4D Flow cardiovascular magnetic resonance consensus statement: 2023 update.

Hemodynamic assessment is an integral part of the diagnosis and management of cardiovascular disease. Four-dimensional cardiovascular magnetic resonance flow imaging (4D Flow CMR) allows comprehensive and accurate assessment of flow in a single acquisition. This consensus paper is an update from the 2015 '4D Flow CMR Consensus Statement'. We elaborate on 4D Flow CMR sequence options and imaging considerations. The document aims to assist centers starting out with 4D Flow CMR of the heart and great vessels with advice on acquisition parameters, post-processing workflows and integration into clinical practice. Furthermore, we define minimum quality assurance and validation standards for clinical centers. We also address the challenges faced in quality assurance and validation in the research setting. We also include a checklist for recommended publication standards, specifically for 4D Flow CMR. Finally, we discuss the current limitations and the future of 4D Flow CMR. This updated consensus paper will further facilitate widespread adoption of 4D Flow CMR in the clinical workflow across the globe and aid consistently high-quality publication standards.

Repeatability and reproducibility of various 4D Flow MRI postprocessing software programs in a multi-software and multi-vendor cross-over comparison study.

BACKGROUND: Different software programs are available for the evaluation of 4D Flow cardiovascular magnetic resonance (CMR). A good agreement of the results between programs is a prerequisite for the acceptance of the method. Therefore, the goal was to compare quantitative results from a cross-over comparison in individuals examined on two scanners of different vendors analyzed with four postprocessing software packages. METHODS: Eight healthy subjects (27 ± 3 years, 3 women) were each examined on two 3T CMR systems (Ingenia, Philips Healthcare; MAGNETOM Skyra, Siemens Healthineers) with a standardized 4D Flow CMR sequence. Six manually placed aortic contours were evaluated with Caas (Pie Medical Imaging, SW-A), cvi42 (Circle Cardiovascular Imaging, SW-B), GTFlow (GyroTools, SW-C), and MevisFlow (Fraunhofer Institute MEVIS, SW-D) to analyze seven clinically used parameters including stroke volume, peak flow, peak velocity, and area as well as typically scientifically used wall shear stress values. Statistical analysis of inter- and intrareader variability, inter-software and inter-scanner comparison included calculation of absolute and relative error (ER), intraclass correlation coefficient (ICC), Bland-Altman analysis, and equivalence testing based on the assumption that inter-software differences needed to be within 80% of the range of intrareader differences. RESULTS: SW-A and SW-C were the only software programs showing agreement for stroke volume (ICC = 0.96; ER = 3 ± 8%), peak flow (ICC: 0.97; ER = -1 ± 7%), and area (ICC = 0.81; ER = 2 ± 22%). Results from SW-A/D and SW-C/D were equivalent only for area and peak flow. Other software pairs did not yield equivalent results for routinely used clinical parameters. Especially peak maximum velocity yielded poor agreement (ICC ≤ 0.4) between all software packages except SW-A/D that showed good agreement (ICC = 0.80). Inter- and intrareader consistency for clinically used parameters was best for SW-A and SW-D (ICC = 0.56-97) and worst for SW-B (ICC = -0.01-0.71). Of note, inter-scanner differences per individual tended to be smaller than inter-software differences. CONCLUSIONS: Of all tested software programs, only SW-A and SW-C can be used equivalently for determination of stroke volume, peak flow, and vessel area. Irrespective of the applied software and scanner, high intra- and interreader variability for all parameters have to be taken into account before introducing 4D Flow CMR in clinical routine. Especially in multicenter clinical trials a single image evaluation software should be applied.

Arterial input functions in dynamic susceptibility contrast MRI (DSC-MRI) in longitudinal evaluation of brain metastases.

