Parallel imaging technique for the external carotid artery and its branches: comparison of balanced turbo field echo, phase contrast, and time-of-flight sequences

PURPOSE: To evaluate the parallel imaging technique in the external carotid artery and its branches using 3D balanced turbo field echo (3D bTFE), 3D phase-contrast (3D PC), and 3D time-of-flight (3D TOF) MR angiography (MRA) sequences. MATERIALS AND METHODS: A total of 26 healthy volunteer subjects underwent 3D bTFE, 3D PC, and 3D TOF MRA with the parallel imaging sensitivity encoding (SENSE) technique. The obtained images were read in a blinded fashion by three radiologists. Interreader and intersequence statistical analyses were performed to compare the visibility of the arteries. RESULTS: Friedman's ranking test demonstrated that there was no significant difference in visibility between any two pairs of sequences for the external carotid artery and its first branches. However, of the three techniques, 3D PC MRA performed the best for the second-order branches (P < 0.01) and for overall visibility of the external carotid artery and its branches (P < 0.01). The 3D bTFE sequence is superior to 3D TOF; however, an effective means of separating arteries from veins and salivary ducts is needed. CONCLUSION: The combination of parallel imaging and the 3D PC technique is a promising approach for face and neck MRA.     

High-resolution magnetic resonance angiography of the internal carotid artery: 2D vs 3D TOF in stenotic disease

The aim of this study was to compare high-resolution 2D TOF with high-resolution 3D TOF in the study of internal carotid artery disease. Sixty-four patients with clinical signs of cerebrovascular insufficiency were studied with a superconductive 1.5 T magnet using two techniques: 2D and 3D TOF. Digital subtraction angiography (DSA) was the gold standard. The 2D TOF technique was performed using the following parameters: TR/TE/FA/MA 49 ms/9 ms/60°/512 × 256; the 3D TOF was performed with the following parameters: TR/TE/FA/MA 50 ms/8 ms/20°/512 × 256. The 2D TOF agreed with DSA in 116 of 128 diagnostic judgments (90 %) and overestimated seven times. The 3D TOF technique agreed with DSA in 125 of 128 diagnostic judgments (97 %) with one overestimation and two underestimations. There was no statistically significant difference (P < 0.05) between the two different techniques. Our study confirms the high reliability of the methodology carried out with the high-resolution 2D and 3D technique. Received 12 September 1997; Revision received 18 December 1997; Accepted 19 December 1997     

Pulsatile motion effects on 3D magnetic resonance angiography: implications for evaluating carotid artery stenoses.

In-plane carotid artery motion during a 3D MR angiography (MRA) scan can significantly degrade the resulting image resolution. This study characterizes the effect of cardiac pulsatility on 3D contrast-enhanced (CE) MRA with elliptical centric acquisitions using a point-spread function (PSF) analysis. Internal carotid artery (ICA) motion was collected from volunteers and patients using both MR and ultrasound (US) scans. After measuring the carotid artery motion displacement, a simulation was performed which calculated the blurring effects for three different protocols: nongated and two different cardiac gating schemes. The motion sensitivity of each protocol was evaluated for different spatial resolutions. The selection of optimal imaging parameters for a given scan time was investigated. The final results showed that cardiac-gated acquisitions only over a limited region of k-space high spatial frequencies are more time-efficient than cardiac gating for the entire k-space, as it allows for higher resolutions to be achieved and for capturing the arterial phase with low spatial frequencies. Selecting the optimal gating parameters depends directly on the motion characteristics of each individual. Our initial clinical experience is presented, and the need for a real-time tool that characterizes motion behavior for each individual as a prescan protocol is discussed.     

