Flow-related Signal Research Articles

Investigation of diffusion time dependence of apparent diffusion coefficient and intravoxel incoherent motion parameters in the human kidney.

To characterize the diffusion time (Δeff) dependence of apparent diffusion coefficient (ADC) and intravoxel incoherent motion-related parameters in the human kidney at 3 T. Sixteen healthy volunteers underwent an MRI examination at 3 T including diffusion-weighted imaging at different Δeff ranging from 24.1 to 104.1 ms. The extended mono-exponential ADC and intravoxel incoherent motion models were fitted to the data for each Δeffand the medullary and cortical ADC, (pseudo-)diffusion coefficients (D* and D) and flow-related signal fraction (f) were calculated. When all the data were used for fitting, a significant trend toward higher ADC with increasing Δeff was observed between 24.1 and 104.1 ms (median and interquartile range: 2.38 [2.19, 2.47] to 2.84 [2.36, 2.90] × 10-3 mm2/s for cortex, and 2.28 [2.18, 2.37] to 2.82 [2.58, 3.11] × 10-3 mm2/s for medulla). In contrast, no significant differences in ADC were found when only the data acquired at b-values higher than 200 s/mm2 were used for fitting. When the intravoxel incoherent motion model was applied, cortical and medullary f increased significantly (cortex: 0.21 [0.15 0.27] to 0.37 [0.32, 0.49] × 10-3 mm2/s; medulla: 0.15 [0.13 0.29] to 0.41 [0.36 0.51] × 10-3 mm2/s). No significant changes in cortical and medullary D and D* were observed as diffusion time increased. Renal perfusion and tubular flow substantially contribute to the observed increase in ADC over a wide range of Δeff between 24 and 104 ms.

Visual assessment of cerebrospinal fluid flow dynamics using 3D T2-weighted SPACE sequence-based classification system.

Flow-related signal void artifacts can be visualized on the T2-weighted (T2W) three-dimensional sampling perfection with application-optimized contrast (3D-SPACE) sequence. Flow void artifacts in the cerebral aqueduct and the fourth ventricle can provide information about cerebrospinal fluid (CSF) flow dynamics. In this study, we aimed to test the performance of the T2W 3D-SPACE sequence in assessing the CSF flow in the aqueduct and/or fourth ventricle. A total of 137 patients (age range = 3-89 years) who underwent CSF flow study were included. The amount of signal loss on T2W 3D-SPACE due to flow in the aqueduct and fourth ventricle was assessed and graded using a 4-point scale of 0 (absence of flow void) to 3 (signal void filling the aqueduct and entire fourth ventricle). A correlation was then sought between the quantitative values obtained by phase-contrast magnetic resonance imaging (PC-MRI) and the amount of signal void in the 3D-SPACE sequence. At the aqueduct level, there was a statistically significant difference in the forward flow velocity and the flow volume among different grades (all P < 0.001). In the grade 3 group, CSF peak systolic flow velocity and mean flow volume were found to be significantly higher than in the other grades (P < 0.001). The mean aqueduct area in the grade 0 group was found to be significantly different from that in the other classes (P < 0.001). The amount of signal loss in the fourth ventricle observed on T2W 3D-SPACE is correlated with the peak systolic velocity and flow volume measured quantitatively in PC-MRI.

Assessment of Hyperacute Cerebral Ischemia Using Laser Speckle Contrast Imaging.

Background: Accurate diagnosis of cerebral ischemia severity is crucial for clinical decision making. Laser speckle contrast imaging-based cerebral blood flow imaging can help assess the severity of cerebral ischemia by monitoring changes in blood flow. Method: In this study, we simulated hyperacute ischemia in rats, isolating arterial and venous flow-related signals from cortical vasculature. Pearson correlation was used to examine the correlation between damaged vessels. Granger causality analysis was used to investigate causality correlation in ischemic vessels. Results: Resting state analysis revealed a negative Pearson correlation between regional arteries and veins. Following cerebral ischemia induction, a positive artery-vein correlation emerged, which vanished after blood flow reperfusion. Granger causality analysis demonstrating enhanced causality coefficients for middle artery-vein pairs during occlusion, with a stronger left-right arterial effect than that of right-left, which persisted after reperfusion. Conclusions: These processing approaches amplify the understanding of cerebral ischemic images, promising potential future diagnostic advancements.

