Time course of contrast enhancement patterns after Gd-BOPTA in correlation to myocardial infarction and viability: a feasibility study.

Our objective was to analyze contrast enhancement patterns (CEP) and their time course after myocardial infarction (MI) following injection of Gd-BOPTA in correlation with recovery of regional function. Seven patients with subacute MI (18 +/- nine days) were examined before, as well as three and six (n = six) months after, revascularization of the infarct-related artery. Regional wall motion abnormalities were assessed by cine-MRI, and repetitive images of one representative slice were acquired up to 45 minutes after 0.05 mmol/kg Gd-BOPTA using a T1-w TSE-sequence. Two patients showed mid-wall/subendocardial, one patient subendocardial enhancement of MI associated with mechanical improvement after revascularization. Three patients without improvement revealed a mid-wall hypoenhanced zone within the first five minutes after injection, which was unchanged at follow-up. One patient with partial functional improvement showed transmural enhancement and a mid-wall hypoenhanced zone in adjacent areas. With this feasibility study, we concluded that mid-wall and/or subendocardial enhancement after Gd-BOPTA was associated with viable myocardium, whereas detection of microvascular obstruction correlating with scar formation is suggested by mid-wall hypoenhancement within the first five minutes after injection.

Assessment of myocardial infarction in humans with (23)Na MR imaging: comparison with cine MR imaging and delayed contrast enhancement.

PURPOSE: To demonstrate the feasibility of sodium 23 ((23)Na) magnetic resonance (MR) imaging for assessment of subacute and chronic myocardial infarction and compare with cine, late enhancement, and T2-weighted imaging. MATERIALS AND METHODS: Thirty patients underwent MR imaging 8 days +/- 4 (subacute, n = 15) or more than 6 months (chronic, n = 15) after myocardial infarction by using a (23)Na surface coil with a double angulated electrocardiogram-triggered three-dimensional gradient-echo sequence at 1.5 T. In addition, cine, inversion-recovery gradient-echo, and, in the subacute group, T2-weighted images (n = 9) were obtained. Myocardial infarction mass was depicted as elevated signal intensity or wall motion abnormalities and expressed as a percentage of total left ventricular mass for all modalities. Correlations were tested with correlation coefficients. RESULTS: All patients after subacute infarction and 12 of 15 patients with chronic infarction had an area of elevated (23)Na signal intensity that significantly correlated with wall motion abnormalities (subacute; r = 0.96, P <.001, and chronic; r = 0.9, P <.001); three patients had no wall motion abnormalities or elevated (23)Na signal intensity. Only 10 patients in the subacute and nine in the chronic group revealed late enhancement; significant correlation with (23)Na MR imaging occurred only in subacute group (r = 0.68, P <.05). Myocardial edema in subacute infarction correlated (r = 0.71, P <.05) with areas of elevated (23)Na signal intensity but was extensively larger. CONCLUSION: (23)Na MR imaging demonstrates dysfunctional myocardium caused by subacute and chronic myocardial infarction.

Optimization of automatic bolus tracking for timing of the arterial phase of helical liver CT.

The aim of this study was to optimize bolus tracking for timing of the arterial phase of biphasic helical liver CT and to compare optimized bolus tracking to a standard delay. One hundred fifty patients were examined with six protocols: 5- or 10-s delay after triggering at a threshold of 50 or 75 or 100 HU enhancement in the aorta at the origin of the celiac arteries after injection of 120 ml contrast material at 3 ml/s. Optimal arterial enhancement was defined as 20-30% of hepatic enhancement in portal venous phase. Another 50 patients were examined with the optimized protocol and compared to 50 gender- and age-matched patients who underwent a 25-s standard delay. A 10-s delay after the 75-HU threshold resulted in the most patients with an optimal arterial phase (p < 0.01). Thirty-one of 75 patients examined with this protocol showed optimal early liver enhancement. Bolus tracking compared with standard delay revealed only a trend for a difference (p = 0.07). The outcome of automatic bolus tracking differs depending on the protocol used; however, optimal arterial phase imaging was seen in only 41% of patients, indicating only a trend for superior timing compared with a standard delay.

Breath-hold 3D MR coronary angiography with a new intravascular contrast agent (feruglose)--first clinical experiences.

