized that qualitative ECHO assessment correlates insufficiently with quantitative CMR data and compared subjective ECHO evaluations with objective measurement of regurgitant fractions (RF) by CMR. Patients who had both ECHO and CMR assessments of AR within 60 days of each other were included. The qualitative ECHO assessment (mild, moderate, severe) of AR and left ventricular dimension at end diastole were recorded. RF was quantified by CMR using phase-contrast velocity mapping. Repeat ECHO review and grading of AR was performed by a blinded single reader in a randomly chosen subgroup of patients. In 43 patients studied, statistical significance was observed in the CMR-RF between mild and moderate, and between mild and severe ECHO grades. There was significant overlap of objective RF between subjective grades. Mild ECHO AR corresponded to an RF (%) of 0-29, moderate 1-40, and severe 5-58. Overlap was more significant at moderate and severe grades. Results were similar in the group in whom a single reader interpreted the ECHO assessment. In conclusion, results derived from a real-life multiple-reader ECHO laboratory showed inconsistencies in ECHO grading of AR, with a wide range of objectively measured RF within a given ECHO grade. ECHO is less reliable in identifying more severe AR, often overestimating severity. Quantitative CMR is a potentially useful supplement to ECHO for management decisions and assessments of medical and surgical therapies in children and young adults with AR.

Cardiovascular applications of phase-contrast MRI

OBJECTIVE

The purpose of this study was to review and illustrate various clinical applications of phase-contrast MRI.

CONCLUSION

Cardiac MRI has emerged as a valuable noninvasive clinical tool for evaluation of the cardiovascular system. Phase-contrast MRI has a variety of established applications in quantifying blood flow and velocity and several emerging applications, such as evaluation of diastolic function and myocardial dyssynchrony.

Aortic stenosis: evaluation with multidetector CT angiography and MR imaging

Aortic valvular stenosis (AS) is the most common valve disease which results in the need for a valve replacement. Although a Doppler echocardiography is the current reference imaging method, the multidetector computerized tomograpghy (MDCT) and magnetic resonance imaging (MRI) have recently emerged as a promising method for noninvasive valve imaging. In this study, we briefly describe the usefulness and comparative merits of the MDCT and MRI for the evaluation of AS in terms of valvular morphology (as the causes of AS), quantification of aortic valve area, pressure gradient of flow (for assessment severity of AS), and the evaluation of the ascending aorta and cardiac function (as the secondary effects of AS). The familiarity with the MDCT and MRI features of AS is considered to be helpful for the accurate diagnosis and proper management of patients with a poor acoustic window.

A practical approach to the quantification of valvular regurgitation

This article reviews the methods of determining the severity of mitral and aortic regurgitation, primarily the quantitation using Doppler echocardiography. The Doppler methods, including spatial mapping, proximal flow convergence, vena contracta, continuous-wave Doppler density, and upstream or downstream effects are explained. Various practical pitfalls and performance issues that impact the reliability of these techniques are discussed.

Value of MR phase-contrast flow measurements for functional assessment of pulmonary arterial hypertension

Goals of our study were to compare the pulmonary hemodynamics between healthy volunteers and patients with pulmonary arterial hypertension (PAH) and correlate MR flow measurements with echocardiography. Twenty-five patients with PAH and 25 volunteers were examined at 1.5 T. Phase-contrast flow measurements were performed in the ascending aorta and pulmonary trunk, resulting in the following parameters: peak velocity (cm/s), average blood flow (l/min), time to peak velocity (ms), velocity rise gradient and pulmonary distensibility (cm(2)). The bronchosystemic shunt was calculated. In PAH patients transthoracic echocardiography and right-heart catheterization (RHC) served as the gold standard. In comparison to volunteers, the PAH patients showed significantly reduced pulmonary velocities (P = 0.002), blood flow (P = 0.002) and pulmonary distensibility (P = 0.008). In patients, the time to peak velocity was shorter (P<0.001), and the velocity rise gradient was steeper (P = 0.002) than in volunteers. While in volunteers the peak velocity in the aorta was reached earlier, it was the reverse in patients. Patients showed a significant bronchosystemic shunt (P = 0.01). No meaningful correlation was found between MRI measurements and echocardiography or RHC. MRI is a feasible technique for the differentiation between PAH and volunteers. Further studies have to be conducted for the absolute calculation of pressure estimates.

