Standard Magnetic Resonance Angiography Research Articles

Visualisation of lenticulostriate arteries using contrast-enhanced time-of-flight magnetic resonance angiography at 7 Tesla

7 Tesla-field-strength (7 T) Magnetic Resonance Imaging allows the small perforating arteries in the brain to be visualised, and this modality may allow visualisation of the arterial pathology in cerebral small vessel disease. Most studies have used standard Time-of-Flight (ToF) Magnetic Resonance Angiography (MRA). Whether the use of contrast enhancement improves perforating artery visualisation at 7 T remains unclear. In a prospective study, we compared standard ToF MRA with contrast-enhanced (CE) ToF MRA at 7 T for the visualisation of the lenticulostriate arteries (LSAs). Ten patients with symptomatic lacunar stroke were recruited (mean age, SD, 64 ± 9.9 years). Visualisation was assessed using a visual rating scale administered by two independent expert readers and length of the LSAs visible. Visualisation of the LSAs was improved with CE ToF MRA. The mean Visibility and Sharpness Score was higher for CE ToF MRA over standard ToF MRA (2.55 ± 0.64 vs. 1.75 ± 0.68; P = 0.0008). The mean length of LSA visualised was significantly longer with CE ToF MRA compared to standard ToF MRA (24.4 ± 4.5 vs. 21.9 ± 4.0 mm; P = 0.01). CE ToF MRA offers improved visualisation of the LSAs over standard ToF MRA. The addition of contrast may improve the ability to visualise cerebral small vessel disease arterial pathology.

Accuracy of Inflow Inversion Recovery (IFIR) for Upper Abdominal Arteries Evaluation: Comparison with Contrast-Enhanced MR and CTA.

Background: Inflow-sensitive inversion recovery (IFIR) is a recently introduced technique to perform unenhanced magnetic resonance angiography (MRA). The purpose of our study is to determine the accuracy of IFIR-MRA in the evaluation of upper abdominal arteries, compared to standard MRA and computed tomography angiography (CTA). Materials and Methods: Seventy patients undergoing upper abdomen Magnetic Resonance Imaging (MRI) in different clinical settings were enrolled. The MRI protocol included an IFIR-MRA sequence that was intra-individually compared by using a qualitative 4-point scale in the same patients who underwent concomitant or close MRA (n = 65) and/or CTA (n = 44). Celiac trunk (CA), common-proper-left-right hepatic artery (C-P-L-R-HA), left gastric artery (LGA), gastroduodenal artery (GDA), splenic artery (SA), renal arteries (RA) and superior mesenteric artery (SMA) were assessed. Results: IFIR-MRA images were better rated in comparison with MRA. Particularly, all arteries obtained a statistically significant higher qualitative rating value (all p < 0.05). IFIR-MRA and MRA exhibited acceptable intraclass correlation coefficients (ICC) values for CA, C-L-R-HA, and SMA (ICC 0.507, 0.591, 0.615, 0.570, 0.525). IFIR-MRA and CTA showed significant correlations in C-P-L-R-HA (τ = 0.362, 0.261, 0.308, 0.307, respectively; p < 0.05), and in RA (τ = 0.279, p < 0.05). Conclusions: Compared to MRA, IFIR-MRA demonstrated a higher image quality in the majority of upper abdomen arterial vessels assessment. LHA and RHA branches could be better visualized with IFIR sequences, when visualizable. Based on these findings, we suggest to routinely integrate IFIR sequences in upper abdomen MRI studies.

7T versus 3T MR Angiography to Assess Unruptured Intracranial Aneurysms.