BACKGROUND: Dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) could be helpful to separate true disease progression from pseudo-progression in brain metastases when assessing the need for retreatment. However, the selection of arterial input functions (AIFs) is not standardized for analysis, limiting its use for this application. PURPOSE: To compare population-based AIFs, AIFs specific to each patient, and AIFs specific to every visit in the longitudinal follow-up of brain metastases. MATERIAL AND METHODS: Longitudinal data were collected from eight patients before treatment (6 of 8 patients) and after treatment (6-17 visits). Imaging was performed using a 1.5-T MRI system. Lesions were segmented by subtracting precontrast images from postcontrast images. Cerebral blood volume (rCBV) and cerebral blood flow (rCBF) were computed, and Pearson's product moment correlation coefficients were calculated to evaluate similarity of DSC parameters dependent on various AIF choices across time. AIF shape characteristics were compared. Parameter differences between white matter (WM) and gray matter (GM) were obtained to determine which AIF choice maximizes tissue differentiation. RESULTS: Although DSC parameters follow similar patterns in time, the various AIF selections cause large parameter variations with relative standard deviations of up to ±60%. AIFs sampled in one patient across sessions more similar in shape than AIFs sampled across patients. Estimates of rCBV based on scan-specific AIFs differentiated better between perfusion in WM and GM than patient-specific or population-based AIFs (P ≤ 0.02). CONCLUSION: Results indicate that scan-specific AIFs are the best choice for DSC-MRI parameter estimations in the longitudinal follow-up of brain metastases.

Flow evaluation software for four-dimensional flow MRI: a reliability and validation study.

PURPOSE: Four-dimensional time-resolved phase-contrast cardiovascular magnetic resonance imaging (4D flow MRI) enables blood flow quantification in multiple vessels, which is crucial for patients with congenital heart disease (CHD). We investigated net flow volumes in the ascending aorta and pulmonary arteries by four different postprocessing software packages for 4D flow MRI in comparison with 2D cine phase-contrast measurements (2D PC). MATERIAL AND METHODS: 4D flow and 2D PC datasets of 47 patients with biventricular CHD (median age 16, range 0.6-52 years) were acquired at 1.5 T. Net flow volumes in the ascending aorta, the main, right, and left pulmonary arteries were measured using four different postprocessing software applications and compared to offset-corrected 2D PC data. Reliability of 4D flow postprocessing software was assessed by Bland-Altman analysis and intraclass correlation coefficient (ICC). Linear regression of internal flow controls was calculated. Interobserver reproducibility was evaluated in 25 patients. RESULTS: Correlation and agreement of flow volumes were very good for all software compared to 2D PC (ICC ≥ 0.94; bias ≤ 5%). Internal controls were excellent for 2D PC (r ≥ 0.95, p < 0.001) and 4D flow (r ≥ 0.94, p < 0.001) without significant difference of correlation coefficients between methods. Interobserver reliability was good for all vendors (ICC ≥ 0.94, agreement bias < 8%). CONCLUSION: Haemodynamic information from 4D flow in the large thoracic arteries assessed by four commercially available postprocessing applications matches routinely performed 2D PC values. Therefore, we consider 4D flow MRI-derived data ready for clinical use in patients with CHD.

A subject-specific assessment of measurement errors and their correction in cerebrospinal fluid velocity maps using 4D flow MRI.

PURPOSE: Phase-contrast MRI (PC-MRI) of cerebrospinal fluid (CSF) velocity is used to evaluate the characteristics of intracranial diseases, such as normal-pressure hydrocephalus (NPH). Nevertheless, PC-MRI has several potential error sources, with eddy-current-based phase offset error being non-negligible in CSF measurement. In this study, we assess the measurement error of CSF velocity maps obtained using 4D flow MRI and evaluate correction methods. METHODS: CSF velocity maps of 10 patients with NPH were acquired using 4D flow MRI (velocity-encoding = 5 cm/s). Distributed phase offset error was estimated for a whole 3D background field by polynomial fitting using robust regression analysis. This estimated phase offset error was then used to correct the CSF velocity maps. The estimated error profiles were compared with those obtained using an existing 2D correction approach involving local background information near the region of interest. RESULTS: The residual standard error of the polynomial fitting against the phase offset error extracted from the measured velocities was within 0.2 cm/s. The spatial dependencies of the phase offset errors showed similar tendencies in all cases, but sufficient differences in these values were found to indicate requirement of velocity correction. Differences of the estimated errors among other correction approaches were in the order of 10-2 cm/s, and the estimated errors were in good agreement with those obtained using existing approaches. CONCLUSION: Our method is capable of estimating the measurement error of CSF velocity maps obtained from 4D flow MRI and provides quantitatively reasonable characteristics for the main CSF profile in the cerebral aqueduct in patients with NPH.

