Hybrid of opposite‐contrast MRA of the brain by combining time‐of‐flight and black‐blood sequences: Initial experience in major trunk stenoocclusive diseases

Purpose:

To assess the feasibility of a new MR angiography (MRA) technique named hybrid of opposite‐contrast MRA (HOP MRA) that combined the time‐of‐flight (TOF) MRA with a flow‐sensitive black‐blood (FSBB) sequence in the diagnosis of major trunk stenoocclusive diseases.

Materials and Methods:

On a 1.5 Tesla imager using a dual‐echo three‐dimensional (3D)‐gradient‐echo sequence, we obtained the first echo for TOF MRA followed by the second echo for FSBB. We then subtracted the FSBB data set from that of TOF MRA followed by maximum intensity projection. In four normal volunteers and 19 patients with chronic stenoocclusive disease of the major trunk, we performed HOP MRA along with 3D‐TOF MRA and compared the findings.

Results:

In the volunteer group, the HOP MRA technique improved the demonstration of distal arterial branches. In 12 of the 19 patients, the HOP MRA better visualized branches distal to the lesion as well as distal branches of normal trunks than 3D‐TOF MRA, while both techniques provided equivalent depiction of branches distal to the lesion but better depiction of normal distal branches in three patients.

Conclusion:

The HOP‐MRA technique is promising in major trunk stenoocclusive diseases as it better demonstrates distal branches probably representing collaterals than 3D‐TOF MRA. J. Magn. Reson. Imaging 2010;31:56–60. © 2009 Wiley‐Liss, Inc.     

Improvement in visualization of carotid artery uniformity using silent magnetic resonance angiography

Three-dimensional time-of-flight magnetic resonance angiography (TOF MRA) has been widely used in clinics. TOF MRA can cause dephasing artifacts, which lead to an intraluminal signal decrease. Silent MRA is a novel imaging technique that uses arterial spin labeling to achieve an ultrashort echo time (uTE), which is expected to decrease these effects and allow for accurate assessment of the flow in blood vessels. This study quantified the accuracy of Silent MRA images for visualizing the turbulent flow in flow-phantom and in vivo studies. The vessel contrast and coefficients of variation (CVs) for Silent MRA and TOF MRA were compared using normal and stenosis phantoms. Then, we performed both types of MRA on seven healthy volunteers. In the phantom study, although the contrast in the TOF MRA images was low distal to the stenosis region and at a high flow velocity, the contrast in the Silent MRA images did not change under these conditions. Furthermore, the mean CV for Silent MRA was smaller than that for TOF MRA under stenosis conditions. In the in vivo study, the mean contrast and vessel uniformity were significantly higher for Silent MRA than for TOF MRA. Although Silent MRA has limited spatial resolution and requires additional imaging time, this method may have the potential to improve the image quality of the carotid artery.     

Phase enhancement for time‐of‐flight and flow‐sensitive black‐blood MR angiography

A magnitude‐based MR angiography method of standard time‐of‐flight (TOF) employing a three‐dimensional gradient‐echo sequence with flow rephasing is widely used. A recently proposed flow‐sensitive black‐blood (FSBB) method combining three‐dimensional gradient‐echo sequence with a flow‐dephasing gradient and a hybrid technique, called hybrid of opposite‐contrast, allow depiction of smaller blood vessels than does standard TOF. To further enhance imaging of smaller vessels, a new enhancement technique combining phase with magnitude is proposed. Both TOF and FSBB pulse sequences were used with only 0th‐order gradient moment nulling, and suitable dephasing gradients were added to increase the phase shift introduced mainly by flow. Magnitude‐based vessel‐to‐background contrast‐to‐noise ratios in TOF and FSBB were further enhanced to increase the dynamic range between positive and negative signals through the use of cosine‐function‐based filters for white‐ and black‐blood imaging. The proposed phase‐enhancement processing both improved visualization of slow‐flow vessels in the brains of volunteer subjects with shorter echo time in TOF, FSBB, and hybrid of opposite‐contrast and reduced wraparound artifacts with smaller b values without sacrificing vessel‐to‐background contrast in FSBB. This method of enhancement processing has excellent potential to become clinically useful. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

MR angiography of the cerebral perforating arteries with magnetization prepared anatomical reference at 7T: Comparison with time‐of‐flight

Purpose

To develop a magnetic resonance imaging (MRI) protocol that visualizes both the perforating arteries and the related anatomy in a single acquisition at 7T.

