Cine MR imaging of valvular heart disease: display and imaging parameters affect the size of the signal void caused by valvular regurgitation

Tricuspid Valve Imaging and Right Ventricular Function Analysis Using Cardiac CT and MRI

Cardiac computed tomography (CT) and cardiac magnetic resonance imaging (CMR) can reveal the detailed anatomy and function of the tricuspid valve and right ventricle (RV). Quantification of tricuspid regurgitation (TR) and analysis of RV function have prognostic implications. With the recently available transcatheter treatment options for diseases of the tricuspid valve, evaluation of the tricuspid valve using CT and CMR has become important in terms of patient selection and procedural guidance. Moreover, CT enables post-procedural investigation of the causes of valve dysfunction, such as pannus or thrombus. This review describes the anatomy of the tricuspid valve and CT and CMR imaging protocols for right heart evaluation, including RV function and TR analyses. We also demonstrate the pre-procedural planning for transcatheter treatment of TR and imaging of postoperative complications using CT.

CMR in Evaluating Valvular Heart Disease: Diagnosis, Severity, and Outcomes

Cardiac magnetic resonance (CMR) is a versatile imaging tool that brings much to the assessment of valvular heart disease. Although it is best known for myocardial imaging (even in valve disease), it provides excellent assessment of all 4 heart valves, with some distinct advantages, including a free choice of image planes and accurate flow and volumetric quantification. These allow the severity of each valve lesion to be characterized, in addition to optimal visualization of the surrounding outflow tracts and vessels, to deliver a comprehensive package. It can assess each valve lesion separately (in multiple valve disease) and is not affected by hemodynamic status. The accurate quantitation of regurgitant lesions and the ability to characterize myocardial changes also provides an ability to predict future clinical outcomes in asymptomatic patients. This review outlines how CMR can be used in cardiac valve disease to compliment echocardiography and enhance the patient assessment. It covers the main CMR methods used, their strengths and limitations, and the optimal way to apply them to evaluate valve disease.

Evolving new concepts in the assessment of aortic stenosis

Echocardiography has been pivotal in evaluating aortic stenosis (AS) over the past several decades. Recent experience has shown a wide spectrum in the clinical presentation of AS. A better understanding of the underlying hemodynamic principles has resulted in emergence of new subtypes of AS. New treatment modalities have also been introduced, requiring precise evaluation of aortic valve (AV) pathology for implementation of these therapies. This review will discuss new concepts and indices in the use of echocardiography in patients with AS. Specifically, we will address the hemodynamic characteristics, clinical presentation, and management of normal-flow, high-gradient; paradoxical low-flow, low-gradient; and classical low-flow, low-gradient aortic stenoses.

Multi-parametric quantification of tricuspid regurgitation using cardiovascular magnetic resonance: A comparison to echocardiography

BACKGROUND

Velocity-encoding is used to quantify tricuspid regurgitation (TR) by cardiovascular magnetic resonance (CMR), but requires additional dedicated imaging. We hypothesized that size and signal intensity (SI) of the cross-sectional TR jet area in the right atrium in short-axis steady-state free-precession images could be used to assess TR severity.

METHODS

We studied 61 patients with TR, who underwent CMR and echocardiography within 24h. TR severity was determined by vena contracta: severe (N=20), moderate or mild (N=41). CMR TR jet area and normalized SI were measured in the plane and frame that depicted maximum area. ROC analysis was performed in 21/61 patients to determine diagnostic accuracy of differentiating degrees of TR. Optimal cutoffs were independently tested in the remaining 40 patients.

RESULTS

Measurable regions of signal loss depicting TR jets were noted in 51/61 patients, while 9/10 remaining patients had mild TR by echocardiography. With increasing TR severity, jet area significantly increased (15±14 to 38±20mm2), while normalized SI decreased (57±27 to 23±11). ROC analysis showed high AUC values in the derivation group and good accuracy in the test group.

CONCLUSION

TR can be quantified from short-axis CMR images in agreement with echocardiography, while circumventing additional image acquisition.