Dynamic susceptibility-contrast magnetic resonance imaging with contrast agent leakage correction aids in predicting grade in pediatric brain tumours: a multicenter study.

BACKGROUND: Relative cerebral blood volume (rCBV) measured using dynamic susceptibility-contrast MRI can differentiate between low- and high-grade pediatric brain tumors. Multicenter studies are required for translation into clinical practice. OBJECTIVE: We compared leakage-corrected dynamic susceptibility-contrast MRI perfusion parameters acquired at multiple centers in low- and high-grade pediatric brain tumors. MATERIALS AND METHODS: Eighty-five pediatric patients underwent pre-treatment dynamic susceptibility-contrast MRI scans at four centers. MRI protocols were variable. We analyzed data using the Boxerman leakage-correction method producing pixel-by-pixel estimates of leakage-uncorrected (rCBVuncorr) and corrected (rCBVcorr) relative cerebral blood volume, and the leakage parameter, K2. Histological diagnoses were obtained. Tumors were classified by high-grade tumor. We compared whole-tumor median perfusion parameters between low- and high-grade tumors and across tumor types. RESULTS: Forty tumors were classified as low grade, 45 as high grade. Mean whole-tumor median rCBVuncorr was higher in high-grade tumors than low-grade tumors (mean ± standard deviation [SD] = 2.37±2.61 vs. -0.14±5.55; P<0.01). Average median rCBV increased following leakage correction (2.54±1.63 vs. 1.68±1.36; P=0.010), remaining higher in high-grade tumors than low grade-tumors. Low-grade tumors, particularly pilocytic astrocytomas, showed T1-dominant leakage effects; high-grade tumors showed T2*-dominance (mean K2=0.017±0.049 vs. 0.002±0.017). Parameters varied with tumor type but not center. Median rCBVuncorr was higher (mean = 1.49 vs. 0.49; P=0.015) and K2 lower (mean = 0.005 vs. 0.016; P=0.013) in children who received a pre-bolus of contrast agent compared to those who did not. Leakage correction removed the difference. CONCLUSION: Dynamic susceptibility-contrast MRI acquired at multiple centers helped distinguish between children's brain tumors. Relative cerebral blood volume was significantly higher in high-grade compared to low-grade tumors and differed among common tumor types. Vessel leakage correction is required to provide accurate rCBV, particularly in low-grade enhancing tumors.

Intelligent Pore Switch of Hollow Mesoporous Organosilica Nanoparticles for High Contrast Magnetic Resonance Imaging and Tumor-Specific Chemotherapy.

Hollow mesoporous organosilica nanoparticles (HMONs) are widely considered as a promising drug nanocarrier, but the loaded drugs can easily leak from HMONs, resulting in the considerably decreased drug loading capacity and increased biosafety risk. This study reports the smart use of core/shell Fe3O4/Gd2O3 (FG) hybrid nanoparticles as a gatekeeper to block the pores of HMONs, which can yield an unreported large loading content (up to 20.4%) of DOX. The conjugation of RGD dimer (R2) onto the DOX-loaded HMON with FG capping (D@HMON@FG@R2) allowed for active tumor-targeted delivery. The aggregated FG in D@HMON@FG@R2 could darken the normal tissue surrounding the tumor due to the high r2 value (253.7 mM-1 s-1) and high r2/r1 ratio (19.13), and the intratumorally released FG as a result of reducibility-triggered HMON degradation could brighten the tumor because of the high r1 value (20.1 mM-1 s-1) and low r2/r1 ratio (7.01), which contributed to high contrast magnetic resonance imaging (MRI) for guiding highly efficient tumor-specific DOX release and chemotherapy.

Brain blood and cerebrospinal fluid flow dynamics during rhythmic handgrip exercise in young healthy men and women.

