Left Ventricular Outflow Tract Obstruction in Hypertrophic Cardiomyopathy: The Utility of Myocardial Strain Based on Cardiac MR Tissue Tracking.

BACKGROUND: Myocardial strain for assessment of hypertrophic cardiomyopathy (HCM) is of importance and may play a role in identifying obstruction in HCM patients. PURPOSE: To evaluate the utility of myocardial strain for detecting left ventricular (LV) outflow tract (LVOT) obstruction in HCM patients based on magnetic resonance tissue tracking. STUDY TYPE: Retrospective. POPULATION: In all, 44 adult HCM patients with LVOT obstruction and 108 adult HCM patients without LVOT obstruction. FIELD STRENGTH/SEQUENCE: 1.5 T; Steady-state free-precession cine sequence; phase-sensitive inversion-prepared segmented gradient echo sequence for late gadolinium enhancement (LGE) imaging. ASSESSMENT: Strain parameters including the local and global levels of LV myocardium and the subtraction (Sub) of myocardial strain variables between interventricular septal segments (IVSS) and noninterventricular septal segments (NIVSS) were measured for differentiating HCM with obstruction from nonobstruction. Average and maximum LV wall thickness (Average and Maximum LVWT) were also analyzed. STATISTICAL TESTS: Univariate and multivariate logistic regression analysis, area under the receiver operating characteristic (ROC) curve (AUC), intraclass correlation coefficient. RESULTS: In multivariate analysis, Average LVWT, Maximum LVWT, and the subtraction of radial peak strain (Sub Radial PS) between NIVSS and IVSS were independently associated with LVOT obstruction. The AUCs were 0.731, 0.840, and 0.890 for Average LVWT, Maximum LVWT, and Sub Radial PS, respectively. Sub Radial PS (cutoff value: 8.1%) demonstrated the highest sensitivity of 75.0% and a high specificity of 87.9% for identifying LVOT; Maximum LVWT (cutoff value: 22.9 mm) showed good sensitivity (72.7%) and specificity (83.3%). Combining Maximum LVWT >22.9 mm and Sub Radial PS > 8.1% achieved a better diagnostic performance (specificity 95.4%, sensitivity 70.5%). DATA CONCLUSION: Combining Maximum LVWT >22.9 mm and Sub Radial PS >8.1% holds promise for objectively evaluating LVOT obstruction in HCM patients with very high specificity and acceptable sensitivity. LEVEL OF EVIDENCE: 3 TECHNICAL EFFICACY STAGE: 2.

Three-Dimensional Free-Breathing Whole-Heart Coronary Magnetic Resonance Angiography at 1.5 T: Gadobutrol-Enhanced Gradient-Echo Acquisition Sequence Versus Non-Contrast-Enhanced Steady-State Free Precession Sequence.

OBJECTIVES: The objective of this study was to compare gadobutrol-enhanced gradient-echo sequence (GRE) acquisition with T2-prepared non-contrast-enhanced steady-state free precession (SSFP) in coronary magnetic resonance angiography at 1.5 T. METHODS: Twenty-one subjects successfully completed GRE and SSFP acquisition. Signal-to-noise ratio (SNR), contrast-to-noise ratio, image quality, sharpness, visibility, length, and lumen diameter of vessels were analyzed by 2 experienced radiologists. RESULTS: The SNR at whole left circumflex artery, left main artery, and proximal left descending artery (LAD) was significantly higher in SSFP acquisition (P < 0.05). The SNR of distal LAD was slightly higher in GRE acquisition (P < 0.05). The contrast-to-noise ratio at distal LAD, proximal and distal RCA were significantly higher with GRE acquisition (P < 0.05). CONCLUSIONS: Double-dose gadobutrol-enhanced GRE and unenhanced SSFP coronary magnetic resonance angiography at 1.5 T have their own characteristics, and the combined use of the 2 methods may be taken into consideration.

Assessment of the acute effects of glucocorticoid treatment on coronary microembolization using cine, first-pass perfusion, and delayed enhancement MRI.