Sudden cardiac death from structural heart diseases in adults: imaging findings with cardiovascular computed tomography and magnetic resonance

Sudden cardiac death (SCD) is defined as the unexpected natural death from a cardiac cause within an hour of the onset of symptoms in the absence of any other cause. Although such a rapid course of death is mainly attributed to a cardiac arrhythmia, identification of structural heart disease by cardiovascular computed tomography (CCT) and cardiovascular magnetic resonance (CMR) imaging is important to predict the long-term risk of SCD. In adults, SCD most commonly results from coronary artery diseases, coronary artery anomalies, inherited cardiomyopathies, valvular heart diseases, myocarditis, and aortic dissection with coronary artery involvement or acute aortic regurgitation. This review describes the CCT and CMR findings of structural heart diseases related to SCD, which are essential for radiologists to diagnose or predict.

Comparative Assessment of Mitral Regurgitation Severity by Transthoracic Echocardiography and Cardiac Magnetic Resonance Using an Integrative and Quantitative Approach

Although transthoracic echocardiography (TTE) and cardiac magnetic resonance (CMR) are validated in quantitation of mitral regurgitation (MR), discrepancies may occur. This study assesses the agreement between TTE and CMR in MR and evaluates characteristics and clinical outcome of patients with discrepancy. From our institutional database, 70 subjects with MR underwent both TTE and CMR within 30 days (median 3 days). MR was evaluated semiquantitatively (n = 70) using a 4-grade scale and quantitatively (n = 60) with calculation of regurgitant volume (RVol) and regurgitant fraction (RF). Of the 70 subjects, qualitative assessment by TTE yielded 30 subjects with mild MR, 17 moderate, and 23 moderately severe or severe MR. Exact concordance in MR grade was seen in 50% and increased to 91% when considering concordance within one grade of severity (κ = 0.44). A modest correlation was observed for RVol and RF between both methods (r = 0.59 and 0.54, respectively, p <0.0001). Ten patients had a significant discrepancy in quantitative MR (difference in RF >20%); the frequency of secondary MR was higher (100% vs 46%; p = 0.003) in patients with discrepancy. Although interobserver variability in RF was higher with TTE compared with CMR (-5.5 ± 15% vs 0.1 ± 7.3%), patients with discrepancy were equally distributed by severity and clinical outcome without an overestimation by either method. In conclusion, there is a modest agreement between TTE and CMR in assessing MR severity. In patients with discrepancy, there is a higher prevalence of functional MR, without a consistent overestimation of MR severity by either method.

Aberration in DNA methylation in B-cell lymphomas has a complex origin and increases with disease severity

Despite mounting evidence that epigenetic abnormalities play a key role in cancer biology, their contributions to the malignant phenotype remain poorly understood. Here we studied genome-wide DNA methylation in normal B-cell populations and subtypes of B-cell non-Hodgkin lymphoma: follicular lymphoma and diffuse large B-cell lymphomas. These lymphomas display striking and progressive intra-tumor heterogeneity and also inter-patient heterogeneity in their cytosine methylation patterns. Epigenetic heterogeneity is initiated in normal germinal center B-cells, increases markedly with disease aggressiveness, and is associated with unfavorable clinical outcome. Moreover, patterns of abnormal methylation vary depending upon chromosomal regions, gene density and the status of neighboring genes. DNA methylation abnormalities arise via two distinct processes: i) lymphomagenic transcriptional regulators perturb promoter DNA methylation in a target gene-specific manner, and ii) aberrant epigenetic states tend to spread to neighboring promoters in the absence of CTCF insulator binding sites.

Follicular lymphomas and diffuse large B-cell lymphomas are the most common non-Hodgkin lymphomas. Although these diseases share many mutant alleles, the underlying cause of the different phenotypes remains unclear. We show that direct comparison of DNA methylation patterning provides insights about gene deregulation during lymphomagenesis and explains the nature of the different clinical behavior.

Diagnostic approach to assessment of valvular heart disease using magnetic resonance imaging, part II: a practical approach for native and prosthetic heart valve stenosis

MRI is already an established diagnostic modality for assessing valvular stenosis although it is not usually used as the initial non-invasive test. The preferred diagnostic modality for valvular stenosis is currently echocardiography. However, MRI has been offered as a good alternative test in the event of inconclusive echocardiography results. During the course of valvular stenosis, the valve orifice area decreases and the pressure gradient across the diseased valve increases. Valvular orifice area is the major core indicator for valvular stenosis severity grading. Compared with valvular regurgitation, assessment with MRI for valvular stenosis is less complicated. The aim of this article is to detail the MRI techniques in assessing native and prosthetic heart valve stenosis.