Material and Methods

T₁‐weighted magnetization prepared imaging (MPRAGE) was empirically modified for use as angiography method at 7T. The resulting sequence depicts the vasculature simultaneously with the surrounding anatomical structures, and is referred to as “magnetization prepared anatomical reference MRA” (MPARE‐MRA). The method was compared to time‐of‐flight (TOF) MRA in seven healthy subjects. The conspicuity of the perforating arteries and the contrast between gray and white matter were evaluated both quantitatively by contrast‐to‐noise (CNR) measurements, and qualitatively by two radiologists who scored the images.

Results

The contrast‐to‐noise ratio (CNR) between blood and background was 28 ± 9 for MPARE‐MRA and 35 ± 16 for TOF‐MRA, indicating good conspicuity of the vessels. CNR values were: internal capsule (IC) vs. caudate head (CH): 4.2 ± 0.7; IC vs. putamen: 3.5 ± 0.6; white matter vs. gray matter: 9.7 ± 2.5.

Conclusion

The benefits of ultra‐high‐field MRI can transform MPRAGE into a new angiography method to image small vessels and associated parenchyma at the same time. This technique can be used to study the correlation between tissue damage and vascular pathology. J. Magn. Reson. Imaging 2008;28:1519–1526. © 2008 Wiley‐Liss, Inc.     

Improved time‐of‐flight magnetic resonance angiography with IDEAL water‐fat separation

Purpose

To implement IDEAL (iterative decomposition of water and fat using echo asymmetry and least squares estimation) water‐fat separation with 3D time‐of‐flight (TOF) magnetic resonance angiography (MRA) of intracranial vessels for improved background suppression by providing uniform and robust separation of fat signal that appears bright on conventional TOF‐MRA.

Materials and Methods

IDEAL TOF‐MRA and conventional TOF‐MRA were performed in volunteers and patients undergoing routine brain MRI/MRA on a 3T magnet. Images were reviewed by two radiologists and graded based on vessel visibility and image quality.

Results

IDEAL TOF‐MRA demonstrated statistically significant improvement in vessel visibility when compared to conventional TOF‐MRA in both volunteer and clinical patients using an image quality grading system. Overall image quality was 3.87 (out of 4) for IDEAL versus 3.55 for conventional TOF imaging (P = 0.02). Visualization of the ophthalmic artery was 3.53 for IDEAL versus 1.97 for conventional TOF imaging (P < 0.00005) and visualization of the superficial temporal artery was 3.92 for IDEAL imaging versus 1.97 for conventional TOF imaging (P < 0.00005).

Conclusion

By providing uniform suppression of fat, IDEAL TOF‐MRA provides improved background suppression with improved image quality when compared to conventional TOF‐MRA methods. J. Magn. Reson. Imaging 2009;29:1367–1374. © 2009 Wiley‐Liss, Inc.     

Dual‐echo arteriovenography imaging with 7T MRI

Purpose:

To implement a dual‐echo sequence MRI technique at 7T for simultaneous acquisition of time‐of‐flight (TOF) MR angiogram (MRA) and blood oxygenation level‐dependent (BOLD) MR venogram (MRV) in a single MR acquisition and to compare the image qualities with those acquired at 3T.

Materials and Methods:

We implemented a dual‐echo sequence with an echo‐specific k‐space reordering scheme to uncouple the scan parameter requirements for MRA and MRV at 7T. The MRA and MRV vascular contrast was enhanced by maximally separating the k‐space center regions acquired for the MRA and MRV and by adjusting and applying scan parameters compatible between the MRA and MRV. The same imaging sequence was implemented at 3T. Four normal subjects were imaged at both 3T and 7T. MRA and MRV at 7T were reconstructed both with and without phase‐mask filtering and were compared quantitatively and qualitatively with those at 3T with phase‐mask filtering.