PURPOSE: To assess the acute effects of methylprednisone treatment (MPT) on coronary microembolization (CME) by cardiac cine, first-pass perfusion, and delayed gadolinium enhancement magnetic resonance imaging (DE-MRI) in an experimental swine model. MATERIALS AND METHODS: Microembolization was established by intracoronary infusion of microspheres into the left anterior artery. Swine received placebo (n = 12) or methylprednisolone (n = 10, 30 mg/kg) intravenously 30 minutes before microembolization. Perfusion and DE-MRI was performed 6 hours after microembolization. Cine MR images of pre-/post-CME were obtained using 1.5T scanner. RESULTS: Cine MRI demonstrated relative amelioration of the post-CME myocardial contractile dysfunction in the glucocorticoid-treated group compared to the placebo group (P < 0.001). Post-CME target myocardial perfusion parameters decreased in both groups after microembolization. The extent of these decreases were the same for the embolized-to-control area ratio of maximum upslope (P = 0.245; 95% confidence interval of the difference [CID], -0.041/0.148) and time to peak ratio (P = 0.122; 95% CID, -0.201/0.026); however, the maximum signal intensity was higher in the glucocorticoid-treated group (P = 0.012; 95% CID, 0.023/0.156). DE-MRI revealed patchy hyperenhancement in all placebo pigs (n = 12/12) after microembolization, but no hyperenhanced regions in the glucocorticoid-pretreated pigs (n = 0/10). CONCLUSION: Standard, readily available, cardiac MRI techniques are useful in demonstrating post-CME myocardial dysfunction and the acute effects of glucocorticoid treatment on CME. Glucocorticoid pretreatment improves myocardial contractile dysfunction, prevents hyperenhancement, and partially ameliorates the decline of myocardial perfusion in the embolized area.

3D coronary MR angiography at 1.5 T: Volume-targeted versus whole-heart acquisition.

PURPOSE: To compare volume-targeted acquisition with whole-heart acquisition in 1.5-T free-breathing 3D coronary magnetic resonance angiography (MRA) with parallel imaging. MATERIALS AND METHODS: The major coronary arteries were imaged in 36 subjects using the whole-heart and volume-targeted acquisitions with comparable imaging parameters. The quantitative and semiquantitative data derived from these two acquisition methods were analyzed statistically, with P < 0.05 considered significant. RESULTS: Both the right coronary artery (RCA) / left circumflex artery (LCX)- and the left main (LM) / left anterior descending (LAD)-targeted acquisitions had similar results in navigator efficiencies and apparent signal-to-noise ratio (SNR) in comparison with whole-heart acquisition. Apparent contrast-to-noise ratio (CNR) of the volume-targeted imaging was significantly higher than that of the whole-heart imaging. The imaging time required for a whole-heart scan was significantly longer than each of the RCA/LCX- and LM/LAD-targeted acquisitions. However, the sum of scanning times derived from volume-targeted imaging was significantly longer than that of whole-heart acquisition. Both RCA/LCX- and LM/LAD-targeted acquisition yield higher vessel sharpness and overall image quality in comparison with whole-heart acquisition. The lengths of the major coronary arteries were not significantly different for the whole-heart and volume-targeted approaches. The whole-heart method was obviously superior to the volume-targeted method in terms of visualization of the posterior descending artery. CONCLUSION: For current 1.5-T navigator coronary MRA, volume-targeted and whole-heart acquisitions have their own advantages and the choice of methods may vary in accordance with the different aims of clinical practice.

Computed tomography of gastrohepatic ligament involvement by gastric carcinoma.

PURPOSE: This study was aimed to analyze the contrast-enhanced CT features of gastrohepatic ligament (GHL) involvement in gastric carcinoma (GC) and to evaluate the influence of GHL on the spread of GC correlating with the anatomic bases. METHODS: CT scans of 41 patients known to have GC and GHL involvement were reviewed retrospectively for the primary tumor and the GHL abnormalities, as well as the role GHL played in the spread of GC. Emphasis was placed on direct invasion, lymph node metastasis, and GHL seeding. The relationship between the accompanying ascites and the different pattern of the GHL involvement were also evaluated statistically. RESULTS: CT features of the GHL abnormalities caused by GC could be summarized as follows: (a) direct invasion (34.1%, 14 of 41), which was visualized as a regional (nine of 14) or diffuse mass (five of 14) in the GHL; (b) GHL seeding (26.8%, 11 of 41), which consists of ''smudged'' appearance (eight of 11), nodular infiltration (two of 11) and "GHL caking" (one of 11); (c) lymph node metastasis (63.4%, 26 of 41), including enlargement of lymph nodes (22 of 26) and cystic lesion (four of 26). We also found direct extension of GC into the transverse fissure and/or the liver via the GHL in three patients. Ascites, which was found in ten patients, seemed to be associated with the pattern of seeding involvement. CONCLUSIONS: GHL can be invaded by GC through several patterns and contrast-enhanced CT scan plays an important role in detecting GHL involvement in GC, which has a variety of CT manifestations. GHL may also serve as a potential conduit for the predictable spread of GC into the neighboring organs such as the liver.