Cardiovascular magnetic resonance physics for clinicians: Part II

This is the second of two reviews that is intended to cover the essential aspects of cardiovascular magnetic resonance (CMR) physics in a way that is understandable and relevant to clinicians using CMR in their daily practice. Starting with the basic pulse sequences and contrast mechanisms described in part I, it briefly discusses further approaches to accelerate image acquisition. It then continues by showing in detail how the contrast behaviour of black blood fast spin echo and bright blood cine gradient echo techniques can be modified by adding rf preparation pulses to derive a number of more specialised pulse sequences. The simplest examples described include T2-weighted oedema imaging, fat suppression and myocardial tagging cine pulse sequences. Two further important derivatives of the gradient echo pulse sequence, obtained by adding preparation pulses, are used in combination with the administration of a gadolinium-based contrast agent for myocardial perfusion imaging and the assessment of myocardial tissue viability using a late gadolinium enhancement (LGE) technique. These two imaging techniques are discussed in more detail, outlining the basic principles of each pulse sequence, the practical steps required to achieve the best results in a clinical setting and, in the case of perfusion, explaining some of the factors that influence current approaches to perfusion image analysis. The key principles of contrast-enhanced magnetic resonance angiography (CE-MRA) are also explained in detail, especially focusing on timing of the acquisition following contrast agent bolus administration, and current approaches to achieving time resolved MRA. Alternative MRA techniques that do not require the use of an endogenous contrast agent are summarised, and the specialised pulse sequence used to image the coronary arteries, using respiratory navigator gating, is described in detail. The article concludes by explaining the principle behind phase contrast imaging techniques which create images that represent the phase of the MR signal rather than the magnitude. It is shown how this principle can be used to generate velocity maps by designing gradient waveforms that give rise to a relative phase change that is proportional to velocity. Choice of velocity encoding range and key pitfalls in the use of this technique are discussed.

Heart valve disease: investigation by cardiovascular magnetic resonance

Cardiovascular magnetic resonance (CMR) has become a valuable investigative tool in many areas of cardiac medicine. Its value in heart valve disease is less well appreciated however, particularly as echocardiography is a powerful and widely available technique in valve disease. This review highlights the added value that CMR can bring in valve disease, complementing echocardiography in many areas, but it has also become the first-line investigation in some, such as pulmonary valve disease and assessing the right ventricle. CMR has many advantages, including the ability to image in any plane, which allows full visualisation of valves and their inflow/outflow tracts, direct measurement of valve area (particularly for stenotic valves), and characterisation of the associated great vessel anatomy (e.g. the aortic root and arch in aortic valve disease). A particular strength is the ability to quantify flow, which allows accurate measurement of regurgitation, cardiac shunt volumes/ratios and differential flow volumes (e.g. left and right pulmonary arteries). Quantification of ventricular volumes and mass is vital for determining the impact of valve disease on the heart, and CMR is the 'Gold standard' for this. Limitations of the technique include partial volume effects due to image slice thickness, and a low ability to identify small, highly mobile objects (such as vegetations) due to the need to acquire images over several cardiac cycles. The review examines the advantages and disadvantages of each imaging aspect in detail, and considers how CMR can be used optimally for each valve lesion.

Diagnostic approach to assessment of valvular heart disease using MRI-Part I: a practical approach for valvular regurgitation

Valvular heart diseases from any cause are divided into two categories: stenosis and regurgitation. Acquired knowledge of the pathological aetiology and disease severity are the important clues for optimal treatment, which may be medication or combination with surgery. The non-invasive techniques have been established for valvular heart disease evaluation for many years especially in demonstrating valvular structure and assessing severity. Transthoracic echocardiography still plays the major role. However, not every case can be clearly evaluated by transthoracic echocardiography because of rib space window limitation. In the present-day practice, MRI has been extensively used for the evaluation of heart diseases in both unique and complementary categories. However, valvular heart disease assessment using cardiac MRI still remains an important challenge.

