Halting the effects of flow enhancement with effective intermittent zeugmatographic encoding (HEFEWEIZEN) in SSFP

Purpose

To describe a new method for performing dark blood (DB) magnetization preparation in TrueFISP (bSSFP) and apply the technique to high‐resolution carotid artery imaging.

Materials and Methods

The developed method (HEFEWEIZEN) provides directional flow suppression, while preserving bSSFP contrast, by periodically applying spatial saturation in short repetition time (TR) TrueFISP. Steady‐state free precession (SSFP) conditions are maintained throughout the acquisition for the imaging slice magnetization. HEFEWEIZEN was implemented on a 1.5 T scanner with standard receiver coils. Studies were performed in phantoms, eight asymptomatic volunteers, and two patients with low‐ and high‐grade carotid artery stenosis.

Results

Average flow suppression was 88% ± 4% (arterial) and 85% ± 3% (venous) in a multislice study. Stationary signal, contrast, and fine details were maintained with only slight signal suppression (11% ± 11%). Comparison to diffusion‐prepared SSFP in the common carotid artery demonstrated significant improvement in wall‐lumen contrast‐to‐noise ratio efficiency (P = 0.024). DB contrast was achieved with only 13% increased acquisition time (14.3 sec). Further acceleration was possible by confining the DB preparation to the central 60% of k‐space.

Conclusion

A fast, short TR, DB TrueFISP pulse sequence was developed and tested in the carotid arteries of asymptomatic volunteers and patients. J. Magn. Reson. Imaging 2009;29:1163–1174. © 2009 Wiley‐Liss, Inc.     

Effect of flip angle on volume flow measurement with nontriggered phase‐contrast MR: In vivo evaluation in carotid and basilar arteries

Purpose

To evaluate the effect of flip angle on volume flow rate measurements obtained with nontriggered phase‐contrast magnetic resonance imaging (MRI) in vivo.

Materials and Methods

We prospectively measured volume flow rates of the bilateral internal carotid artery and the basilar artery with cine and nontriggered phase‐contrast MRI. For nontriggered phase‐contrast imaging, flip angles of 4, 15, 60, and 90° were used for 40 volunteers and of 8, 15, and 30° for 54 volunteers. Lumen boundaries were semiautomatically determined by pulsatility‐based segmentation using cine phase‐contrast MRI. Identical lumen boundaries were used for nontriggered phase‐contrast imaging.

Results

The ratio of volume flow rate obtained with nontriggered phase‐contrast imaging to that obtained with cine phase‐contrast imaging significantly increases with an increase in the flip angle. The mean ratios lie within a relatively narrow range of ±15% with a wide range of flip angles of 8–90°. As the flip angle increases, ghost artifacts become prominent and signal‐to‐noise and contrast‐to‐noise ratios increase.

Conclusion

Flip angles between 8 and 60° are most appropriate for nontriggered phase‐contrast MR measurements in the internal carotid and the basilar artery. J. Magn. Reson. Imaging 2009;29:1218–1223. © 2009 Wiley‐Liss, Inc.     

Perfusion imaging of the pancreas using an arterial spin labeling technique

Purpose

To investigate the feasibility of perfusion imaging of the pancreas using an arterial spin labeling (ASL) technique.

Materials and Methods

An adapted flow‐sensitive alternating inversion recovery (FAIR)‐TrueFISP ASL technique was implemented on a 1.5T scanner. Anatomical and perfusion imaging in three different parts of the pancreas were performed in 10 healthy volunteers. Quantitative perfusion values were calculated using the extended Bloch equations.

Results

Perfusion images of all subjects showed diagnostic image quality in the pancreatic tail and the head. Assessment of pancreatic tissue perfusion was possible in all organ parts. Mean perfusion values were 271 ± 79 mL/100g/min in the head, 351 ± 112 mL/100g/min in the body, and 243 ± 55 mL/100g/min in the tail of the pancreas. Total examination time for perfusion imaging of the entire organ was 15.4 minutes.

