Time-resolved Magnetic Resonance Angiography Research Articles

Using Magnetic Resonance Imaging as a Means to Study Chronic Cerebral Spinal Venous Insufficiency in Multiple Sclerosis Patients

The goal of this work is to present a broad magnetic resonance imaging (MRI) protocol for use in the study of chronic cerebrospinal venous insufficiency (CCSVI). The CCSVI MRI protocol includes the following sequences: time-resolved contrast-enhanced 3D MR angiography, 2D time-of-flight MR venography, and 3D volumetric interpolated breath-hold examination to assess venous structural abnormalities; phase-contrast MR imaging at different levels in the neck and thoracic cavity to quantify flow through the veins, arteries, and cerebrospinal fluid; T2-weighted imaging, T2-weighted fluid-attenuated inversion recovery, and pre- and post-contrast T1-weighted imaging of the brain for examinations of parenchymal lesions; and finally, susceptibility-weighted imaging for quantification of iron deposition in the brain. Data from 111 clinically definite multiple sclerosis patients were assessed for potential structural and flow CCSVI risk criteria, including stenosis, atresia, aplasia, dominant to subdominant venous flow ratio (D:sD), and the sum of their flow rates. Of the 111 patients, 50 (45%) were determined to be nonstenotic (NST) with no stenosis or atresia in their internal jugular veins (IJV), and the rest 61 (55%) were stenotic (ST) having at least one internal jugular vein stenosis or atresia. No occurrence of aplasia was observed. A D:sD of greater than 3:1 was observed in 15 (24.6%) patients of the ST group and 2 (4.0%) patients of the NST group. A sum of dominant and subdominant venous flow rate of <8 mL/s was observed in 22 (36.1%) patients of the ST group and 6 (12.0%) patients of the NST group. MRI provides valuable information in the observation of potential CCSVI risk factors. Low total flow in the 2 dominant veins seemed to be the strongest indicator for risk of having stenoses in the multiple sclerosis population.

A comparison of four dimensional time-resolved with keyhole and three dimensional time-of-flight MR angiography for the evaluation of cerebral aneurysms

Objective To evaluate the accuracy and reliability of 4D time-resolved MRA with keyhole (4D-TRAK) for the detection and characterization of cerebral aneurysms ( CAs),with a comparison of 3D time-of-flight MRA (3D-TOF-MRA).Methods 3D-TOF-MRA,4D-TRAK and 3D-DSA were performed sequentially in 52 patients with suspected CAs.4D-TRAK was acquired using a combination of sensitivity encoding (SENSE) and contrast-enhanced (CE) timing robust angiography ( CENTRA ) k-space sampling techniques at a contrast dose of 10 ml at 3 T scanner. Accuracy,sensitivity,specificity of 4D-TRAK and 3D-TOF-MRA were calculated and compared for the detection of CAs on patient-based and aneurysm-based evaluation using 3D-DSA as a reference. Wilcoxon signed rank test were used. Results The overall image quality of 4D-TRAK was appropriate for the diagnostic purpose,but yet not comparable with that of 3D-TOF-MRA.In 52 patients with suspected GAs,58 CAs were confirmed on 3D-DSA finally.Fifty-one (with 2 false-positives and 9 false-negatives) and 58 (with 1 false-positive and 1 false-negative)CAs were visualized on 4D-TRAK and 3D-TOF-MRA,respectively.Accuracy,sensitivity and specificity on patient-based evaluation of 4D-TRAK and 3D-TOF-MRA were 92.31％ ( 48/52 ),93.33％ ( 42/45 ),85.71 ％ (6/7) and 98.08％ ( 51/52 ),100.00％ ( 45/45 ),85.71％ ( 6/7 ),respectively,and 74.07％(20/27),75.00％ ( 18/24),66.67％ (2/3) and 96.30％ (26/27),95.83％ (26/27),100.00％ (3/3)on aneurysm-based evaluation in patients with multiple CAs,respectively.Subgroup analysis revealed that for 19 very small CAs ( maximal diameter ＜3 mm,measured on 3D-DSA),9 were missed on 4D-TRAK and 1 on 3D-TOF-MRA( Z =- 2.464,P ＜ O.01 ). However,for 39 CAs with maximal diameter more than 3 mm,there was no significantly difference in the diagnostic accuracy (39 on 4D-TRAK vs.39 on 3D-TOFMRA) (Z =0.000,P ＞0.05).In 4 large CAs with maximal diameter more than 10 mm,4D-TRAK provided a better characterization of morphology than 3D-TOF-MRA.Conclusions 4D-TRAK with a combination of SENSE and CENTRA at 3 T shows potential value in the diagnosis of cerebral aneurysms.However,due to the compromise in spatial resolution and vascular edge artifacts,it does not yet have a diagnostic accuracy of CAs comparable with 3D-TOF-MRA.TRAK imaging can be of great help in patients with large-giant CAs to characterize the morphology of CAs and to diminish the risk of NSF in patients with renal impairment by using a lower-dose contrast. Key words: Magnetic resonance imaging; Angiography,digital subtraction; Comparative study