[Magnetic resonance imaging in the assessment of valvular heart disease]

Although Doppler echocardiography remains the most frequently used imaging modality for assessing valvular heart disease, the technique has a number of limitations that could affect the quality of imaging studies and make the results difficult to interpret. Cardiac magnetic resonance (CMR) imaging could be superior to echocardiography in a number of ways: for example, for assessing ventricular dimensions, volumes, function and mass, for quantifying valvular regurgitation, and for investigating areas of myocardial fibrosis and extracardiac structures. In carrying out these tasks, CMR uses a variety of pulse sequences that are specially created to obtain information on specific tissue characteristics or on particular aspects of blood flow through heart valves. This general review article focuses on the usefulness of CMR in the clinical diagnosis of valvular heart disease and reviews how the data acquired using the technique can be incorporated into algorithms for the clinical management of patients with significant valvular heart lesions.

Hemodynamic aspects of mitral regurgitation assessed by generalized phase-contrast MRI

PURPOSE

To investigate the utility of MRI measurement of left atrial (LA) flow patterns and turbulent kinetic energy (TKE) in patients with clinically significant mitral regurgitation.

MATERIALS AND METHODS

Three-dimensional cine phase-contrast MRI (PC-MRI) data were acquired in five patients with posterior mitral leaflet prolapse and two normal volunteers. LA flow patterns were assessed using particle trace visualization. Specifically, vortices were recognized by closed streamlines. LA flow distortion was assessed by estimation of TKE. In addition, the regurgitant volume was measured.

RESULTS

Four of the mitral regurgitation patients had eccentric regurgitant jets directed toward the septum; one patient had a central jet. The dominant systolic vortex was located in proximity to the regurgitant jet. The LA flow was highly disturbed with elevated values of TKE; peak LA TKE ranged from 13 to 37 mJ and occurred consistently at late systole. The average LA TKE per cardiac cycle was significantly related to the regurgitant volume (TKE = 0.573 + 0.179·RegVol, R(2) = 0.983).

CONCLUSION

MRI permits investigations of atrial flow patterns and TKE in significant mitral regurgitation. The degree of LA flow distortion, as measured by the average LA TKE over one cardiac cycle, appears to reflect the severity of regurgitation.

Hakki's formula for measurement of aortic valve area by magnetic resonance imaging

Hakki's formula (simplified Gorlin formula) can be used during cardiac catheterization to calculate the stenosed cardiac valve areas and can also be adapted to magnetic resonance imaging (MRI) to measure the stenosed cardiac valve areas. We evaluated the reliability of this approach to determine the severity of aortic stenosis compared to the continuity equation using transthoracic echocardiography and planimetry using MRI. We included all eligible symptomatic patients with known aortic stenosis referred to our department during a 1-year period. The aortic valve area (AVA) was estimated using Hakki's formula (MRI), planimetry (MRI), and the continuity equation (transthoracic echocardiography). The agreement among the measurement methods was analyzed using the Bland-Altman method. A total of 63 patients were included (mean age 72 +/- 10 years, 35 men [56%]). The mean AVA was 0.70 +/- 0.21 cm(2) using the continuity equation (transthoracic echocardiography), 0.67 +/- 0.18 cm(2) using planimetry (MRI), and 0.64 +/- 0.21 cm(2) using Hakki's formula (MRI). The mean difference was 0.03 cm(2) (95% limits of agreement -0.32 to 0.25) between planimetry and the continuity equation, 0.05 cm(2) (95% limits of agreement -0.40 to 0.29) between Hakki's formula and the continuity equation, 0.02 cm(2) (95% limits of agreement -0.20 to 0.25) between Hakki's formula and planimetry. The inter- and intraobserver reproducibility using Hakki's formula was excellent. In conclusion, measurement of the AVA using Hakki's formula yielded similar results to those obtained using planimetry and slightly different ones from those obtained using the continuity equation. However, Hakki's formula has the advantage of being easy to use, fast, and reproducible and can be used regardless of the status of the valve (in contrast to planimetry).

Valvular heart disease: what does cardiovascular MRI add?

Although ischemic heart disease remains the leading cause of cardiac-related morbidity and mortality in the industrialized countries, a growing number of mainly elderly patients will experience a problem of valvular heart disease (VHD), often requiring surgical intervention at some stage. Doppler-echocardiography is the most popular imaging modality used in the evaluation of this disease entity. It encompasses, however, some non-negligible constraints which may hamper the quality and thus the interpretation of the exam. Cardiac catheterization has been considered for a long time the reference technique in this field, however, this technique is invasive and considered far from optimal. Cardiovascular magnetic resonance imaging (MRI) is already considered an established diagnostic method for studying ventricular dimensions, function and mass. With improvement of MRI soft- and hardware, the assessment of cardiac valve function has also turned out to be fast, accurate and reproducible. This review focuses on the usefulness of MRI in the diagnosis and management of VHD, pointing out its added value in comparison with more conventional diagnostic means.

