Ursula Reiter

Magnetic resonance-derived 3-dimensional blood flow patterns in the main pulmonary artery as a marker of pulmonary hypertension and a measure of elevated mean pulmonary arterial pressure.

Background—Pulmonary hypertension is a disease characterized by an elevation in pulmonary arterial pressure that is diagnosed invasively via right heart catheterization. Such pathological altered pressures in the pulmonary vascular system should lead to changes in blood flow patterns in the main pulmonary artery. Methods and Results—Forty-eight subjects (22 with manifest pulmonary hypertension, 13 with latent pulmonary hypertension, and 13 normal control subjects) underwent time-resolved 3D magnetic resonance phase-contrast imaging of the main pulmonary artery. Velocity fields that resulted from measurements were calculated, visualized, and analyzed with dedicated software. Main findings were as follows: (1) Manifest pulmonary hypertension coincides with the appearance of a vortex of blood flow in the main pulmonary artery (sensitivity and specificity of 1.00, 95% confidence intervals of 0.84 to 1.00 and 0.87 to 1.00, respectively), and (2) the relative period of existence of the vortex correlates significantly with mean pulmonary arterial pressure at rest (correlation coefficient of 0.94). To test the diagnostic performance of the vortex criterion, we furthermore investigated 55 patients in a blinded prospective study (22 with manifest pulmonary hypertension, 32 with latent pulmonary hypertension, and 1 healthy subject), which resulted in a sensitivity of 1.00 and specificity of 0.91 (95% confidence intervals of 0.84 to 1.00 and 0.76 to 0.98, respectively). Comparison of catheter-derived mean pulmonary artery pressure measurements and calculated mean pulmonary artery pressure values resulted in a standard deviation of differences of 3.6 mm Hg. Conclusions—Vortices of blood flow in the main pulmonary artery enable the identification of manifest pulmonary hypertension. Elevated mean pulmonary arterial pressures can be measured from the period of vortex existence.

The Emerging Role of Magnetic Resonance Imaging in the Diagnosis and Management of Pulmonary Hypertension

Pulmonary hypertension is a life-threatening chronic disorder of the pulmonary circulation. Elevated pressure and resistance in the pulmonary vessels lead to progressive right heart failure which results in functional limitations and ultimately the death of most patients. Thus, the monitoring of right ventricular (RV) function is of great importance. Cardiac magnetic resonance imaging (cardiac MRI) has several advantages over other imaging methods. The use of cine acquisition techniques allows precise description of characteristic volumetric and functional variables, such as right ventricular volumes, muscle mass, stroke volume, ejection fraction, or cardiac output. Impaired right ventricular contractility and function have also been assessed using measures like ventricular septal bowing and pressure-volume loops. MRI investigations have been performed to monitor medical treatment, and the improvement in well-established prognostic factors, such as the 6-min walk, were correlated with measures of right ventricular function. Flow-derived parameters of the pulmonary arteries (such as peak velocity, acceleration time and volume, or pulmonary flow profile) are available using velocity-encoded imaging, and may detect early signs of remodelling. Additionally, magnetic resonance angiography is a promising new tool to visualise pulmonary perfusion and to diagnose chronic thromboembolic pulmonary hypertension. The purpose of this review is to summarise recent advances of cardiovascular magnetic resonance imaging, which will play an increasing role in the comprehensive diagnostic work-up of patients with pulmonary hypertension as a tool to monitor the course of the disease and to evaluate new therapeutic approaches.

Normal Diastolic and Systolic Myocardial T1 Values at 1.5-T MR Imaging: Correlations and Blood Normalization

PURPOSE To introduce blood normalization for myocardial T1 values at magnetic resonance (MR) imaging and to evaluate regional differences between systolic and diastolic myocardial T1 values in healthy subjects. MATERIALS AND METHODS This prospective study (ClinicalTrials.gov identification number, NCT01728597) was approved by the institutional review board, and volunteer informed consent was obtained. Forty healthy subjects (20 women; age range, 20-35 years) underwent electrocardiographically gated 1.5-T MR imaging. A modified Look-Locker inversion recovery sequence was used to acquire myocardial T1 maps in systole and diastole. Regional T1 values were evaluated in 16 myocardial segments; blood T1 was derived from the blood pool in the center of the left ventricular cavity. Linear regression slopes between myocardial and blood T1 values were used to normalize myocardial T1 to the mean blood T1 of the study population. Mean T1 values were compared by using the t test, with P < .05 considered to indicate a significant difference. RESULTS Mean myocardial T1 (984 msec ± 28 [standard deviation] in diastole, 959 msec ± 21 in systole) and all segmental T1 values between diastole and systole differed significantly (P < .001). Blood T1 correlated well with segmental myocardial T1 (R = 0.73 for diastole, R = 0.72 for systole). After normalization to blood T1, significant sex differences in myocardial T1 disappeared and variances in mean myocardial T1 decreased. Blood-normalized diastolic and systolic myocardial T1 values correlated strongly with each other on segmental (r = 0.72) and global (r = 0.89) levels. Subregional myocardial T1 distribution characteristics in diastole were similar to those in systole. CONCLUSION In normal myocardium, diastolic and systolic myocardial T1 values differ significantly but correlate strongly. Blood normalization eliminates sex differences in myocardial T1 values and reduces their variability.