Arterial phase carotid and vertebral artery imaging in 3D contrast-enhanced MR angiography by combining fluoroscopic triggering with an elliptical centric acquisition order

Arterial-phase three-dimensional (3D) contrast-enhanced MR angiograms of the carotid and vertebral arteries from their origins through the carotid bifurcations were obtained in 20 patients using acquisition times over 30 sec by using an MR fluoroscopy-triggered pulse sequence with elliptical centric view order. The typical pixel size was 0.8 mm (x) × 1.6 mm (y) × 1.5 mm (z), and 32–48 coronal slices were acquired. The fluoroscopic monitoring of bolus arrival was effective in 18 of the 20 cases; two failures were attributed directly to a poor choice of RF coil. To exploit peak arterial-to-venous contrast, the central 3D views were acquired first in the most compact time period possible for the given TR. For the 18 successfully triggered cases, arterial-phase 3D images were obtained with excellent venous suppression as demonstrated by an average internal jugular vein to common carotid signal enhancement ratio of only 0.05 ± 0.04.     

3D volume-selective turbo spin echo for carotid artery wall imaging with navigator detection of swallowing

PURPOSE: To improve 3D volume-selective turbo spin echo (TSE) carotid artery wall imaging by incorporating navigators to reduce artifacts caused by swallowing. MATERIALS AND METHODS: Images were acquired on a Siemens Magnetom Sonata 1.5T scanner. 3D volume-selective TSE scans of the carotid arteries were acquired in six healthy volunteers. A cross-pair navigator placed on the back of the tongue was used to detect swallowing and movement. Two swallowing patterns were tested: 1) a single swallow approximately halfway through the scan time, at the center of k(z), and 2) repeated swallowing as often as possible throughout the scan period. Images were acquired with and without navigators for comparison. Signal intensity in the lumen was quantified for the quality of blood suppression, and the clarity of the vessel wall in the common carotid was ranked by four independent blinded observers. RESULTS: In general, lower signal intensity was recorded in the lumen, and decreased blurring and ghosting were observed on scans with navigator control. This reduction in lumen signal intensity signifies an improvement in the black-blood imaging technique. The differences likely reflect the improved double inversion/blood suppression efficiency due to cycles being rejected when the heart rate changed at the point of swallowing, or decreased motional blurring/ghosting of tissue when the navigator is used, or a combination of these two effects. A statistical analysis of image quality showed a significant difference between navigated and non-navigated scans as scored by four independent, blinded observers. For both swallowing patterns, the mean score for the navigator images was on average 0.6 greater than that of non-navigator images (on a scoring scale of 0-5, where 0 = no vessel visible, and 5 = good delineation and blood suppression) and P-values for all observers were less than 0.01. Overall, the central swallow scans were scored higher than the repeated swallow scans. One reason for this may be the fact that the heart rate increased on swallowing, and this often lasted for one or two cardiac cycles after the navigator returned to the normal acceptance position. The effect of the increased heart rate after swallowing is likely to have an effect on double inversion blood suppression efficiency. Therefore, the increased amount of heart rate changes with repeated swallowing may have a greater adverse effect, even if the navigator rejects data views during the swallowing motion. CONCLUSION: The clarity of vessel wall delineation and the apparent efficiency of blood suppression are reduced by swallowing during acquisition. Both motion blurring and quality of blood suppression are factors that can be improved with the use of a navigator accept/reject method.     

Dose comparison of single- vs. double-dose in contrast-enhanced magnetic resonance angiography of the carotid arteries: Intraindividual cross-over blinded trial using Gd-DTPA