Results:

The depiction of small cortical arteries and veins on MRA and MRV at 7T was substantially better than that at 3T, due to about twice higher contrast‐to‐noise ratio (CNR) for both arteries (164 ±57 vs. 77 ± 26) and veins (72 ± 8 vs. 36 ± 6). Even without use of the phase‐masking filtering, the venous contrast at 7T (65 ± 7) was higher than that with the filtering at 3T (36 ± 6).

Conclusion:

The dual‐echo arteriovenography technique we implemented at 7T allows the improved visualization of small vessels in both the MRA and MRV because of the greatly increased signal‐to‐noise ratio (SNR) and susceptibility contrast, compared to 3T. J. Magn. Reson. Imaging 2010;31:255–261. © 2009 Wiley‐Liss, Inc.     

STAR and STARFIRE for flow‐dependent and flow‐independent noncontrast carotid angiography

Signal Targeting with Alternating Radiofrequency (STAR) and STAR and Flow‐Independent Relaxation Enhancement (STARFIRE) are noncontrast methods for flow‐dependent and flow‐independent magnetic resonance angiography (MRA). The methods rely on the acquisition and complex subtraction of two image sets alternately labeled by spatially selective or spatially nonselective inversion radio frequency (RF) pulses. Experimental results show that the RF labeling period affects the extent of the carotid vessels seen with STAR imaging, and the conspicuity of cerebrospinal fluid (CSF) and fat in the STARFIRE images. Both methods were found to provide more detailed depiction of the carotid arteries than the alternative noncontrast MRA technique of time‐of‐flight (TOF) angiography. Magn Reson Med 61:117–124, 2009. © 2008 Wiley‐Liss, Inc.     

Imaging and analysis of lenticulostriate arteries using 7.0‐Tesla magnetic resonance angiography

The purpose of this study was to analyze human lenticulostriate arteries (LSAs) obtained non‐invasively by 7.0‐T MRI. A three‐dimensional time‐of‐flight (3D TOF) magnetic resonance angiography (MRA) technique was used with an investigational 7.0‐T MRI scanner with a radio‐frequency coil that was optimized and designed for angiographic purposes. We obtained images from 16 healthy volunteers (8 males and 8 females, mean age 21 ± 2.7 years). For direct comparison of LSA images with digital subtraction angiography (DSA), we also obtained 7.0‐T MRA and DSA images from one patient, a 27‐year‐old woman with a posterior fossa arteriovenous malformation (AVM). We then analyzed the characteristics of LSAs using a custom data analysis method with MatLab for quantitative analysis. Analysis of LSA images included shape and number of branches and origins, findings that are essential and useful for quantification of LSA abnormalities in both healthy controls and patients. Ultra–high‐field MRA provided clear anatomic delineation of the LSAs, thereby suggesting that 7.0‐T MRA may be a promising technique for microvascular imaging of the LSAs. Magn Reson Med 61:136–144, 2009. © 2008 Wiley‐Liss, Inc.     

Compatible dual‐echo arteriovenography (CODEA) using an echo‐specific K‐space reordering scheme

An improved dual‐echo sequence magentic resonance (MR) imaging technique was developed to simultaneously acquire a time‐of‐flight MR angiogram (MRA) and a blood oxygenation level‐dependent MR venogram (MRV) in a single MR acquisition at 3 T. MRA and MRV require conflicting scan conditions (e.g., excitation RF profile, flip angle, and spatial presaturation pulse) for their optimal image quality. This conflict was not well counterbalanced or reconciled in previous methods reported for simultaneous acquisition of MRA and MRV. In our dual‐echo sequence method, an echo‐specific K‐space reordering scheme was used to uncouple the scan parameter requirements for MRA and MRV. The MRA and MRV vascular contrast was enhanced by maximally separating the K‐space center regions acquired for the MRA and MRV, and by adjusting and applying scan parameters compatible between the MRA and MRV. As a preliminary result, we were able to acquire a simultaneous dual‐echo MRA and MRV with image quality comparable to that of the conventional single‐echo MRA and MRV that were acquired separately at two different sessions. Furthermore, integrated with tilted optimized nonsaturating excitation and multiple overlapping thin‐slab acquisition techniques, our dual‐echo MRA and MRV provided seamless vascular continuity over a large coverage volume of the brain anatomy. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Nonenhanced methods for lower-extremity MRA: a phantom study examining the effects of stenosis and pathologic flow waveforms at 1.5T

