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.     

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.     

Three‐dimensional flow‐independent balanced steady‐state free precession vessel wall MRI of the popliteal artery: Preliminary experience and comparison with flow‐dependent black‐blood techniques

Purpose:

To examine the feasibility of flow‐independent T2‐prepared inversion recovery (T2IR) black‐blood (BB) magnetization preparation for three‐dimensional (3D) balanced steady‐state free precession (SSFP) vessel wall MRI of the popliteal artery, and to evaluate its performance relative to flow‐dependent double inversion recovery (DIR), spatial presaturation (SPSAT), and motion‐sensitizing magnetization preparation (MSPREP) BB techniques in healthy volunteers.

Materials and Methods:

Eleven subjects underwent 3D MRI at 1.5 Tesla with four techniques performed in a randomized order. Wall and lumen signal‐to‐noise ratio (SNR), wall‐to‐lumen contrast‐to‐noise ratio (CNR), vessel wall area, and lumen area were measured at proximal, middle, and distal locations of the imaged popliteal artery. Image quality scores based on wall visualization and degree of intraluminal artifacts were also obtained.

Results:

In the proximal region, DIR and SPSAT had higher wall SNR and wall‐to‐lumen CNR than both MSPREP and T2IR. In the middle and distal regions, DIR and SPSAT failed to provide effective blood suppression, whereas MSPREP and T2IR provided adequate black blood contrast with comparable wall‐to‐lumen CNR and image quality.

Conclusion:

The feasibility of 3D SSFP imaging of the popliteal vessel wall using flow‐independent T2IR was demonstrated with effective blood suppression and good vessel wall visualization. Although DIR and SPSAT are effective for thin slab imaging, MSPREP and T2IR are better suited for 3D thick slab imaging. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, 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.     

New look at renal vasculature: 7 tesla nonenhanced T1-weighted FLASH imaging

Purpose:

To investigate the feasibility of 7 Tesla (T) nonenhanced high field MR imaging of the renal vasculature and to evaluate the diagnostic potential of various nonenhanced T1‐weighted (T1w) sequences.

Materials and Methods:

Twelve healthy volunteers were examined on a 7T whole‐body MR system (Magnetom 7T, Siemens Healthcare Sector) using a custom‐built eight‐channel radiofrequency (RF) transmit/receive body coil. Subsequent to RF shimming, the following sequences were acquired (i) fat‐saturated two‐dimensional (2D) FLASH, (ii) fat‐saturated 3D FLASH, and a (iii) fat‐saturated 2D time‐of‐flight MR angiography (TOF MRA). SNR and CNR were measured in the aorta and both renal arteries. Qualitative analysis was performed with regard to vessel delineation (5‐point scale: 5 = excellent to 1 = nondiagnostic) and presence of artifacts (5‐point scale: 5 = no artifact present to 1 = strong impairment).

Results:

The inherently high signal intensity of the renal arterial vasculature in T1w imaging enabled moderate to excellent vessel delineation in all sequences. Qualitative (mean, 4.7) and quantitative analysis (SNR_mean: 53.9; CNR_mean: 28.0) demonstrated the superiority of TOF MRA, whereas 2D FLASH imaging provided poorest vessel delineation and was most strongly impaired by artifacts (overall impairment 3.7). The 3D FLASH MRI demonstrated its potential for fast high quality imaging of the nonenhanced arterial vasculature, providing homogeneous hyperintense vessel signal.

Conclusion:

Nonenhanced T1w imaging in general and, TOF MRA in particular, appear to be promising techniques for good quality nonenhanced renal artery assessment at 7 Tesla. J. Magn. Reson. Imaging 2012;36:714–721. © 2012 Wiley Periodicals, Inc.     

3D flow‐independent peripheral vessel wall imaging using T2‐prepared phase‐sensitive inversion‐recovery steady‐state free precession

Purpose:

To develop a 3D flow‐independent peripheral vessel wall imaging method using T₂‐prepared phase‐sensitive inversion‐recovery (T₂PSIR) steady‐state free precession (SSFP).

Materials and Methods:

A 3D T₂‐prepared and nonselective inversion‐recovery SSFP sequence was designed to achieve flow‐independent blood suppression for vessel wall imaging based on T₁ and T₂ properties of the vessel wall and blood. To maximize image contrast and reduce its dependence on the inversion time (TI), phase‐sensitive reconstruction was used to restore the true signal difference between vessel wall and blood. The feasibility of this technique for peripheral artery wall imaging was tested in 13 healthy subjects. Image signal‐to‐noise ratio (SNR), wall/lumen contrast‐to‐noise ratio (CNR), and scan efficiency were compared between this technique and conventional 2D double inversion recovery – turbo spin echo (DIR‐TSE) in eight subjects.