Conclusion

FAIR‐TrueFISP permits analysis of pancreatic tissue perfusion with good image quality in a clinically applicable measuring time. Assessment of perfusion disorders may be useful in the diagnosis of inflammatory pancreatic pathologies, endocrine and exocrine pancreatic disorders, and in monitoring of pancreatic transplants. J. Magn. Reson. Imaging 2008;28:1459–1465. © 2008 Wiley‐Liss, Inc.     

Efficient flow suppressed MRI improves interscan reproducibility of carotid atherosclerosis plaque burden measurements

Purpose:

To determine if better flow suppression can meaningfully improve the reproducibility of measurements associated with carotid atherosclerotic disease, particularly for lumen and wall areas.

Materials and Methods:

Eighteen subjects with carotid artery stenosis identified by duplex ultrasound (11 with 16%–49% stenosis; 7 with 50%–79% stenosis) underwent two carotid magnetic resonance imaging (MRI) examinations on a 3T scanner with a 4‐channel phased array coil. High‐resolution intermediate‐weighted TSE (TR/TE = 4000/8.5 msec, 0.55 mm in‐plane resolution, 2 mm slice thickness, 16 slices, 3‐minute scan time) with two different flow‐suppression techniques (multislice double inversion recovery [mDIR] and motion‐sensitized driven‐equilibrium [MSDE]) were obtained separately. For each subject, bilateral arteries were reviewed. One radiologist blinded to timepoints, flow suppression techniques, and clinical information measured the arterial lumen area, wall area, and total vessel wall area.

Results:

Compared to mDIR, the MSDE technique had a smaller interscan standard deviation (SD) in lumen (SD: 3.6 vs. 5.2 mm², P = 0.02), wall area measurements (SD: 4.5 vs. 6.4 mm², P = 0.02), and a trend towards smaller SD in total vessel area measurement (SD: 4.4 vs. 4.9 mm², P = 0.07).

Conclusion:

The results from this study demonstrate that vessel wall imaging could quantify atherosclerotic plaque measurements more reliably with an improved blood suppression technique. This relationship between flow‐suppression efficiency and reproducibility of plaque measurements is important, as more reliable area measurements will be useful in clinical diagnosis and in serial MRI studies that monitor carotid atherosclerotic lesion progression and regression. J. Magn. Reson. Imaging 2010;32:452–458. © 2010 Wiley‐Liss, Inc.     

Assessment of carotid stenosis using three-dimensional T2-weighted dark blood imaging: Initial experience

Purpose:

To evaluate the use of a T2‐weighted SPACE sequence (T2w‐SPACE) to assess carotid stenosis via several methods and compare its performance with contrast‐enhanced magnetic resonance angiography (ceMRA).

Materials and Methods:

Fifteen patients with carotid atherosclerosis underwent dark blood (DB)‐MRI using a 3D turbo spin echo with variable flip angles sequence (T2w‐SPACE) and ceMRA. Images were coregistered and evaluated by two observers. Comparisons were made for luminal diameter, luminal area, degree of luminal stenosis (NASCET: North American Symptomatic Endarterectomy Trial; ECST: European Carotid Surgery Trial, and area stenosis), and vessel wall area. Degree of NASCET stenosis was clinically classified as mild (<50%), moderate (50%–69%), or severe (>69%).

Results:

Excellent agreement was seen between ceMRA and T2w‐SPACE and between observers for assessment of lumen diameter, lumen area, vessel wall area, and degree of NASCET stenosis (r > 0.80, P < 0.001). ECST stenosis was consistently higher than NASCET stenosis (48 ± 14% vs. 24 ± 22%, P < 0.001). Area stenosis (72 ± 2%) was significantly higher (P < 0.001) than both ESCT and NASCET stenosis.

