Whole-heart coronary vein imaging: a comparison between non-contrast-agent- and contrast-agent-enhanced visualization of the coronary venous system.

The feasibility of three-dimensional (3D) whole-heart imaging of the coronary venous (CV) system was investigated. The hypothesis that coronary magnetic resonance venography (CMRV) can be improved by using an intravascular contrast agent (CA) was tested. A simplified model of the contrast in T(2)-prepared steady-state free precession (SSFP) imaging was applied to calculate optimal T(2)-preparation durations for the various deoxygenation levels expected in venous blood. Non-contrast-agent (nCA)- and CA-enhanced images were compared for the delineation of the coronary sinus (CS) and its main tributaries. A quantitative analysis of the resulting contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) in both approaches was performed. Precontrast visualization of the CV system was limited by the poor CNR between large portions of the venous blood and the surrounding tissue. Postcontrast, a significant increase in CNR between the venous blood and the myocardium (Myo) resulted in a clear delineation of the target vessels. The CNR improvement was 347% (P < 0.05) for the CS, 260% (P < 0.01) for the mid cardiac vein (MCV), and 430% (P < 0.05) for the great cardiac vein (GCV). The improvement in SNR was on average 155%, but was not statistically significant for the CS and the MCV. The signal of the Myo could be significantly reduced to about 25% (P < 0.001).     

心脏再同步化治疗慢性心衰的短期疗效观察

目的 观察心脏再同步化治疗慢性心力衰竭(CHF)的短期临床疗效.方法 26例慢性心力衰竭患者行双心室再同步起搏治疗,全部患者均经冠状静脉窦植入左心室导线1根至心脏静脉,术后随访13.8±10.4(3～34)个月,观察心功能,患者活动度及夜间心率、QRS波时限,左心室收缩、舒张末内径,左室收缩、舒张末容积,左心室射血分数,左室舒张充盈时间,左室内各室壁收缩期达峰时间等.结果 26例患者中,1例于术后2个月时猝死;25例于术后3个月随访时发现心功能改善,有效率96.2%,心功能NY-HA分级,从Ⅲ-Ⅳ级改善为Ⅱ-Ⅲ级,患者活动度从0.31±0.40h/d增加至2.35±1.20h/d,夜间心率由84.8±15.7/min降低至63.4±4.5/min,心律变异性从47.3±7.1ms提高至96.4±15.1ms,QRS波从158.6±31.8ms缩短至129.5±30.2ms(P＜0.05),左心室收缩末内径、舒张末内径分别从67.6±8.2mm、77.0±9.4mm缩小至62.1±12.3mm、71.6±8.7mm(P＜0.05),左心室收缩末容积、舒张末容积分别从213±54ml、266±68ml缩小至151±62ml、212±63m1(P＜0.05),左心室射血分数从21.2%±4.5%提高至32.5%±6.4%(P＜0.05),左室舒张充盈时间从329±140ms提高至423±118ms(P＜05),左室12个节段收缩达峰时间标准差(Ts-Sd-12)从48.4±17.9ms减少至33.5±19.7ms(P＜0.05).结论 双心室再同步起搏是慢性心力衰竭治疗的有效方法.     

Optimization of on‐resonant magnetization transfer contrast in coronary vein MRI

Magnetization transfer contrast has been used commonly for endogenous tissue contrast improvements in angiography, brain, body, and cardiac imaging. Both off‐resonant and on‐resonant RF pulses can be used to generate magnetization transfer based contrast. In this study, on‐resonant magnetization transfer preparation using binomial pulses were optimized and compared with off‐resonant magnetization transfer for imaging of coronary veins. Three parameters were studied with simulations and in vivo measurements: flip angle, pulse repetitions, and binomial pulse order. Subsequently, first or second order binomial on‐resonant magnetization transfer pulses with eight repetitions of 720° and 240° flip angle were used for coronary vein MRI. Flip angles of 720° yielded contrast enhancement of 115% (P < 0.0006) for first order on‐resonant and 95% (P < 0.0006) for off‐resonant magnetization transfer. There was no statistically significance difference between off‐resonant and on‐resonant first order binomial Magnetization transfer at 720°. However, for off‐resonance pulses, much more preparation time is needed when compared with the binomials but with considerably reduced specific absorption rate. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

Time‐resolved analysis of coronary vein motion and cross‐sectional area

Purpose:

To quantify periods of low motion and cross‐sectional area changes of the coronary veins during the cardiac cycle for planning magnetic resonance coronary venograms (MRCV).