KEY POINTS: The cerebral fluid response to exercise, including the arterial and venous cerebral blood flow (CBF) and cerebrospinal fluid (CSF), currently remains unknown. We used time-resolved phase-contrast magnetic resonance imaging to assess changes in CBF and CSF flow dynamics during moderate-intensity rhythmic handgrip (RHG) exercise in young healthy men and women. Our data demonstrated that RHG increases the cerebral arterial inflow and venous outflow while decreasing the pulsatile CSF flow during RHG. Furthermore, changes in blood stroke volume at the measured arteries, veins, and sinuses and CSF stroke volume at the cerebral aqueduct were positively correlated with each other during RHG. Male and female participants exhibited distinct blood pressure responses to RHG, but their cerebral fluid responses were similar. These results collectively suggest that RHG influences both CBF and CSF flow dynamics in a way that is consistent with the Monro-Kellie hypothesis to maintain intracranial volume-pressure homeostasis in young healthy adults. ABSTRACT: Cerebral blood flow (CBF) increases during exercise, but its impact on cerebrospinal fluid (CSF) flow remains unknown. This study investigated CBF and CSF flow dynamics during moderate-intensity rhythmic handgrip (RHG) exercise in young healthy men and women. Twenty-six participants (12 women) underwent the RHG and resting control conditions in random order. Participants performed 3 sets of RHG, during which cine phase-contrast magnetic resonance imaging (PC-MRI) was performed to measure blood stroke volume (SV) and flow rate in the internal carotid (ICA) and vertebral (VA) arteries, the internal jugular vein (IJV), the superior sagittal (SSS) and straight sinuses (SRS), and CSF SV and flow rate in the cerebral aqueduct of Sylvius. Blood pressure, end-tidal CO2 (EtCO2 ), heart rate (HR), and respiratory rate were simultaneously measured during cine PC-MRI scans. Compared with control conditions, RHG showed significant elevations of HR, mean arterial pressure, and respiratory rate with a mild reduction of EtCO2 (all P < 0.05). RHG decreased blood SV in the measured arteries, veins, and sinuses and CSF SV in the aqueduct (all P < 0.05). Conversely, RHG increased blood flow in the ICA, VA, and IJV (all P < 0.05). At the aqueduct, RHG decreased the absolute CSF flow rate (P = 0.0307), which was calculated as a sum of the caudal and cranial CSF flow rates. Change in the ICA SV was positively correlated with changes in the IJV, SSS, SRS, and aqueductal SV during RHG (all P < 0.05). These findings demonstrate a close coupling between the CBF and CSF flow dynamics during RHG in young healthy adults.

Phase-contrast acceleration mapping with synchronized encoding.

PURPOSE: To develop a phase-contrast (PC) -based method for direct and unbiased quantification of the acceleration vector field by synchronization of the spatial and acceleration encoding time points. The proposed method explicitly aims at in-vitro applications, requiring high measurement accuracy, as well as the validation of clinically relevant acceleration-encoded sequences. METHODS: A velocity-encoded sequence with synchronized encoding (SYNC SPI) was modified to allow direct acceleration mapping by replacing the bipolar encoding gradients with tripolar gradient waveforms. The proposed method was validated in two in-vitro flow cases: a rotation and a stenosis phantom. The thereby obtained velocity and acceleration vector fields were quantitatively compared to those acquired with conventional PC methods, as well as to theoretical data. RESULTS: The rotation phantom study revealed a systematic bias of the conventional PC acceleration mapping method that resulted in an average pixel-wise relative angle between the measured and theoretical vector field of (7.8 ± 3.2)°, which was reduced to (-0.4 ± 2.7)° for the proposed SYNC SPI method. Furthermore, flow features in the stenosis phantom were displaced by up to 10 mm in the conventional PC data compared with the acceleration-encoded SYNC SPI data. CONCLUSIONS: This work successfully demonstrates a highly accurate method for direct acceleration mapping. It thus complements the existing velocity-encoded SYNC SPI method to enable the direct and unbiased quantification of both the velocity and acceleration vector field for in vitro studies. Hence, this method can be used for the validation of conventional acceleration-encoded PC methods applicable in-vivo.

Intra-Left Ventricular Hemodynamics Assessed with 4D Flow Magnetic Resonance Imaging in Patients with Left Ventricular Thrombus.