Analysis of the Influence of 4D MR Angiography Temporal Resolution on Time-to-Peak Estimation Error for Different Cerebral Vessel Structures

Time-resolved MRA imaging is a promising technique for blood flow evaluation in case of cerebrovascular malformations. Unfortunately, 4D MRA imaging is a trade-off between spatial and temporal resolution. The aim of this study was to investigate the influence of temporal resolution on the error associated with TTP estimation from indicator dilution curves derived from different vascular structures. Monte Carlo simulation was performed to compute indicator dilution curves with known criterion standard TTP at temporal resolutions between 0.1 and 5 seconds. TTPs were estimated directly and by using 4 hemodynamic models for each curve and were compared with criterion standard TTP. Furthermore, clinical evaluation was performed by using 226 indicator dilution curves from different vessel structures obtained from clinical datasets. The temporal resolution was artificially decreased, and TTPs were estimated and compared with those obtained at the original temporal resolutions. The results of the clinical evaluations were further stratified for different vessel structures. The results of both evaluations show that the TTP estimation error increases exponentially when one lowers the temporal resolution. TTP estimation by using hemodynamic model curves leads to lower estimation errors compared with direct estimation. A temporal resolution of 1.5 seconds for arteries and 2.5 seconds for venous and arteriovenous malformation vessel structures appears to be reasonable to achieve TTP estimations adequate for clinical application. Different vessel structures require different temporal resolutions to enable comparable TTP estimation errors, which should be considered for achieving a case-optimal temporal and spatial resolution.

4D blood flow visualization fusing 3D and 4D MRA image sequences

To present and evaluate the feasibility of a novel automatic method for generating 4D blood flow visualizations fusing high spatial resolution 3D and time-resolved (4D) magnetic resonance angiography (MRA) datasets. In a first step, the cerebrovascular system is segmented in the 3D MRA dataset and a surface model is computed. The hemodynamic information is extracted from the 4D MRA dataset and transferred to the surface model using rigid registration where it can be visualized color-coded or dynamically over time. The presented method was evaluated using software phantoms and 20 clinical datasets from patients with an arteriovenous malformation. Clinical evaluation was performed by comparison of Spetzler-Martin scores determined from the 4D blood flow visualizations and corresponding digital subtraction angiographies. The performed software phantom validation showed that the presented method is capable of producing reliable visualization results for vessels with a minimum diameter of 2 mm for which a mean temporal error of 0.27 seconds was achieved. The clinical evaluation based on 20 datasets comparing the 4D visualization to DSA images revealed an excellent interrater reliability. The presented method enables an improved combined representation of blood flow and anatomy while reducing the time needed for clinical rating.

Combined renal MRA and perfusion with a single dose of contrast

Both anatomical and functional scans are often performed when diagnosing renovascular diseases, which in many cases require two separate contrast injections. With nephrogenic systemic fibrosis being associated with gadolinium, minimizing contrast injection dosage is desirable. In this study, a technique which performs time-resolved renal magnetic resonance angiography (MRA) and perfusion with a single scan and single dose of contrast has been evaluated in six healthy volunteers. A previously developed three-dimensional MRA technique called Contrast-enhanced Angiography with Multi-Echo and Radial k-space (CAMERA) has been used to acquire images, and perfusion analysis was performed using deconvolution methods. Time-resolved MRA, as well as renal blood flow, renal volume of distribution and mean transit time maps, were acquired.