Materials and Methods:

Images were acquired from 19 patients with coronary artery disease (CAD) and 13 patients scheduled for cardiac resynchronization therapy (CRT). The displacement and cross‐sectional area of the coronary sinus was tracked, and periods of low motion were defined as consecutive time points during which the position of the coronary sinus remained within a 0.67‐mm diameter region. Patients were classified as systolic dominant or diastolic dominant based on the relative duration of their low motion periods.

Results:

All CRT patients were classified as systolic dominant, and 32% of these had no separate diastolic rest period. All CAD patients with ejection fraction < 35% were classified as systolic dominant, while all CAD patients with ejection fraction > 35%were diastolic dominant. In 77% of all subjects, the cross‐sectional area of the coronary sinus was larger in systole than in diastole.

Conclusion:

The movement of the coronary sinus can be used to classify patients as either having a longer systolic or diastolic rest period. The classification of the CRT patients as systolic dominant suggests that MRCVs be acquired in systole for CRT planning; however, each patient's low motion periods should be categorized to ensure the correct period is being used to minimize motion artifacts. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.     

Quantification of left ventricular internal flow from cardiac magnetic resonance images in patients with dyssynchronous heart failure

PURPOSE: To develop a method for quantifying left ventricular (LV) internal flow as a measure of dyssynchrony using standard cine cardiac magnetic resonance (CMR) images. MATERIALS AND METHODS: CMR images were obtained from 10 healthy controls and 10 patients with dyssynchronous heart failure (class III/IV, LV ejection fraction <35%, pattern seen in an electrocardiogram QRS duration > 150 msec). The LV volume was reconstructed and divided into 16 regions. Internal flow was defined as the sum of the regional volume changes minus the global volume change during each time step in the cardiac cycle. Internal flow fraction (IFF) was defined as the total internal flow as a percentage of stroke volume during systole (IFF(systole)), diastole (IFF(diastole)), or the whole cycle (IFF(whole)). RESULTS: IFF(whole) was significantly increased in the patients (9.9 +/- 5.0% vs. 1.5 +/- 0.5% in the controls, P < 0.001). An IFF(whole) threshold of 4% discriminated between patients and controls with 90% sensitivity and 100% specificity. IFF(diastole) (2.3 +/- 0.8%) was greater than IFF(systole) (0.8 +/- 0.5%) in the normal controls (P < 0.001) while the patients had similar IFF(diastole) (7.8 +/- 4.2%) and IFF(systole) (12.0 +/- 7.8%). CONCLUSION: Left ventricular internal flow fraction can be quantified from standard CMR images. In this preliminary study, Left ventricular internal flow fraction discriminated patients with dyssynchronous heart failure from normal controls with 95% accuracy.     

Whole heart magnetization‐prepared steady‐state free precession coronary vein MRI

Purpose

To compare two coronary vein imaging techniques using whole‐heart balanced steady‐state free precession (SSFP) and a targeted double‐oblique spoiled gradient‐echo (GRE) sequences in combination with magnetization transfer (MT) preparation sequence for tissue contrast improvement.

Materials and Methods

Nine healthy subjects were imaged with the proposed technique. The results are compared with optimized targeted MT prepared GRE acquisitions. Both quantitative and qualitative analyses were performed to evaluate each imaging method.

Results

Whole‐heart images were successfully acquired with no visible image artifact in the vicinity of the coronary veins. The anatomical features and visual grading of both techniques were comparable. However, the targeted small slab acquisition of the left ventricular lateral wall was superior to whole‐heart acquisition for visualization of relevant information for cardiac resynchronization therapy (CRT) lead implantation.

Conclusion

We demonstrated the feasibility of whole‐heart coronary vein MRI using a 3D MT‐SSFP imaging sequence. A targeted acquisition along the lateral left ventricular wall is preferred for visualization of branches commonly used in CRT lead implantation. J. Magn. Reson. Imaging 2009;29:1293–1299. © 2009 Wiley‐Liss, Inc.     