Left ventricular thrombus (LVT) has been identified to be crucial in patients with reduced ejection fraction (EF). Three-dimensional cine phase-contrast magnetic resonance imaging (4D flow MRI) can visualize the intra-LV vortex during diastole and quantify the maximum flow velocity (Vmax) at the apex. In this study, we investigated whether the change in the intra-LV vortex was associated with the presence of LVT in patients with cardiac disease.In total, 36 patients (63.5 ± 11.9 years, 28 men, 12/24 with/without LVT) with diffuse LV dysfunction underwent 4D flow MRI. The relative vortex area using streamline images and Vmax of blood flow toward the apex at the apical left ventricle were evaluated. The correlation between the relative vortex area and Vmax was assessed using Pearson's correlation coefficient. The ability to detect LVT was evaluated using the area under the curve (AUC) of the receiver operating characteristic.The relative vortex area was found to be smaller (27 ± 10% versus 45 ± 11%, P = 0.000026), whereas Vmax at the apical left ventricle was lower (19.1 ± 4.4 cm/second versus 27.4 ± 8.9 cm/second, P = 0.0006) in patients with LVT. Vmax at the apical left ventricle demonstrated significant correlations with the relative vortex area (r = 0.43, P = 0.01) and relative transverse length of the vortex (r = 0.45, P = 0.007). The AUC was 0.91 for the relative vortex area, whereas it was 0.80 for Vmax in the apical left ventricle.A smaller LV vortex and lower flow velocity at the LV apex were associated with LVT in patients with reduced EF.

Pulmonary flow assessment by phase-contrast MRI can predict short-term mortality of fibrosing interstitial lung diseases.

BACKGROUND: Phase-contrast magnetic resonance imaging (PC-MRI) can determine pulmonary hemodynamics non-invasively. Pulmonary hypertension causes changes in pulmonary hemodynamics and is a factor for acute exacerbation and death in interstitial lung diseases (ILD). PURPOSE: To determine associations between pulmonary hemodynamics measured by PC-MRI and short-term mortality in patients with ILD. MATERIAL AND METHODS: Pulmonary hemodynamics, measured by PC-MRI in 43 patients with ILD, were reviewed retrospectively. Evaluation parameters included heart rate, right cardiac output, average flow, average velocity, acceleration time, acceleration volume (AV), maximal change in flow rate during ejection (M), M/AV, maximum area, minimum area, and relative area change in the pulmonary artery (PA). All causes of death within one year from the day of the MRI examination were assessed by reviewing medical records. Associations between evaluation parameters and outcome were determined by univariate and multivariate Cox regression analysis. RESULTS: Six patients (13.9%) died by the one-year follow-up. Age (hazard ratio [HR] 1.116, 95% confidence interval [CI] 1.015-1.269), average flow (HR 0.932, 95% CI 0.870-0.984), average velocity (HR 0.778, 95% CI 0.573-0.976), right cardiac output (HR 0.870, 95% CI 0.758-0.967), AV (HR 0.840, 95% CI 0.669-0.985), M/AV (HR 1.008, 95% CI 1.001-1.014), and PA relative area change (HR 0.715, 95% CI 0.459-0.928) predicted death in univariate Cox analysis. Multivariate Cox analysis showed decreased right cardiac output (HR 0.547, 95% CI 0.160-0.912) and decreased PA relative area change (HR 0.538, 95% CI 0.177-0.922) were independently associated with death. CONCLUSION: Reduction in right cardiac output and decreased PA relative area change, detected by PC-MRI, were associated with increased mortality in ILD.

Validation of a mathematical model for understanding intracranial pressure curve morphology.

The physiology underlying the intracranial pressure (ICP) curve morphology is not fully understood. Recent research has suggested that the morphology could be dependent on arterial cerebral inflow and the physiological and pathophysiological properties of the intracranial cavity. If understood, the ICP curve could provide information about the patient's cerebrovascular state important in individualizing treatment in neuro intensive care patients. A mathematical model based on known physiological properties of the intracranial compartment was created. Clinical measurements from ten neuro intensive care patients in whom intracranial arterial blood inflow, venous blood outflow and cerebrospinal fluid flow over the foramen magnum had been measured with phase contrast MRI, concomitant with ICP measurements were used to validate the model. In nine patients the mathematical model was able to create an ICP curve mimicking the measured by using arterial intracranial inflow and adjusting physiological parameters of the model. The venous outflow and cerebrospinal fluid (CSF) flow over the foramen magnum predicted by the model were within physiologically reasonable limits and in most cases followed the MRI measured values in close adjunct. The presented model could produce an ICP curve in close resemblance of the in vivo measured curves. This strengthens the hypothesis that the ICP curve is shaped by the arterial intracranial inflow and the physiological properties of the intracranial cavity.