ABSTRACTBACKGROUND AND PURPOSEAneurysm size and neck measurements are important for treatment decisions. The introduction of 7T magnetic resonance angiography (MRA) led to new possibilities assessing aneurysm morphology and flow due to the higher signal‐to‐noise ratio. However, it is unknown if the size measurements on 7T MRA are similar to those on the standard 3T MRA. This study aimed to compare aneurysm size measurements between 7T and 3T MRA.METHODSWe included 18 patients with 22 aneurysms who underwent both 3T and 7T MRA. Three acquisition protocols were compared: 3T time of flight (TOF), 7T TOF, and 7T contrast‐enhanced MRA. Each aneurysm on each protocol was measured by at least two experienced neuroradiologists. Subsequently, the differences were evaluated using scatterplots and the intraclass correlation coefficients (ICC) of agreement.RESULTSThere was a good agreement among the neuroradiologists for the height and width measurements (mean ICC: .78‐.93); the neck measurements showed a moderate agreement with a mean ICC of .57‐.72. Between the MR acquisition protocols, there was a high agreement for all measurements with a mean ICC of .81‐.96. Measurement differences between acquisition protocols (0‐2.9 mm) were in the range of the differences between the neuroradiologists (0‐3.6 mm).CONCLUSIONOur study showed that 7T MRA, both nonenhanced and contrast‐enhanced, has a high agreement in aneurysm size measurements compared to 3T. This suggests that 7T is useful for reliable aneurysm size assessment.

Altered 4-D magnetic resonance imaging flow characteristics in complex congenital aortic arch repair

Interrupted aortic arch (IAA) is a rare but severe congenital abnormality often associated with bicuspid aortic valve (BAV). Complex re-interventions are often needed despite surgical advances, but the impact of aortic hemodynamics in repaired patients is unknown. Investigate effect of IAA repairs on aortic hemodynamics, wall shear stress and flow derangements via 4-D flow MRI. We retrospectively analyzed age- and gender-matched cohorts (IAA [n=6], BAV alone [n=6], controls [n=6]) undergoing cardiac MRI including 4-D flow. Aortic dimensions were measured from standard MR angiography. We quantified peak systolic velocities, regurgitant fractions and wall shear stress in the ascending aorta (AAo), transverse arch and descending aorta (DAo) from 4-D flow, and we graded helix/vortex flow patterns from 3-D blood flow visualization. Children and young adults with IAA had a wide range of arch dimensions, peak systolic velocities, regurgitant fractions and flow grades. Peak transverse arch systolic velocities were higher in patients with IAA versus controls (P=0.02). Flow derangements in the AAo were found in patients with IAA (median grade=2, 5/6 patients, P=0.04) and BAV (median grade=3, 5/6 patients, P=0.03) versus controls. Flow derangements in the DAo were only seen in patients with IAA (median grade=1, 5/6 patients, P=0.04), and 5/6 people with IAA had helical flow in head and neck vessels. Wall shear stress was increased in people with IAA along the superior transverse arch and proximal DAo versus controls (P=0.02). Complex congenital aortic arch repairs can change aortic hemodynamics. Associated cardiac defects can further alter findings. Studies are warranted to investigate clinical implications in larger cohorts.

Single-Shot Coronary Quiescent-Interval Slice-Selective Magnetic Resonance Angiography Using Compressed Sensing: A Feasibility Study in Patients With Congenital Heart Disease.

The aim of this study was to determine whether it is feasible to visualize the coronary origins in patients with congenital heart disease (CHD) using single-shot coronary quiescent-interval slice-selective (QISS) magnetic resonance angiography (MRA) with compressed sensing (CS). This retrospective study leveraged a parent study, which aimed to compare breath-hold, 2.1-fold accelerated, 2-shot coronary QISS MRA and clinical standard contrast-enhanced (CE) MRA in 14 patients with CHD (mean age, 17.0 ± 8.6 years, 6 females and 8 males). We evaluated the feasibility of single-shot coronary QISS MRA by retrospectively undersampling the 2-shot data set by an additional factor of 2, performing CS reconstruction, and comparing the retrospectively derived single-shot QISS MRA to 2-shot coronary QISS MRA and clinical standard CE MRA. For quantitative analysis, structural similarity index and normalized root mean square error were calculated. For qualitative analysis, 2 experienced readers scored the conspicuity of coronary origins on a 5-point Likert scale (1 = nondiagnostic, 2 = poor, 3 = clinically acceptable, 4 = good, 5 = excellent). Compared with 2-shot QISS, single-shot QISS produced normalized root mean square error of 5.8% ± 0.8% and structural similarity index of 95.4% ± 1.6%, suggesting high data fidelity by CS reconstruction. Compared with the mean conspicuity scores for clinical CE MRA (4.2 ± 0.5 and 4.1 ± 0.6 for right and left coronary origins, respectively), the mean conspicuity scores were not significantly different (P > 0.3) for 2-shot QISS (4.4 ± 0.9 and 4.2 ± 1.1, respectively) and single-shot QISS with CS (4.3 ± 1.1 and 3.8 ± 1.3, respectively) and deemed clinically acceptable to good (scores ≥3.0). This study shows that it is feasible to visualize the coronary origins in patients with CHD with clinically acceptable to good image quality using single-shot coronary QISS MRA with CS.