Evaluation of elevated mean pulmonary arterial pressure based on magnetic resonance 4D velocity mapping: comparison of visualization techniques.

Purpose Three-dimensional (3D) magnetic resonance phase contrast imaging (PC-MRI) allows non-invasive diagnosis of pulmonary hypertension (PH) and estimation of elevated mean pulmonary arterial pressure (mPAP) based on vortical motion of blood in the main pulmonary artery. The purpose of the present study was to compare the presence and duration of PH-associated vortices derived from different flow visualization techniques with special respect to their performance for non-invasive assessment of elevated mPAP and diagnosis of PH. Methods Fifty patients with suspected PH (23 patients with and 27 without PH) were investigated by right heart catheterization and time-resolved PC-MRI of the main pulmonary artery. PC-MRI data were visualized with dedicated prototype software, providing 3D vector, multi-planar reformatted (MPR) 2D vector, streamline, and particle trace representation of flow patterns. Persistence of PH-associated vortical blood flow (tvortex) was evaluated with all visualization techniques. Dependencies of tvortex on visualization techniques were analyzed by means of correlation and receiver operating characteristic (ROC) curve analysis. Results tvortex values from 3D vector visualization correlated strongly with those from other visualization techniques (r = 0.98, 0.98 and 0.97 for MPR, streamline and particle trace visualization, respectively). Areas under ROC curves for diagnosis of PH based on tvortex did not differ significantly and were 0.998 for 3D vector, MPR vector and particle trace visualization and 0.999 for streamline visualization. Correlations between elevated mPAP and tvortex in patients with PH were r = 0.96, 0.93, 0.95 and 0.92 for 3D vector, MPR vector, streamline and particle trace visualization, respectively. Corresponding standard deviations from the linear regression lines ranged between 3 and 4 mmHg. Conclusion 3D vector, MPR vector, streamline as well as particle trace visualization of time-resolved 3D PC-MRI data of the main pulmonary artery can be employed for accurate vortex-based diagnosis of PH and estimation of elevated mPAP.

Blood Flow Vortices along the Main Pulmonary Artery Measured with MR Imaging for Diagnosis of Pulmonary Hypertension

PURPOSE To approximate the functional relationship between invasively measured mean pulmonary arterial pressure (mPAP) and the phase-contrast magnetic resonance (MR) imaging-derived duration of vortical blood flow along the main pulmonary artery and to analyze its applicability for noninvasive diagnosis of pulmonary hypertension (PH) and borderline mPAP. MATERIALS AND METHODS The local ethics review board approved this prospective study of 145 patients suspected of having PH (69 patients with PH, 19 patients with borderline mPAP, and 57 patients with normal mPAP) who underwent right heart catheterization (RHC) and three-directional phase-contrast MR imaging of the main pulmonary artery. Velocity fields were viewed with dedicated software and evaluated for the duration of vortical blood flow in the main pulmonary artery (tvortex, the percentage of cardiac phases with vortex present). The relationship between mPAP at RHC and tvortex was assessed by means of a segmented linear regression model, and by Bland-Altman and receiver operating characteristic curve analyses. RESULTS The relationship between mPAP and tvortex was described adequately (R(2) = 0.95) as linearly increasing, from tvortex of 0% (mPAP ≤ 16.0 mm Hg) with a slope of 1.59% per millimeter of mercury. The standard deviation between mPAP values derived from RHC and those estimated by using tvortex was 3.9 mm Hg. The area under the curve for tvortex-based diagnosis of PH was 0.994 (95% confidence interval [CI]: 0.982, 0.998), and the calculated PH cut-off value (tvortex ≥ 14.3%) resulted in sensitivity of 0.97 (95% CI: 0.90, 0.99) and specificity of 0.96 (95% CI: 0.89, 0.99). Vortical blood flow with tvortex less than 14.3% was specific for borderline mPAP. CONCLUSION Duration of vortical blood flow in the main pulmonary artery that is determined by using phase-contrast MR imaging allows accurate estimation of elevated mPAP and diagnosis of PH. Clinical trial registration no. NCT00575692.