[The myocardial infarction size measuring using modern methods].

An accurate quantitative assessment of myocardium necrosis area and the viable zone (stunned and hibernating) in patients with myocardial infarction is crucial for the preoperative patient selection and predicting the cardiac surgery effectiveness. Currently, researchers and clinicians are most interested in the problem of determining the viable myocardium zone. However, only the necrosis zone area directly correlates with the patients prognosis and determines the heart pathological remodeling processes. In the distant period, the data obtained can be used to predict the post-infarction period course or for analysis the relationship of the necrosis zone with arrhythmogenesis, and a number of other indicators. Thus, the necrosis zone and the viable myocardium zone are two parameters that need to be monitored in dynamics in all patients after myocardial infarction. The most accurate and reproducible method for determining the necrosis area is contrast magnetic resonance imaging of the heart, however, this technique is still inaccessible in most hospitals. In this regard, it remains relevant to estimate the necrotic myocardium area by ubiquitous non-invasive methods such as electrocardiography and echocardiography.

Reconciling PC-MRI and CFD: An in-vitro study.

Several well-resolved 4D Flow MRI acquisitions of an idealized rigid flow phantom featuring an aneurysm, a curved channel as well as a bifurcation were performed under pulsatile regime. The resulting hemodynamics were processed to remove MRI artifacts. Subsequently, they were compared with CFD predictions computed on the same flow domain, using an in-house high-order low dissipative flow solver. Results show that reaching a good agreement is not straightforward but requires proper treatments of both techniques. Several sources of discrepancies are highlighted and their impact on the final correlation evaluated. While a very poor correlation (r2 = 0.63) is found in the entire domain between raw MRI and CFD data, correlation as high as r2 = 0.97 is found when artifacts are removed by post-processing the MR data and down sampling the CFD results to match the MRI spatial and temporal resolutions. This work demonstrates that, in a well-controlled environment, both PC-MRI and CFD might bring reliable and correlated flow quantities when a proper methodology to reduce the errors is followed.

Optimization of 3D phase contrast venography for the assessment of the cranio-cervical venous system at 1.5 T.

PURPOSE: The aim of this work was to optimize a three-dimensional (3D) phase-contrast venography (PCV) product MR pulse sequence in order to obtain clinically reliable images with less artifacts for an improved depiction of the cranio-cervical venous vessels. METHODS: Starting from the product sequence, the 3D PCV protocol was optimized in eight steps with respect to the velocity encoding (Venc) direction and value, slice thickness, reduction of susceptibility artifacts and arterial contamination, gradient mode and radio-frequency (RF)-spoiling, B0-Shimming, asymmetric echo technique and RF-pulse type, and flip angle. The product and optimized protocol was used to perform 3D PCV in 12 healthy male volunteers with a median age of 50 years using a state-of-the-art 1.5-T MR system. For evaluation, the cranio-cervical venous system was divided into 15 segments. These segments were evaluated by three radiologists with experience in neuroradiology. An ordinal scoring system was used to access the overall diagnostic quality, arterial contamination, and the quality of visualization. RESULTS: Image quality in the optimized 3D PCV was graded as "excellent" by all readers in 65.3% of the cases (p < 0.0001). The visualization of venous segments was strongly improved: it was considered diagnostic in 81.8% of all cases using the optimized sequence and in 47.6% for the product 3D PCV (p < 0.0001), respectively. The optimized protocol improved the imaging of all venous segments (p < 0.0001). CONCLUSION: The optimized 3D PCV pulse sequence showed superior results compared to the product 3D PCV for the visualization and evaluation of the venous system in all healthy volunteers.

Magnitude and direction of aqueductal cerebrospinal fluid flow: large variations in patients with intracranial aneurysms with or without a previous subarachnoid hemorrhage.