Assessment of blood flow and valvular heart disease using phase-contrast cardiovascular magnetic resonance

Measurement of blood flow is important for assessing the severity of disease processes involving the cardiovascular system. Phase-contrast cardiovascular magnetic resonance (PC-CMR) can be used to measure blood flow noninvasively without ionizing radiation or limitations imposed by body habitus. This review describes the performance of PC-CMR and its clinical utility in assessing patients with cardiovascular or valvular heart disease.

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.

Fast Measurements of Flow through Mitral Regurgitant Orifices with Magnetic Resonance Phase Velocity Mapping

Magnetic-resonance (MR) phase velocity mapping (PVM) shows promise in measuring the mitral regurgitant volume. However, in its conventional nonsegmented form, MR-PVM is slow and impractical for clinical use. The aim of this study was to evaluate the accuracy of rapid, segmented k-space MR-PVM in quantifying the mitral regurgitant flow through a control volume (CV) method. Two segmented MR-PVM schemes, one with seven (seg-7) and one with nine (seg-9) lines per segment, were evaluated in acrylic regurgitant mitral valve models under steady and pulsatile flow. A nonsegmented (nonseg) MR-PVM acquisition was also performed for reference. The segmented acquisitions were considerably faster (<10 min) than the nonsegmented (>45 min). The regurgitant flow rates and volumes measured with segmented MR-PVM agreed closely with those measured with nonsegmented MR-PVM (differences <5%, p > 0.05), when the CV was large enough to exclude the region of flow acceleration and aliasing from its boundaries. The regurgitant orifice shape (circular vs. slit-like) and the presence of aortic outflow did not significantly affect the accuracy of the results under both steady and pulsatile flow (p > 0.05). This study shows that segmented k-space MR-PVM can accurately quantify the flow through regurgitant orifices using the CV method and demonstrates great clinical potential.

[Pericardium and cardiac valves: value of MRI and Multislice CT]

Color Doppler echocardiography has limitations, particularly in the assessment of valvular regurgitation and pericardial diseases. MRI, with the help of three dimensional morphologic data, dynamic acquisitions with cine techniques and functional evaluation with flow sensitive techniques can be envisioned as a complementary noninvasive procedure able to provide the complete information required for planning therapeutic options. Qualitative as well as accurate and reproducible quantitative information (volume measurements, cardiac function and flow velocity profiles) are unique for the evaluation of the severity of valve or pericardial diseases. Multislice CT is unique in precisely demonstrating valvular and pericardial calcifications. This article reviews both imaging techniques used in assessing valvular and pericardial disease and discusses the advantages and limitations of these techniques in current clinical applications.

Regurgitant jet evaluation using three-dimensional echocardiography and magnetic resonance

BACKGROUND

Three-dimensional assessment of regurgitant jet volume is the prerequisite for stratifying valve insufficiency. However, systematic comparison of three-dimensional methods is lacking. Therefore, we evaluated magnetic resonance imaging and three-dimensional echocardiography experimentally.

METHODS

An insufficiency chamber (22 x 18.5 x 27 cm; ostia 10, 16, and 20 mm; regurgitant volumes 2.3 to 25 mL) within experimental circulation (BioMedicus pump, tubes, pulsatile flow 0.2 to 1.9 L/min) was used for three-dimensional echocardiography (HP Sonos 2500) and magnetic resonance imaging (Siemens Magnetom Vision). Doppler flowmeter served as a gold standard. Segmentation used thresholding and surface integration of velocity vectors. Jet volume was evaluated qualitatively by polynom fitting.

RESULTS

Jet volume calculated by magnetic resonance (r = 0.99, p < 0.0001) and by echocardiography (r = 0.99, p < 0.0001) correlated identically to the gold standard. Jet volume derived from imaging correlated with each other by r = 0.98 (p < 0.0001). Polynom fits indicated a more paraboloid shape of magnetic resonance jet volume.

CONCLUSIONS

Experimentally, three-dimensional echocardiography and magnetic resonance imaging possess identical accuracy for determining regurgitant jet volume. Magnetic resonance imaging seems to provide qualitatively better image data for three-dimensional reconstruction.