磁共振门静脉血流动力学改变与肝功能相关性

目的：通过磁共振相位对比法成像测量慢性肝病患者门静脉主干的平均血流速度及每分血流量,并将其与肝功能终末期肝病模型（MELD）评分进行相关性研究,探讨磁共振相位对比法成像在评价慢性肝病肝功能的应用价值。方法：60例慢性肝病患者行肝脏磁共振相位对比法成像（包括15例治疗前后的随访复查）,测量病例组60例及15例治疗前、后门静脉主干的平均血流速度及每分血流量,分析它们与MELD评分的相关性。结果：病例组60例门静脉主干的平均血流速度与MELD评分有显著性负相关（R=-0.40,P〈0.05）,每分血流量与MELD评分无显著性相关（R=-0.22,P〉0.05）。治疗前后15例门静脉主干的平均血流速度变化量与MELD评分变化量有显著性负相关（R=-0.69,P〈0.01）,每分血流量变化量与MELD评分变化量也有显著性负相关（R=-0.51,P〈0.05）。结论：门静脉主干的平均血流速度及每分血流量与MELD评分有较密切的相关性,对慢性肝病患者的肝功能评估及疗效观测有较高的临床应用价值。     

Fast, high-resolution in vivo cine magnetic resonance imaging in normal and failing mouse hearts on a vertical 11.7 T system

PURPOSE: To establish fast, high-resolution in vivo cine magnetic resonance imaging (cine-MRI) on a vertical 11.7-T MR system and to investigate the stability of normal and failing mouse hearts in the vertical position. MATERIALS AND METHODS: To optimize the method on a high-field system, various MR-related parameters, such as relaxation times and the need for respiratory gating, were quantitatively investigated. High-resolution cine-MRI was applied to normal mice and to a murine heart failure model. Cardiac functional parameters were compared to matched mice imaged previously on a horizontal MR system. RESULTS: A T(1) of 1.10 +/- 0.27 seconds and a T(2) of 18.5 +/- 3.9 msec were measured for murine myocardial tissue. A quantitative analysis also proved respiratory gating to be essential for obtaining artifact-free cine images in the vertical position at this field strength. Cardiac functional parameters of mice, obtained within one hour, agreed well with those from previous studies of mice in the horizontal position. CONCLUSION: This work shows that MR systems with a vertical bore design can be used to accurately measure cardiac function in both normal and chronically failing mouse hearts within one hour. The increased signal-to-noise ratio (SNR) due to the higher field strength could be exploited to obtain higher temporal and spatial resolution compared to previous studies that were performed on horizontal systems with lower field strengths.     

High-resolution anatomic, diffusion tensor, and magnetization transfer magnetic resonance imaging of the optic chiasm at 3T

PURPOSE: To evaluate techniques for anatomical and physiological imaging of the intracranial optic nerve (ON), optic chiasm (OC), and optic tract (OT) at 3T with the aim of visualizing axonal damage in multiple sclerosis (MS). MATERIALS AND METHODS: Imaging was performed on a 3T scanner employing a custom-designed head coil that consisted of a coil array with four coils (30 x 30 cm(2)). Oblique fast spin echo (FSE) images, magnetization transfer (MT)-enhanced 3D gradient-echo (GRE) time-of-flight (TOF) images, and line scan diffusion images (LSDI) were obtained. Full diffusion tensor (DT) analysis was performed, and apparent diffusion coefficient (ADC), fractional anisotropy (FA), and fiber direction maps were obtained. RESULTS: FSE anatomic images were obtained with an in-plane resolution of 0.39 x 0.52 mm(2). The in-plane resolution of the MT and LSDI images was 0.78 x 0.78 mm(2). The OC, intracranial ON, and OT can be seen on these images. The dominant fiber orientations in the OC, ON, and OT, as derived from the DT images, are displayed. CONCLUSION: This study shows that by using 3T and a custom-designed, four-channel head coil, it is possible to acquire high-resolution anatomical and physiological images of the OC, ON, and OT. The pilot results presented here pave the way for imaging the anterior visual pathway in patients with MS.     