Misinterpretation of ischaemic infarct location in relationship to the cerebrovascular territories

PurposeCerebral perfusion territories are known to vary widely among individuals. This may lead to misinterpretation of the symptomatic artery in patients with ischaemic stroke to a wrong assumption of the...

Improved characterization of popliteal aneurysms using gadofosveset-enhanced equilibrium phase magnetic resonance angiography

Although standard magnetic resonance angiography (MRA) has many advantages in the evaluation of peripheral artery disease, it has poorer spatial resolution compared with computed tomographic angiography and digital subtraction angiography. The MRA blood pool contrast agents have an extended half-life. By allowing longer imaging times, MRA enables the acquisition of high-resolution images as well as providing simultaneous visualization of both arteries and veins. Two cases of popliteal artery aneurysm are presented, in which MRA with a blood pool contrast agent provided critical clues to the correct diagnosis: a traumatic pseudoaneurysm of the popliteal artery caused by a femoral osteochondroma and a large fusiform popliteal aneurysm compressing the adjacent popliteal vein, causing venous congestion and leg pain.

Anomalous origin of the occipital artery diagnosed by magnetic resonance angiography

It is well known that the occipital artery (OA) can arise from the internal carotid artery (ICA) or vertebral artery (VA). However, the incidence of an anomalously originating OA has not been reported. We investigate its incidence and characteristic features on magnetic resonance angiography (MRA). We retrospectively reviewed MRA images of 2,866 patients that included the carotid bifurcation; images were obtained using a standard noncontrast MRA protocol and two 1.5-T MR units. We diagnosed six cases (seven arteries) of anomalously originating OA, which represented an incidence of 0.21%. The OA arose from the ICA in four patients (five arteries), from the carotid bifurcation in one, and from the VA in one. Five of the seven arteries occurred on the right. Anomalously originating OA is rare and occurs with right-side predominance. Correct diagnosis is necessary before or during cerebral angiography, especially when selective catheterization to the OA is required.

4D phase contrast MRI at 3 T: Effect of standard and blood‐pool contrast agents on SNR, PC‐MRA, and blood flow visualization

Time-resolved phase contrast (PC) MRI with velocity encoding in three directions (flow-sensitive four-dimensional MRI) can be employed to assess three-dimensional blood flow in the entire aortic lumen within a single measurement. These data can be used not only for the visualization of blood flow but also to derive additional information on vascular geometry with three-dimensional PC MR angiography (MRA). As PC-MRA is sensitive to available signal-to-noise ratio, standard and novel blood pool contrast agents may help to enhance PC-MRA image quality. In a group of 30 healthy volunteers, the influence of different contrast agents on vascular signal-to-noise ratio, PC-MRA quality, and subsequent three-dimensional stream-line visualization in the thoracic aorta was determined. Flow-sensitive four-dimensional MRI data acquired with contrast agent provided significantly improved signal-to-noise ratio in magnitude data and noise reduction in velocity data compared to measurements without contrast media. The agreement of three-dimensional PC-MRA with reference standard contrast-enhanced MRA was good for both contrast agents, with improved PC-MRA performance for blood pool contrast agent, particularly for the smaller supra-aortic branches. For three-dimensional flow visualization, a trend toward improved results for the data with contrast agent was observed.