Role of MRI in clinical cardiology

Rapid progress has been made in cardiac MRI (CMRI) over the past decade, which has firmly established it as a reliable and clinically important technique for assessment of cardiac structure, function, perfusion, and myocardial viability. Its versatility and accuracy is unmatched by any other individual imaging modality. CMRI is non-invasive and has high spatial resolution and avoids use of potentially nephrotoxic contrast agent or radiation. It has been extensively studied against other established non-invasive imaging modalities and has been shown to be superior in many scenarios, particularly with respect to assessment of cardiac and great vessel morphology and left ventricular function. Furthermore, its clinical use continues to expand with increasing experience and proliferation of CMRI centres. As worldwide prevalence of cardiovascular disease continues to rise, CMRI provides opportunity for improved and cost-effective non-invasive assessment. Continued progress in CMRI technology promises to further widen its clinical application in coronary imaging, myocardial perfusion, comprehensive assessment of valves, and plaque characterisation.

Breath-hold signal-loss sequence for the qualitative assessment of flow disturbances in cardiovascular MR

PURPOSE

To develop a breath-hold segmented sequence which generates similar patterns of signal loss to a non-breath-hold, relatively long echo time, conventional gradient echo sequence for the qualitative assessment of valvular heart disease.

MATERIALS AND METHODS

Both velocity-sensitized and acceleration-sensitized segmented sequences were developed. The sensitivities were empirically adjusted to give similar degrees of signal loss to a conventional sequence. These sequences were compared with a conventional sequence in eight patients with flow disturbances and in four healthy subjects.

RESULTS

There was no significant difference in the extent of signal loss observed when using the breath-hold velocity- and acceleration-sensitized sequences developed and the conventional sequence (1862 mm(2), 1831 mm(2), and 1782 mm(2), respectively; P = ns). However, the image quality obtained was significantly better with the breath-hold sequences (both P < 0.01). Furthermore, the image quality achieved with the acceleration-sensitized sequence was significantly better than that achieved with the velocity-sensitized sequence (P < 0.01) where artifacts from beat-to-beat variations in blood-flow velocities were a frequent problem.

CONCLUSION

Signal loss in complex flow is best demonstrated using the breath-hold acceleration-sensitized sequence where the signal from both stationary and constant velocity material is rephased at the echo time.

Cine MR imaging of heart valve dysfunction with segmented true fast imaging with steady state free precession

PURPOSE

To evaluate the value of cine true fast imaging with steady-state free precession (SSFP) for semiquantitative assessment of valvular dysfunction in the heart and to compare the results to that obtained with a standard breath-hold segmented gradient-recalled echo-planar imaging sequence (GE-EPI).

MATERIALS AND METHODS

Twenty-three patients with known valvular dysfunction (main component: 16 with aortic valve stenosis, nine with aortic valve insufficiency, three with mitral stenosis, two with mitral regurgitation, two with tricuspidal regurgitation, and one with pulmonary stenosis) and 23 control subjects with normal valvular function underwent MR imaging on a 1.5-T system (ACS-NT, Philips, Best, The Netherlands). Cine SSFP and GE-EPI images were acquired in identical long-axis views. Images were evaluated for the presence and extent of the signal void arising from the valves and for image quality consensus by two experienced radiologists. Results were compared to those obtained by cardiac catheterization (in 16 patients) or color Doppler (in the remaining seven patients).

RESULTS

On SSPF images, the complex flow pattern in valvular regurgitant or stenotic lesions caused signal void within the bright blood pool of the atria or ventricles, similar to GE-EPI, in all patients. Valvular dysfunction was delineated using SSFP with the same high sensitivity (100%) as using the GE-EPI sequence. Results correlated to those obtained by cardiac catheterization or color Doppler ultrasonography (P < 0.001, r = 0.97). However, the jet phenomenon was slightly more pronounced in five patients on GE-EPI. There was no significant signal void in the 23 control subjects with both sequences. In all 46 subjects, the image quality of SSFP images was rated higher (P < 0.05; 2.6 +/- 0.1; using a scale ranging from 0-3) compared to GE-EPI (1.7 +/- 0.1).

CONCLUSION

The results of this study suggest that valvular dysfunction can be semiquantitatively assessed using SSFP cine MR imaging.