Acute ischemic stroke in a caucasian male with long chiari network, interatrial septal aneurysm and patent foramen ovale: A case report

A 49-year-old Caucasian male, left-handed, with no known comorbidities, working as a middle school teacher, presented to the emergency room with a sudden-onset left hand weakness described as difficulty gripping with no other associated symptoms. A non-smoker, non-alcoholic beverage drinker, with no illicit drug use. There was no significant history of any neurological disease in the family background but his father has a history of interatrial septal aneurysm. Physical, cardiologic and neurologic examination at the emergency department were unremarkable aside from the weakness on his left hand and a mild sensory deficit on the left upper extremity. A cranial magnetic resonance imaging with magnetic resonance angiography was done which showed a hyperacute infarct in the right frontal lobe, with paucity of vessels and attenuation of flow-related signals in the M4 perforators of the right middle cerebral artery and contour irregularities along the intradural segment of the right vertebral artery relating to atherosclerotic changes (Figure 1). Patient was given a recombinant tissue plasminogen activator since he came in at the 3rd hour post-ictus. Laboratory tests done at the emergency department showed normal complete blood count, routine blood chemistry, A further work-up was done which showed a slightly elevated LDL on Lipid profile, and other parameters within normal limit.

The Hiccup of Villarrica volcano (Chile) during the 2015 eruption and its expression in LP activity and VLP ground motion

SUMMARY Volcano seismology is an essential tool for monitoring volcanic processes in the advent and during eruptions. A variety of seismic signals can be recorded at volcanoes, of which some are thought to be related to the migration of fluids which is of primary importance for the anticipation of imminent eruptions. We investigate the volcanic crises at Villarrica volcano in 2015 and report on a newly discovered very-long-period (VLP) signal that accompanies phases of periodic long period (LP) signal burst. Despite their low amplitude emergent character, we can locate the source region of the 1 Hz LP signals to the close vicinity of the volcano using a network-based correlation method. The source of the VLP signal with a period of about 30–100 s appears to locate in the vicinity of two stations a few kilometres from the summit. Both stations record very similar VLP waveforms that are correlated with the envelope of the LP bursts. A shallow magma reservoir was inferred by Contreras from surface deformation as the source of inflation following the eruption in 2015. Cyclic volume changes of 6 m3 in this reservoir at 3 km depth can explain the observed amplitudes of the vertical VLP signal. We propose that the LP signal is generated by the migration of gas or gas-rich magma that is periodically released from the inflating reservoir through a non-linear valve structure which modulates the flux, and thereby causes bursts of flow-related LP signals and pressure changes observed as VLP deformation. Our model predicts that the correlated occurrence of LP bursts and VLP surface motion depends on the intensity of the fluid flux. A weaker flux of fluids may not exceed the opening pressure of valve structure, and higher rates might maintain pressure above the closing pressure. In both cases, the VLP signal vanishes. Our observation provides constrains for models of fluid transport inside volcanoes. At Villarrica the VLP signal, and its relation to the LP activity, reveal additional information about fluxes in the magmatic reservoir that might aide forecasting of volcanic activity.

Measuring Cerebrovascular Reactivity: Sixteen Avoidable Pitfalls.

An increase in arterial PCO2 is the most common stressor used to increase cerebral blood flow for assessing cerebral vascular reactivity (CVR). That CO2 is readily obtained, inexpensive, easy to administer, and safe to inhale belies the difficulties in extracting scientifically and clinically relevant information from the resulting flow responses. Over the past two decades, we have studied more than 2,000 individuals, most with cervical and cerebral vascular pathology using CO2 as the vasoactive agent and blood oxygen-level-dependent magnetic resonance imaging signal as the flow surrogate. The ability to deliver different forms of precise hypercapnic stimuli enabled systematic exploration of the blood flow-related signal changes. We learned the effect on CVR of particular aspects of the stimulus such as the arterial partial pressure of oxygen, the baseline PCO2, and the magnitude, rate, and pattern of its change. Similarly, we learned to interpret aspects of the flow response such as its magnitude, and the speed and direction of change. Finally, we were able to test whether the response falls into a normal range. Here, we present a review of our accumulated insight as 16 “lessons learned.” We hope many of these insights are sufficiently general to apply to a range of types of CO2-based vasoactive stimuli and perfusion metrics used for CVR.

Non-Pathological Opacification of the Cavernous Sinus on Brain CT Angiography: Comparison with Flow-Related Signal Intensity on Time-of-Flight MR Angiography.