Conclusion:

DB‐MRI of carotid arteries using T2w‐SPACE is clinically feasible. It provides accurate measurements of lumen size and degree of stenosis in comparison with ceMRA and offers a more reproducible measure of ECST stenosis than ceMRA. J. Magn. Reson. Imaging 2012;449‐455. © 2011 Wiley Periodicals, Inc.     

Magnetic resonance imaging and three‐dimensional ultrasound of carotid atherosclerosis: Mapping regional differences

Purpose

To evaluate differences in carotid atherosclerosis measured using magnetic resonance imaging (MRI) and three‐dimensional ultrasound (3DUS).

Materials and Methods

Ten subject volunteers underwent carotid 3DUS and MRI (multislice black blood fast spin echo, T1‐weighted contrast, double inversion recovery, 0.5 mm in‐plane resolution, 2 mm slice, 3.0 T) within 1 hour. 3DUS and MR images were manually segmented by two observers providing vessel wall and lumen contours for quantification of vessel wall volume (VWV) and generation of carotid thickness maps.

Results

MRI VWV (1040 ± 210 mm³) and 3DUS VWV (540 ± 110 mm³) were significantly different (P < 0.0001). When normalized for the estimated adventitia volume, mean MRI VWV decreased 240 ± 50 mm³ and was significantly different from 3DUS VWV (P < 0.001). Two‐dimensional carotid maps showed qualitative evidence of regional differences in the plaque and vessel wall thickness between MR and 3DUS in all subjects. Power Doppler US confirmed that heterogeneity in the common carotid artery in all patients resulted from apparent flow disturbances, not atherosclerotic plaque.

Conclusion

MRI and 3DUS VWV were significantly different and carotid maps showed homogeneous thickness differences and heterogeneity in specific regions of interest identified as MR flow artifacts in the common carotid artery. J. Magn. Reson. Imaging 2009;29:901–908. © 2009 Wiley‐Liss, Inc.     

Evaluation of bowel peristalsis by dynamic cine MRI: detection of relevant functional disturbances--initial experience

Purpose:

To investigate the diagnostic performance of a cine magnetic resonance imaging (MRI) sequence in the visualization and detection of impaired bowel peristalsis.

Materials and Methods:

In all, 91 consecutive patients (mean age 45 years) were prospectively examined on a 1.5 T system and stratified into a surgery group (n = 22) and a nonsurgery group (n = 69). A coronal fast imaging with steady‐state precession (TrueFISP) sequence with 30 acquisitions per slice covered the abdomen in 10–15 slices each 7–12 mm thick (temporal resolution: 6–8 sec per frame). Image evaluation for reduced bowel peristalsis and relevant bowel stenosis was compared to surgical findings or clinical follow‐up.

Results:

Cine MRI reached 96% accuracy (94% sensitivity; 100% specificity) in detecting a relevant reduction in bowel peristalsis and 85% of relevant stenosis was identified in the surgery group. Twenty of 69 patients of the nonsurgery group showed reduced peristalsis on cine MR which was attributed to underlying disease; 49/69 patients in this group had no findings on cine MR and were uneventfully followed up.

Conclusion:

Cine MRI of the bowel provides functional information of bowel passage. The visualization of a reduction in peristalsis may improve the assessment of the functional impact of suspected bowel adhesions or stenosis. Standard bowel MR protocols can be easily complemented by cine MR, extending scan time by <4 minutes. J. Magn. Reson. Imaging 2012;35:859–867. © 2012 Wiley Periodicals, Inc.     

Cardiovascular magnetic resonance imaging for accurate sizing of the left atrium: predictability of pulmonary vein isolation success in patients with atrial fibrillation

Purpose

To prospectively determine the most reproducible approach for left‐atrial size assessment using cardiovascular magnetic resonance (CMR) imaging in patients with atrial fibrillation and its value for prediction of pulmonary vein isolation (PVI) treatment success.