Demonstration of the initial results of breath-hold 3D MR coronary angiography with patients using a new intravascular contrast agent (feruglose). Contrast-enhanced 3D MR-coronary angiography was performed in 5 patients with coronary artery disease after administration of feruglose in three different doses (0.5 (n = 3), 2, 5 mg Fe/kg body weight for each patient). MR coronary angiography was performed with an ECG-triggered 3D-FLASH-sequence during breath-hold at 1.5 T (TR 6.8 ms, TE 2.5 ms, flip-angle 30 degrees ). To reduce data acquisition time, only the two anterior elements of the phased-array body coil were activated. The data acquisition window within the cardiac cycle ranged between 217-326 ms depending on the matrix. Signal-to-noise (SNR) and contrast-to-noise ratios (CNR) of the coronary arteries were analyzed, and the results for the detection of coronary artery stenoses were compared with those obtained by conventional coronary angiography. SNR and CNR revealed an improved image quality at a dose of 2 mg Fe/kg compared with the lower dose, but no further improvement was obtained by rising the dose to 5 mg Fe/kg. Except for the left circumflex artery of one patient, at minimum the proximal parts of all four main coronary arteries could be imaged for all patients. Within the visible parts of the coronary arteries, six of eight significant coronary stenoses were identified correctly. Imaging of the proximal parts of the coronary arteries including detection of stenoses is possible during breath-hold using an intravascular contrast agent.

Deep venous thrombosis and consecutive pulmonary embolism as the first sign of an ovarian cancer: MR angiography using an intravascular contrast agent (CLARISCAN).

We describe a case of progressive deep venous thrombosis and chest pain studied by contrast-enhanced magnetic resonance (MR) angiography with the new intravascular contrast medium CLARISCAN (NC100150 Injection). Combined MR venography and angiography demonstrated pelvic vein thrombosis and consecutive pulmonary embolism caused by a large abdominal tumor, diagnosed as an ovarian cancer after surgery. The potential role of an intravascular contrast medium for studying the vascular system in multiple regions of the body within a single examination without the need for bolus timing is discussed. J. Magn. Reson. Imaging 2000;12:497-500.

Changes in left and right ventricular cardiac function after valve replacement for aortic stenosis determined by cine MR imaging.

The purpose of this study was to determine the changes in function of both the left and the right ventricles (LV, RV) before and after aortic valve replacement (AVR), compared with age-matched healthy volunteers using magnetic resonance (MR) imaging. Fourteen patients with aortic stenosis underwent MR imaging (1.5 T) before and 3 (n = 14) and 12 (n = 9) months after surgical valve replacement. An electrocardiographically triggered two-dimensional cine fast low-angle shot sequence was used for the evaluation of absolute values and indices related to 1 m(2) body surface area for function, mass, and LV wall thickening. Fourteen age-matched healthy volunteers served as controls. Before surgery, all patients showed significant abnormalities of LV mass and function, whereas RV mass and function were not different from those of volunteers and remained mostly unchanged. After surgery, normalization of LV ejection fraction, absolute mass, and end-systolic wall thickness was observed, whereas the LV mass index failed to normalize, and LV volumes remained elevated. Aortic stenosis combined with a significant, but not severe reduction in LV function only affects the LV, whereas the RV remains unaffected at this stage of disease. AVR leads to improved LV function and reduced hypertrophy, but without normalization of LV volumes or the LV mass index within 1 year.

Analysis of first-pass and delayed contrast-enhancement patterns of dysfunctional myocardium on MR imaging: use in the prediction of myocardial viability.

OBJECTIVE: The purpose of the study was to analyze first-pass and delayed contrast-enhancement patterns of dysfunctional myocardial regions on MR imaging after injection of gadopentetate dimeglumine to predict myocardial viability in patients with coronary artery disease. SUBJECTS AND METHODS: Twelve patients with wall motion abnormalities and related coronary artery disease revealed by conventional coronary angiography underwent MR imaging at 1.5-T before and 3 months after revascularization therapy. Short-axis images were acquired using a cine gradient-echo sequence. Each slice was divided into eight segments. Overall, 73 segments with impaired contractility were imaged during the first-pass and 14 +/- 2 min after injection of 0.05-mmol/kg gadopentetate dimeglumine at a flow of 3 ml/sec using a T1-weighted turbo fast low-angle shot sequence. Improved systolic wall thickening 3 months after revascularization served as the criterion of viability. RESULTS: At study entry, 26 dysfunctional segments showed delayed hyperenhancement compared with the adjacent functional segments within the same slice, and 47 did not reveal hyperenhancement. After revascularization, 25 (96%) of the 26 hyperenhanced segments did not recover function, whereas 39 (83%) of the 47 segments without hyperenhancement showed mechanical improvement. Segment-related sensitivity and specificity for the correlation of lack of delayed hyperenhancement with myocardial viability were 39 (98%) of 40 and 25 (76%) of 33, respectively. Hypoenhancement during first-pass did not serve as a reliable criterion of viability. CONCLUSION: Evidence of delayed hyperenhancement of dysfunctional myocardium may be used to predict lack of mechanical improvement or nonviability, whereas the lack of hyperenhancement can be correlated with improvement of regional contractility or viability after revascularization.