BACKGROUND: Net cerebrospinal fluid (CSF) flow within the cerebral aqueduct is usually considered to be antegrade, i.e., from the third to the fourth ventricle with volumes ranging between 500 and 600 ml over 24 h. Knowledge of individual CSF flow dynamics, however, is hitherto scarcely investigated. In order to explore individual CSF flow rate and direction, we assessed net aqueductal CSF flow in individuals with intracranial aneurysms with or without a previous subarachnoid hemorrhage (SAH). METHODS: A prospective observational study was performed utilizing phase-contrast magnetic resonance imaging (PC-MRI) to determine the magnitude and direction of aqueductal CSF flow with an in-depth, pixel-by-pixel approach. Estimation of net flow was used to calculate CSF flow volumes over 24 h. PC-MRI provides positive values when flow is retrograde. RESULTS: The study included eight patients with intracranial aneurysms. Four were examined within days after their SAH; three were studied in the chronic stage after SAH while one patient had an unruptured intracranial aneurysm. There was a vast variation in magnitude and direction of aqueductal CSF flow between individuals. Net aqueductal CSF flow was retrograde, i.e., directed towards the third ventricle in 5/8 individuals. For the entire patient cohort, the estimated net aqueductal CSF volumetric flow rate (independent of direction) was median 898 ml/24 h (ranges 69 ml/24 h to 12.9 l/24 h). One of the two individuals who had a very high estimated net aqueductal CSF volumetric flow rate, 8.7 l/24 h retrograde, later needed a permanent CSF shunt. CONCLUSIONS: The magnitude and direction of net aqueductal CSF flow vary extensively in patients with intracranial aneurysms. Following SAH, PC-MRI may offer the possibility to perform individualized assessments of the CSF circulation.

The intracranial pressure curve correlates to the pulsatile component of cerebral blood flow.

Current methods to measure cerebral blood flow (CBF) in the neuro critical care setting cannot monitor the CBF continuously. In contrast, continuous measurement of intracranial pressure (ICP) is readily accomplished, and there is a component of ICP that correlates with arterial inflow of blood into the cranial cavity. This property may have utility in using continuous ICP curve analysis to continuously estimate CBF. We examined the data from 13 patients, monitored with an intraventricular ICP device determining the pulsatile amplitude ICPamp as well as the area under the ICP curve (AUCICP). Using an elastance measurement, the ICP curve was converted to craniospinal volume (AUCΔV). The patients were examined with Phase Contrast Magnetic Resonance Imaging (MRI), measuring flow in the carotid and vertebral arteries. This made it possible to calculate CBF for one cardiac cycle (ccCBFMRtot) and divide it into the pulsatile (ccCBFMRpuls) and non-pulsatile (ccCBFMRconst) flow. ICP derived data and MRI measurements were compared. Linear regression was used to establish wellness of fit and ANOVA was used to calculate the P value. No correlation was found between ICPamp and the ccICPMRpuls (P = 0.067). In contrast there was a correlation between the AUCICP and ccCBFMRpuls (R2 = 0.440 P = 0.013). The AUCΔV correlated more appropriately with the ccCBFMRpuls. (R2 = 0.688 P < 0.001). Our findings suggests that the pulsatile part of the intracranial pressure curve, especially when transformed into a volume curve, correlates to the pulsatile part of the CBF.

Dynamic Contrast-Enhanced Magnetic Resonance Imaging as a Diagnostic Tool in the Assessment of Tumour Angiogenesis in Urinary Bladder Cancer.

PURPOSE: The aim of study is to assess the role of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and correlation with tumour angiogenesis in evaluation of urinary bladder cancer. MATERIAL AND METHODS: The study included 81 patients with recent presumed diagnosis of bladder tumour or who came for follow up after management of histopathologically proven bladder cancer. All had DCE-MRI with time-signal intensity curve. The radiologic results then correlated with the histopathologic results using both haematoxylin and eosin stain and immuno-histochemical staining for localization and evaluation of CD34 immunoreactivity as a detector for the microvessel density (MVD) and tumour angiogenesis. RESULTS: Seventy-one cases were pathologically proven to be malignant: 41 cases (58%) showed type III time-signal intensity curve (descending); 22 cases (31%) showed type II (plateau); and 8 cases (11%) showed type I (ascending) curve. The sensitivity of DCE-MRI in stage T1 bladder tumour was 80%; in stage T2, it was (90.9%); and in stage T3, it was (96.9%). Overall accuracy of DCE-MRI in tumour staging was 89.5% and P = .001 (significant). Values more than the cutoff value = 76.13 MVD are cystitis with sensitivity (90%), specificity (91%), and P value is .001, which is statistically highly significant. CONCLUSION: There is a strong positive association between DCE-MRI (staging and washout slope of the time-signal intensity curve) with histopathologic grade, tumour stage, and MVD in bladder cancer. So, DCE-MRI can be used as reliable technique in preoperative predictions of tumour behavior and affect the planning of antiangiogenetic therapy.