Automated image registration of gated cardiac single-photon emission computed tomography and magnetic resonance imaging

PURPOSE: To develop an automatic registration method for electrocardiogram-gated myocardial perfusion single-photon emission computed tomography (SPECT) and cardiac cine-magnetic resonance imaging (MRI). MATERIALS AND METHODS: Paired myocardial perfusion SPECT (MPS) and MRI from 20 patients were considered. MR images were presegmented by heart localization based on detection of cardiac motion and optimal thresholding. A registration algorithm based on mutual information was subsequently applied to all time frames or a selected subset from both modalities. RESULTS: A preprocessing step significantly improved the accuracy of the registration when compared to automatic registration performed without preprocessing. Errors in translation parameters (T(x), T(y), T(z)) averaged (1.0 +/- 1.5, 1.1 +/- 1.3, 0.9 +/- 0.9) pixels with MRI segmentation and (4.6 +/- 3.2, 3.4 +/- 2.6, 3.0 +/- 3.4) pixels without MRI segmentation. Errors in rotation parameters (R(x), R(y), R(z)) averaged (5.4 +/- 2.9, 3.4 +/- 2.7, 4.5 +/- 3.6) degrees with MRI segmentation and (9.3 +/- 6.1, 4.8 +/- 4.3, 14.6 +/- 12.6) degrees without MRI segmentation. Error was calculated as the absolute difference between the expert manual and the automatic registration transformation. CONCLUSION: Automatic registration of gated MPS and cine MRI is possible with the use of a mutual information-based technique when MR images are presegmented. Cardiac motion can be used to isolate the left ventricle (LV) on the MR images automatically, and subsequently the segmented MR images can be coregistered with gated MPS.     

Coronary anomalies assessed by whole‐heart isotropic 3D magnetic resonance imaging for cardiac morphology in congenital heart disease

Purpose

To determine the value of whole‐heart three‐dimensional magnetic resonance imaging (MRI) for coronary artery imaging in children/adolescents with congenital heart disease (CHD).

Materials and Methods

Forty children/adolescents (median age: 14 years, range 2.6–25.8) with CHD underwent free‐breathing navigator‐gated isotropic three‐dimensional steady‐state free‐precession (3D‐SSFP) MRI for cardiac morphology. Two observers independently evaluated visibility of origin, course, vessel lengths, image quality (IQ), and contrast between coronary lumen and myocardium. A subgroup was compared with cardiac catheter.

Results

The total scan time was 6.3 ± 3.2 minutes (mean ± SD, at mean heart rate 76 ± 15/min). The mean vessel length for right coronary artery (RCA) by observer 1 was 97 ± 43 mm (observer 2: 94 ± 37 mm), for left main and anterior descending artery (LM/LAD) 91 ± 40 mm (observer 2: 90 ± 40 mm), and for left circumflex artery (LCX) 64 ± 28mm (observer 2: 66 ± 28 mm). The mean vessel contrast was 0.34 ± 0.05 (range: 0.23–0.45; maximum = 1, minimum = 0). On a 4‐level score (1 = nondiagnostic, 4 = excellent), mean IQ scores ranged between 2.3–2.9 (±0.8–1.0). Both observers agreed on the presence/proximal course of RCA in 40/40, LM/LAD in 38/40, and LCX in 36/40 patients. There was complete agreement with invasive coronary angiography available in 12/40 patients (six anomalies).

Conclusion

Isotropic whole‐heart 3D‐MRI for cardiac morphology allows reliable discrimination between normal and abnormal coronary anatomy in children/adolescents with CHD. J. Magn. Reson. Imaging 2009;29:320–327. © 2009 Wiley‐Liss, Inc.     