Rapid time-resolved magnetic resonance angiography via a multiecho radial trajectory and GraDeS reconstruction

Contrast-enhanced magnetic resonance angiography is challenging due to the need for both high spatial and temporal resolution. A multishot trajectory composed of pseudo-random rotations of a single multiecho radial readout was developed. The trajectory is designed to give incoherent aliasing artifacts and a relatively uniform distribution of projections over all time scales. A field map (computed from the same data set) is used to avoid signal dropout in regions of substantial field inhomogeneity. A compressed sensing reconstruction using the GraDeS algorithm was used. Whole brain angiograms were reconstructed at 1-mm isotropic resolution and a 1.1-s frame rate (corresponding to an acceleration factor > 100). The only parameter which must be chosen is the number of iterations of the GraDeS algorithm. A larger number of iterations improves the temporal behavior at cost of decreased image signal-to-noise ratio. The resulting images provide a good depiction of the cerebral vasculature and have excellent arterial/venous separation.

Brain arteriovenous malformation diagnosis: value of time-resolved contrast-enhanced MR angiography at 3.0T compared to DSA

This study was conducted in order to evaluate the value of time-resolved contrast-enhanced magnetic resonance angiography (TR-CE-MRA) with a 3.0-T magnetic field compared to digital subtraction angiography (DSA) as the reference standard for the diagnosis of brain arteriovenous malformation (bAVM). Nineteen patients with 19 angiographically confirmed untreated bAVM were investigated with both DSA and TR-CE-MRA for the initial diagnosis. Examinations were compared by two independent readers. Interobserver agreement and intermodality agreement with respect to nidus size, arterial feeders, and venous drainage were determined using the K statistic test. Also, the quality of the TR-CE-MRA images was evaluated. Seventeen of the 19 bAVM (89.5%) detected with DSA were diagnosed with TR-CE-MRA. Interobserver agreement for TR-CE-MRA was good for nidus size, venous drainage, and arterial feeders (K = 0.75, 95% CI 0.50-1.00; K = 0.77, 95% CI 0.54-1.00; and K = 0.80, 95% CI 0.59-1.00 respectively). Intermodality agreement was good for nidus size and venous drainage (K = 0.75, 95% CI 0.49-1.00 and K = 0.77, 95% CI 0.54-1.00, respectively) and moderate for arterial feeders (K = 0.44, 95% CI 0.17-0.70). TR-CE-MRA at 3.0 T has a good sensitivity for bAVM detection and good agreement with DSA for determining nidus size and the type of venous drainage, suggesting that TR-CE-MRA is potentially a reliable tool for the diagnosis and assessment of bAVMs. However, it still suffers from low spatial resolution and vessel superposition, making differentiation of the arterial feeders of the nidus difficult at times.

Maximizing time-resolved MRA for differentiation of hemangiomas, vascular malformations and vascularized tumors

Contrast-enhanced magnetic resonance angiography (MRA) using time-resolved imaging is a relatively new and increasingly popular technique. We will describe the technique utilized at our institution, Time-Resolved Imaging of Contrast Kinetics (TRICKS; GE Healthcare, Milwaukee, WI), and the parameters that can be adjusted to optimize the exam. We will review key imaging features of hemangiomas and vascular malformations in various modalities, with a special emphasis on the TRICKS appearance.

Time-Resolved MR Angiography of the Legs at 3 T Using a Low Dose of Gadolinium: Initial Experience and Contrast Dynamics

This article describes our initial clinical experience with time-resolved MR angiography (MRA) of the legs using the time-resolved imaging with stochastic trajectories (TWIST) technique with a half dose of gadolinium. Thirty-four patients underwent a TWIST examination of the legs at 3 T. Thirty-three patients also underwent a bolus-chase MRA examination in the same setting. Times elapsed between the start of contrast injection and the appearance of contrast material (t(A)) and peak enhancement of the arteries in the legs (t(B)) were analyzed. The number of patients with examinations affected by venous contamination was determined. The differences in t(A) and t(B) between cases in which venous contamination was present or absent were evaluated using a two-tailed Student t test. The TWIST technique using a half dose of gadolinium provided diagnostic-quality images of all patients. The mean t(A) was 35.5 ± 8.8 (SD) seconds (range, 17.8-60.4 seconds), and the mean t(B) was 59.1 ± 15.1 seconds (range, 31-98.8 seconds). Venous contamination was observed in bolus-chase MRA images of 52.9% of patients. The relationship between venous contamination and t(A) was not statistically significant (p = 0.13). The incidence of venous contamination was higher in patients with lower values of t(B) (p = 0.01). The described low-dose clinical experience with TWIST and the contrast dynamics information gained from this study could aid radiologists in planning protocols for leg MRA examinations.