PURPOSE: To compare and contrast the pattern and characteristics of the cerebral blood volume (CBV) response to ethanol (EtOH) in rats under awake and anesthetized conditions. MATERIALS AND METHODS: Acute EtOH (0.75 g/kg) challenge-induced CBV changes were measured using a contrast-enhanced functional MRI CBV method in 15 male Sprague Dawley rats under three experimental conditions: 1.0% to 1.2% isoflurane (N = 5); 0.8% halothane (N = 5); and awake with no anesthetic (N = 5). Physiological parameters were collected from bench settings in nine rats from the above different conditions. Four parameters: 1) area under the curve (AUC%); 2) the maximum signal change (Max%); 3) EtOH absorption rate (alpha(2)); and 4) EtOH elimination rate (alpha(1)) were employed to compare EtOH-induced MRI signals between the awake and anesthetized groups. RESULTS: Both awake and anesthetized animals responded with an increase in CBV to EtOH challenge. However, the presence of anesthesia promoted a significant preferential flow to subcortical areas not seen in the awake condition. CONCLUSION: Unclear mechanisms of anesthesia add a layer of uncertainty to the already complex interpretation of EtOH's influence on neuronal activity, cellular metabolism, and hemodynamic coupling.     

Effects of cardiac motion on 3D contrast-enhanced MR angiography of the carotid arteries

Purpose:

To determine the effect of cardiac‐related carotid artery motion on the image quality of 3D contrast‐enhanced MR angiography (CEMRA) in patients presenting with suspected carotid artery disease.

Materials and Methods:

Twenty patients with suspected carotid artery disease underwent cardiac‐gated cinematic steady‐state free precession of the carotid arteries followed by standard 3D CEMRA at 1.5 T. Using postprocessing, computer programs determined the degree of vessel wall dilation and translation across the cardiac cycle from the cinematic exam and related this to vessel wall sharpness in 3D CEMRA, which was determined objectively by computer analysis and subjectively by a panel of expert neuroradiologists.

Results:

In patients, across 40 arteries the average carotid vessel movement due to cardiac pulsation was 0.36 ± 0.17 mm and translation 1.53 ± 0.94 mm. When using computer analysis of sharpness, the mean carotid wall motion had a weak negative correlation with 3D CEMRA vessel sharpness (Pearson's correlation ?0.23, P < 0.01). However, the same trend was not present from the radiological review.

Conclusion:

In standard 3D CEMRA in patients with suspected carotid artery disease, cardiac‐related carotid movement was a statistically significant source of degradation in vessel sharpness, but did not appear to be clinically significant. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.

     

Effects of doubling and tripling the spatial resolution in standard 3D contrast-enhanced magnetic resonance angiography of carotid artery disease

PURPOSE: To determine whether three-dimensional (3D) contrast-enhanced MR angiography (CE-MRA) of carotid artery disease may be more effective when performed at double or triple the spatial resolution of the present common clinical standard at 1.5T. MATERIALS AND METHODS: A total of 110 consecutive patients with suspected carotid artery disease were imaged with elliptical centric 3D CE-MRA. The total acquisition time was increased from the standard clinical protocol of 21 seconds up to 60 seconds in 10-second steps, with corresponding voxel volume reductions from 0.95 mm(3) down to 0.35 mm(3). Quantitative and blinded qualitative measurements were then performed to determine the preferred imaging time. RESULTS: In patients with significant stenosis, the 40-second acquisition with 0.53-mm(3) voxels produced significantly sharper images of the carotid bifurcation than the 21-second standard using 0.95-mm(3) voxels, but did not have a significant effect in patients without disease. CONCLUSION: In patients with carotid artery stenosis, decreasing the voxel volume to 0.5 mm(3) by increasing the scan time from 21 to 40 seconds resulted in sharper depiction of the carotid stenosis. Further decreases in voxel volume, by extending the acquisition time further, did not improve the vessel depiction due to both signal-to-noise ratio (SNR) and sharpness losses.     

Novel technique used to detect swallowing in volume‐selective turbo spin‐echo (TSE) for carotid artery wall imaging

Purpose

To improve three‐dimensional (3D) volume‐selective turbo spin‐echo (TSE) carotid wall imaging by the addition of a novel body surface swallowing detection device.