Purpose

To evaluate the signal properties of 2D time of flight (TOF), quiescent‐interval single‐shot (QISS), ECG‐gated 3D fast spin‐echo (FBI), and ungated 3D fast spin‐echo ghost (Ghost) magnetic resonance angiography (MRA) over a range of flow velocities in a pulsatile flow phantom with a 50% diameter stenosis at 1.5T.

Materials and Methods

Blood‐mimicking fluid was pumped at eight peak flow velocities through a stenotic region in triphasic and monophasic waveforms. Vascular signal proximal, within, and distal to the stenosis was measured from the source images of the four MRA methods. Coronal maximum intensity projection images were used to compare image quality.

Results

TOF and QISS signal trends were similar, but QISS exhibited the most consistent signal across velocities. At high velocities (≥42.4 cm/s), TOF showed poststenotic signal loss that was not observed with QISS. FBI and Ghost signals peaked at low velocities (3.9–9.7 cm/s) without flow compensation and at high velocities (≥64.6 cm/s) with flow compensation.

Conclusion

FBI and Ghost demonstrated dependence on blood flow velocity and flow compensation. TOF was sensitive to flow artifacts at high velocities. QISS proved most robust for accurately depicting the normal lumen and stenosis under a wide range of flow conditions. Monophasic and triphasic flow did not appreciably affect the signal performance of any method. J. Magn. Reson. Imaging 2011;33:401–408. © 2011 Wiley‐Liss, Inc.     

Time‐resolved three‐dimensional magnetic resonance digital subtraction angiography without contrast material in the brain: Initial investigation

Purpose

To evaluate a novel magnetic resonance (MR) angiography (MRA) of three‐dimensional (3D) MR digital subtraction angiography (MRDSA) without contrast material, which is essentially 3D true steady‐state free precession (SSFP) with selected inversion recovery (IR) pulse using multiple cardiac phase acquisitions with a short increment delay in the assessment of normal cranial arteries, as a feasibility study before clinical use.

Materials and Methods

Serial MRA images using 3D MRDSA without contrast material were acquired from 10 healthy volunteers. Visualization of normal cranial arteries with time‐spatial labeling inversion pulse (Time‐SLIP) MRDSA was qualitatively compared with the conventional MRA method, 3D time‐of‐flight (TOF)‐MRA.

Results

In all volunteers, serial 3D MRDSAs containing hemodynamic information were successfully imaged. The results of visualization of the branches of the cranial arteries with Time‐SLIP MRDSA were comparable to those of 3D TOF‐MRA. The mean scores ± standard deviations for normal cerebral arteries (internal carotid arteries, middle cerebral arteries, anterior cerebral arteries, posterior cerebral arteries, and basilar arteries) were 2.4 ± 0.5, 2.3 ± 0.5, 2.0 ± 0.7, 2.3 ± 0.7, and 2.5 ± 0.7, respectively.

Conclusion

Time‐SLIP 3D MRDSA is a simple method for obtaining hemodynamic information. Although more MR sequence improvement is needed, it can play an important role in assessing cranial arteries without contrast material. J. Magn. Reson. Imaging 2009;30:214–218. © 2009 Wiley‐Liss, Inc.     