Materials and Methods

Eighty patients underwent CMR imaging prior to PVI; the CMR examination included standard cine sequences, a multislice cine sequence in 4‐chamber orientation with full left‐atrial coverage, and a contrast‐enhanced MR angiography of the left atrium. Left‐atrial size was determined as: diameter, area, volume segmented from angiography, and diastolic/systolic volumes from cine imaging (Simpson's rule). All measurements were carried out by two independent observers and repeated by one observer to assess inter‐ and intrareader variability. Treatment success was defined as persisting sinus rhythm after PVI (follow‐up period 12.6 ± 6.6 months).

Results

All left‐atrial measurements showed substantial intrareader agreement. Interreader agreement was substantial for diastolic/systolic left‐atrial volumes only. Calculated bias was found to be minimal (0.1%–4.9%). Predictability of PVI treatment success was best using cine volumetric measurements (cutoff value for diastolic volume, 112 mL) yielding a sensitivity and specificity of 80% and 70%, respectively.

Conclusion

Left‐atrial volumetry based on cine imaging represented the most reproducible approach to determine left‐atrial size. PVI success was predicted best using cine volumetry. J. Magn. Reson. Imaging 2011;33:455–463. © 2011 Wiley‐Liss, Inc.     

Circumferential strain in the wall of the common carotid artery: Comparing displacement‐encoded and cine MRI in volunteers

The walls of conduit arteries undergo cyclic stretching from the periodic fluctuation of arterial pressure. Atherosclerotic lesions have been shown to localize to regions of excessive stretching of the arterial wall. We employed a displacement encoding with stimulated echoes (DENSE) sequence to image the motion of the common carotid artery wall and map the two‐dimensional (2D) circumferential strain. The sequence utilizes a fully‐balanced steady‐state free‐precession (SSFP) readout with 0.60 mm in‐plane resolution. Preliminary results in volunteers at 1.5T (N = 4) and 3.0T (N = 17) are compared to measurements of the lumen circumference from cine images. The agreement between the two independent measurements at both field strengths (P ≤ 0.001) supports the use of DENSE as a means to map the pulsatile strain in the carotid artery wall. Magn Reson Med 60:8–13, 2008. © 2008 Wiley‐Liss, Inc.     

MRI measurements of carotid plaque in the atherosclerosis risk in communities (ARIC) study: Methods,reliability and descriptive statistics

Purpose:

To measure carotid plaque components using MRI and estimate reliability in the population‐based Atherosclerosis Risk in Communities (ARIC) study.

Materials and Methods:

Contrast‐enhanced high‐resolution (0.51 × 0.58 × 2 mm³) MRI images were acquired through internal (ICA) and common carotid arteries (CCA) of 2066 ARIC participants at four sites. Sixty‐one exams were repeated and 164 pairs had repeated interpretations. Plaque component thicknesses, areas and volumes over eight slices (1.6‐cm segment) were measured. Intraplaque hemorrhage was recorded. Reliability was evaluated by intraclass correlations and κ statistics.

Results:

There were 1769 successful MRI exams (mean age 71 years; 57% females; 81% white; 19% African‐Americans). Repeat scan reliability was highest for CCA lumen area (0.94) and maximum wall thickness (0.89), ICA lumen area (0.89) and maximum wall thickness (0.77) and total wall volume (0.79), and lowest for small structures—core volume (0.30) and mean cap thickness (0.38). Overall reliability was primarily related to reader variability rather than scan acquisition. K's for presence of core, calcification and hemorrhage were fair to good. White men had the thickest plaques (average maximum ICA wall thickness = 2.3 mm) and the most cores (34%).

Conclusion:

The most important limiting factor for MRI measurements of plaque components is reader variability. Measurement error depends largely on the analyzed structure's size. J. Magn. Reson. Imaging 2010; 31: 406–415. © 2010 Wiley‐Liss, Inc.     

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.     