3.0 T unenhanced Dixon water-fat separation whole-heart coronary magnetic resonance angiography: compressed-sensing sensitivity encoding imaging versus conventional 2D sensitivity encoding imaging.

This study was aimed to investigate 3.0 T unenhanced Dixon water-fat whole-heart CMRA (coronary magnetic resonance angiography) using compressed-sensing sensitivity encoding (CS-SENSE) and conventional sensitivity encoding (SENSE) in vitro and in vivo. The key parameters of CS-SENSE and conventional 1D/2D SENSE were compared in vitro phantom study. In vivo study, fifty patients with suspected coronary artery disease (CAD) completed unenhanced Dixon water-fat whole-heart CMRA at 3.0 T using both CS-SENSE and conventional 2D SENSE methods. We compared mean acquisition time, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and the diagnostic accuracy between two techniques. In vitro study, CS-SENSE achieved better effectiveness between higher SNR/CNR and shorter scan times using the appropriate acceleration factor compared with conventional 2D SENSE. In vivo study, CS-SENSE CMRA had better performance than 2D SENSE in terms of the mean acquisition time, SNR and CNR (7.4 ± 3.2 min vs. 8.3 ± 3.4 min, P = 0.001; SNR: 115.5 ± 35.4 vs. 103.3 ± 32.2; CNR: 101.1 ± 33.2 vs. 90.6 ± 30.1, P < 0.001 for both). The diagnostic accuracy between CS-SENSE and 2D SENSE had no significant difference on a patient-based analysis (sensitivity: 97.3% vs. 91.9%; specificity: 76.9% vs. 61.5%; accuracy: 92.0% vs. 84.0%; P > 0.05 for each). Unenhanced CS-SENSE Dixon water-fat separation whole-heart CMRA at 3.0 T can improve the SNR and CNR, shorten the acquisition time while providing equally satisfactory image quality and diagnostic accuracy compared with 2D SENSE CMRA.

Conjugates of folic acids with BSA-coated quantum dots for cancer cell targeting and imaging by single-photon and two-photon excitation.

Bovine serum albumin (BSA)-coated CdTe/ZnS quantum dots (BSA-QDs) were selected to conjugate with folic acid (FA), forming FA-BSA-QDs. This study aims to develop these small FA-BSA-QDs (less than 10 nm) for the diagnosis of cancers in which the FA receptor (FR) is overexpressed. The enhancement of cellular uptake in FR-positive human nasopharyngeal carcinoma cells (KB cells) for FA-BSA-QDs was found by means of confocal fluorescence microscopy under single-photon and two-photon excitation. The uptake enhancement for FA-BSA-QDs was further evaluated by flow-cytometric analysis in 10(4) KB cells, and was about 3 times higher than for BSA-QDs on average. The uptake enhancement was suppressed when KB cells had been pretreated with excess FA, reflecting that the enhancement was mediated by the association of FR at cell membranes with FA-BSA-QDs. When human embryonic kidney cells (293T) (FR-negative cells) and KB cells, respectively, were incubated with FA-BSA-QDs (1 µM) for 40 min, the FA-BSA-QD uptake by 293T cells was much weaker than that by KB cells, demonstrating that FA-BSA-QDs could undergo preferential binding on FR-positive cancer cells. These characteristics suggest that FA-BSA-QDs are potential candidates for cancer diagnosis.

Influence of applying nitroglycerin in whole-heart free-breathing 3D coronary MR angiography.

