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Objective: The objective of this study is to evaluate the ability of spleen volume, blood flow, and an index incorporating multiple measures to predict cirrhosis-associated hypersplenism., Materials and Methods: A total of 39 patients (14 women and 25 men; mean [± SD] age, 52 ± 10 years) with cirrhosis and sequelae of portal hypertension underwent 4D flow MRI and anatomic 3-T MRI performed before and after contrast administration. Unenhanced 4D flow MRI was used to assess abdominal hemodynamics, and splenic volumes were measured on T1-weighted gradient-recalled echo MRI. Relationships among demographic characteristics, blood component counts, splenic volume, arterial flow, venous flow, and the percentage of shunted portal flow were assessed in 29 consecutive patients (i.e., the derivation group), to develop a splenic flow index. This index was assessed along with splenic volume and blood flow alone in 10 additional consecutive patients (i.e., the validation group) via ROC curve analysis, to identify platelet counts of less than 50 × 10 3 cells/μL, leukocyte counts of less than 3.0 × 10 3 cells/μL, or both., Results: In the derivation cohort (platelet count, 129 ± 76 × 10 3 cells/μL), splenic volume, arterial flow, venous flow, and the percentage of shunted portal flow were inversely correlated with platelet counts (ρ = -0.68, -0.68, -0.56, and -0.36, respectively; p < 0.05). Adding splenic volume to arterial flow and the product of venous flow and the percentage of shunted portal flow indexed to the body surface area yielded superior correlations with platelet counts, leukocyte counts, and the degree of severity of hypersplenism (ρ = -0.75, -0.48, and -0.75, respectively; p ≤ 0.001) and predicted severe hypersplenism (sensitivity, 100%; specificity, 100%) in the validation cohort (platelet count, 93 ± 71 × 10 3 cells/μL)., Conclusion: A splenic flow index that incorporates both splenic volume and blood flow is a better indicator of hypersplenism than is splenic volume alone.

Objectives: To assess changes in portal and splanchnic arterial haemodynamics in patients undergoing transjugular intrahepatic portosystemic shunt (TIPS) using four-dimensional (4D) flow MRI, a non-invasive, non-contrast imaging technique., Methods: Eleven patients undergoing TIPS implantation were enrolled. K-t GRAPPA accelerated non-contrast 4D flow MRI of the liver vasculature was applied with acceleration factor R = 5 at 3Tesla. Flow analysis included three-dimensional (3D) blood flow visualization using time-resolved 3D particle traces and semi-quantitative flow pattern grading. Quantitative evaluation entailed peak velocities and net flows throughout the arterial and portal venous (PV) systems. MRI measurements were taken within 24 h before and 4 weeks after TIPS placement., Results: Three-dimensional flow visualization with 4D flow MRI revealed good image quality with minor limitations in PV flow. Quantitative analysis revealed a significant increase in PV flow (562 ± 373 ml/min before vs. 1831 ± 965 ml/min after TIPS), in the hepatic artery (176 ± 132 ml/min vs. 354 ± 140 ml/min) and combined flow in splenic and superior mesenteric arteries (770 ml/min vs. 1064 ml/min). Shunt-flow assessment demonstrated stenoses in two patients confirmed and treated at TIPS revision., Conclusions: Four-dimensional flow MRI might have the potential to give new information about the effect of TIPS placement on hepatic perfusion. It may explain some unexpected findings in clinical observation studies., Key Points: • 4D flow MRI, a non-invasive, non-contrast imaging technique, is feasible after TIPS. • Provides visualization and quantification of hepatic arterial, portal venous, collateral and TIPS haemodynamics. • Better understanding of liver blood flow changes after TIPS and patient management.