3D noncontrast MR angiography of the distal lower extremities using flow‐sensitive dephasing (FSD)‐prepared balanced SSFP

While three‐dimensional contrast‐enhanced MR angiography (MRA) is becoming the method of choice for clinical peripheral arterial disease (PAD) examinations, safety concerns with contrast administration in patients with renal insufficiency have triggered a renaissance of noncontrast MRA. In this work, a noncontrast‐MRA technique using electrocardiography‐triggered three‐dimensional segmented balanced steady‐state free precession with flow‐sensitive dephasing (FSD) magnetization preparation was developed and tested in the distal lower extremities. FSD preparation was used to induce arterial flow voids at systolic cardiac phase while having little effect on venous blood and static tissues. High‐spatial‐resolution MRA was obtained by means of magnitude subtraction between a dark‐artery scan with FSD preparation at systole and a bright‐artery scan without FSD preparation at mid‐diastole. In nine healthy volunteers, FSD parameters, including the gradient waveform and the first‐order gradient moment, were optimized for excellent MRA image quality. Furthermore, arterial stenosis and occlusion in two peripheral arterial disease patients were identified using the noncontrast‐MRA technique, as confirmed by contrast‐enhanced MRA. In conclusion, FSD‐prepared balanced steady‐state free precession in conjunction with electrocardiography gating and image subtraction provides a promising noncontrast‐MRA strategy for the distal lower extremities. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Non‐contrast‐enhanced vascular magnetic resonance imaging using flow‐dependent preparation with subtraction

Recent concerns over contrast agent safety have encouraged new developments in non‐contrast‐enhanced vascular imaging techniques. This work investigates the potential for imaging both arteries and veins with vascular anatomy by nonenhanced static subtraction angiography (VANESSA), a method using controllable flow suppression together with subtraction of bright‐ and dark‐blood images. The lower legs of eight healthy volunteers and three patients were imaged using a modified motion‐sensitized driven equilibrium preparation, with three‐dimensional balanced steady‐state free precession readout. The vascular signal decreased with increasing motion‐suppression gradient amplitude, and was suppressed when the velocity‐encoding parameter was (approximately) less than the measured flow velocity. Selected pairs of images were subtracted to depict vessels with either fast flow (e.g. arteries), slow flow (e.g. veins), or both. Several methodological modifications improved image quality and reduced the background signal from static tissues. Subjectively assessed image quality in volunteers was rated as excellent for 56/64 arterial segments, and good or excellent for 35/64 veins. In conclusion, VANESSA enables rapid non‐contrast‐enhanced imaging of arteries and veins, combining information on both morphology and flow. This study demonstrates good technical performance in volunteers and evaluation in patients with vascular disease is warranted. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.     

Quantitative evaluation of k‐space reordering schemes for compatible dual‐echo arteriovenography (CODEA)

Compatible dual‐echo arteriovenography (CODEA) is a recently developed technique for simultaneous acquisition of time‐of‐flight MR angiogram (MRA) and blood oxygenation level–dependent MR venogram (MRV) using an echo‐specific k‐space reordering scheme. In this study, we evaluated and compared the image quality of CODEA MRA/MRV implemented with two different schemes of echo‐specific k‐space reordering: one along the 1st phase‐encode direction (one‐dimensional) only and the other along both phase‐encode directions (two‐dimensional). Our results showed that use of the two‐dimensional reordering scheme improved contrast‐to‐noise ratio of small arteries by ～8%, although not statistically significant (P > 0.1). Contrast‐to‐noise ratio of the CODEA MRAs was better than that for the non‐CODEA dual‐echo MRA without k‐space reordering (contrast‐to‐noise ratio increased in large arteries by ～10% and small arteries by ～45%; P < 0.1). Contrast‐to‐noise ratio of the CODEA MRAs was comparable with that of the conventional single‐echo MRA for large arteries but reduced by ～20% for small arteries. Contrast‐to‐noise ratio of veins on the CODEA MRVs was equivalent to that of the conventional single‐echo and the non‐CODEA dual‐echo MRVs. However, some veins in the CODEA MRVs showed stronger contrast than those in the single‐echo MRV in relation to the contrast of neighboring arterial signals. Magn Reson Med 63:1404–1410, 2010. © 2010 Wiley‐Liss, Inc.     