Quantitative Flow Measurements in the Internal Jugular Veins of Multiple Sclerosis Patients Using Magnetic Resonance Imaging

To study the blood flow through the internal jugular veins (IJVs) of the MS population. Two hundred MS patients and 14 normal volunteers were evaluated with magnetic resonance imaging (MRI) at 3T. Contrast-enhanced time-resolved 3D MR angiography and 2D time-of-flight imaging were performed to assess abnormalities in the extracranial vascular anatomy. Based on this assessment, the MS population was divided into subgroups of non-stenotic (NST), cervical 1 stenotic only (C1ST) and cervical 6 stenotic (C6ST) subjects. In this study, 2D phase contrast MR imaging was used to quantify blood flow through major veins and arteries in the neck and flow differences among the groups were analyzed. Of the 200 MS patients, 87 (43.5%) belonged to the NST group, 50 (25%) belonged to the C1ST group and 63 (31.5%) belonged to the C6ST group. The total IJV flow normalized to the total arterial flow of the NST group was 75.12 ± 12.22 %. This was significantly higher than that of the C1ST group, 63.93 ± 16.08 % (p < 0.0001), which in turn was significantly higher than that of the C6ST group, 52.13 ± 20.71 % (p = 0.001). Seventy-nine percent of the stenotic groups had a normalized subdominant IJV flow of less than 20%, a combined IJV flow of less than 5o% and/or a sub-dominant IJV flow vs. dominant IJV flow ratio of less than 1/3. Only 2% of the NST group had a combined IJV flow of less than 50%, compared to 35% of the stenotic groups. Blood flow through the IJVs was reduced in the MS population with stenoses compared to those without.

Abstract No. 412: MRA as a problem-solving tool for identifying and classifying endoleak after EVAR

Review indications, imaging findings, and MR techniques to perform magnetic resonance angiography (MRA) for the evaluation of endoleak (EL) after EVAR. Endovascular repair of aortic aneurysms is increasingly common. Lifetime imaging surveillance is recommended, and EL and continued sac growth are potential issues. Although CTA is the mainstay in EVAR surveillance in our practice, MRA is useful for identifying subtle leaks not detected or well-characterized with CTA. Time-resolved (dynamic) MRA further increases diagnostic accuracy when compared to static MRA by frequently enabling EL-type assessment (15 vs 9, n=23 [65 vs 40%]). Recently TR-MRA has been shown comparable to gold standard DSA for classification of EL type (97% n=30/31), and remains more sensitive than CTA. In our practice, CE-MRA is often performed when routine three-phase CTA (non-contrast, arterial, and delayed) fails to demonstrate the etiology of an expanding, excluded aneurysm sac during EVAR surveillance. We will review potential advantages both of view-shared and non-view-shared TR-MRA with newer contrast agents and parallel imaging techniques and highlight successful use of MRA for endoleak detection, characterization, and treatment planning through clinical examples. 1MRA is extremely helpful for detecting and characterizing endoleaks which are not well seen on CTA.2Higher contrast-to-background ratio, very high combined spatial and temporal resolution, and ability to obtain multiple time-points without exposing the patient to increased ionizing radiation are factors which give MRA an advantage over CTA for detecting and characterizing endoleaks.3MRA should be considered as a first-line or second-line test for problem solving in patients for whom CTA does not provide a definitive diagnosis.