OBJECTIVE: The purpose of our study was to assess the impact of sublingual nitroglycerin (NTG) spray on free-breathing 3D whole-heart coronary MR angiography (MRA). SUBJECTS AND METHODS: We compared the timing parameters; measured the lumen diameter of the major coronary arteries; calculated coronary vasodilation, apparent signal-to-noise ratio (SNR), and apparent contrast-to-noise ratio (CNR); and evaluated the image quality on pre- and post-NTG coronary MRA in 15 volunteers. Statistical analysis was performed with p value less than 0.05 considered significant. RESULTS: The mean trigger delay and optimal acquisition window were shortened significantly and the mean scanning time was prolonged statistically after NTG administration. There was no significant alteration in terms of apparent SNR and apparent CNR. The lumen diameters were significantly larger in coronary MRA post-NTG than in that of pre-NTG, with an average 25.35% +/- 6.51% (SD) increase, and the left circumflex coronary artery (LCX) had slightly lower vasodilation in comparison with the right coronary artery. Image quality scores of 53 (39.3%, 53/135) segments were increased and 15 segments (11.1%, 15/135) decreased after NTG administration, and the remaining 67 segments (49.6%, 67/135) were unchanged. CONCLUSION: In general, sublingual NTG is useful for improving visualization of the coronary artery lumen and alleviating the impact of artifact. However, several alterations and disadvantages should be taken into consideration in view of the disturbed assessment of vasodilatory response in the LCX and the impaired quality in a minority of segments after NTG administration. Further studies are needed to evaluate the effect of beta-blockade on eliminating the disadvantages of sublingual NTG.

Noninvasive test of nitrate-induced coronary vasomotion by 1.5-T whole-heart 3D magnetic resonance angiography using a T2-prepared SSFP sequence.

This study was aimed to investigate the use of 1.5-T whole-heart 3D coronary MRA employing a T2-prepared SSFP sequence for assessing epicardial coronary artery vasodilation following exogenous nitrates. Navigator-gated whole-heart 3D coronary MRA was performed before and after sublingual nitroglycerin (NTG) in 22 volunteers and a T2-prepared SSFP sequence was used for imaging of coronary arteries without MR contrast agent. Coronary cross-sectional area was measured on pre- and post-NTG images of equivalent coronary segments in the major coronary arteries and whole-heart coronary vasodilation was analyzed quantitatively. Measurements were obtained by two independent investigators. Coronary vasodilation could be observed directly on multiplanar reformatted and three-dimensional volume-rendered MR images. On quantitative analysis, NTG administration results in the whole-heart coronary vasodilation by an average of 37.3 ± 12.7%. There was moderate yet significant correlation between the NTG-induced vasodilation and age (r = -0.52, P = 0.02). The mean absolute cross-sectional area of the coronary arteries was significantly higher after sublingual NTG in all the major coronary arteries. The coronary area measurements had an interobserver variability of 8 ± 3% and an intraobserver variability of 4 ± 2%. Non-contrast-enhanced 1.5-T SSFP whole-heart coronary MRA can noninvasively measure endothelium-independent coronary vasodilation over the entire heart with high feasibility and is a promising noninvasive method to explore whole-heart coronary smooth muscle cell function following exogenous nitrates in clinical practice.

A study of in vitro and in vivo MR of free-breathing whole-heart 3D coronary angiography using parallel imaging.

To evaluate parallel-imaging methods in free-breathing whole-heart 3D coronary magnetic resonance angiography and assess the navigator techniques and visualization rates of the major coronary arteries. We compared key parameters of the generalized autocalibrating partially parallel acquisition and modified sensitive encoding images in vitro phantom MRI; performed the MRA with GRAPPA parallel imaging in healthy volunteers; compared 1D- and 2D-prospective acquisition correction and analyzed the differences; and evaluated the visualization of major coronary arterial branches. GRAPPA images had higher signal-to-noise ratio and contrast-to-noise ratio and fewer aliasing artifacts. The coronary arteries were adequately visualized in 38 volunteers. 2D-PACE had a higher navigator efficiency, shorter scan time, and gave clearer reconstructed images in comparison with 1D-PACE. GRAPPA images were superior to mSENSE images. Whole-heart 3D coronary MRA along with parallel-imaging technique is a potential clinical method, and 2D-PACE is a better navigation technique than 1D-PACE.