Evaluation of a resistance-based model for the quantification of pulmonary arterial hypertension using MR flow measurements

PURPOSE

To establish an estimate for the mean pulmonary arterial pressure (mPAP) derived from noninvasive data acquired with magnetic resonance (MR) velocity-encoded sequences.

MATERIALS AND METHODS

In seven sedated pigs synchronous catheter-based invasive pressure measurements (IPM) and noninvasive MR were acquired in the main pulmonary artery (MPA) at different severities of pulmonary arterial hypertension (PAH) that were caused by infusion of thromboxane A2 (TxA2). The invasively measured mPAP was correlated with the noninvasive MR velocity data and linear combination equations (LCE) were computed.

RESULTS

Intravenously applied TxA2 induced a dose dependent level of severity of PAH with an mPAP of up to 54 mmHg without systemic effects. The acceleration time (AT) measured with MR demonstrated the best correlation with the mPAP (r(2) = 0.75). The LCE with the highest correlation (R = 0.945, alpha < 0.01) between IPM and MR revealed a mean difference of 0, a SD of s = 4.66 and a maximal difference of 12.2 mmHg using the Bland-Altman analysis.

CONCLUSION

Applying the identified LCE allowed the estimation of the mPAP in an acute and resistance-based model of PAH with high accuracy using noninvasive MR velocity-encoded sequences.

Three-dimensional morphological magnetic resonance imaging in infants and children with congenital heart disease

BACKGROUND

Cardiac MRI has become a clinically useful supplement to ECHO and conventional X-ray angiography in the diagnostic work-up of patients with congenital heart disease (CHD). Three-dimensional (3D) sequences are capable of depicting both intracardiac and extracardiac structures with high accuracy in adults and adolescents. However, diagnostic image quality in infants and young children has not yet been reported.

OBJECTIVE

To apply an optimized 3D steady-state free-precession (SSFP) MR sequence in infants and children with CHD.

MATERIALS AND METHODS

In 20 patients (median age 1.8 years; ten male) with CHD, whole-chest imaging was performed with navigator-gated, isotropic 3D SSFP MRI at 1.5 T. Sequence parameters were adapted to special requirements in infancy. Measurements of intra- and extracardiac structures were performed by two independent observers and compared to spin-echo and cine gradient-recalled-echo sequences.

RESULTS

Diagnostic image quality was achieved with the 3D SSFP technique in all patients, allowing the establishment of a diagnosis in all cases. Interobserver comparison of measurements from reformatted 3D SSFP datasets revealed only minor differences with standard deviations ranging from 0.3-1.3 mm for intracardiac and 0.3-0.7 mm for extracardiac anatomy (P = ns).

CONCLUSION

Isotropic 3D SSFP MRI allows reliable and accurate assessment of CHD, even in free-breathing infants and young children.

Cardiac Valve Assessment with MR Imaging and 64-Section Multi–Detector Row CT

A variety of noninvasive techniques are available to assess cardiac valve morphologic features and function, with echocardiography currently being the most widely used modality for this purpose. Technical advances in electrocardiographically gated multi-detector row computed tomography (CT) and magnetic resonance (MR) imaging allow the noninvasive visualization of the cardiac valves. At present, 64-section multi-detector row CT and MR imaging are commonly being used for comprehensive examination of the heart. Information about the cardiac valves is routinely provided by MR imaging of cardiac function or coronary CT angiography. Thus, the interpreting physician may have additional information available that can aid in making the diagnosis. Supplemental movie clips are available at http://radiographics.rsnajnls.org/cgi/content/full/26/6/1769/DC1.