Thyroid Incidentaloma Detected by Time-Resolved Magnetic Resonance Angiography at 3T: Prevalence and Clinical Significance

ObjectiveTo determine the prevalence of thyroid incidentalomas detected by time-resolved magnetic resonance angiography (TRMRA) and to evaluate their clinical significance by using an ultrasonographic (US) and cytologic correlation.Materials and MethodsWe retrospectively reviewed 2010 consecutive TRMRA examinations performed at our institution between August 2006 and April 2010. The TRMRA findings of thyroid incidentalomas were analyzed according to location, size, as well as vascularity, and were correlated with the US findings and cytologic results. Each nodule was classified as suspiciously malignant, indeterminate or probably benign according to the US criteria recommended by the Korean Society of Thyroid Radiology.ResultsA total of 102 incidentalomas were detected in 90 of 2010 patients (5%). TRMRA showed homogenous hypervascularity in 48 (47%), inhomogeneous hypervascularity in 46 (45%), and hypovascularity in 8 (8%) thyroid nodules. At follow-up study, out of 26 patients with 30 incidentalomas on TRMRA, 27 nodules were identified on US. Of the 27 nodules, 24 (89%) nodule were classified as indeterminate, two (7%) as probably benign, and one (4%) as suspiciously malignant. Among the 16 nodules with available cytopathologic results, 14 (82%) were benign, one (6%) was indeterminate, and one (6%) was malignant.ConclusionThyroid incidentalomas are found in 5% of TRMRA examinations. Although their presence does not necessarily indicate malignancy, nonspecific findings of detected incidentalomas on TRMRA require further evaluation by US.

Pseudostenosis at the Origin of the Vertebral Artery on Contrast-enhanced MRA: Correlation with Aortic Motion on Dynamic 3D Time-Resolved Contrast-Enhanced MRA

Purpose : The origin of the vertebral artery (VA) is a frequent site of pseudostenosis on contrast-enhanced MRA (CEMRA). The purpose of this study is to evaluate the relationship between the motion of the aortic arch and pseudostenosis at the origin of the VA. Materials and Methods: Our study had approval of our institutional review board. 47 patients underwent CT angiography (CTA), CE-MRA, and 3D time-resolved contrast-enhanced MRA (TR-CEMRA) within 6.87±9.89 days (mean±SD). Percent stenosis using the NASCET criteria was measured on CTA and CE-MRA. CTA was used as a reference standard to classify the CE-MRA into pseudostenosis and control group. Pseudostenosis was determined as 50%99% stenosis observed on CE-MRA but normal to less than 50% stenosis on CTA. Aortic motion (distance between the highest position and lowest position of aortic arch) was measured on TR-CEMRA. Age, route of intravenous contrast media, motion of aortic arch, and normal distal diameter of VA were compared between the two groups. Results: There were 17 patients and 23 vertebral arteries of pseudostenosis. Patients with pseudostenosis showed more aortic motion (3.61±1.88 vs. 2.05±1.97 mm) and older age (71.29±8.88 vs. 62.32±13.19 year-old). Route of intravenous contrast media and normal distal diameter of VA were not associated with pseudostenosis. Conclusion: VA origin is a frequent site of pseudostenosis. Older age and more motion of aortic arch are associated with pseudostenosis on CE-MRA.

Hemodynamic Change in Pulmonary Vein Stenosis after Radiofrequency Ablation: Assessment with Magnetic Resonance Angiography

We present a case of pulmonary vein (PV) stenosis after radio-frequency (RF) ablation, in which a hemodynamic change in the pulmonary artery was similar to that of congenital PV atresia on time-resolved contrast-enhanced magnetic resonance angiography (TR-MRA). A 48-year-old man underwent RF ablation due to atrial fibrillation. The patient subsequently complained of hemoptysis, dyspnea on exertion, and right chest pain. Right PV stenosis after catheter ablation was diagnosed through chest computed tomography and lung perfusion scan. Pulmonary TR-MRA revealed the pulmonary artery via systemic arterial collaterals and draining systemic collateral veins. On a velocity-encoded cine image, the flow direction of the right pulmonary artery was reversed in the diastolic phase and the left pulmonary artery demonstrated continuous forward flow throughout the cardiac cycle. These hemodynamic changes were similar to those seen in congenital unilateral PV atresia.