Purpose: To investigate the non-pathological opacification of the cavernous sinus (CS) on brain computed tomography angiography (CTA) and compare it with flow-related signal intensity (FRSI) on time-of-flight magnetic resonance angiography (TOF-MRA). Methods: Opacification of the CS was observed in 355 participants who underwent CTA and an additional 77 participants who underwent examination with three diagnostic modalities: CTA, TOF-MRA, and digital subtraction angiography (DSA). Opacification of the CS, superior petrosal sinus (SPS), inferior petrosal sinus (IPS), and pterygoid plexus (PP) were also analyzed using a five-point scale. The Wilcoxon test was used to determine the frequencies of the findings on each side. Additionally, the findings on CTA images were compared with those on TOF-MRA images in an additional 77 participants without dural arteriovenous fistula (DAVF) using weighted kappa (κ) statistics. Results: Neuroradiologists identified non-pathological opacification of the CS (n = 100, 28.2%) on brain CTA in 355 participants. Asymmetry of opacification in the CS was significantly correlated with the grade difference between the right and left CS, SPS, IPS, and PP (p < 0.0001 for CS, p < 0.0001 for SPS, p < 0.0001 for IPS, and p < 0.05 for PP). Asymmetry of the opacification and FRSI in the CS was observed in 77 participants (CTA: n = 21, 27.3%; TOF-MRA: n = 22, 28.6%). However, there was almost no agreement between CTA and TOF-MRA (κ = 0.10, 95% confidence interval: −0.12–0.32). Conclusion: Asymmetry of non-pathological opacification and FRSI in the CS may be seen to some extent on CTA and TOF-MRA due to anatomical variance. However, it shows minimal reliable association with the FRSI on TOF-MRA.

3D-Visualization of Neurovascular Compression at the Ventrolateral Medulla in Patients with Arterial Hypertension

PurposeControversy exists on the association of arterial hypertension (HTN) and neurovascular compression (NVC) at the ventrolateral medulla (VLM). No standardized and reproducible technique has been introduced yet for detection of NVC in HTN. This study aimed to generate, analyze and compare different results of exact reproducible anatomical 3D-representations of the VLM in patients with HTN, based on magnetic resonance imaging (MRI).MethodsA 3T scanner provided MRI (T2-constructive interference in steady state (CISS) high resolution imaging and three-dimensional Time-of-flight (3D-TOF) angiography) from the posterior fossa of 44 patients with clinical treatment-resistant HTN. Image processing consists of segmentation of the CISS data, registration and fusion of the CISS and TOF data and visualization. For each patient two 3D-visualizations (before and after fusion) were obtained. The reproduction quality of the vessels, flow-related signal variability and pulsation artifacts were analyzed and compared, using a ranking score.ResultsIntegrating vascular information from TOF into CISS data reduced artifacts in 3D-visualizations of exclusively processed CISS data. The quality of 3D-visualization of the vessels near the brain stem was significantly improved (p = 0.004). The results were reproducible and reliable. The quality of the 3D-presentations of neurovascular relationships at the VLM improved significantly (p < 0.001).ConclusionThe 3D-visualization of fused image data provides an excellent overview of the relationship between cranial nerves and vessels at the VLM and simplifies the detection of NVC in HTN. It provides a powerful tool for future clinical and scientific research. Although microvascular decompression (MVD) in treatment resistant HTN is not a standard procedure, it can be discussed in selected patients with intractable severe HTN.

LACK OF BLOOD FLOW BLOCKS MOUSE HSC DEVELOPMENT AT THE PRO-HSC STAGE

Hematopoietic stem cells (HSCs) emerge from aortic hemogenic endothelium through a continuum of precursors, the pro- and pre-HSCs. Studies in zebrafish have implicated blood flow in this process. In the mouse, embryos without blood flow die before transplantable HSCs appear, precluding a direct assessment of the role of flow in HSC emergence. With the recent identification of pro-HSCs that emerge early in development and can be matured ex vivo into functional HSCs, it is now possible to address this question. Here, we assessed the specification and development of the HSC lineage in Ncx1-/- embryos lacking a heartbeat and circulation. We found that hemogenic endothelium and pro-HSCs emerge at a normal frequency, although in reduced numbers. However, Ncx1-/- pro-HSCs were severely impaired in their function and did not give rise to functional HSCs ex vivo. These data indicate that although the first steps of HSC lineage development take place in the absence of circulation, HSC precursors fail to complete their maturation, possibly due to the absence of key signaling events triggered by blood flow. Single cell gene expression profiling showed an aberrant signature in pro-HSCs and hemogenic endothelium isolated from Ncx1-/- embryos, with evidence of a block in hematopoietic development. Moreover, our data showed a decrease in Jag1-mediated Notch signaling in E9.5 Ncx1-/- hemogenic endothelium and pro-HSC, with a role for Notch signaling in the maturation of pro-HSC into HSCs further supported by functional assays. Finally, we found that lack of blood flow resulted in defects in the microenvironment, with absence of peri-aortic smooth muscle and a decrease of macrophages. Exploring what other flow-related signals affect the maturation of pro-HSC along the HSC lineage will be of interest in light of the future optimizing of in vitro HSC generation for therapeutic purposes.