Evaluation of mechanical dyssynchrony and myocardial perfusion using phase analysis of gated SPECT imaging in patients with left ventricular dysfunction

Background. Using phase analysis of gated single photon emission computed tomography (SPECT) imaging, we examined the relation between myocardial perfusion, degree of electrical dyssynchrony, and degree of SPECT-derived mechanical dyssynchrony in patients with left ventricular (LV) dysfunction. Methods and Results. We retrospectively examined 125 patients with LV dysfunction and ejection fraction of 35% or lower. Fourier analysis converts regional myocardial counts into a continuous thickening function, allowing resolution of phase of onset of myocardial thickening. The SD of LV phase distribution (phase SD) and histogram bandwidth describe LV phase dispersion as a measure of dyssynchrony. Heart failure (HF) patients with perfusion abnormalities have higher degrees of dyssynchrony measured by median phase SD (45.5° vs 27.7°, P<.0001) and bandwidth (117.0° vs 73.0°, P=.0006). HF patients with prolonged QRS durations have higher degrees of dyssynchrony measured by median phase SD (54.1° vs 34.7°, P<.0001) and bandwidth (136.5° vs 99.0°, P=.0005). Mild to moderate correlations exist between QRS duration and phase analysis indices of phase SD (r=0.50) and bandwidth (r=0.40). Mechanical dyssynchrony (phase SD >43°) was 43.2%. Conclusions. HF patients with perfusion abnormalities or prolonged QRS durations have higher degrees of mechanical dyssynchrony. Gated SPECT myocardial perfusion imaging can quantify myocardial function, perfusion, and dyssynchrony and may help in evaluating patients for cardiac resynchronization therapy. (J Nucl Cardiol 2008;15:663-70.) This study was funded by a research grant from the Medtronic-Duke Strategic Alliance, and Dr Trimble is the primary investigator.     

Central nervous system aspergillosis: magnetic resonance imaging, diffusion-weighted imaging, and magnetic resonance spectroscopy features

Aspergillus infection is invasive in nature in the immunosuppressed population and disseminates throughout the body, with the brain being a common site. Conventional magnetic resonance imaging (MRI) combined with diffusion-weighted imaging (DWI) and magnetic resonance spectroscopy (MRS) play a life-saving role in the early diagnosis and treatment monitoring of this potentially fatal infection. We present MRI, DWI, and MRS findings of a case of central nervous system aspergillosis with treatment follow-up.     

Fast phase contrast cardiac magnetic resonance imaging: improved assessment and analysis of left ventricular wall motion

PURPOSE: To evaluate the use of CINE phase contrast magnetic resonance imaging (MRI) to assess and characterize left ventricular wall motion by two- or three-directional velocity vector fields that reflect the temporal evolution of myocardial velocities over the whole cardiac cycle.MATERIAL AND METHODS: A fast imaging protocol is presented that permits the assessment of the pixel-wise full in-plane velocity information of the beating heart within a single breath-hold measurement. Temporal resolution of the acquired images is improved by the use of high-speed gradients and application of view sharing to black blood k-space segmented gradient echo imaging. A novel tool for data analysis is presented based on correlating locally different myocardial motion patterns to averaged left ventricular velocities reflecting nonpathological myocardial function.RESULTS: Measurement protocol and postprocessing options were evaluated in a study with 16 normal volunteers. Simulations showed that correlation analysis can be used to differentiate regions with altered velocity waveforms from global radial velocities. Results of patient examinations are presented on an exemplary basis and demonstrate that correlation analysis provides an effective method for identification and classification of myocardial dynamics.CONCLUSION: Within the framework of our volunteer and patient examinations, fast phase contrast cardiac MRI has proven to be a reliable method to assess and analyze myocardial performance on the basis of two-directional velocity vector fields.     

Three-dimensional true-FISP imaging of the coronary arteries: improved contrast with T2-preparation

PURPOSE: To evaluate the effectiveness of a T2-magnetization preparation scheme for improving coronary artery imaging with true fast imaging with steady-state precession (True-FISP). MATERIALS AND METHODS: Simulations were performed to compare the blood-myocardium signal difference with no T2-preparation to that with various T2-preparation times (24, 40, and 60 msec) using an electrocardiogram (ECG)-triggered, segmented True-FISP acquisition. Seven volunteers were imaged to evaluate the effectiveness of T2-preparation for coronary artery delineation using True- FISP and to optimize the T2-preparation time. RESULTS: Simulations showed that T2-preparation improved the signal difference between blood and myocardium over that without T2-preparation. The optimal T2- preparation time was determined to be 40 msec. In volunteer studies, a T2- preparation time of 40 msec provided a significant improvement in contrast- to-noise ratio (CNR) between the coronary arteries and myocardium over that without T2-preparation. It also showed a significant improvement in visualizing the distal portions of the coronary arteries. CONCLUSION: T2-preparation improves coronary artery delineation with True-FISP.     