Results:

3D T₂PSIR SSFP provided more efficient data acquisition (32 slices and 64 mm in 4 minutes, 7.5 seconds per slice) than 2D DIR‐TSE (2–3 minutes per slice). SNR of the vessel wall and CNR between vessel wall and lumen were significantly increased as compared to those of DIR‐TSE (P < 0.001). Vessel wall and lumen areas of the two techniques are strongly correlated (intraclass correlation coefficients: 0.975 and 0.937, respectively; P < 0.001 for both). The lumen area of T₂PSIR SSFP is slightly larger than that of DIR‐TSE (P = 0.008). The difference in vessel wall area between the two techniques is not statistically significant.

Conclusion:

T₂PSIR SSFP is a promising technique for peripheral vessel wall imaging. It provides excellent blood signal suppression and vessel wall/lumen contrast. It can cover a 3D volume efficiently and is flow‐ and TI‐independent. J. Magn. Reson. Imaging 2010;32:399–408. © 2010 Wiley‐Liss, Inc.     

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.     

Coronary anomalies assessed by whole‐heart isotropic 3D magnetic resonance imaging for cardiac morphology in congenital heart disease

Purpose

To determine the value of whole‐heart three‐dimensional magnetic resonance imaging (MRI) for coronary artery imaging in children/adolescents with congenital heart disease (CHD).

Materials and Methods

Forty children/adolescents (median age: 14 years, range 2.6–25.8) with CHD underwent free‐breathing navigator‐gated isotropic three‐dimensional steady‐state free‐precession (3D‐SSFP) MRI for cardiac morphology. Two observers independently evaluated visibility of origin, course, vessel lengths, image quality (IQ), and contrast between coronary lumen and myocardium. A subgroup was compared with cardiac catheter.

Results

The total scan time was 6.3 ± 3.2 minutes (mean ± SD, at mean heart rate 76 ± 15/min). The mean vessel length for right coronary artery (RCA) by observer 1 was 97 ± 43 mm (observer 2: 94 ± 37 mm), for left main and anterior descending artery (LM/LAD) 91 ± 40 mm (observer 2: 90 ± 40 mm), and for left circumflex artery (LCX) 64 ± 28mm (observer 2: 66 ± 28 mm). The mean vessel contrast was 0.34 ± 0.05 (range: 0.23–0.45; maximum = 1, minimum = 0). On a 4‐level score (1 = nondiagnostic, 4 = excellent), mean IQ scores ranged between 2.3–2.9 (±0.8–1.0). Both observers agreed on the presence/proximal course of RCA in 40/40, LM/LAD in 38/40, and LCX in 36/40 patients. There was complete agreement with invasive coronary angiography available in 12/40 patients (six anomalies).

Conclusion

Isotropic whole‐heart 3D‐MRI for cardiac morphology allows reliable discrimination between normal and abnormal coronary anatomy in children/adolescents with CHD. J. Magn. Reson. Imaging 2009;29:320–327. © 2009 Wiley‐Liss, Inc.     

Scan‐rescan reproducibility of carotid atherosclerotic plaque morphology and tissue composition measurements using multicontrast MRI at 3T

Purpose:

To evaluate interscan reproducibility of both vessel morphology and tissue composition measurements of carotid atherosclerosis using a fast, optimized, 3T multicontrast protocol.

Materials and Methods:

A total of 20 patients with carotid stenosis >15% identified by duplex ultrasound were recruited for two independent 3T MRI (Philips) scans within one month. A multicontrast protocol including five MR sequences was applied: TOF, T1‐/T2‐/PD‐weighted and magnetization‐prepared rapid acquisition gradient‐echo (MP‐RAGE). Carotid artery morphology (wall volume, lumen volume, total vessel volume, normalized wall index, and mean/maximum wall thickness) and plaque component size (lipid rich/necrotic core, calcification, and hemorrhage) were measured over two time points.