Purpose: To evaluate the feasibility of time-resolved flow-sensitive MRI for the three-dimensional (3D) visualization and quantification of normal and pathological portal venous (PV) hemodynamics., Materials and Methods: Portal venous hemodynamics were evaluated in 18 healthy volunteers and 5 patients with liver cirrhosis. ECG- and adaptive respiratory navigator gated flow-sensitive 4D MRI (time-resolved 3D MRI with three-directional velocity encoding) was performed on a 3 Tesla MR system (TRIO, Siemens, Germany). Qualitative flow analysis was achieved using 3D streamlines and time-resolved particle traces originating from seven emitter planes precisely placed at anatomical landmarks in the PV system. Quantitative analysis included retrospective extraction of regional peak and mean velocities and vessel area. Results were compared with standard 2D flow-sensitive MRI and to the reference standard Doppler ultrasound., Results: Qualitative flow analysis was successfully used in the entire PV system. Venous hemodynamics in all major branches in 17 of 18 volunteers and 3 of 5 patients were reliably depicted with good interobserver agreement (kappa = 0.62). Quantitative analysis revealed no significant differences and moderate agreement for peak velocities between 3D MR and 2D MRI (r = 0.46) and Doppler ultrasound (US) (r = 0.35) and for mean velocities between 3D and 2D MRI (r = 0.41). The PV area was significantly (P < 0.01) higher in 3D and 2D MRI compared with US., Conclusion: We successfully applied 3D MR velocity mapping in the PV system, providing a detailed qualitative and quantitative analysis of normal and pathological hemodynamics., (2010 Wiley-Liss, Inc.)

Purpose: Detection of pulmonary metastases is still a challenging task for magnetic resonance imaging (MRI). It was the aim of this study to evaluate the potential of a free-breathing move-during-scan turbo inversion recovery magnitude sequence for the detection of pulmonary nodules., Materials and Methods: The sensitivities and positive-predictive values of 2 radiologists to detect pulmonary nodules in 41 move-during-scan MRI examinations of 38 patients with different malignancies were calculated and subgroup analyses according to lesion size and localization were performed. Multidetector computed tomography served as the standard of reference. Additionally, 6 radiologists rated the confidence for the presence of nodular lesions in 212 regions-of-interest, which were randomly selected to represent lesions of various sizes as well as negative findings. Receiver-operator-characteristic was performed., Results: Three hundred twenty-one nodules were found in 30 patients by multidetector computed tomography. Sensitivity and specificity of MRI to detect pulmonary nodules larger than 3 mm on a per-patient basis were 81.8% and 94.7%, respectively. On a per-lesion basis, MRI revealed a sensitivity of 79.0% to 80.7% for lesions larger than 3 mm, if high conspicuity ratings were counted as positive, and 84.6%, if medium and high conspicuity ratings were counted as positive. Sensitivity increased uniformly with lesion size, and all lesions larger than 12 mm were detected. Receiver-operator-characteristic analysis revealed a mean accuracy of 0.90 and sensitivities over 90% for lesions larger than 3 mm with a specificity of 96.1%. For lesions larger than 6 mm the accuracy was 0.99., Conclusion: Detection of pulmonary nodules with a move-during-scan turbo inversion recovery magnitude sequence is feasible. Excellent detection of lesions larger than 6 mm is achievable with free-breathing moving-table MRI.

Objective: We sought to evaluate the feasibility of k-t parallel imaging for accelerated 4D flow MRI in the hepatic vascular system by investigating the impact of different acceleration factors. Materials and methods: k-t GRAPPA accelerated 4D flow MRI of the liver vasculature was evaluated in 16 healthy volunteers at 3T with acceleration factors R = 3, R = 5, and R = 8 (2.0 × 2.5 × 2.4 mm, TR = 82 ms), and R = 5 (TR = 41 ms); GRAPPA R = 2 was used as the reference standard. Qualitative flow analysis included grading of 3D streamlines and time-resolved particle traces. Quantitative evaluation assessed velocities, net flow, and wall shear stress (WSS). Results: Significant scan time savings were realized for all acceleration factors compared to standard GRAPPA R = 2 (21-71 %) ( p < 0.001). Quantification of velocities and net flow offered similar results between k-t GRAPPA R = 3 and R = 5 compared to standard GRAPPA R = 2. Significantly increased leakage artifacts and noise were seen between standard GRAPPA R = 2 and k-t GRAPPA R = 8 ( p < 0.001) with significant underestimation of peak velocities and WSS of up to 31 % in the hepatic arterial system ( p <0.05). WSS was significantly underestimated up to 13 % in all vessels of the portal venous system for k-t GRAPPA R = 5, while significantly higher values were observed for the same acceleration with higher temporal resolution in two veins ( p < 0.05). Conclusion: k-t acceleration of 4D flow MRI is feasible for liver hemodynamic assessment with acceleration factors R = 3 and R = 5 resulting in a scan time reduction of at least 40 % with similar quantitation of liver hemodynamics compared with GRAPPA R = 2. [ABSTRACT FROM AUTHOR]