Detection of myocardial viability by low-dose dobutamine Cine MR imaging.

The purpose of this work was to test the diagnostic value of dobutamine stress magnetic resonance imaging (MRI) for predicting recovery of regional myocardial contractility after revascularization. Cardiac wall motion abnormalities are due to either non-viable and/or scarred, or viable, but hibernating, myocardial tissue. Dobutamine stress leads to increased systolic wall thickening only in viable myocardium. Twenty-five patients with akinetic or dyskinetic myocardial regions were examined with a Cine FLASH-2D sequence at rest and during dobutamine stress (10 microg/kg/min). Patients were re-examined at rest 3, and in case of persisting wall motion defects, 6 months after revascularization. Criterion of viability was increasing end-systolic wall thickening during stress and/or at follow-up. Akinetic regions related either to the LAD (n = 19) or to the RCA (n = 6) were judged viable if > or = 50% of the affected segments improved. MR studies were completed in all subjects without arrhythmia or need for early terminations due to symptoms. Sensitivity, specificity, and positive predictive value for the prediction of myocardial viability were 61%, 90%, and 87% for the segment-related analysis, and 76%, 100%, and 100% for the patient-related analysis based on coronary artery distribution, respectively. Dobutamine stress MRI allows to predict global functional recovery of akinetic myocardial regions after revascularization with a high positive predictive value and high specificity.

Three-dimensional MR coronary angiography using the navigator technique compared with conventional coronary angiography.

OBJECTIVE: We evaluated the diagnostic accuracy of three-dimensional (3D) MR coronary angiography with the navigator technique for the detection of coronary artery stenoses in comparison with that of conventional radiographic angiography. SUBJECTS AND METHODS: Thirty patients with coronary artery disease were examined with an ECG-triggered 3D fast low-angle shot sequence using retrospective respiratory gating and the navigator technique on a 1.5-T MR scanner. The data set was evaluated as a 3D view with a surface rendering technique. RESULTS: Imaging of the proximal coronary arteries was possible in all patients. The average visualized lengths of the left main, left anterior descending, left circumflex, and right coronary arteries were 1.9+/-0.5 cm (mean +/- SD), 5.2+/-2.3 cm, 4.2+/-1.9 cm, and 5.2+/-2.5 cm, respectively. Irregular breathing reduced image quality in seven of the 30 patients, making diagnosis of stenoses impossible. In the 77% of patients whose examinations resulted in high-quality images, the sensitivity and specificity for detection of significant stenoses and occlusions in all four main coronary arteries were 81% and 89%, respectively. CONCLUSION: The navigator technique allows reproducible imaging of the proximal course of coronary arteries. This technique obviates breath-hold studies, thus allowing more patients to be examined. In patients whose examinations resulted in high-quality images, significant coronary artery lesions could be seen. However, for widespread clinical use, further technical improvement is necessary to increase sensitivity and specificity.

Cine MR imaging after myocardial infarction--assessment and follow-up of regional and global left ventricular function.

Myocardial infarction often leads to regional wall motion defects and in case of large defects to remodeling of the left ventricle. With this study, changes in regional and global myocardial function of 12 patients 3 weeks after myocardial infarction and after revascularization therapy were determined using MRI. Cine MRI was performed at study entry at rest and during low-dose dobutamine stimulation. All patients were re-examined at rest 3 and 6 months after the revascularization, including analysis of wall thickening and of left ventricular end-diastolic volume index (LVEDVI), end-systolic volume index (LVESVI), ejection fraction (LVEF), and mass index. After revascularization. 6 patients with stress-induced improvement of regional wall thickening recovered, 4 patients without improvement did not, but 2 patients without stress-induced improvement of wall thickening also recovered. Concerning global cardiac function, patients with mainly improved regional wall motion also showed a lower LVESVI and a higher LVEF than patients without improvement of regional contractility 6 months after revascularization in comparison to study entry. In conclusion, improvement of global myocardial function after revascularization is higher in patients with improved contractility in the infarcted region. The extent of the response of regions with wall motion defects to dobutamine stress correlates with the actual improvement after revascularization, and, therefore, dobutamine stress MRI may be helpful in selecting patients that will have a higher benefit from a revascularization therapy.