Intravascular contrast agent improves magnetic resonance angiography of carotid arteries in minipigs

This study was designed to optimize three-dimensional (3D) time-of-flight (TOF) magnetic resonance angiography (MRA) sequences and to determine whether contrast-enhanced MRA could improve the accuracy of lumen definition in stenosed carotid arteries of minipigs. 3D TOF MRA was acquired with use of either an intravascular (n = 13) and/or an extravascular contrast agent (n = 5) administrated at 2 to 4 weeks after balloon-induced injury to a carotid artery in 16 minipigs. Vascular contrast, defined as signal intensity differences between blood vessels and muscle normalized to the signal intensity of muscle, was compared before and after the injection of each contrast agent and between the two agents. Different vascular patencies were observed among the animals, including completely occluded vessels (n = 5), stenotic vessels (n = 3), and vessels with no visible stenosis (n = 8). Superior vascular contrast improvement was observed for small arteries and veins and for large veins with the intravascular contrast agent when compared with the extravascular contrast agent. In addition, preliminary studies in two of the animals showed a good correlation for the extent of luminal stenosis defined by digital subtraction angiography compared with MRA obtained after administration of the intravascular contrast agent (R2 = .71, with a slope of .96 ± .04 by a linear regression analysis). We concluded that use of an intravascular contrast agent optimizes 3D TOF MRA and may improve its accuracy compared with digital subtraction angiography.     

数字减影-时间飞跃磁共振血管造影的临床应用研究

目的评价数字减影-时间飞跃磁共振血管造影(DS-TOF MRA)在亚急性及慢性脑出血中的临床应用价值。资料与方法58例T1WI呈高信号的亚急性、慢性脑内血肿患者,行常规静脉血流饱和3D-TOF MRA序列(A)及反向动脉血流饱和3D-TOF MRA序列(B),应用数字减影方法,将反向动脉血流饱和B序列源图像作为蒙片,A序列源图像减去B序列源图像即为DS-TOF MRA的源图像,将其进行最大信号强度投影(MIP)重建产生无高信号组织背景干扰的DS-TOF MRA图像。测量血肿区对比度/噪声比(C/Ns)值并比较动脉血管边缘的显示情况,对减影效果进行评价。结果除2例患者因运动而无法产生清晰图像外,其余56例在3D-TOF MRA上有高信号背景组织干扰影像,在DS-3D MRA图像上均被完全消除。DS-TOF MRA源图像血管-血肿区C/Ns值为19.30±1.72,常规TOFMRA源图像血管-血肿区C/Ns值为2.62±0.31(t=17.3828,P<0.01)。DS-TOF MRA源图像血管-血肿区C为(1.40±0.01)%(P<0.01)。减影后DS-TOF MRA图像脑动脉管壁显示情况明显优于常规TOF-MRA(u=-8.8452,P<0.01)。结论DS-TOF MRA能有效消除常规TOF MRA源图像血肿高信号对血管影像的干扰,增加血管与周围组织的对比度,有利于准确地评价脑动脉的病变     

Fast inversion recovery magnetic resonance angiography of the intracranial arteries

Inversion‐prepared pulse sequences can be used for noncontrast MR angiography (MRA) but suffer from long scan times when acquired using conventional nonaccelerated techniques. This work proposes a subtraction‐based spin‐labeling, three‐dimensional fast inversion recovery MRA (FIR‐MRA) method for imaging the intracranial arteries. FIR‐MRA uses alternating cycles of nonselective and slab‐selective inversions, leading to dark‐blood and bright‐blood images, respectively. The signal difference between these images eliminates static background tissue and generates the angiogram. To reduce scan time, segmented fast gradient recalled echo readout and parallel imaging are applied. The inversion recovery with embedded self‐calibration method used allows for parallel acceleration at factors of 2 and above. An off‐resonance selective inversion provides effective venous suppression, with no detriment to the depiction of arteries. FIR‐MRA was compared against conventional three‐dimensional time‐of‐flight angiography at 3 T in eight normal subjects. Results showed that FIR‐MRA had superior vessel conspicuity in the distal vessels (P < 0.05), and equal or better vessel continuity and venous suppression. However, FIR‐MRA had inferior vessel sharpness (P < 0.05) in four of nine vessel groups. The clinical utility of FIR‐MRA was demonstrated in three MRA patients. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

Measuring aortic diameter with different MR techniques: Comparison of three‐dimensional (3D) navigated steady‐state free‐precession (SSFP), 3D contrast‐enhanced magnetic resonance angiography (CE‐MRA), 2D T2 black blood,and 2D cine SSFP

Purpose:

To compare nongated three‐dimensional (3D) contrast‐enhanced magnetic resonance angiography (CE‐MRA) with 3D‐navigated cardiac‐gated steady‐state free‐precession bright blood (3D‐nav SSFP) and noncontrast 2D techniques for ascending aorta dimension measurements.