4D retrospective black blood trueFISP imaging of mouse heart

The purpose of this study was to demonstrate the feasibility of steady‐state True fast imaging with steady precession (TrueFISP) four‐dimensional imaging of mouse heart at high resolution and its efficiency for cardiac volumetry. Three‐dimensional cine‐imaging of control and hypoxic mice was carried out at 4.7 T without magnetization preparation or ECG‐triggering. The k‐space lines were acquired with the TrueFISP sequence (pulse repetition time/echo time = 4/2 ms) in a repeated sequential manner. Retrospective reordering of raw data allowed the reconstruction of 10 three‐dimensional images per cardiac cycle. The acquisition scheme used an alternating radiofrequency phase and sum‐of‐square reconstruction method. Black‐blood three‐dimensional images at around 200 μm resolution were produced without banding artifact throughout the cardiac cycle. High contrast to noise made it possible to estimate cavity volumes during diastole and systole. Right and left ventricular stroke volume was significantly higher in hypoxic mice vs controls (20.2 ± 2 vs 15.1 ± 2; P < 0.05, 24.9 ± 2 vs 20.4 ± 2; P < 0.05, respectively). In conclusion, four‐dimensional black‐blood TrueFISP imaging in living mice is a method of choice to investigate cardiac abnormalities in mouse models. Magn Reson Med, 2009. © 2009 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.     

Comparison of 2D and multislab 3D magnetic resonance techniques for measuring carotid wall volumes

Purpose

To compare a multislab three‐dimensional volume‐selective fast spin‐echo (FSE) magnetic resonance (MR) sequence with a routine two‐dimensional FSE sequence for quantification of carotid wall volume.

Materials and Methods

One hundred normal subjects (50 men, mean age 44.6 years) underwent carotid vessel wall MR using 2D and 3D techniques. Carotid artery total vessel volume, lumen volume, wall volume, and wall/outer wall (W/OW) ratio were measured over 20 contiguous slices. Two‐ (2D) and three‐dimensional (3D) results were compared.

Results

The mean difference between 2D and 3D datasets (as a percentage of the mean absolute value) was 1.7% for vessel volume, 4.9% for lumen volume, 4.7% for wall volume, and 5.8% for W/OW ratio. There was good correlation between 2D and 3D models for total vessel volume (R² = 0.93, P < 0.001), lumen area (R² = 0.92, P < 0.001), and wall volume (R² = 0.77, P < 0.001). The correlation for the W/OW ratio was weaker (R² = 0.30; P < 0.001). The signal‐to‐noise ratio (SNR) for the 3D technique was 2.1‐fold greater than for the 2D technique (P < 0.001). When using the 3D sequence, scan time was reduced by 63%.

Conclusion

Multislab volume selective 3D FSE carotid arterial wall imaging performs similarly to a conventional 2D technique, but with over twice the SNR and substantially reduced scan time. J. Magn. Reson. Imaging 2008;28:1476–1482. © 2008 Wiley‐Liss, Inc.     

Quantitative contrast‐enhanced perfusion measurements of the human lung using the prebolus approach

Purpose

To investigate dynamic contrast‐enhanced MRI (DCE‐MRI) for quantification of pulmonary blood flow (PBF) and blood volume (PBV) using the prebolus approach and to compare the results to the global lung perfusion (GLP).

Materials and Methods

Eleven volunteers were examined by applying different contrast agent doses (0.5, 1.0, 2.0, and 3.0 mL gadolinium diethylene triamine pentaacetic acid [Gd‐DTPA]), using a saturation‐recovery (SR) true fast imaging with steady precession (TrueFISP) sequence. PBF and PBV were determined for single bolus and prebolus. Region of interest (ROI) evaluation was performed and parameter maps were calculated. Additionally, cardiac output (CO) and lung volume were determined and GLP was calculated as a contrast agent–independent reference value.