Material and Methods

A 3D volume‐selective TSE sequence was used to image the carotid artery. A novel carbon‐fiber motion device, positioned over the laryngeal prominence, was used to detect swallowing movement. An electrical output generated by coil movement was used to detect motion, and an algorithm was programmed to reject data acquired during swallowing and for a short period afterwards. Images were acquired with and without the algorithm and scored on a scale of 0–5 by four independent blinded observers according to the clarity of the vessel wall, e.g., 0 = poor image quality and 5 = excellent quality images with little or no artifact.

Results

The scans with the rejection algorithm on were scored higher than the scans without the algorithm. The comparison of scores with the algorithm on vs. the algorithm off were as follows: mean ± standard deviation (SD) = 3.76 ± 0.25, 95% confidence interval (CI) = 3.27–4.25 vs. 2.64 ± 0.25, 95% CI = 2.15–3.13; with good interobserver correlation (Kendall's W score 0.77).

Conclusion

Image quality can be improved by the algorithm during acquisition. This can be achieved by a novel, anatomically positioned superficial device. This may help in prolonged 3D scans where a single movement can corrupt the entire acquisition. J. Magn. Reson. Imaging 2009;29:211–216. © 2008 Wiley‐Liss, Inc.     

Reduction of slab boundary artifact with multiple overlapping thin slab acquisition in MR angiography of the cervical carotid artery

Multiple overlapping thin slab acquisition (MOTSA) is a magnetic resonance (MR) angiography technique combining advantages of two- and three-dimensional time-of-flight techniques. The authors studied three image acquisition parameters (flip angle, TR, and the slab excitation fraction [SEF]) and a postprocessing algorithm, to evaluate their effect on MOTSA image quality, including contrast-to-noise ratio (C/N) and the severity of the slab boundary artifact. By increasing SEF from 0.75 to 1.10, the slab boundary artifact was reduced by 29%-56% (P <.0001). The boundary artifact can be reduced an additional 46% by postprocessing of the overlapping section data. In the healthy volunteers studied, C/N of the cervical carotid artery could be increased sixfold (P <.0001) by increasing the flip angle from 10° to 50°, without significant worsening of the boundary artifact due to top-of-slab saturation. The effect of TR on image quality was not statistically significant for the range studied (52-70 msec). We conclude that the slab boundary artifact seen with the MOTSA MR angiography technique can be reduced significantly by optimizing imaging acquisition parameters and using a postprocessing algorithm to combine overlapping section information.     

High-resolution selective three-dimensional magnetic resonance coronary angiography with navigator-echo technique: segment-by-segment evaluation of coronary artery stenosis

PURPOSE: To investigate the feasibility of high-resolution selective three-dimensional (3D) magnetic resonance coronary angiography (MRCA) in the evaluation of coronary artery stenoses. MATERIALS AND METHODS: In 12 patients with coronary artery stenoses, MRCA of the coronary artery groups, including the coronary segments with stenoses of 50% or greater based on conventional x-ray coronary angiography (CAG), was performed with double-oblique imaging planes by orienting the 3D slab along the major axis of each right coronary artery-left circumflex artery (RCA-LCX) group and each left main trunk-left anterior descending artery (LMT-LAD) group. Ten RCA-LCX and five LMT-LAD MR angiograms were obtained, and the results were compared with those of conventional x-ray angiography. RESULTS: Among 70 coronary artery segments expected to be covered, a total of 49 (70%) segments were fully demonstrated in diagnostic quality. The identification of segmental location of stenoses showed as high an accuracy as 96%. The retrospective analysis for stenosis of 50% or greater yielded the sensitivity, specificity, and accuracy of 80%, 85%, and 84%, respectively. CONCLUSION: Selective 3D MRCA has the potential for segment-by-segment evaluation of major portions of the right and left coronary arteries with high accuracy.     