Improving the image quality of contrast-enhanced MR angiography by automated image registration: A prospective study in peripheral arterial disease of the lower extremities

Objective If a patient has moved during digital subtraction angiography (DSA), manual pixel shift can improve the image quality. This study investigated whether such image registration can also improve the quality of contrast-enhanced magnetic resonance angiography (MRA) in patients with peripheral arterial disease of the lower extremities. Materials and methods 404 leg MRAs of patients likely to have peripheral artery disease were included in this prospective study. The standard non-registered MRAs were compared to automatically linear, affine and warp registered MRAs by four image quality parameters, including the vessel detection probability (VDP) in maximum intensity projection (MIP) images and contrast-to-noise ratios (CNR). The different registration types were compared by analysis of variance. Results All studied image quality parameters showed similar trends. Generally, registration improved the leg MRA quality significantly ( P < 0.05). The 12% of lower legs with a body shift of 1 mm or more showed the highest gain in image quality when using linear registration instead of no registration, with an average VDP gain of 20–49%. Warp registration improved the image quality slightly further. Conclusion Automated image registration can improve the MRA image quality especially in the lower legs, which is comparable to the effect of pixel shift in DSA.

Dual-Energy CTA with Bone Removal for Transcranial Arteries: Intraindividual Comparison with Standard CTA without Bone Removal and TOF-MRA

Dual-source computed tomography enables bone removal on computed tomographic angiographic data on the basis of simultaneous dual-energy (DE) acquisition. The aim of this study was to evaluate the impact of this technique for the assessment of transcranial arteries. Therefore, the degree of stenosis of the transcranial arteries on DE computed tomographic angiography (CTA) with bone removal was compared to those on standard CTA and time-of-flight (TOF) magnetic resonance angiography (MRA). DE-CTA was performed using a dual-source computed tomographic scanner in 50 patients with suspected cerebrovascular disease. From the source images on DE-CTA, data sets with and without bone removal were reconstructed. TOF-MRA was performed on a 1.5-T scanner. Two blinded radiologists evaluated the segments of the internal carotid artery (C2-C7), the vertebral artery (V4), and the basilar artery for degree of stenosis. A five-step scale (0%-49%, 50%-69%, 70%-89%, 90%-99%, and 100% [occlusion]) for degree of stenosis was applied. Wilcoxon's signed-rank test was used for statistical analysis. The degrees of stenosis on standard CTA were consistent with those on TOF-MRA in all segments. In contrast, DE-CTA showed significantly higher degrees of stenosis compared to standard CTA and TOF-MRA in both C2 segments (P < .001). In addition, DE-CTA revealed a significantly higher degree of stenosis compared to standard CTA and TOF-MRA in the left C4 segment (P < .01 and P < .005, respectively). All other segments showed no significant differences of stenosis among TOF-MRA, DE-CTA, and standard CTA. Compared to TOF-MRA, standard CTA showed similar results. In contrast, DE-CTA revealed significant overestimation of stenosis for segments with close relations to bony structures as well as in calcified stenosis. Consequently, such findings on DE-CTA require confirmation with standard CTA or MRA to eliminate false-positive results.

Peripheral Bolus-Chase MR Angiography: Analysis of Risk Factors for Nondiagnostic Image Quality of the Calf Vessels—A Combined Retrospective and Prospective Study

The objective of our study was to evaluate the influence of endogenous and exogenous risk factors on the rate of nondiagnostic examinations of the calves in peripheral bolus-chase MR angiography (MRA). Peripheral bolus-chase MRA runoff studies in 177 patients with peripheral arterial occlusive disease (PAOD) were retrospectively assessed with regard to the rate of nondiagnostic image quality due to substantial venous overlay in the calf arteries requiring repeated MRA examinations. Logistic regression was used to analyze the rate of nondiagnostic MRA examinations as a function of several endogenous and exogenous risk factors and of the stage of PAOD. To probe the retrospective data, 22 consecutive patients were prospectively included and underwent a standard peripheral MRA examination if the probability of a nondiagnostic examination was less than 50% based on the results of logistic regression; otherwise, a hybrid MRA examination was ordered. Nondiagnostic image quality of the calf arteries was found in 53 patients (30%). The incidence increased with each stage of PAOD up to 39% for stage IV. For each increase in the stage of PAOD, the probability of nondiagnostic image quality increased by a factor of 1.5561 (p = 0.0024). With an increasing number of risk factors, a significantly (p = 0.0074) higher rate of nondiagnostic images was found. Based on the retrospective statistical analysis of PAOD stages and risk factors, selected patients can be triaged to undergo a specific hybrid MRA technique and thus circumvent the occurrence of nondiagnostic images and the need for repeated MRA examinations.