Results:

After exclusion of images with poor image quality, 257 matched locations from 18 subjects were available for analysis. For the quantitative carotid morphology measurements, coefficient of variation (CV) ranged from 2% to 15% and intraclass correlation coefficient (ICC) ranged from 0.87 to 0.99. Except for maximum wall thickness (ICC = 0.87), all ICC were larger than 0.90. For the quantitative plaque composition measurements, the ICC of the volume and relative content of lipid rich/necrotic core and calcification were larger than 0.90 with CV ranging from 22% to 32%.

Conclusion:

The results from the multicontrast high‐resolution 3T MR study show high reliability for carotid morphology and plaque component measurements. 3T MRI is a reliable tool for longitudinal clinical trials, with shorter scan time compared to 1.5T. J. Magn. Reson. Imaging 2010;31:168–176. © 2009 Wiley‐Liss, Inc.     

3D fat-saturated T1 SPACE sequence for the diagnosis of cervical artery dissection

Introduction

This study aims to demonstrate the added value of a 3D fat-saturated (FS) T1 sampling perfection with application-optimised contrast using different flip angle evolutions (SPACE) sequence compared to 2D FS T1 spin echo (SE) for the diagnosis of cervical artery dissection.

Methods

Thirty-one patients were prospectively evaluated on a 1.5-T MR system for a clinical suspicion of acute or subacute cervical artery dissection with 3D T1 SPACE sequence. In 23 cases, the axial 2D FS T1 SE sequence was also used; only these cases were subsequently analysed. Two neuroradiologists independently and blindly assessed the 2D and 3D T1 sequences. The presence of recent dissection (defined as a T1 hyperintensity in the vessel wall) and the quality of fat suppression were assessed. The final diagnosis was established in consensus, after reviewing all the imaging and clinical data.

Results

Overall sensitivity and specificity were 0.929 and 1 for axial T1 SE, and 0.965 and 0.945 for T1 SPACE (P?>?0.05), respectively. The two readers had excellent agreement for both sequences (k?=?1 and 0.8175 for T1 SE and T1 SPACE, respectively; P?>?0.05). The quality of the fat saturation was similar. Very good fat saturation was obtained in the upper neck. Multiplanar reconstructions were very useful in tortuous regions, such as the atlas loop of the vertebral artery or the carotid petrous entry. 3D T1 SPACE sequence has a shorter acquisition time (3 min 25 s versus 5 min 32 s for one T1 SE sequence) and a larger coverage area.

Conclusion

3D T1 SPACE sequence offers similar information with its 2D counterpart, in a shorter acquisition time and larger coverage area.     

Depicting the semicircular canals with inner‐ear MRI: A comparison of the SPACE and TrueFISP sequences

Purpose:

To assess the ability of magnetic resonance imaging (MRI) to depict the semicircular canals of the inner ear by comparing results from the sampling perfection with application‐optimized contrasts by using different flip angle evolutions (SPACE) sequence with those from the true free induction with steady precession (TrueFISP) sequence.

Materials and Methods:

A 1.5‐T MRI system was used to perform an in vivo study of 10 healthy volunteers and 17 patients. A three‐point visual score was employed for assessing the depiction of the semicircular canals and facial and vestibulocochlear nerves and the contrast‐to‐noise ratio (CNR) was computed for the vestibule and pons on images with the SPACE and TrueFIPS sequences.

Results:

There were no susceptibility artifact‐related filling defects with the SPACE sequence. However, the TrueFISP sequence showed filling defects for at least one semicircular canal on both sides in seven cases for healthy subjects and in 10 cases for patients. The CNR with the SPACE sequence was significantly higher than with the TrueFISP sequence (P < 0.05). There was no statistically significant difference in depicting the facial and the vestibulocochlear nerves (P = 0.32).

Conclusion:

For the depiction of the semicircular canal, the SPACE sequence is superior to the TrueFISP sequence. J. Magn. Reson. Imaging 2013;37:652–659. © 2012 Wiley Periodicals, Inc.     

Diffusion‐weighted imaging of human carotid artery using 2D single‐shot interleaved multislice inner volume diffusion‐weighted echo planar imaging (2D ss‐IMIV‐DWEPI) at 3T: Diffusion measurement in atherosclerotic plaque

Purpose:

To determine if 2D single‐shot interleaved multislice inner volume diffusion‐weighted echo planar imaging (ss‐IMIV‐DWEPI) can be used to obtain quantitative diffusion measurements that can assist in the identification of plaque components in the cervical carotid artery.