Results

The prebolus results showed good agreement with low‐dose single‐bolus and GLP: PBF (mean ± SD in units of mL/minute/100 mL) = single bolus 190 ± 73 (0.5‐mL dose) and 193 ± 63 (1.0‐mL dose); prebolus 192 ± 70 (1.0–2.0‐mL dose) and 165 ± 52 (1.0–3.0‐mL dose); GLP (mL/minute/100 mL) = 187 ± 34. Higher single‐bolus resulted in overestimated values due to arterial input function (AIF) saturation.

Conclusion

The prebolus approach enables independent determination of appropriate doses for AIF and tissue signal. Using this technique, the signal‐to‐noise ratio (SNR) from lung parenchyma can be increased, resulting in improved PBF and PBV quantification, which is especially useful for the generation of parameter maps. J. Magn. Reson. Imaging 2009;30:104–111. © 2009 Wiley‐Liss, Inc.     

Black-blood steady-state free precession (SSFP) coronary wall MRI for cardiac allografts: a feasibility study

Purpose:

To assess the hypothesis that steady‐state free procession (SSFP) allows for imaging of the coronary wall under the conditions of fast heart rate in heart transplantation (HTx) patients.

Materials and Methods:

With the approval of our Institutional Review Board, 28 HTx patients were scanned with a 1.5T scanner. Cross‐sectional black‐blood images of the proximal portions of the left main artery, left anterior descending artery, and right coronary artery were acquired with both a 2D, double inversion recovery (DIR) prepared turbo (fast) spin echo (TSE) sequence and a 2D DIR SSFP sequence. Image quality (scored 0–3), vessel wall area, thickness, signal‐to‐noise ratio (SNR, vessel wall), and contrast‐to‐noise ratio (CNR, wall‐lumen) were compared between TSE and SSFP.

Results:

The overall image quality of SSFP was higher than TSE (1.23 ± 0.95 vs. 0.88 ± 0.69, P < 0.001). SSFP had a higher coronary wall SNR (20.1 ± 8.5 vs. 14.9 ± 4.8, P < 0.001) and wall‐lumen CNR (8.2 ± 4.6 vs. 6.8 ± 3.7, P = 0.005) than TSE.

Conclusion:

Black‐blood SSFP coronary wall MRI provides higher image quality, SNR, and CNR than traditional TSE does in HTx recipients. It has the potential to become an alternative means to noninvasive imaging of cardiac allografts. J. Magn. Reson. Imaging 2012;35:1210‐1215. © 2012 Wiley Periodicals, Inc.     

Carotid arterial wall MRI at 3T using 3D variable‐flip‐angle turbo spin‐echo (TSE) with flow‐sensitive dephasing (FSD)

Purpose:

To evaluate the effectiveness of flow‐sensitive dephasing (FSD) magnetization preparation in improving blood signal suppression of three‐dimensional (3D) turbo spin‐echo (TSE) sequence (SPACE) for isotropic high‐spatial‐resolution carotid arterial wall imaging at 3T.

Materials and Methods:

The FSD‐prepared SPACE sequence (FSD‐SPACE) was implemented by adding two identical FSD gradient pulses right before and after the first refocusing 180°‐pulse of the SPACE sequence in all three orthogonal directions. Nine healthy volunteers were imaged at 3T with SPACE, FSD‐SPACE, and multislice T2‐weighted 2D TSE coupled with saturation band (SB‐TSE). Apparent carotid wall‐lumen contrast‐to‐noise ratio (aCNR_w‐l) and apparent lumen area (aLA) at the locations with residual‐blood (rb) signal shown on SPACE images were compared between SPACE and FSD‐SPACE. Carotid aCNR_w‐l and lumen (LA) and wall area (WA) measured from FSD‐SPACE were compared to those measured from SB‐TSE.