57-Year-Old Man With Vertigo

57-Year-Old Man With Vertigo

ISING MODEL OF CHORIOCAPILLARIS FLOW.

To develop a mathematical model of local blood flow in the choriocapillaris using an Ising model. A JavaScript Ising model was used to create images that emulated the development of signal voids as would be seen in optical coherence tomography angiography of the choriocapillaris. The model was produced by holding the temperature near criticality and varying the field strength. Individual frames were evaluated, and a movie video was created to show the hypothetical development of flow-related signal voids over a lifetime. Much the same as actual choriocapillaris images in humans, the model of flow-related signal voids followed a power-law distribution. The slope and intercept both decreased with age, as is seen in human subjects. This model is a working hypothesis, and as such can help predict system characteristics, evaluate conclusions drawn from studies, suggest new research questions, and provide a way of obtaining an estimate of behavior in which experimental data are not yet available. It may be possible to understand choriocapillaris blood flow in health and disease states by determining by observing deviations from an expected model.

Internal Jugular Microembolic Signal Detection in a Patient with Cerebral Sinus Thrombosis Complicated by Pulmonary Embolism

A 40-year-old woman with prior history of headaches, left-sided weakness, and diplopia was diagnosed with right sigmoid and transverse sinus thrombosis; increased intracranial pressure and associated cerebral venous infarction that underwent 12 months anticoagulation and then stopped. She has been off anticoagulation for about a year then started not “feeling right,” and was diagnosed with pneumonia and pulmonary embolism. During her course of hospitalization, she presented with progressive headache, possible left-sided weakness, associated blurry vision, nausea, and vomiting. Magnetic resonance venogram (MRV) shows lack of flow-related signals within the left half of the distal superior sagittal sinus, left transverse sinus, and nonocclusive thrombus in the left sigmoid sinus. Mechanical sinus thrombectomy attempted without significant difference in clot burden. A transcranial Doppler (TCD) emboli monitoring exam was ordered and was performed on the bilateral internal jugular for 15 min each. Microembolic signals detected: 52 emboli per hour right internal jugular vein (IJV), and 32 emboli per hour left IJV. She was discharged on methazolamide, furosemide, topiramate, and lifelong warfarin. No major events have been reported since discharge from 2008 to 2016.

An intravoxel oriented flow model for diffusion-weighted imaging of the kidney.

By combining intravoxel incoherent motion (IVIM) and diffusion tensor imaging (DTI) we introduce a new diffusion model called intravoxel oriented flow (IVOF) that accounts for anisotropy of diffusion and the flow-related signal. An IVOF model using a simplified apparent flow fraction tensor (IVOFf ) is applied to diffusion-weighted imaging of human kidneys. The kidneys of 13 healthy volunteers were examined on a 3T scanner. Diffusion-weighted images were acquired with six b values between 0 and 800s/mm(2) and 30 diffusion directions. Diffusivity and flow fraction were calculated for different diffusion models. The Akaike information criterion was used to compare the model fit of the proposed IVOFf model to IVIM and DTI. In the majority of voxels the proposed IVOFf model with a simplified apparent flow fraction tensor performs better than IVIM and DTI. Mean diffusivity is significantly higher in DTI compared with models that account for the flow-related signal. The fractional anisotropy of diffusion is significantly reduced when flow fraction is considered to be anisotropic. Anisotropy of the apparent flow fraction tensor is significantly higher in the renal medulla than in the cortex region. The IVOFf model describes diffusion-weighted data in the human kidney more accurately than IVIM or DTI. The apparent flow fraction in the kidney proved to be anisotropic.

Current Developments on Optical Feedback Interferometry as an All-Optical Sensor for Biomedical Applications.