三维快速场回波序列在先心病患儿 气管支气管树MRI中的应用

目的 对比分析三维快速场回波（3D-TFE）序列、三维平衡快速场回波（3D b-TFE）序列以及对比增强MR血管成像（CE-MRA）3种序列在显示气道时影像质量,探讨3D-TFE序列在先心病患儿气管支气管树成像中的应用价值。方法 连续收集2016年9月-12月间我院62例经超声心电图确诊的先心病患儿,其中男32例,女30例,年龄2~141个月,中位年龄为12.7个月。在1.5 T MR扫描设备上进行常规心脏MRI检查,常规扫描序列3D b-TFE、CE-MRA主要显示大血管病变,3D TFE进行气管支气管成像,测量气管支气管影像信噪比（SNR）及信号强度（SI）,客观评价影像质量及气管边界清晰度。由2位医生采用双盲5分法评价影像噪声及影像质量,并采用Kappa分析对2位医生的评分结果行一致性评价。采用单因素方差分析比较3种序列影像的SNR、SI、气管边界清晰度和影像质量主观评分。结果 3D-TFE序列在显示气道的SNR、SI、气管边界清晰度及其影像质量主观评分均分别高于3D b-TFE和 CE-MRA序列（均P<0.05）。2位医生对3种序列影像质量的主观评分的结果一致性极好,κ值均>0.80。结论 3D-TFE序列显示气管支气管树的影像质量优于3D b-TFE和 CE-MRA序列,可应用于心脏MRI检查时辅助观察有无先心病伴随的气道异常,是先心病心脏MRI检查中不可缺少的辅助序列,可为先心病患儿术前评估提供更多信息。     

Low-dose 3D time-resolved magnetic resonance angiography (MRA) of the supraaortic arteries: correlation with high spatial resolution 3D contrast-enhanced MRA

Purpose

To evaluate the feasibility of low‐dose, 3D time‐resolved contrast‐enhanced magnetic resonance angiography (TR‐CEMRA) in the assessment of the supraaortic vessel, and to compare the results with high‐resolution contrast‐enhanced MRA (HR‐CEMRA).

Materials and Methods

This was an Institutional Review Board‐approved retrospective study. Forty‐five consecutive patients underwent contrast‐enhanced 3D TR‐CEMRA and 3D HR‐CEMRA for evaluation of neurovascular disease at 3.0 T. Gadobutrol was administered at a constant dose of 1 mL for TR‐CEMRA (independent of patient weight), and 0.1 mmol/kg for HR‐CEMRA. Two readers evaluated image quality using a four‐point scale (from 0 = excellent to 3 = nondiagnostic), and subsequently graded each stenosis into clinically relevant categories: normal (0%), mild stenosis (<50%), moderate to severe (>50%), and occlusion.

Results

The overall image quality for low‐dose TR‐CEMRA was in the diagnostic range (median 0, range 0–3). On the grading of stenosis, TR‐CEMRA using the TWIST sequence correlated with HR‐CEMRA (r = 0.668, P < 0.001). In terms of the comparison of TR‐CEMRA with HR‐CEMRA, of the 675 supraaortic arterial segments evaluated for stenosis or occlusion, agreement occurred in 611 of 675 (90.5%), overestimation in 41 of 675 (6.1%), and underestimation 23 of 675 (3.4%).

Conclusion

TR‐CEMRA achieved by administration of a small contrast dose (1 cc) yields rapid and important functional and anatomical information in the evaluation of supraaortic arteries. Due to limited spatial resolution, TR‐CEMRA at the current parameters has a tendency to overestimate the stenosis of smaller intracranial arteries compared to HR‐CEMRA. J. Magn. Reson. Imaging 2011;33:71–76. © 2010 Wiley‐Liss, Inc.     

Optimization of 3D contrast-enhanced pulmonary magnetic resonance angiography in pediatric patients with congenital heart disease.