Numerical and experimental study of a novel phase contrast magnetic resonance (PC-MR) imaging technique: sparse interleaved referencing PC-MR imaging

PURPOSE: To use numerical simulation and experimental approaches to introduce a novel phase contrast magnetic resonance (PC-MR) data processing technique termed Sparse Interleaved Referencing PC-MR, with potential to improve accuracy, temporal resolution, and signal-to-noise ratio (SNR) of PC-MR data. MATERIALS AND METHODS: Computational fluid dynamics data were generated for a two-chamber orifice flow model simulating valvular regurgitation. The numerical results were validated and used to simulate conventional and Sparse Interleaved Referencing PC-MR data acquisitions. Common data sets were processed using conventional and Sparse Interleaved Referencing approaches and quantitative errors in velocity-time waveforms were measured and compared. In vitro phantom jet flow data and in vivo ascending aorta data were acquired and used to simulate Sparse Interleaved Referencing PC-MR. RESULTS: The Sparse Interleaved Referencing PC-MR data showed significantly better representation of the velocity-time waveform in three areas: (i) lower root-mean-square errors (9.0 +/- 1.0% versus 24.0 +/- 0.2%; P < 0.005), (ii) simulation of conventionally processed data showed a pattern of peak velocity overestimation, which was experimentally demonstrated in in vitro data, whereas overestimation of peak velocity was dramatically attenuated using Sparse Interleaved Referencing (2.8 +/- 0.4% versus 16.9 +/- 6.4%, P < 0.005), and (iii) compared with the conventional scan, an average of 119.4 +/- 26.6% (P < 0.005) SNR was realized in in vitro and in vivo Sparse Interleaved Referencing PC-MR data. CONCLUSION: Simulation and in vitro/in vivo results show that Sparse Interleaved Referencing PC-MR processed data in pulsatile and jet flow showed higher accuracy, better peak velocity representation, and improved SNR compared with the data processed using the conventional PC-MR method.     

Real-time imaging of two-dimensional cardiac strain using a harmonic phase magnetic resonance imaging (HARP-MRI) pulse sequence.

The harmonic phase (HARP) method provides automatic and rapid analysis of tagged magnetic resonance (MR) images for quantification and visualization of myocardial strain. In this article, the development and implementation of a pulse sequence that acquires HARP images in real time are described. In this pulse sequence, a CINE sequence of images with 1-1 spatial modulation of magnetization (SPAMM) tags are acquired during each cardiac cycle, alternating between vertical and horizontal tags in successive heartbeats. An incrementing train of imaging RF flip angles is used to compensate for the decay of the harmonic peaks due to both T(1) relaxation and the applied imaging pulses. The magnitude images displaying coarse anatomy are automatically reconstructed and displayed in real time after each heartbeat. HARP strain images are generated offline at a rate of four images per second; real-time processing should be possible with faster algorithms or computers. A comparison of myocardial contractility in non-breath-hold and breath-hold experiments in normal humans is presented.     

Hepatic caudate vein in Budd-Chiari syndrome: Depiction by using magnetic resonance imaging

Objective

To study the visibility of the caudate vein and its diameter on MR imaging in healthy people and in patients with Budd-Chiari syndrome.

Materials and methods

In this study there were 14 patients with Budd-Chiari syndrome and 54 healthy subjects without hepatic lesion or liver disease, all of whom had upper abdominal enhanced MRI. The visibility of the caudate vein and its diameter on MR images was compared between Budd-Chiari patients and healthy subjects, and among Budd-Chiari patients, the correlation between the visibility of caudate vein and extrahepatic collaterals were compared.