[Arterial duplex and aortic valve stenosis: sensitivity and specificity of findings]

Purposes. In this prospective study, we sought to determine the sensitivity and the specificity of arterial Doppler findings of valvular aortic stenosis (VAS).

PATIENTS AND METHODS

20 control subjects and 20 patients with various degrees of VAS underwent Doppler ultrasound of the carotids, abdominal aorta, renal arteries and limb arteries. We analyzed and compared the shape of the spectral profiles, peak systolic velocity (PSV), systolic upstroke time (SUT) and systolic upstroke index (SUI) of every tracing. The protodiastolic notch (PDN) of the common femoral arteries were recorded too.

RESULTS

VAS hardly modifies the overall shape of the Doppler spectrums of the aorta or limb arteries but it implies a biphasic deformation or a doubling of the systolic peak of the neck vessels. We also encountered biphasic profiles in renal arteries of patients with tight VAS. The PSV, SUI and depth of the PDN tend to diminish in cases of VAS but the variations are inconstant and rarely proportional to the severity of the narrowing. The increase of the SUT, on the contrary, is linearly correlated to the severity of the stenosis in every arterial system: SUTs in the common carotid artery, internal carotid artery or brachial artery that are shorter than or equal to 70 milliseconds (msec) are the obvious marks of the absence of VAS. It was not possible to differentiate between the intermediate stenoses (aortic valve area between 0.8 and 2 square centimeters) whereas critical aortic stenoses, whose area is less than or equal to 0.7 square centimeter, can be detected by the presence of at least two of the four following criteria of SUT: equal to or above 180 msec for the common carotid, 200 msec for the internal carotid, 130 msec for the aorta and 110 msec for the common femoral artery.

CONCLUSION

During routine arterial Doppler ultrasound, a precise analysis of the spectrums and some SUT measurements allow the assessment of the aortic valve.

Operator-Independent Isotropic Three-Dimensional Magnetic Resonance Imaging for Morphology in Congenital Heart Disease

Background— Operator-independent isotropic 3D MRI may greatly simplify the assessment of complex morphology in congenital heart disease. We sought to evaluate the reliability of this new approach.

Methods and Results— In 31 adolescent and adult patients (age, 6 to 42 years; median, 16 years) with congenital heart disease, cardiac morphology was determined with free-breathing (navigator-gated), isotropic, 3D steady-state free-precession (3D SSFP) MRI and independently evaluated by 2 observers. Cardiac diagnoses and multiple distance measurements were compared with conventional MR reference sequences (ie, spin-echo, cine gradient-echo, contrast-enhanced MR angiography) and with echocardiography/cine cardioangiography or surgery. Of the 31 patients, 24 had native congenital heart defects or residual defects after repair that warranted immediate treatment. None of these defects was missed by 3D SSFP. Novel diagnostic issues were discovered in 4 of 31 patients (coronary anomalies, n=3; left juxtaposition of the right atrial appendage in double-outlet right ventricle and transposition of the great arteries, 1). For sizes of valves and vessels, we found minor mean differences of −1.1 to 1.6 mm, with SD ranging from 1.2 to 2.9 mm, demonstrating overall good agreement with standard MRI (Bland-Altman analysis). Interobserver variability of 3D SSFP distance measures was low; mean differences ranged from −1.5 to 1.0 mm, and SD ranged from 0.8 to 2.5 mm. Scatter was lower for extracardiac than intracardiac measures.

Conclusions— In adolescents and adults, isotropic 3D SSFP MRI allows reliable assessment of complex cardiac morphology. Distance measurements are accurate and reproducible. Thus, a single operator-independent acquisition may substitute for conventional 2D MRI sequences to accelerate and simplify MR scanning in congenital heart disease.