Materials and Methods:

Twenty‐five clinical exams were reviewed to evaluate the ascending aorta at 1.5T using: breathhold cine bright blood (SSFP), cardiac‐triggered T2 black blood (T2 BB), axial 3D‐nav SSFP, and nongated 3D CE‐MRA. Three radiologists independently measured aortic size at three specified locations for each sequence. Means, SDs, interobserver correlation, and vessel edge sharpness were statistically evaluated.

Results:

Measurements were greatest for 3D‐nav SSFP and 3D CE‐MRA and smallest for T2 BB. There was no significant difference between 3D‐nav SSFP and 3D CE‐MRA (P = 0.43–0.86), but significance was observed comparing T2 BB to all sequences. Interobserver agreement was uniformly >0.9, with T2 BB best, followed closely by 3D‐nav SSFP and 2D cine SSFP, and 3D CE‐MRA being the worst. Edge sharpness was significantly poorer for 3D CE‐MRA compared to the other sequences (P < 0.001).

Conclusion:

If diameter measurements are the main clinical concern, 3D‐nav SSFP appears to be the best choice, as it has a sharp edge profile, is easy to acquire and postprocess, and shows very good interobserver correlation. J. Magn. Reson. Imaging 2010;31:177–184. © 2009 Wiley‐Liss, Inc.     

Three-dimensional time-of-flight MR angiography in the evaluation of cerebral aneurysms

We review our preliminary experience with the use of three-dimensional (3D) time-of-flight (TOF) magnetic resonance (MR) angiography (MRA) in the assessment of intra- and extracranial aneurysms. Six patients were examined: Five had intracranial aneurysms and one had a cervical carotid pseudoaneurysm. A 3D rephased gradient recalled echo pulse sequence and maximum intensity projection (MIP) reconstruction algorithm were used. Magnetic resonance angiography, spin echo MR, and conventional angiography were retrospectively reviewed with specific regard to individual vessel visualization, aneurysm depiction, and presence of artifact related to acquisition techniques or MIP reconstruction. All aneurysms were detected on MRA, and anatomical correlation with conventional angiography was excellent. Significant problems included loss of visualization of small vessels, intraluminal signal loss in large vessels, subacute thrombus simulating flow on MIP reconstructions, and limited projections obtainable with MIP techniques. Adequate MRA assessment of aneurysms can be obtained using a combination of T1-weighted spin echo images and 3D TOF MRA. Review of all components of the MRA is required. MRA may be useful in screening asymptomatic patients for intracranial aneurysms as well as in the follow-up of patients treated with balloon occlusion.     

Effective use of flow‐spoiled FBI and time‐SLIP methods in the diagnostic study of an aberrant vessel of the head and neck: “Left jugular venous steal by the right jugular vein”

Three‐dimensional (3D) time‐of‐flight (TOF) is now commonly used in routine magnetic resonance angiography (MRA) studies of the head and neck. However, there are limits to its diagnostic abilities in the clinical field and, in some instances, a more invasive supplementary examination may be required. We incidentally discovered a patient with an aberrant vessel of the head and neck that ran alongside the left carotid artery and contained a constant, slowly pulsating efferent blood flow. 3D‐TOF and carotid ultrasonography could not determine the nature and origin of this vessel. Additional studies using flow‐spoiled fresh blood imaging (flow‐spoiled FBI) and time spatial labeling inversion pulse (time‐SLIP) methods were effective in determining that the vessel was the left jugular vein, and that the continuous venous reflux was a result of a venous steal by the right jugular vein. We show that by combining different MRA techniques we can effectively achieve diagnosis without resorting to more invasive examinations. J. Magn. Reson. Imaging 2010;32:429–433. © 2010 Wiley‐Liss, Inc.