Results:

Plaque‐mimicking flow artifacts identified in seven carotids on SPACE images were eliminated on FSD‐SPACE images. The FSD preparation resulted in slightly reduced aCNR_w‐l (P = 0.025), but significantly improved aCNR between the wall and rb regions (P < 0.001) and larger aLA (P < 0.001). Compared to SB‐TSE, FSD‐SPACE offered comparable aCNR_w‐l with much higher spatial resolution, shorter imaging time, and larger artery coverage. The LA and WA measurements from the two techniques were in good agreement based on intraclasss correlation coefficient (0.988 and 0.949, respectively; P < 0.001) and Bland‐Altman analyses.

Conclusion:

FSD‐SPACE is a time‐efficient 3D imaging technique for carotid arterial wall with superior spatial resolution and blood signal suppression. J. Magn. Reson. Imaging 2010;31:645–654. © 2010 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.     

Image analysis in time-resolved large field of view 3D MR-angiography at 3T

Purpose

To qualitatively and quantitatively evaluate the image quality in accelerated time‐resolved 3D contrast‐enhanced MR angiography (tr‐CE‐MRA) at 3T.

Materials and Methods

In all, 113 MRA were performed in 107 patients on a 3T MR system after written informed consent and approval by the ethics committee. Twenty consecutive thoracic (n = 87) or craniocervical (n = 26) 3D data volumes were acquired. The timeframes with maximum arterial and venous contrast were determined and a total of 663 arterial and venous segments were analyzed by two blinded observers. Diagnostic image quality was graded by applying a 0 (low) to 3 (excellent) scale. Additionally, local signal‐to‐noise (SNR) and contrast‐to‐noise ratios (relative CNR) were evaluated.

Results

Tr‐CE‐MRA was successfully performed in all patients. Good to excellent image quality (2.42 ± 0.31) was observed in all individuals with preserved discrimination of arteries (2.43 ± 0.48) and veins (2.20 ± 0.56). Minor image degradation due to artifacts (2.62 ± 0.25) and constantly high vascular signal and contrast were detected. There was a significant superiority of coronal orientation during thoracic MRA (P < 0.05). In 18 cases tr‐CE‐MRA provided additional information on vascular pathologies.

Conclusion

Large field of view tr‐CE‐MRA enables constantly high‐quality thoracic and craniocervical angiographies. In addition, the dynamics of tr‐CE‐MRA can offer additional information on vascular pathologies. J. Magn. Reson. Imaging 2008;28:1116–1124. © 2008 Wiley‐Liss, Inc.     

Impact of T2 decay on carotid artery wall thickness measurements

Purpose:

To investigate the impact of T2 relaxation of the carotid wall on measurements of its thickness.

Materials and Methods:

The common carotid artery wall was imaged using a spin echo sequence acquired at four echo times (17 ms to 68 ms) in 65 participants as part of VALIDATE study. Images were acquired transverse to the artery 1.5 cm proximal to the flow divider. Mean wall thickness, mean wall signal intensity, lumen area, and outer wall area were measured for each echo. Contours were also traced on the image from the fourth echo and then propagated to the images from the preceding echoes. This was repeated using the image from the first echo. Mean wall signal intensity measurements at the four echo times were fit to a mono‐exponential decay curve to derive the mean T2 relaxation time for each set of contours.

Results:

Mean wall thickness decreased with increasing echo time, with an average thickness reduction of 8.6% between images acquired at the first and last echo times (TE) (0.93 mm at TE 17 ms versus 0.85 mm at TE 68 ms, P < 0.001). Average T2 relaxation time of the carotid wall decreased by 3% when the smaller contours from the last echo were used, which excluded the outer‐most layer (54.3 ± 7.6 ms versus 52.7 ± 6.6 ms, P = 0.03).

Conclusion:

Carotid wall thickness measurements decrease with echo time as expected by the fast T2 relaxation time of the outer‐most layer, namely the adventitia. A short echo time is needed for thickness measurements to include adventitia, which plays an important role in plaque development. J. Magn. Reson. Imaging 2013;37:1493–1498. © 2012 Wiley Periodicals, Inc.