Materials and Methods:

The 2D ss‐DWEPI sequence was combined with interleaved multislice inner volume region localization to obtain diffusion weighted images with 1 mm in‐plane resolution and 2 mm slice thickness. Eleven subjects, six of whom have carotid plaque, were studied with this technique. The apparent diffusion coefficient (ADC) images were calculated using DW images with b = 10 s/mm² and b = 300 s/mm².

Results:

The mean ADC measurement in normal vessel wall of the 11 subjects was 1.28 ± 0.09 × 10^?3 mm²/s. Six of the 11 subjects had carotid plaque and ADC measurements in plaque ranged from 0.29 to 0.87 × 10^?3 mm²/s. Of the 11 common carotid artery walls studied (33 images), at least partial visualization of the wall was obtained in all ADC images, more than 50% visualization in 82% (27/33 images), and full visualization in 18% (6/33 images).

Conclusion:

2D ss‐IMIV‐DWEPI can perform diffusion‐weighted carotid magnetic resonance imaging (MRI) in vivo with reasonably high spatial resolution (1 × 1 × 2 mm³). ADC values of the carotid wall and plaque are consistent with similar values obtained from ex vivo endarterectomy specimens. The spread in ADC values obtained from plaque indicate that this technique could form a basis for plaque component identification in conjunction with other MRI/MRA techniques. J. Magn. Reson. Imaging 2009;30:1068–1077. © 2009 Wiley‐Liss, Inc.

     

Volume‐targeted and whole‐heart coronary magnetic resonance angiography using an intravascular contrast agent

Purpose

To compare volume‐targeted and whole‐heart coronary magnetic resonance angiography (MRA) after the administration of an intravascular contrast agent.

Materials and Methods

Six healthy adult subjects underwent a navigator‐gated and ‐corrected (NAV) free breathing volume‐targeted cardiac‐triggered inversion recovery (IR) 3D steady‐state free precession (SSFP) coronary MRA sequence (t‐CMRA) (spatial resolution = 1 × 1 × 3 mm³) and high spatial resolution IR 3D SSFP whole‐heart coronary MRA (WH‐CMRA) (spatial resolution = 1 × 1 × 2 mm³) after the administration of an intravascular contrast agent B‐22956. Subjective and objective image quality parameters including maximal visible vessel length, vessel sharpness, and visibility of coronary side branches were evaluated for both t‐CMRA and WH‐CMRA.

Results

No significant differences (P = NS) in image quality were observed between contrast‐enhanced t‐CMRA and WH‐CMRA. However, using an intravascular contrast agent, significantly longer vessel segments were measured on WH‐CMRA vs. t‐CMRA (right coronary artery [RCA] 13.5 ± 0.7 cm vs. 12.5 ± 0.2 cm; P < 0.05; and left circumflex coronary artery [LCX] 11.9 ± 2.2 cm vs. 6.9 ± 2.4 cm; P < 0.05). Significantly more side branches (13.3 ± 1.2 vs. 8.7 ± 1.2; P < 0.05) were visible for the left anterior descending coronary artery (LAD) on WH‐CMRA vs. t‐CMRA. Scanning time and navigator efficiency were similar for both techniques (t‐CMRA: 6.05 min; 49% vs. WH‐CMRA: 5.51 min; 54%, both P = NS).

Conclusion

Both WH‐CMRA and t‐CMRA using SSFP are useful techniques for coronary MRA after the injection of an intravascular blood‐pool agent. However, the vessel conspicuity for high spatial resolution WH‐CMRA is not inferior to t‐CMRA, while visible vessel length and the number of visible smaller‐diameter vessels and side‐branches are improved. J. Magn. Reson. Imaging 2009;30:1191–1196. © 2009 Wiley‐Liss, Inc.     

Whole‐heart coronary magnetic resonance angiography at 3.0T using short‐TR steady‐state free precession,vastly undersampled isotropic projection reconstruction

Purpose

To evaluate the feasibility of improving 3.0T steady‐state free precession (SSFP) whole‐heart coronary magnetic resonance angiography (MRA) using short‐TR (repetition time) VIPR (vastly undersampled isotropic projection reconstruction).

Materials and Methods

SSFP is highly sensitive to field inhomogeneity. VIPR imaging uses nonselective radiofrequency pulses, allowing short TR and reduced banding artifacts, while achieving isotropic 3D resolution. Coronary artery imaging was performed in nine healthy volunteers using SSFP VIPR. TR was reduced to 3.0 msec with an isotropic spatial resolution of 1.3 × 1.3 × 1.3 mm³. Image quality, vessel sharpness, and lengths of major coronary arteries were measured. Comparison between SSFP using Cartesian trajectory and SSFP using VIPR trajectory was performed in all volunteers.