Contrast-enhanced magnetic resonance angiography in carotid artery disease: does automated image registration improve image quality?

Contrast-enhanced magnetic resonance angiography (MRA) is a noninvasive imaging alternative to digital subtraction angiography (DSA) for patients with carotid artery disease. In DSA, image quality can be improved by shifting the mask image if the patient has moved during angiography. This study investigated whether such image registration may also help to improve the image quality of carotid MRA. Data from 370 carotid MRA examinations of patients likely to have carotid artery disease were prospectively collected. The standard nonregistered MRAs were compared to automatically linear, affine and warp registered MRA by using three image quality parameters: the vessel detection probability (VDP) in maximum intensity projection (MIP) images, contrast-to-noise ratio (CNR) in MIP images, and contrast-to-noise ratio in three-dimensional image volumes. A body shift of less than 1 mm occurred in 96.2% of cases. Analysis of variance revealed no significant influence of image registration and body shift on image quality (p > 0.05). In conclusion, standard contrast-enhanced carotid MRA usually requires no image registration to improve image quality and is generally robust against any naturally occurring body shift.

Evaluation of Intracranial Aneurysms with 7 T versus 1.5 T Time-of-Flight MR Angiography – Initial Experience

The purpose of this study was to compare the depiction of intracranial aneurysms by 3D time-of-flight (TOF) magnetic resonance angiography (MRA) at 7 Tesla (T) with the clinical standard TOF MRA at 1.5 T and with digital subtraction angiography (DSA). 7 T and 1.5 T TOF MRA images optimized for both field strengths were compared in ten patients with an unruptured intracranial aneurysm. Two blinded neuroradiologists independently rated the image quality of the dome, the neck, and the vessel of origin of all aneurysms in MRA source and maximum intensity projection (MIP) images. DSA was obtained in all subjects and served as reference standard. The mean values of image quality were compared by Wilcoxon signed rank test. In all patients the number and location of the aneurysms was confirmed by DSA. Both readers identified twelve aneurysms in ten patients in 7 T, 1.5 T TOF MRA and DSA. The image quality of the aneurysm dome was rated higher in 8 of 12 aneurysms and the image quality of the aneurysm neck was superior in 9 of 12 aneurysms at 7 T TOF MRA compared to 1.5 T TOF MRA. The depiction of the parent vessel was graded almost equally by both readers. Our initial results indicate that image quality of intracranial aneurysms may benefit from the increased spatial resolution of 7 T TOF MRA compared with 1.5 T TOF MRA. Tailored scan protocols and optimized radiofrequency head coils are needed to further improve the image quality of 7 T TOF MRA.

3D Time-Resolved MR Angiography (MRA) of the Carotid Arteries with Time-Resolved Imaging with Stochastic Trajectories: Comparison with 3D Contrast-Enhanced Bolus-Chase MRA and 3D Time-Of-Flight MRA

Time-resolved MR angiography (MRA) offers the combined advantage of large anatomic coverage and hemodynamic flow information. We applied parallel imaging and time-resolved imaging with stochastic trajectories (TWIST), which uses a spiral trajectory to undersample k-space, to perform time-resolved MRA of the extracranial internal carotid arteries and compare it to time-of-flight (TOF) and high-resolution contrast-enhanced (HR) MRA. A retrospective review of 31 patients who underwent carotid MRA at 1.5T using TOF, time-resolved and HR MRA was performed. Images were evaluated for the presence and degree of ICA stenosis, reader confidence, and number of pure arterial frames attained with the TWIST technique. With a consensus interpretation of all sequences as the reference standard, accuracy for identifying stenosis was 90.3% for TWIST MRA, compared with 96.0% and 88.7% for HR MRA and TOF MRA, respectively. HR MRA was significantly more accurate than the other techniques (P < .05). TWIST MRA yielded datasets with high in-plane spatial resolution and distinct arterial and venous phases. It provided dynamic information not otherwise available. Mean diagnostic confidence was satisfactory or greater for TWIST in all patients. The TWIST technique consistently obtained pure arterial phase images while providing dynamic information. It is rapid, uses a low dose of contrast, and may be useful in specific circumstances, such as in the acute stroke setting. However, it does not yet have spatial resolution comparable with standard contrast-enhanced MRA.