Time-resolved imaging of contrast kinetics does not improve performance of follow-up MRA of embolized intracranial aneurysms

SummaryBackgroundThe use of contrast media and the time-resolved imaging of contrast kinetics (TRICKS) technique have some theoretical advantages over time-of-flight magnetic resonance angiography (TOF-MRA) in the follow-up of intracranial aneurysms after endovascular treatment. We prospectively compared the diagnostic performance of TRICKS and TOF-MRA with digital subtracted angiography (DSA) in the assessment of occlusion of embolized aneurysms.Material/MethodsSeventy-two consecutive patients with 72 aneurysms were examined 3 months after embolization. Test characteristics of TOF-MRA and TRICKS were calculated for the detection of residual flow. The results of quantification of flow were compared with weighted kappa. Intraobserver and interobserver reproducibility was determined.ResultsThe sensitivity of TOF-MRA was 85% (95% CI, 65–96%) and of TRICKS, 89% (95% CI, 70–97%). The specificity of both methods was 91% (95% CI, 79–98%). The accuracy of the flow quantification ranged from 0.76 (TOF-MRA) to 0.83 (TRICKS). There was no significant difference between the methods in the area under the ROC curve regarding both the detection and the quantification of flow. Intraobserver reproducibility was very good with both techniques (kappa, 0.86–0.89). The interobserver reproducibility was moderate for TOF-MRA and very good for TRICKS (kappa, 0.74–0.80).ConclusionsIn this study, TOF-MRA and TRICKS presented similar diagnostic performance; therefore, the use of time-resolved contrast-enhanced MRA is not justified in the follow-up of embolized aneurysms.

Patients with Multiple Sclerosis with Structural Venous Abnormalities on MR Imaging Exhibit an Abnormal Flow Distribution of the Internal Jugular Veins

Purpose To evaluate extracranial venous structural and flow characteristics in patients with multiple sclerosis (MS). Materials and Methods Two hundred subjects with MS from two sites (n = 100 each) were evaluated with magnetic resonance (MR) imaging at 3 T. Contrast-enhanced time-resolved MR angiography and time-of-flight MR venography were used to assess vascular anatomy. Two-dimensional phase-contrast MR imaging was used to quantify blood flow. The MS population was divided into two groups: those with evident internal jugular vein (IJV) stenoses (stenotic group) and those without (nonstenotic group). Results Of the 200 patients, 136 (68%) showed IJV structural abnormalities, including unilateral or bilateral stenoses at different levels in the neck (n = 101; 50.5%) and atresia (n = 35; 17.5%). The total IJV flow normalized to the total arterial flow of the stenotic group (56% ± 22) was significantly lower than that of the nonstenotic group (77% ± 14; P < .001). The arterial/venous flow mismatch in the stenotic group (12% ± 15) was significantly greater than that in the nonstenotic group (6% ± 12; P < .001). The ratio of subdominant venous flow rate (Fsd) to dominant venous flow rate (Fd) for the stenotic group (0.38 ± 0.27) was significantly lower than for the nonstenotic group (0.59 ± 0.23; P < .001). The majority of the stenotic group (67%) also had an Fsd of less than 3 mL/s, a Fd/Fsd ratio greater than 3:1, and/or a total IJV flow rate of less than 8 mL/s. Conclusions MR imaging provides a noninvasive means to separate stenotic from nonstenotic MS cases. The former group was more prevalent in the present MS population and carried significantly less flow in the IJVs than the latter.

高空間分解能Multiple Echo Planar Imaging Based Signal Targeting and Alternating Radiofrequencyによる頭蓋内非造影Time-resolved MR Angiography

Detailed information on anatomy and hemodynamics in cerebrovascular disorders such as AVM and Moyamoya disease is mandatory for defined diagnosis and treatment planning. Arterial spin labeling technique has come to be applied to magnetic resonance angiography (MRA) and perfusion imaging in recent years. However, those non-contrast techniques are mostly limited to single frame images. Recently we have proposed a non-contrast time-resolved MRA technique termed contrast inherent inflow enhanced multi phase angiography combining spatial resolution echo planar imaging based signal targeting and alternating radiofrequency (CINEMA-STAR). CINEMA-STAR can extract the blood flow in the major intracranial arteries at an interval of 70 ms and thus permits us to observe vascular construction in full by preparing MIP images of axial acquisitions with high spatial resolution. This preliminary study demonstrates the usefulness of the CINEMA-STAR technique in evaluating the cerebral vasculature.