Optical feedback interferometry (OFI) sensors are experiencing a consistent increase in their applications to biosensing due to their contactless nature, low cost and compactness, features that fit very well with current biophotonics research and market trends. The present paper is a review of the work in progress at UPC-CD6 and LAAS-CNRS related to the application of OFI to different aspects of biosensing, both in vivo and ex vivo. This work is intended to present the variety of opportunities and potential applications related to OFI that are available in the field. The activities presented are divided into two main sensing strategies: The measurement of optical path changes and the monitoring of flows, which correspond to sensing strategies linked to the reconstruction of changes of amplitude from the interferometric signal, and to classical Doppler frequency measurements, respectively. For optical path change measurements, measurements of transient pulses, usual in biosensing, together with the measurement of large displacements applied to designing palliative care instrumentation for Parkinson disease are discussed. Regarding the Doppler-based approach, progress in flow-related signal processing and applications in real-time monitoring of non-steady flows, human blood flow monitoring and OFI pressure myograph sensing will be presented. In all cases, experimental setups are discussed and results presented, showing the versatility of the technique. The described applications show the wide capabilities in biosensing of the OFI sensor, showing it as an enabler of low-cost, all-optical, high accuracy biomedical applications.

Abstract TP118: New Markers for Basilar Artery Atherosclerotic Plaque on Conventional T2-weighted MR Imaging

Backgrounds and purpose: In vivo visualization of intracranial atherosclerotic plaque has been studied with high-resolution wall MRI (HRMRI). However, HRMRI is not widely available in routine clinical practice. We hypothesized that increased outer wall and partial loss of flow-void of basilar artery (BA) in conventional T2 axial imaging might be suggestive of positive remodeling and atherosclerotic plaque. Methods: Using a consecutive stroke registry, patients with basilar artery atherosclerotic steno-occlusion were identified. Subjects with same range of age who were negative for abnormal wall thickening of the BA in HRMRI served as controls. Using conventional T2 axial images, maximal diameter and T2 plaque sign (an eccentric or complete obscuration of normal flow-related T2 signal void) within the BA were measured. We tested the diagnostic value of T2 plaque sign and maximal diameter to distinguish patients from controls. Results: Seventy-five patients (age range, 51-81) and 36 controls (50-81) were identified. Maximal diameter was significantly larger in patients than controls (3.87 ± 0.868 mm vs 2.68 ± 0.447 mm, p&lt;0.001). Positivity of T2 plaque sign were 61.3% in patients with BA atherosclerosis, 71.2% in patients with &gt;30% BA stenosis, 77.5% in &gt;50% BA stenosis, and 96.3% in patients with &gt;70% BA stenosis. Receiver operating characteristic curve showed high predictive power (the area under the curve 0.921, 95% CI 0.872 - 0.970, p&lt;0.001) of maximal BA diameter to distinguish patients and controls with an optimal cutoff of 3.185 mm, (sensitivity, 78.7%; specificity, 94.4%). Sensitivity and specificity of T2 plaque sign were 61.3% and 100.0% for BA atherosclerosis of any degree. Increasing sensitivity and decreasing specificity were noted for the diagnosis of higher degree stenosis. Conclusion: Our data suggest that increased BA diameter and plaque sign on conventional T2 imaging are markers of basilar artery atherosclerosis. This would be helpful for earlier identification of causative stroke mechanism. Further study is needed for validation of these findings among different stroke etiologies.

Transient Global Amnesia as a Presenting Manifestation of Cerebral Venous Thrombosis

Transient Global Amnesia as a Presenting Manifestation of Cerebral Venous Thrombosis

Large Enhancement of Perfusion Contribution on fMRI Signal

The perfusion contribution to the total functional magnetic resonance imaging (fMRI) signal was investigated using a rat model with mild hypercapnia at 9.4 T, and human subjects with visual stimulation at 4 T. It was found that the total fMRI signal change could be approximated as a linear superposition of 'true' blood oxygenation level-dependent (BOLD; T(2)/T(2)(*)) effect and the blood flow-related (T(1)) effect. The latter effect was significantly enhanced by using short repetition time and large radiofrequency pulse flip angle and became comparable to the 'true' BOLD signal in response to a mild hypercapnia in the rat brain, resulting in an improved contrast-to-noise ratio (CNR). Bipolar diffusion gradients suppressed the intravascular signals but had no significant effect on the flow-related signal. Similar results of enhanced fMRI signal were observed in the human study. The overall results suggest that the observed flow-related signal enhancement is likely originated from perfusion, and this enhancement can improve CNR and the spatial specificity for mapping brain activity and physiology changes. The nature of mixed BOLD and perfusion-related contributions in the total fMRI signal also has implication on BOLD quantification, in particular, the BOLD calibration model commonly used to estimate the change of cerebral metabolic rate of oxygen.