Contrast-enhanced magnetic resonance angiography in peripheral arterial disease: Improving image quality by automated image registration

In peripheral arterial disease, contrast-enhanced MR angiography (MRA) is a noninvasive imaging alternative for catheter-based digital subtraction angiography (DSA). In DSA, final images are generated by subtracting a native mask image from subsequent contrast-enhanced images. Image quality is routinely improved by digitally shifting the mask image prior to subtraction if the patient has moved during angiography. This study investigated whether such image registration may also help to improve the image quality of MRA. In all, 545 MRA examinations of pelvic and leg arteries in patients with symptoms of peripheral arterial disease were studied retrospectively. Standard nonregistered MRA was compared to automatically linear, affine, and warp registered MRA by visual analysis and by three image quality parameters, including vessel detection probability (VDP) of angiographic maximum intensity projections. Most MRA of pelvic and upper leg arteries showed good nonregistered image quality. However, the 15% of lower legs with a body shift of 1 mm or more had relatively low nonregistered image quality, which improved significantly with image registration (VDP gain more than 18%, P < 0.05). The visual analysis gave similar results. In conclusion, image registration can improve image quality of MRA in peripheral arterial disease, especially in the lower legs.

Peripheral Arteries in Diabetic Patients: Standard Bolus-Chase and Time-resolved MR Angiography

To prospectively determine the diagnostic performance of a combination of standard bolus-chase magnetic resonance (MR) angiography and MR angiography with time-resolved imaging of contrast kinetics (TRICKS) for depicting severity of peripheral vascular disease of the lower extremity, including the pedal arteries, in diabetic patients with digital subtraction angiography (DSA) as the reference standard. An ethical committee approved this study; written informed consent was obtained from patients. Standard three-station and TRICKS MR angiography of the calf and foot were performed in 31 consecutive diabetic patients (23 men, eight women; mean age, 67 years; range, 43-81 years). Two readers separately assessed images of arterial segments as diagnostic or nondiagnostic and graded stenosis. Results were compared with those at DSA when the corresponding arterial segments were considered diagnostic at DSA. Wilcoxon signed rank test was used to determine if a significant difference between imaging techniques existed, and kappa statistics were used to determine interobserver agreement. The difference between standard MR angiography and DSA regarding the number of diagnostic segments in the thigh was not significant (P = .50). A significantly higher number of calf and foot segments was considered diagnostic at TRICKS MR angiography than at standard MR angiography (P < .025). Sixteen of 26 segments in the foot that were considered nondiagnostic at DSA were considered diagnostic at TRICKS MR angiography. Average sensitivity of standard MR angiography for depicting hemodynamically significant arterial stenosis was 84% (reader 1) and 83% (reader 2) in the thigh and 78% (reader 1) and 80% (reader 2) in the calf. For both readers, average specificity was 97% in the thigh and 90% in the calf. Sensitivity and specificity of TRICKS MR angiography in the calf and foot were improved compared with those at standard MR angiography. TRICKS MR angiography of the distal calf and pedal vessels is superior to standard MR angiography regarding the number of diagnostic segments and assessment of the degree of luminal narrowing.

Regular Blood Transfusion Does Not Prevent Progression of Cerebral Lesions Evidenced by Magnetic Resonance Imaging in Children with Sickle Cell Disease (SCD).