Contrast kinetics were studied in the main pulmonary artery (MPA) and ascending aorta (AAo) of 12 children with congenital heart disease. This information was used to optimize the timing of data acquisition for contrast-enhanced MR angiography in these vessels. To reduce contrast-agent dosage in these fragile patients, contrast enhancement was measured during routine diagnostic 3D magnetic resonance (MR) angiography instead of using test-bolus methods. This was possible by acquiring 2D cross-sectional images of the MPA and AAo during the 3D scan. Time-to-peak in the MPA and AAo was 4.9 +/- 2.2 and 6.1 +/- 2.2 s, respectively, while the transit time between the two vessels was 4.5 +/- 0.6 s. A point-spread-function analysis showed that intravascular signal strength was maximized if data acquisition began 4.7 +/- 2.3 s after the first arrival of contrast in the MPA and 5.6 +/- 2.3 s in the AAo. Little signal loss and artifact resulted when longer acquisition delays were used because contrast-agent clearance was slow. Based on these results, MR angiography of both the MPA and the AAo in children with congenital heart disease can be performed using elliptic-centric k-space sampling and a trigger delay of 7.9 s after contrast arrival in the AAo (i.e., time-to-peak signal strength in the AAo plus one SD to account for intersubject variability).     

Pseudoaneurysm of the internal carotid artery after shrapnel injury in World War II: demonstration by CT angiography with 3D MIP reconstruction

A case of pseudoaneurysm of the left internal carotid artery (ICA) after shrapnel injury is demonstrated by intra-arterial digital subtraction angiography (DSA) and computed tomography angiography (CTA) with subtraction technique. Although the pseudoaneurysm was well demonstrated by intra-arterial DSA, CTA was the only modality to demonstrate the three-dimensional shape of the perfused part of pseudoaneurysm and the aneurysmal neck, which affected the therapeutic strategy. The CTA technique is useful in the assessment of large pseudoaneurysms and for therapeutic planning. Received: 2 July 1998; Revision received: 5 November 1998; Accepted: 7 December 1998     

Visualization of external carotid artery and its branches: Non–contrast‐enhanced MR angiography using balanced steady‐state free‐precession sequence and a time‐spatial labeling inversion pulse

Purpose

To evaluate visibility of the external carotid artery (ECA) and its branches using three‐dimensional (3D) balanced steady‐state free‐precession (SSFP) MR angiography with a time‐spatial labeling inversion pulse (Time‐SLIP), and to provide an optimal value of the inversion time (TI).

Materials and Methods

Peripheral‐pulse‐wave‐gated 3D balanced SSFP images were obtained in 20 healthy volunteers. Images with a Time‐SLIP using four different TIs (600, 900, 1200, and 1500 ms) and without a Time‐SLIP, referred to as sequence A to E, were acquired for each subject and compared for visibility scores of ECA system and relative signal intensity (SI) of ECA.

Results

Average Friedman rank for overall visibility was 1.63, 3.01, 3.59, 3.58, and 3.20 for sequence A to E, respectively. Sequence C and D yielded significantly higher visibility than sequence A, B, and E. The mean relative SI value was 0.97, 0.87, 0.81, 0.76, and 0.67 for sequence A to E, respectively.

Conclusion

Balanced SSFP MR angiography with a Time‐SLIP is superior to that without a Time‐SLIP, showing excellent visualization of ECA system in approximately 3 min in average with sufficient background suppression including veins and salivary ducts. A TI of 1200 ms was considered to be optimal for this purpose. J. Magn. Reson. Imaging 2009;30:678–683. © 2009 Wiley‐Liss, Inc.     

Visualization of the lenticulostriate artery with flow‐sensitive black‐blood acquisition in comparison with time‐of‐flight MR angiography

Purpose

To evaluate the capability of flow‐sensitive black blood (FSBB) acquisition to visualize the lenticulostriate artery (LSA) in comparison with time‐of‐flight (TOF) angiography.

Materials and Methods

Twenty‐one healthy subjects (13 males and 8 females, 19–44 years old) were enrolled in this study after obtaining written informed consent. Magnetic resonance imaging (MRI) examinations were performed with FSBB and TOF to visualize the LSA using a 1.5T MRI unit. In FSBB acquisition a motion probing gradient of b = 4 sec/mm² was applied to dephase blood flow. Images were reconstructed into coronal sections and were evaluated in terms of number, length, and image quality at origins and distal areas of visualized LSA branches with a four‐point scale.

