Clinical ADC measurements of abdominal organs and lesions using parallel imaging appear to be reliable and useful, and the effect of parallel imaging on calculated values is considered to be minimal.

Purpose: To assess regional differences in quantitative pulmonary perfusion parameters, i.e., pulmonary blood flow (PBF), mean transit time (MTT), and pulmonary blood volume (PBV) in the entire lung on a pixel-by-pixel basis in normal volunteers and pulmonary hypertension patients. Materials and Methods:Three-dimensional ultrafast dynamic contrast-enhanced MR imaging was performed in 15 normal volunteers and 25 patients with pulmonary hypertension. From the signal intensity-time course curves, PBF, MTT and PBV maps were generated using deconvolution analysis, indicator dilution theories, and the central volume principle, on a pixel-by-pixel basis. From pulmonary perfusion parameter maps of normal volunteers and pulmonary hypertension patients, regional PBF, MTT, and PBV were statistically evaluated.Results: Regional PBF, MTT, and PBV showed significant differences in the gravitational and isogravitational directions (P Ͻ 0.05). The quantitative pulmonary perfusion parameter maps demonstrated significant differences between normal volunteers and pulmonary hypertension patients (P Ͻ 0.05). Conclusion:Three-dimensional ultrafast dynamic contrast-enhanced MR imaging is feasible for the assessment of regional quantitative pulmonary perfusion parameters in the entire lung on a pixel-by-pixel basis in normal volunteers and pulmonary hypertension patients.

No abstract

With the advent of thrombolytic therapy, hemorrhagic myocardial infarction (HMI) has been observed in experimental and human autopsy studies. However, its clinical implications remain undetermined, because of the absence of a reliable method to detect its presence in vivo. This study was designed to evaluate the clinical implications of HMI detected by magnetic resonance (MR) imaging in vivo after coronary reperfusion. Thirty-nine patients with acute myocardial infarction (AMI) were studied. Percutaneous transluminal coronary angioplasty (PTCA) was used to reopen the occluded coronary artery. Electrocardiogram (ECG)-gated T2*-weighted gradient-echo MR imaging was performed to detect intramyocardial hemorrhage, using a 1.5-T magnet within 2 weeks after coronary reperfusion (average, 5.7 days). Thirteen patients (33%) showed intramyocardial hemorrhage as a distinct hypointense zone by gradient-echo MR imaging and 26 patients showed homogeneous intensity consistent with absence of intramyocardial hemorrhage. Coronary angiograms showed lesser development of collateral flow in the patients with HMI than in those without (81% vs. 37%). Infarct size, estimated 1 month after coronary reperfusion by thallium-201 scintigraphy, was larger among patients with HMI than in those without (37 +/- 14% vs. 21 +/- 14%, respectively, p < 0.05). Left ventricular ejection fraction at 1 month follow-up showed less recovery in patients with HMI than in those without (47 +/- 9 to 51 +/- 10%; p = 0.47, vs. 53 +/- 10 to 60 +/- 9%, respectively, p < 0.05). ECG-gated T2*-weighted gradient-echo MR imaging offers a noninvasive means of detection of intramyocardial hemorrhage in patients with reperfused AMI. HMI occurred even after primary PTCA and may be a common finding associated with severely injured myocardium.

Purpose: To compare the utility of phase contrast MR imaging (PC-MRI) for assessment of pulmonary flow and pressure estimation with that of right heart catheterization and echocardiography (cardiac US) in patients with pulmonary arterial hypertension (PAH). Materials and Methods:Twenty consecutive patients with suspected PAH underwent PC-MRI, cardiac US, and right heart catheterization. In each patient, PC-MRI was acquired by cine 2D-PC method on a 1.5 Tesla scanner, and stroke volume (SV) and pulmonary arterial systolic pressure (PASP) were assessed by using the modified Bernoulli's equation. To evaluate the agreements of SV and PASP among the three methods, correlations and limits of agreement among the three methods were statistically assessed by using the Bland-Altman's analyses. Results:The correlations and limits of agreement for SV and PASP between PC-MRI and catheterization (r ¼ 0.96, r 2 ¼ 0.94, 1.1 AE 6.9 mL and r ¼ 0.94, r 2 ¼ 0.88, À3.2 AE 14.5 mmHg, respectively) were better than between cardiac US and catheterization (r ¼ 0.01, r 2 < 0.01, 8.9 AE 42.1 mL and r ¼ 0.86, r 2 ¼ 0.72, À5.9 AE 27.7 mmHg, respectively).Conclusion: PC-MRI is more compatible with right heart catheterization than cardiac US in pulmonary flow and pressure estimation. EVALUATIONS OF PULMONARY flow and pressure are essential for proper and prompt therapy for pulmonary arterial hypertension (PAH), and many different modalities have been developed to quantify the pulmonary circulation (1,2).To assess disease severity and therapeutic effect in PAH patients, objective method for assessment of pulmonary flow and pressure has been right heart catheterization based on indicator dilution theory, which is considered the most accurate method in routine clinical practice (3). Despite accuracy of this technique, this method is invasive and cannot be adapted to all PAH patients. Therefore, other alternative noninvasive measurements are warranted. Currently, Doppler echocardiography (cardiac US) is the most widely adopted method for noninvasive measurement of pulmonary arterial pressure, and its clinical applications have already been confirmed (4,5); however, cardiac US basically has a disadvantage in quantitative measurement due to limited acoustic window especially for evaluation of pulmonary circulation and the observer dependency for data acquisition.Recently, two-dimensional (2D) or three-dimensional (3D) phase-contrast (PC) MR imaging is considered as another noninvasive method for assessment of hemodynamics of pulmonary or cardiac circulation (6-8). These techniques provide us the opportunity for accurate estimation of pulmonary circulation