Results

Short‐TR SSFP VIPR resulted in whole‐heart images without any banding artifacts, leading to excellent coronary artery visualization. The average image quality score for VIPR‐SSFP was 3.12 ± 0.42 out of four while that for Cartesian SSFP was 0.92 ± 0.61. A significant improvement (P < 0.05) in image quality was shown by Wilcoxon comparison. The visualized coronary artery lengths for VIPR‐SSFP were: 10.13 ± 0.79 cm for the left anterior descending artery (LAD), 7.90 ± 0.91 cm for the left circumflex artery (LCX), 7.50 ± 1.65 cm for the right coronary artery (RCA), and 1.84 ± 0.23 cm for the left main artery (LM). The lengths statistics for Cartesian SSFP were 1.57 ± 2.02 cm, 1.54 ± 1.93 cm, 0.94 ± 1.17 cm, 0.46 ± 0.53 cm, respectively. The image sharpness was also increased from 0.61 ± 0.13 (mm^?1) in Cartesian‐SSFP to 0.81 ± 0.11 (mm^?1) in VIPR‐SSFP.

Conclusion

With VIPR trajectory the TR is substantially decreased, reducing the sensitivity of SSFP to field inhomogeneity and resulting in whole‐heart images without banding artifacts at 3.0T. Image quality improved significantly over Cartesian sampling. J. Magn. Reson. Imaging 2010; 31:1230–1235. © 2010 Wiley‐Liss, Inc.

     

Multi-sequence whole-brain intracranial vessel wall imaging at 7.0 tesla

Objectives

Intracranial vessel wall magnetic resonance imaging (MRI) may improve the diagnosis of vessel wall abnormalities. Current methods are hampered by limited coverage and few contrast weightings. We present a multi-sequence protocol with whole-brain coverage for vessel wall imaging on 7.0-T MRI.

Methods

A modified magnetisation-preparation inversion recovery turbo-spin-echo (MPIR-TSE) sequence was used to obtain proton density (PD)-, T₁-, and T₂-weighting with 190-mm whole-brain coverage. Three observers independently scored the visibility of arterial vessel walls in five healthy volunteers, and compared the conspicuity and image contrast of all sequences. Clinical applicability was demonstrated in 17 patients with cerebrovascular disease.

Results

Conspicuity was good for all acquisitions, with best scores for the original limited-coverage sequence, followed by whole-brain coverage T₂-_, PD- and T₁-weighted sequences, respectively. Mean vessel wall/background MR signal intensity ratios for all whole-brain sequences were similar, with higher scores for the limited-coverage MPIR-TSE sequence. Signal intensity ratios were highest in patients, for the whole-brain T₁-weighted sequence.

Conclusions

The whole-brain multi-sequence vessel wall protocol can assess intracranial arterial vessel walls with full brain coverage, for different image contrast weightings. These sequences could eventually characterise intracranial vessel wall abnormalities similar to current techniques for assessing carotid artery plaques.

Key points

- Intracranial vessel wall imaging using MRI improves diagnosis of cerebrovascular diseases. - Conventional 7-T MRI sequences cannot image the whole cerebral arterial tree. - New whole-brain 7-T MRI sequences compare favourably with smaller-coverage sequences. - These whole-brain sequences can demonstrate the entire cerebral arterial tree. - These sequences should help in the diagnosis of vessel wall abnormalities.     

Fast dixon‐based multisequence and multiplanar MRI for whole‐body detection of cancer metastases

Purpose

To develop and demonstrate the feasibility of multisequence and multiplanar MRI for whole‐body cancer detection.

Materials and Methods

Two fast Dixon‐based sequences and a diffusion‐weighted sequence were used on a commercially available 1.5 T scanner for whole‐body cancer detection. The study enrolled 19 breast cancer patients with known metastases and in multistations acquired whole‐body axial diffusion‐weighted, coronal T2‐weighted, axial/sagittal pre‐ and postcontrast T1‐weighted, as well as triphasic abdomen images. Three radiologists subjectively scored Dixon images of each series for overall image quality and fat suppression uniformity on a 4‐point scale (1 = poor, 2 = fair, 3 = good, and 4 = excellent).