Comparison of hemodialysis arteriovenous fistula blood flow rates measured by Doppler ultrasound and phase-contrast magnetic resonance imaging.

OBJECTIVE: The objective of this study was to compare blood flow rates measured by Doppler ultrasound (DUS) and phase-contrast magnetic resonance imaging (MRI) in patients having a hemodialysis arteriovenous fistula (AVF) and to identify scenarios in which there was significant discordance between these two approaches. METHODS: Blood flow rates in the proximal artery (PA) and draining vein (DV) of newly created upper extremity AVFs were measured and compared using DUS and phase-contrast MRI at 1 day, 6 weeks, and 6 months postoperatively. RESULTS: Blood flow rates in the PA measured by DUS (1155 ± 907 mL/min, mean ± standard deviation) and by MRI (1170 ± 657 mL/min) were not statistically different (P = .812) based on 78 data pairs from 49 patients. DV DUS flow (1277 ± 995 mL/min) and MRI flow (1130 ± 655 mL/min) were also not statistically different (P = .071) based on 64 data pairs. In both PA and DV, the two methods substantially agreed with each other (Cohen κ: PA, 0.66; DV, 0.67) when flow rates were put into four clinically relevant categories (<300, 300-599, 600-1499, and ≥1500 mL/min). The Bland-Altman analyses of DUS and MRI flow identified six and four outliers for PA and DV, respectively. Seven outliers had higher DUS than MRI flow, with all DUS scan sites having a large lumen or significant local curvature; the other three had lower DUS flow, partly due to an underestimation of lumen diameter by DUS. CONCLUSIONS: DUS and MRI flow rates are generally comparable in both PA and DV. When DUS is used for flow measurements, careful attention to accurate lumen diameter measurements is needed and scan sites with marked curvature should be avoided. Our result may improve the accuracy of DUS-measured AVF blood flow rate.

MRI-based measurements of whole-brain global cerebral blood flow: Comparison and validation at 1.5T and 3T.

BACKGROUND: Whole-brain global cerebral blood flow (CBF) determined by MRI techniques, calculated using total CBF (TCBF) from phase-contrast MRI (PC-MRI), and brain parenchyma volume (BPV) from T1 -weighted image, have become increasingly popular in many applications. PURPOSE/HYPOTHESIS: To determine if MRI-based measurements of whole-brain global CBF data obtained across different field strengths could be merged, TCBF and BPV data acquired at 1.5T and 3T were compared. STUDY TYPE: Prospective study. POPULATION: Seventeen healthy subjects (eight females, aged 21-29 years old). FIELD STRENGTH/SEQUENCE: Fast spoiled gradient echo (FSPGR) and PC-MRI at both 1.5T and 3T. ASSESSMENT: TCBF and BPV data acquired at 1.5T and 3T were compared. STATISTICAL TESTS: The relationships of TCBF and whole-brain global CBF between two field strengths were examined by using the Pearson correlation coefficient analysis and intraclass correlation coefficient (ICC). RESULTS: Regression analysis revealed a strong correlation between TCBF at two field strengths (R2 = 0.78, P < 0.001), and the ICC was 0.85, suggesting measurements of TCBF at 1.5T were comparable and correlated with those at 3T. There was a significant difference in BPV between field strengths, where the white matter estimate was significantly larger at 1.5T when compared with that at 3T (P < 0.001). When TCBF was further normalized to the brain parenchyma mass to obtain whole-brain global CBF, it only showed a moderate correlation between measurements at the two field strengths (R2 = 0.46, P = 0.003) and lower ICC of 0.66, reflecting the slightly higher interstrength variability in the whole-brain global CBF measurements. DATA CONCLUSION: TCBF measurements could be performed equally well with comparable results at both field strengths, but specific attention should be given when TCBF is further normalized to BPV to obtain whole-brain global CBF. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:1273-1280.