Background: The purpose of this study was to investigate 3D flow patterns and vessel wall parameters in patients with dilated ascending aorta, age-matched subjects, and healthy volunteers. Methods: Thoracic time-resolved 3D phase contrast CMR with 3-directional velocity encoding was applied to 33patients with dilated ascending aorta (diameter ≥40 mm, age=60±16 years), 15 age-matched normal controls (diameter ≤37 mm, age=68±7.5 years) and 15 young healthy volunteers (diameter ≤30 mm, age=23±2 years). 3D blood flow was visualized and flow patterns were graded regarding presence of supra-physiologic-helix and vortex flow using a semi-quantitative 3-point grading scale. Blood flow velocities, regional wall shear stress (WSS), and oscillatory shear index (OSI) were quantified. Results: Incidence and strength of supra-physiologic-helix and vortex flow in the ascending aorta (AAo) was significantly higher in patients with dilated AAo (16/33 and 31/33, grade 0.9±1.0 and 1.5±0.6) than in controls (2/15 and 7/15, grade 0.2 ± 0.6 and 0.6 ± 0.7, P<.05) or healthy volunteers (1/15 and 0/15, grade 0.1 ± 0.3 P<.05). Greater strength of the ascending aortic helix and vortex flow were associated with significant differences in AAo diameters (P<.05). Peak systolic WSS in the ascending aorta and aortic arch was significantly lower in patients with dilated AAo (P<.0157-.0488). AAo diameter positively correlated to time to peak systolic velocities (r=0.30-0.53, P<.04), OSI (r=0.33-0.49, P<0.02) and inversely correlated to peak systolic WSS (r=0.32-0.40, P<.03). Peak systolic WSS was significantly lower in AAo aneurysms at the right and outer curvature within the AAo and proximal arch (P<.01-.05). Conclusions: Increase in AAo diameter is significantly correlated with the presence and strength of supra-physiologic-helix and vortex formation in the AAo, as well with decrease in systolic WSS and increase in OSI. [ABSTRACT FROM AUTHOR]

Background Thoracic and abdominal 4D flow MRI is typically acquired in combination with navigator respiration control which can result in highly variable scan efficiency (S eff ) and thus total scan time due to inter-individual variability in breathing patterns. The aim of this study was to test the feasibility of an improved respiratory control strategy based on diaphragm navigator gating with fixed S eff , respiratory driven phase encoding, and a navigator training phase. Methods 4D flow MRI of the thoracic aorta was performed in 10 healthy subjects at 1.5 T and 3 T systems for the in-vivo assessment of aortic time-resolved 3D blood flow velocities. For each subject, four 4D flow scans (1: conventional navigator gating, 2–4: new implementation with fixed S eff = 60%, 80% and 100%) were acquired. Data analysis included semi-quantitative evaluation of image quality of the 4D flow magnitude images (image quality grading on a four point scale), 3D segmentation of the thoracic aorta, and voxel-by-voxel comparisons of systolic 3D flow velocity vector fields between scans. Results Conventional navigator gating resulted in variable S eff = 74 ± 13% (range = 56%–100%) due to inter-individual variability of respiration patterns. For scans 2–4, the new navigator implementation was able to achieve predictable total scan times with stable S eff, only depending on heart rate. Semi- and fully quantitative analysis of image quality in 4D flow magnitude images was similar for the new navigator scheme compared to conventional navigator gating. For aortic systolic 3D velocities, good agreement was found between all new navigator settings (scan 2–4) with the conventional navigator gating (scan 1) with best performance for S eff = 80% (mean difference = − 0.01 m/s; limits of agreement = 0.23 m/s, Pearson's ρ = 0.89, p < 0.001). No significant differences for image quality or 3D systolic velocities were found for 1.5 T compared to 3 T. Conclusions The findings of this study demonstrate the feasibility of the new navigator scheme to acquire 4D flow data with more predictable scan time while maintaining image quality and 3D velocity information, which may prove beneficial for clinical applications. [ABSTRACT FROM AUTHOR]