Double Bolus Application in TWIST-MR-Angiography of the Cervical Arteries

Purpose. The aim of the present work was to test the feasibility of the time-resolved MR-angiography (TWIST-MRA) of cervical arteries using double bolus injection. Material and Methods. TWIST-MRA with a temporal resolution of 8.4 seconds for each frame and a spatial resolution with a voxel size of 0.61 × 0.58 × 0.8 mm3 was performed in 24 patients. A biphasic bolus injection protocol was used with the second injection being started 21 seconds after the first contrast dye bolus. Diagnostic image quality was rated according to a 4-point scale. Results. In 12 patients (50%) no clear separation between the cervical venous and arterial vessels was evident after the first bolus injection. Using TWIST-MRA data acquired after the second bolus a sufficient diagnostic image quality (rating ≥3, mean 3.5) could be obtained in 22 of 24 patients (92%). Discussion. The double bolus injection protocol using TWIST-MRA allows for very good separation of the cervical arteries.

Magnetic Resonance Angiography in Paced Complex Heterotaxy Syndrome with Fontan Conduit Obstruction and Venovenous Collateral Decompression

Imaging of complex congenital heart diseases (CHDs) in children is challenging. This article reviews the complementary role of high temporal and high spatial resolution magnetic resonance (MR) angiographic imaging techniques in evaluation of a patient with complex congenital cardiovascular disease and related postsurgical complications. A 4-year-old female patient with complex CHD and multiple previous palliative surgical procedures underwent MR angiography to evaluate the cause of refractory hypoxia. High-resolution MR angiography demonstrated the complex postsurgical cardiovascular anatomy and also assisted in the evaluation of cavopulmonary shunt patency and secondary venovenous shunt formation. Time-resolved MR angiography evaluated pulmonary perfusion and demonstrated a significant pulmonary arteriovenous malformation. This information guided physicians in planning further managements, which resulted in a satisfactory clinical outcome.

Combined large field-of-view MRA and time-resolved MRA of the lower extremities: Impact of acquisition order on image quality

PurposeDifferent approaches exist for hybrid MRA of the calf station. So far, the order of the acquisition of the focused calf MRA and the large field-of-view MRA has not been scientifically evaluated. Therefore the aim of this study was to evaluate if the quality of the combined large field-of-view MRA (CTM MR angiography) and time-resolved MRA with stochastic interleaved trajectories (TWIST MRA) depends on the order of acquisition of the two contrast-enhanced studies. MethodsIn this retrospective study, 40 consecutive patients (mean age 68.1±8.7 years, 29 male/11 female) who had undergone an MR angiographic protocol that consisted of CTM-MRA (TR/TE, 2.4/1.0ms; 21° flip angle; isotropic resolution 1.2mm; gadolinium dose, 0.07mmol/kg) and TWIST-MRA (TR/TE 2.8/1.1; 20° flip angle; isotropic resolution 1.1mm; temporal resolution 5.5s, gadolinium dose, 0.03mmol/kg), were included. In the first group (group 1) TWIST-MRA of the calf station was performed 1–2min after CTM-MRA. In the second group (group 2) CTM-MRA was performed 1–2min after TWIST-MRA of the calf station. The image quality of CTM-MRA and TWIST-MRA were evaluated by 2 two independent radiologists in consensus according to a 4-point Likert-like rating scale assessing overall image quality on a segmental basis. Venous overlay was assessed per examination. ResultsIn the CTM-MRA, 1360 segments were included in the assessment of image quality. CTM-MRA was diagnostic in 95% (1289/1360) of segments. There was a significant difference (p<0.0001) between both groups with regard to the number of segments rated as excellent and moderate. The image quality was rated as excellent in group 1 in 80% (514/640 segments) and in group 2 in 67% (432/649), respectively (p<0.0001). In contrast, the image quality was rated as moderate in the first group in 5% (33/640) and in the second group in 19% (121/649) respectively (p<0.0001). The venous overlay was disturbing in 10% in group 1 and 20% in group 2 (p=n.s.). ConclusionIf a combined hybrid MRA approach with large field-of-view and time-resolved MRA is acquired the large field-of-view MRA should be acquired first in order for optimal image quality.