Posterior fossa dural arteriovenous fistulas: diagnosis and follow-up with time-resolved imaging of contrast kinetics (TRICKS) at 1.5T

Time-of-flight MR angiography (TOF MRA) is currently the most widely used non-invasive imaging tool to diagnose dural arteriovenous fistula (DAVF). It is, however, not as sensitive as invasive digital subtraction angiography (DSA) for detecting the arteriovenous shunting inherent in DAVF. Dynamic contrast-enhanced MR angiography allows separation of arterial and venous phases of contrast passage though the brain and can thus demonstrate early venous filling through the arteriovenous shunt. To compare the diagnostic value of TOF MRA and a commercially available dynamic contrast-enhanced MR angiography sequence (TRICKS) at 1.5T in detecting posterior fossa DAVF. We retrospectively collected image data for 19 patients who underwent TOF MRA, TRICKS, and DSA either for primary diagnosis or for follow-up of posterior fossa DAVF and assessed the performance of TOF MRA and TRICKS in demonstrating the arteriovenous shunt, with DSA as the reference standard. TRICKS detected early arterial filling at 94.4% sensitivity and 83.3% specificity. TOF MRA detected high flow-related signal within venous structures at 64.7% sensitivity and 80% specificity. The commercially available dynamic MR angiography sequence TRICKS with fully automatic vendor postprocessing at 1.5T is more sensitive than TOF MRA in detecting the arteriovenous shunt in posterior fossa DAVF.

The Usefulness of the Source Images of Magnetic Resonance Angiogram in the Carotid Cavernous Fistula

The cortical venous drainage from carotid-cavernous fistula (CCF) is associated with increased risk of intraparenchymal hemorrhage and may be the clue for the urgent indication of an endovascular treatment [1]. However it is difficult to infer direction of venous drainage from the clinical signs or symptoms of a patient with CCF. The source images of magnetic resonance angiogram (MRA) may useful to detect the direction and magnitude of the collateral circulations in the patient with carotid-cavernous fistula (CCF) [2]. A 68-year-old woman presented with progressive bilateral pulsatile tinnitus, headache and diplopia accompanied by swelling of both eyes, the right eye being more severely affected. She underwent surgical reconstruction of fractured facial bone 6 weeks ago due to car accident. From the 30th days after reconstruction, she suffered persistent progressive pulsatile tinnitus and periorbital pain. The MRA revealed marked leakage signals of arterial blood around cavernous sinus (Figure 1). The source image of MRA revealed increased transsellar collaterals, enlarged both sphenoparietal sinus and right side predominant elongated bilateral tortuous superior ophthalmic veins (Figure 2). Figure 1 The magnetic resonance angiogram (MRA) of the patient showed increased flow related signals around both cavernous sinuses. Figure 2 The source image of magnetic resonance angiogram (MRA) revealed increased transsellar collaterals (a, b), enlarged both inferior cerebral veins (C; arrow) and right side predominant elongated bilateral tortuous superior ophthalmic veins (c, d; arrow head). ...

Three-dimensional time-of-flight (3d tof) magnetic resonance angiography (mra) and contrast-enhanced mra of intracranial aneurysms treated with platinum coils

Contrast-enhanced magnetic resonance angiography (CE-MRA) is less prone to flow-related signal intensity loss than three-dimensional time-of-flight (3D TOF) MRA and may therefore be more sensitive for detection of residual patency in platinum coil-treated intracranial aneurysms. To compare MRA and CE-MRA in the follow-up of intracranial aneurysms treated with platinum coils. CE-MRA and 3D TOF MRA (pre- and postcontrast injection) of the intracranial vasculature was performed at 1.5T in 38 patients (47 aneurysms) referred for DSA in the follow-up of coiled intracranial aneurysms. DSA showed aneurysm patency in 22/47 investigations. Patent aneurysm components were observed with CE-MRA in 18/22 cases, and with 3D TOF MRA in 21/22 cases. There was no significant difference in patent aneurysm component size between CE-MRA and 3D TOF MRA. In addition, CE-MRA showed six, 3D TOF MRA before contrast injection showed seven, and 3D TOF MRA after contrast injection showed eight cases with patent aneurysm components not observed on DSA. 3D TOF MRA was highly sensitive for detection of patent aneurysm components, and at least as sensitive as CE-MRA. Residual aneurysm patency seems to be better visualized with MRA than with DSA in some cases.