Clinical applications of cardiovascular magnetic resonance.

The clinical role of magnetic resonance in diseases of the heart and great vessels is rapidly evolving. Cardiovascular magnetic resonance (CMR) has become an established non-invasive imaging modality for the assessment of various cardiac disorders, such as congenital heart disease, cardiac masses, cardiomyopathies, aortic and pericardial diseases. Moreover, due to its accuracy and reproducibility, CMR is currently considered the gold standard for quantification of ventricular volumes, function, and mass. Thus, this technique is ideally suited to assess the efficacy of therapeutic interventions on ventricular hypertrophy and remodelling, which may allow a reduction in sample size to show clinically relevant effects. Comprehensive functional assessment is possible by CMR due to its capability to measure flow velocity and flow volume, which is a basic requirement to quantify lesion severity in valvular heart disease. Within the past years, major technical advances have considerably improved acquisition speed and image quality making CMR a useful tool for the evaluation of patients with ischaemic heart disease. Although the clinical robustness of coronary magnetic resonance angiography still needs improvement, CMR currently provides valuable information to detect reversible ischemia, myocardial infarction, and residual viability. In this review we will present in detail the well-established indications of CMR accompanied by an outlook on new applications that are likely to enter the clinical arena in the near future.

Impact of 13.56-MHz radiofrequency identification systems on the quality of stored red blood cells

BACKGROUND: Radiofrequency identification (RFID) technology is emerging as one of the most pervasive computing technologies due to its broad applicability. Storage of red blood cells (RBCs) is a routine procedure worldwide. Depending on the additive solution, RBCs can be stored at 4 ± 2°C up to 49 days. To support the decision of discarding or further using a blood product, temperature measurement of each unit could be provided by RFID application. The safety evaluation of RFID devices was demonstrated in a regulatory agency required study. It has been concluded in limit tests that high frequency–based RFID technology performed safely for blood products; therefore, a longer exposure of radiofrequency (RF) energy on blood units was performed in this study to detect any biologic effects in RBC samples.

Core and surface temperatures in a red-blood-cell unit during storage and transport.

Background and Objectives  Temperature tracing of stored red‐blood‐cell concentrates (RBCs) is inevitable with respect to RBC quality control. RBC temperature, which should not exceed 10°C, is usually assessed by devices attached to the surface of the RBC pouch, assuming that surface temperature adequately represents the thermal state of RBC. We investigated under which conditions this assumption is true.

Gd-EOB-DTPA enhanced MRI of the liver: correlation of relative hepatic enhancement, relative renal enhancement, and liver to kidneys enhancement ratio with serum hepatic enzyme levels and eGFR.

OBJECTIVES To assess the correlation of relative hepatic enhancement (RHE), relative renal enhancement (RRE) and liver to kidneys enhancement ratio (LKR) with serum hepatic enzyme levels and eGFR in Gd-EOB-DTPA enhanced MRI of the liver and to assess threshold levels for predicting enhancement of the liver parenchyma. METHODS Data of 75 patients who underwent Gd-EOB-DTPA enhanced MRI of the liver were collected. Images were obtained before contrast injection, during the early arterial phase, late arterial phase, venous phase, delayed phase, and hepatobiliary phase which was 20 min after Gd-EOB-DTPA administration. Signal intensity of the liver and the kidneys in all phases was defined using region-of-interest measurements for relative enhancement calculation. Serum hepatic enzyme levels and eGFR were available in all patients. Spearman correlation test was used to test the correlation of RHE, RRE and LKR with serum hepatic enzyme levels and eGFR. RESULTS In the hepatobiliary phase all serum hepatic enzymes were significantly correlated with RHE; total bilirubin (TBIL) and cholin esterase (CHE) showed strongest correlations. TBIL and CHE were significantly correlated with RRE in the arterial phases. TBIL and CHE were significantly correlated with LKR in the arterial phase and hepatobiliary phase. eGFR showed no correlation. CONCLUSIONS In Gd-EOB-DTPA enhanced MRI, TBIL and CHE levels may predict RHE, RRE and LKR.

Intimal Sarcoma of the Pulmonary Valve

Pulmonary artery intimal sarcoma is a rare tumor of the cardiovascular system. Intimal sarcoma of the pulmonary valve itself has not been described. Embolization into pulmonary arteries originating from the pulmonary valve intimal sarcoma can mimic chronic thromboembolic pulmonary hypertension and mislead the diagnosis. We present and discuss a patient initially diagnosed as chronic thromboembolic pulmonary hypertension, treated by pulmonary endarterectomy. After 24 months, a tumor of the pulmonary valve was detected by echocardiography. The patient underwent removal and replacement of the pulmonary valve. Histology revealed pulmonary valve intimal sarcoma.