Purpose: The effects of chronic transfusion on the cerebral vessel abnormalities in SCD patients are unknown. Chronic transfusion has been reported to be effective in preventing recurrence of overt strokes, and occurrence of a first stroke in children with abnormal transcranial Doppler ultrasonography (TCD). However, cerebrovascular events may occur despite adequate prevention, suggesting that transfusion therapy does not cure nor even stabilize vessels disease. We conducted a single center retrospective study to determine the evolution of cerebral lesions in SCD children on regular transfusion therapy using magnetic resonance imaging.Material and methods: Children with homozygous sickle cell anemia chronically transfused for first or secondary prevention of stroke were included in the study. All patients had been started in a program of monthly transfusions, maintaining constantly hemoglobin S level below 30%, in the month following the stroke or the abnormal TCD. They underwent cerebral magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) every one to two years. An expert neuroradiologist unaware of the date of the imaging and unaware of the identity of the patients reviewed resulting images. Standard MRI criteria were used to identify lacunae, cerebral atrophy, infarcts and leucoencephalopathy, with progressive grading. Standard MRA criteria were used to identify arterial tortuosity, stenosis/occlusion and moya-moya with progressive grading. All MRI and MRA were scored, and these scores were compared longitudinally in each patient using a Paired Rank test.Results: 18 children (9 males, 9 females) were enrolled. Chronic transfusion therapy was prescribed and initiated for 10 patients with initial strokes (mean age at the stroke 6,8 +/− 2,5 yrs) and 8 patients with abnormal TCD (mean age at the TCD 7,2 +/− 2,9 yrs). Mean follow-up was 6,8 +/− 4,1 yrs in the stroke group, 1,7 +/− 1,0 yrs in the abnormal TCD group. A total of 45 MR images were reviewed (median MR/patient: 3 [2–4]). Initial scores were lower in the abnormal TCD group than in the stroke group (mean score respectively 1 [0–7] versus 12 [2–26]). Comparison of longitudinal scores in the group of patients with initial stroke evidenced progression of lesions (p=0,008). The longitudinal scores were not significantly different in the abnormal TCD group, but this may be explained by the shorter follow-up.Conclusion: Blood transfusion maintaining permanently HbS level <30% does not prevent progression of cerebral micro or macro vascular lesions in SCD children having had a 1st stroke. A lengthier follow-up is needed to reach a conclusion in the case of children with abnormal TCD. Our results support the case that early bone marrow transplant therapy should be applied to prevent progression of cerebral vasculopathy in SCD children at risk.

Time-resolved 3D contrast-enhanced MRA with GRAPPA on a 1.5-T system for imaging of craniocervical vascular disease: initial experience

For three-dimensional (3D) imaging with magnetic resonance angiography (MRA) of the cerebral and cervical circulation, both a high temporal and a high spatial resolution with isovolumetric datasets are of interest. In an initial evaluation, we analyzed the potential of contrast-enhanced (CE) time-resolved 3D-MRA as an adjunct for neurovascular MR imaging. In ten patients with various cerebrovascular disorders and vascularized tumors in the cervical circulation, high-speed MR acquisition using parallel imaging with the GeneRalized Autocalibrating Partially Parallel Acquisitions (GRAPPA) algorithm on a 1.5-T system with a temporal resolution of 1.5 s per dataset and a nearly isovolumetric spatial resolution was applied. The results were assessed and compared with those from conventional MRA and digital subtraction angiography (DSA). CE time-resolved 3D-MRA enabled the visualization and characterization of high-flow arteriovenous shunts in cases of vascular malformations or hypervascularized tumors. In steno-occlusive disease, the method provided valuable additional information about altered vessel perfusion compared to standard MRA techniques such as time-of-flight (TOF) MRA. The use of a nearly isovolumetric voxel size allowed a free-form interrogation of 3D datasets. Its comparatively low spatial resolution was found to be the major limitation. In this preliminary analysis, CE time-resolved 3D-MRA was revealed to be a promising complementary MRA sequence that enabled the visualization of contrast flow dynamics in various types of neurovascular disorders and vascularized cervical tumors.

On improving temporal and spatial resolution of 3D contrast-enhanced body MR angiography with parallel imaging.

Use of a parallel imaging technique to improve temporal and spatial resolution at three-dimensional contrast-enhanced magnetic resonance (MR) angiography was investigated. Thirty experiments were performed in five groups of healthy subjects. In groups 1-3, the technique was used to improve imaging speed by a factor of two or four while maintaining spatial resolution. Contrast agent concentration was two to four times higher than at standard MR angiography, to take advantage of the faster imaging speed. In groups 4 and 5, the technique was used to double spatial resolution in the phase-encoding direction while maintaining imaging speed and contrast agent concentration. At a two to four times faster imaging speed, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) almost equaled those at standard MR angiography, likely a result of increased contrast agent concentration. The use of parallel imaging to achieve higher spatial resolution was also proved feasible, but with substantial reduction in SNR and CNR.