Results

In all, 145 LSA branches were visualized with FSBB and 66 branches with TOF. There was no LSA visualized only with TOF. In all evaluated terms, FSBB was significantly better than TOF.

Conclusion

We could better visualize the LSA with FSBB than with TOF, both quantitatively and qualitatively. FSBB is a promising method, although it remains to be evaluated in clinical cases. J. Magn. Reson. Imaging 2009;29:65–69. © 2008 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.     

Multislice breath-hold spiral magnetic resonance coronary angiography in patients with coronary artery disease: effect of intravascular contrast medium

PURPOSE: First, to apply a breath-hold multislice 2D spiral magnetic resonance (MR) approach in patients acquiring within 16 heartbeats (acquisition window, 116 msec) a 10-mm-thick stack of four slices (resolution, 1.3 x 1.3 mm(2)); and second, to evaluate the effect of an intravascular Fe-based contrast medium (CM) on a signal-to-noise ratio (SNR) and a contrast-to-noise ratio (CNR). MATERIALS AND METHODS: In each patient one or two coronary arteries were imaged prior to and following cumulative doses of 0.25, 0.5, and 0.75 mg of Fe/kg of body weight (bw) of an intravascular CM (CLARISCAN trade mark, Nycomed-Amersham, Princeton, NJ, USA) containing ultrasmall superparamagnetic iron oxide (USPIO) particles. RESULTS: On precontrast maximum intensity projection (MIP) images generated from the stack of slices, 10 and 11 stenoses of 12 stenoses confirmed by coronary angiography were detected by readers 1 and 2, respectively. SNR and CNR in the coronary arteries peaked at 0.50 mg of Fe/kg of bw, yielding a slight increase of 15.5% and 18.4%, respectively (P < 0.05 vs. precontrast), which did not improve detection of coronary artery stenoses. CONCLUSION: The presented multislice spiral approach allows display of coronary anatomy in MIP formats for convenient display of coronary stenoses. The pulse sequence did not benefit from an intravascular USPIO-based CM, since little improvement in SNR and CNR was achieved.     

Direct comparison of sensitivity encoding (SENSE) accelerated and conventional 3D contrast enhanced magnetic resonance angiography (CE‐MRA) of renal arteries: Effect of increasing spatial resolution

Purpose:

To assess the effect of attaining higher spatial resolution in contrast‐enhanced magnetic resonance angiography (MRA) of renal arteries using parallel imaging, sensitivity encoding (SENSE), by comparing the SENSE contrast‐enhanced (CE) MRA against a conventional CE‐MRA protocol with identical scan times, injection protocol, and other acquisition parameters.

Materials and Methods:

Numerical simulations and a direct comparison of SENSE‐accelerated versus conventional acquisitions were performed. A total of 41 patients (18 male) were imaged using both protocols for a direct comparison. Both protocols used fluoroscopic triggering, centric encoding, breath‐holding, equivalent injection protocol, and lasted ≈30 seconds.

Results:

Simulated point‐spread functions were narrower for the SENSE protocol compared to the conventional protocol. In the patient study, although the SENSE protocol produced images with lower signal‐to‐noise ratio (SNR), image quality was better for all segments of the renal arteries. In addition, ringing of kidney parenchyma and renal artery blurring were significantly reduced in the SENSE protocol. Finally, reader confidence improved with the SENSE protocol.

Conclusion:

Despite a reduction in SNR, the higher‐resolution SENSE CE‐MRA provided improved image quality, reduced artifacts, and increased reader confidence compared to the conventional protocol. J. Magn. Reson. Imaging 2010;31:149–159. © 2009 Wiley‐Liss, Inc.