Results

Eighteen of the 19 patients completed the whole‐body MRI successfully. The mean acquisition time and overall patient table time were 46 ± 3 and 69 ± 5 minutes, respectively. The average radiologists' scores for overall image quality and fat suppression uniformity were both 3.4 ± 0.5. The image quality was consistent between patients and all completed whole‐body examinations were diagnostically adequate.

Conclusion

Whole‐body MRI offering essentially all the most optimal tumor‐imaging sequences in a typical 1‐hour time slot can potentially become an appealing “one‐stop‐shop” for whole‐body cancer imaging. J. Magn. Reson. Imaging 2009;29:1154–1162. © 2009 Wiley‐Liss, Inc.     

Optimization of the contrast dose and injection rates in whole‐body MR angiography at 3.0T

Purpose:

To optimize the contrast agent dose and delivery rate used in a novel whole‐body magnetic resonance angiography (MRA) protocol using a 3.0T MR scanner.

Materials and Methods:

Six groups of 20 consenting volunteers underwent whole‐body MRA, with each group receiving a different contrast dose and contrast delivery rate. The arterial tree was divided into 16 segments and the image quality at each of the anatomical locations, covering the whole body, was assessed. Qualitative analysis was carried out using a scoring assessment of image quality, and quantitative assessments were performed by measuring contrast‐to‐noise (CNR) and a signal‐to‐noise (SNR) index.

Results:

Reducing the contrast dose from 40 mL to 25 mL was found to significantly increase the CNR in several vessels of interest in the arterial tree. There was also a significant increase in the qualitative image quality score (P < 0.001).

Conclusion:

This study demonstrates that reducing the contrast dose at 3.0T can result in an increase in the CNR in the vessels of interest without significantly affecting the SNR. J. Magn. Reson. Imaging 2009;30:1059–1067. © 2009 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.     

Flow‐independent 3D whole‐heart vessel wall imaging using an interleaved T2‐preparation acquisition

Current techniques to visualize the arterial vessel wall are limited in coverage because most of them are flow dependent. In this study, we present a novel technique for flow‐independent vessel wall imaging that takes advantage of the differences in T2 relaxation time of arterial blood and surrounding tissues using the T2‐preparation prepulse. The technique is based on the acquisition and subtraction of two data sets, one obtained with and one without T2‐preparation prepulse. This approach allows for nulling the signal of arterial blood while maintaining signal from muscle and vessel wall. The result of the subtraction is a flow‐independent black‐blood vessel wall image. To minimize the motion sensitivity of the subtraction step, we developed an interleaved acquisition for the T2‐preparation prepulse and non‐T2‐preparation prepulse images, which allows obtaining coronary vessel wall images from a whole‐heart acquisition with minimal misregistration artefacts. In this article, we present the technique and preliminary results in healthy subjects. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.     

Improved blood suppression in three‐dimensional (3D) fast spin‐echo (FSE) vessel wall imaging using a combination of double inversion‐recovery (DIR) and diffusion sensitizing gradient (DSG) preparations

Purpose:

To provide improved blood suppression in three‐dimensional inner‐volume fast spin‐echo (3D IV‐FSE) carotid vessel wall imaging by using a hybrid preparation consisting of double inversion‐recovery (DIR) and diffusion sensitizing gradients (DSG).

Materials and Methods:

Multicontrast black‐blood MRI is widely used for vessel wall imaging and characterization of atherosclerotic plaque composition. Blood suppression is difficult when using 3D volumetric imaging techniques. DIR approaches do not provide robust blood suppression due to incomplete replacement of blood spins, and DSG approaches compromise vessel wall signal, reducing the lumen‐wall contrast‐to‐noise ratio efficiency (CNR_eff). In this work a hybrid DIR+DSG preparation is developed and optimized for blood suppression, vessel wall signal preservation, and vessel‐wall contrast in 3D IV‐FSE imaging. Cardiac gated T₁‐weighted carotid vessel wall images were acquired in five volunteers with 0.5 × 0.5 × 2.5 mm³ spatial resolution in 80 seconds.

Results:

Data from healthy volunteers indicate that the proposed method yields a statistically significant (P < 0.01) improvement in blood suppression and lumen‐wall CNR_eff compared to standard DIR and standard DSG methods alone.

Conclusion:

A combination of DIR and DSG preparations can provide improved blood suppression and lumen‐wall CNR_eff for 3D IV‐FSE vessel wall imaging. J. Magn. Reson. Imaging 2010; 31: 398–405. © 2010 Wiley‐Liss, Inc.