Magnetic resonance imaging features of aortic diseases

The usefulness of magnetic resonance imaging (MRI) for aortic diseases is discussed, with special attention given to the MRI features of aortic dissection and Takayasu arteritis. Computed tomography (CT) and MRI provide excellent visualization of vessels and their relationship to surrounding structures; however, CT depicts the vessel lumen optimally only when contrast enhancement is used. MRI, with its inherent multiplanar imaging capability, is well suited for evaluation of the thoracic and abdominal aorta and can be used with or without contrast enhancement. Basic technical considerations in cardiac imaging, which include conventional spin-echo, fast spin-echo, cine gradient, and echo-planar imaging, with time-of-flight and phase-contrast methods, are discussed and applied to aortic aneurysm, aortic dissection, and Takayasu arteritis. The diagnostic capacity of spin-echo MRI in patients with suspected aortic dissection is enhanced when it is combined with cine MRI. Despite the ability of CT and MRI to demonstrate luminal and mural changes of aortic abnormalities, conventional angiography still may be necessary at first admission for selected patients in the late occlusive phase to provide additional information on the degree and extent of the arteritis. CT angiography and MR angiography are promising imaging techniques that will overcome difficulties in visualizing distal branch vessel lesions and obviate the need for conventional angiography in the near future.

Visualization of the pulmonary valve using cine MR imaging

PURPOSE

To evaluate the capability of bright-blood cine MR to directly visualize the leaflets of the valve replacement in pulmonary position following Ross operation.

MATERIAL AND METHODS

Long and short axis views of the pulmonary valve were obtained in 10 normal subjects and 14 patients after Ross operation. Valve morphology and function were analyzed and signal-to-noise (SNR) and contrast-to-noise ratios (CNR) were calculated. Flow measurements were performed in the pulmonary trunk to assess pulmonary regurgitation.

RESULTS

In all subjects, tricuspid morphology of the pulmonary valve was visualized. SNR of the leaflets in normal subjects (9.8 +/- 3.0) and in patients after Ross operation (7.5 +/- 2.2) differed significantly from blood (12.6 +/- 3.2 and 11.3 +/- 2.5, respectively, p < 0.05). Valvular regurgitation was seen in 5 patients as an insufficient closure of the valve which was confirmed by flow measurements.

CONCLUSION

Cine MR enables in-plane visualization of the pulmonary valve and allows for functional and morphological evaluation in patients after pulmonary valve surgery.

Assessment of valve disease: qualitative and quantitative

Evaluation of valve disease has changed significantly with the development of color Doppler echocardiography. Nevertheless, this technique has limitations, particularly in the assessment of valvular regurgitation. MR imaging, with its ability to provide three-dimensional morphologic data, dynamic cine information, and functional evaluation with flow-sensitive techniques, can be envisioned as a complementary noninvasive modality, able to provide the complete information required for planning therapeutic options. With MR imaging, qualitative as well as accurate and reproducible quantitative information such as volume measurements, cardiac function, and flow velocity profiles are unique for the evaluation of the severity of valve disease. This article reviews the different MR imaging techniques used in assessing valvular heart disease and discusses the advantages and limitations of these techniques in current clinical applications in comparison with classical imaging methods.

Cardiac MR imaging

There has been tremendous progress for MR imaging depiction of cardiac morphology and function. Further advances toward achieving faster acquisition with real-time imaging, higher resolution for plaque imaging, and quantitative analysis are taking place at a rapid pace.

Detection and quantification of valvular heart disease with dynamic cardiac MR imaging

Magnetic resonance (MR) imaging is rapidly gaining acceptance as an accurate, reproducible, noninvasive method for optimal assessment of structural and functional parameters in patients with valvular heart disease. The severity of valvular regurgitation can be evaluated with cine gradient-echo MR imaging, which allows measurement of the area of the signal void corresponding to the abnormal flow jet. Alternatively, this modality can be used to obtain ventricular volumetric measurements and calculate the regurgitant fraction, or velocity-encoded cine (VEC) MR imaging can be used to quantify regurgitant blood flow. The severity of valvular stenosis can be determined by evaluating the flow jet and associated findings with either modality or by using VEC MR imaging to calculate the transvalvular pressure gradient and valve area. Dynamic MR imaging allows accurate assessment of ventricular function and comprehensive evaluation of pathophysiologic changes. In addition, good interstudy reproducibility suggests a role for VEC MR imaging in assessing the effects of therapeutic intervention and monitoring regurgitant fraction, thereby helping in surgical planning and the prevention of ventricular dysfunction. With greater cost-effectiveness and the increasing availability of new hardware and more advanced techniques, MR imaging will become a routine procedure in valvular heart disease.