Results

Caudate vein was noted in 64% of patients with Budd-Chiari syndrome and in 7% of healthy subjects (P = 0.000). The diameter of the caudate vein visualized on MR imaging in Budd-Chiari syndrome was significantly larger than that in healthy group (7.3 ± 3.9 mm vs 2.6 ± 0.6 mm, P = 0.037). Among Budd-Chiari patients, both caudate vein and extrahepatic collateral veins were noted in 9 patients, only extrahepatic collateral veins were noted in 4 patients and neither caudate vein nor extrahepatic collateral veins were noted in 1 patient. No correlation was found between the visibility of caudate vein and that of extrahepatic collateral vein in patients with Budd-Chiari (P = 0.375).

Conclusion

Gadolinium enhanced dynamic MR imaging can visualize hepatic caudate vein frequently. The visibility and dilation of hepatic caudate veins on MR imaging in Budd-Chiari syndrome were more frequent than in control subjects. MR depiction of a caudate vein may help differentiate Budd-Chiari from cirrhosis.     

Persistent decline in longitudinal and radial strain after coronary microembolization detected on velocity encoded phase contrast magnetic resonance imaging

Purpose

To use velocity‐encoded phase contrast (PC) MRI in assessing the effect of coronary microembolization on longitudinal and radial myocardial strain.

Materials and Methods

A combined X‐ray and MR system (XMR) was used for selective left anterior descending artery catheterization and microinfarct assessment in swine (n = 6). The embolized area at risk was defined on perfusion MRI followed by administration of a 7500 count (size = 100–300 μm) of the embolic agent. Quantification of strain and microinfarction was performed at 1 h and 1 week using PC‐MRI and delayed enhancement (DE) MRI, respectively. At postmortem, sliced hearts were stained to define microinfarction.

Results

Baseline longitudinal and radial strain did not differ between area‐at‐risk and remote myocardium. The embolized territory (area at risk) showed significant decline in longitudinal strain from ?11.5 ± 3.2% to 1.8 ± 2.5% at 1 h (P < 0.05) and ?3.9 ± 1.1% at 1 week (P < 0.05). Similarly, regional radial strain progressively declined from 23.6 ± 2.5% at baseline to 12.5 ± 3.7% at 1 h (P < 0.05) and 4.8 ± 5.0% at 1 week (P < 0.01). The size of microinfarction was not significantly different between DE‐MRI and histochemical staining.

Conclusion

PC‐MRI is sensitive in assessing changes in regional longitudinal and radial strain after coronary embolization. Longitudinal and radial strain of the hyperenhanced patchy microinfarction demonstrates persistent decline over the course of 1 week. J. Magn. Reson. Imaging 2009;30:69–76. © 2009 Wiley‐Liss, Inc.

     

Mechanical dyssynchrony or myocardial shortening as MRI predictor of response to biventricular pacing?

Purpose

To investigate whether mechanical dyssynchrony (regional timing differences) or heterogeneity (regional strain differences) in myocardial function should be used to predict the response to cardiac resynchronization therapy (CRT).

Materials and Methods

Baseline mechanical function was studied with MRI in 29 patients with chronic heart failure. Using myocardial tagging, two mechanical dyssynchrony parameters were defined: the standard deviation (SD) in onset time (T_onset) and in time to first peak (T_peak,first) of circumferential shortening. Electrical dyssynchrony was described by QRS width. Further, two heterogeneity parameters were defined: the coefficient of variation (CV) in end‐systolic strain and the difference between peak septal and lateral strain (DiffSLpeakCS). The relative increase in maximum rate of left ventricle pressure rise (dP/dt_max) quantified the acute response to CRT.

Results

The heterogeneity parameters correlated better with acute response (CV: r = 0.58, DiffSLpeakCS: r = 0.63, P < 0.005) than the mechanical dyssynchrony parameters (SD(T_onset): r = 0.36, SD(T_peak,first) r = 0.47, P = 0.01, but similar to electrical dyssynchrony (r = 0.62, P < 0.001). When a heterogeneity parameter was combined with electrical dyssynchrony, the correlation increased (r > 0.70, P_incr < 0.05).

Conclusion

Regional heterogeneity in myocardial shortening correlates better with response to CRT than mechanical dyssynchrony, but should be combined with electrical dyssynchrony to improve prediction of response beyond the prediction from electrical dyssynchrony only. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.