Evaluation of the heart with magnetic resonance imaging

After compensating for two kinds of motion artifacts caused by cardiac beating and respiration, cardiac magnetic resonance (MR) imaging is now feasible for the diagnosis of various cardiac diseases. Taking cost-effectiveness into consideration, this paper reviews the experiences of preferable indications of cardiac MR imaging by demonstrating the characteristic preciseness and uniqueness that play an important role in obtaining time-volume curves consisting of the theoretically most accurate measurements of left and right ventricular volumes, in overall evaluation of the left ventricular apex and the right ventricle, in delineating the wide range of the coronary arterial tree, in measuring the most precise blood flow volume through the cross-sectional images of the vessels, and in assessing the spatial derivative of the blood flow velocity at the vessel wall, i.e., wall shear rate.

Morphologic and functional evaluation of congenital heart disease by magnetic resonance imaging

Magnetic resonance imaging (MRI) has evolved sufficiently to be recognized as a useful complementary noninvasive method to echocardiography in the evaluation of congenital heart disease (CHD). In some cases, MRI is superior to other imaging modalities, particularly in the evaluation of thoracic aortic anomalies and in defining the anatomy of central pulmonary arteries; it is also the procedure of choice in the postoperative follow-up of patients with CHD. Recent technological advances permit not only morphological evaluation (provided by spin-echo and MR angiographic techniques) but functional and flow information (provided by fast cine-GE and velocity-encoded sequences), causing it to be recognized by pediatric cardiologists and cardiac surgeons as an unavoidable technique for pre- and postoperative evaluation of some CHD. This review describes the various techniques used in the evaluation of CHD with emphasis on recent developments as well as recognized clinical applications. J. Magn. Reson. Imaging 1999;10:639-655.

Magnetic resonance imaging of valvular heart disease

The optimum management of patients with valvular heart diseases requires accurate and reproducible assessment of the valvular lesion and its hemodynamic consequences. Magnetic resonance imaging (MRI) techniques, such as volume measurements, signal-void phenomena, and velocity mapping, can be used in an integrated approach to gain qualitative and quantitative information on valvular heart disease as well as ventricular dimensions and functions. Thus, MRI may be advantageous to the established diagnostic tools in assessing the severity of valvular heart disease as well as monitoring the lesion and predicting the optimal timing for valvular surgery. This paper reviews the validation of these MRI techniques in assessing valvular heart disease and discusses some typical pitfalls of the techniques, including suggestions for solutions.J. Magn. Reson. Imaging 1999;10:627-638.

Quantification of mitral regurgitation with MR phase-velocity mapping using a control volume method

Reliable diagnosis and quantification of mitral regurgitation are important for patient management and for optimizing the time for surgery. Previous methods have often provided suboptimal results. The aim of this in vitro study was to evaluate MR phase-velocity mapping in quantifying the mitral regurgitant volume (MRV) using a control volume (CV) method. A number of contiguous slices were acquired with all three velocity components measured. A CV was then selected, encompassing the regurgitant orifice. Mass conservation dictates that the net inflow into the CV should be equal to the regurgitant flow. Results showed that a CV, the boundary voxels of which excluded the region of flow acceleration and aliasing at the orifice, provided accurate measurements of the regurgitant flow. A smaller CV provided erroneous results because of flow acceleration and velocity aliasing close to the orifice. A large CV generally provided inaccurate results because of reduced velocity sensitivity far from the orifice. Aortic outflow, orifice shape, and valve geometry did not affect the accuracy of the CV measurements. The CV method is a promising approach to the problem of quantification of the MRV.

Imaging cardiac structure and pump function

This article describes magnetic resonance imaging approaches for assessing cardiac structure and myocardial pump function. The article is divided into cardiac structure and ventricular function. Throughout, representative images are included. There are numerous applications of magnetic resonance imaging for assessing cardiac structure and function, and magnetic resonance imaging compared favorably to other imaging modalities.