Single-dose time-resolved contrast enhanced hybrid MR angiography in diagnosis of peripheral arterial disease: compared with digital subtraction angiography

Purpose:

To validate cardiovascular magnetic resonance (CMR) arterial wall volume measurement using whole arterial specimens ex vivo.

Materials and Methods:

Twenty cadaveric carotid arteries (from 10 patients) were fixed in formaldehyde and imaged with a clinical T1‐weighted 2D CMR sequence and, for imaging validation, with a high‐resolution 3D sequence. Histological validation was performed by sectioning the arteries and microscopically determining area and volume.

Results:

Comparison between the clinical 2D CMR sequence and the 3D high‐resolution validation sequence showed equivalent luminal volumes (889 vs. 880 mm³; P = 0.54; R² = 0.99), and slightly higher 2D CMR arterial wall volumes (982 vs. 916 mm³; +7%; P < 0.01; R² = 0.96) and adventitial volumes (1901 vs. 1826 mm³; +4%; P < 0.01; R² = 0.99). Comparison between 2D CMR and microscopy, performed over a similar longitudinal extent of vessel, showed slightly higher 2D CMR volumes for the lumen (354 vs. 308 mm³; +14%; P < 0.01; R² = 0.97), arterial wall (388 vs. 351 mm³; +10%; P < 0.01; R² = 0.97) and total volumes (750 vs. 665 mm³; +12%; P < 0.01; R² = 0.95).

Conclusion:

The accuracy of the clinical 2D CMR vessel wall sequence for measuring carotid lumen, adventitial, and wall volumes is good against ex vivo measurements, with minor overestimation. This study validates carotid arterial wall quantification by CMR for atherosclerosis research. J. Magn. Reson. Imaging 2010;31:935–941. ©2010 Wiley‐Liss, 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.     

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.     

Noninvasive detection of coronary artery wall thickening with age in healthy subjects using high resolution MRI with beat-to-beat respiratory motion correction

Purpose:

To demonstrate coronary artery wall thickening with age in a small healthy cohort using a highly efficient, reliable, and reproducible high‐resolution MR technique.

Materials and Methods:

A 3D cross‐sectional MR vessel wall images (0.7 × 0.7 × 3 mm resolution) with retrospective beat‐to‐beat respiratory motion correction (B2B‐RMC) were obtained in the proximal right coronary artery of 21 healthy subjects (age, 22–62 years) with no known cardiovascular disease. Lumen and outer wall (lumen + vessel wall) areas were measured in one central slice from each subject and average wall thickness and wall area/outer wall area ratio (W/OW) calculated.

Results:

Imaging was successful in 18 (86%) subjects with average respiratory efficiency 99.3 ± 1.7%. Coronary vessel wall thickness and W/OW significantly correlate with subject age, increasing by 0.088 mm and 0.031 per decade respectively (R = 0.53, P = 0.024 and R = 0.48, P = 0.046). No relationship was found between lumen area and vessel wall thickness (P = NS), but outer wall area increased significantly with vessel wall thickness at 19 mm² per mm (P = 0.046). This is consistent with outward vessel wall remodeling.

Conclusion:

Despite the small size of our healthy cohort, using high‐resolution MR imaging and B2B‐RMC, we have demonstrated increasing coronary vessel wall thickness and W/OW with age. The results obtained are consistent with outward vessel wall remodeling. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, 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.     

In vivo differentiation of two vessel wall layers in lower extremity peripheral vein bypass grafts: Application of high‐resolution inner‐volume black blood 3D FSE

Lower extremity peripheral vein bypass grafts (LE‐PVBG) imaged with high‐resolution black blood three‐dimensional (3D) inner‐volume (IV) fast spin echo (FSE) MRI at 1.5 Tesla possess a two‐layer appearance in T1W images while only the inner layer appears visible in the corresponding T2W images. This study quantifies this difference in six patients imaged 6 months after implantation, and attributes the difference to the T₂ relaxation rates of vessel wall tissues measured ex vivo in two specimens with histologic correlation. The visual observation of two LE‐PVBG vessel wall components imaged in vivo is confirmed to be significant (P < 0.0001), with a mean vessel wall area difference of 6.8 ± 2.7 mm² between contrasts, and a ratio of T1W to T2W vessel wall area of 1.67 ± 0.28. The difference is attributed to a significantly (P < 0.0001) shorter T₂ relaxation in the adventitia (T₂ = 52.6 ± 3.5 ms) compared with the neointima/media (T₂ = 174.7 ± 12.1 ms). Notably, adventitial tissue exhibits biexponential T₂ signal decay (P < 0.0001 vs monoexponential). Our results suggest that high‐resolution black blood 3D IV‐FSE can be useful for studying the biology of bypass graft wall maturation and pathophysiology in vivo, by enabling independent visualization of the relative remodeling of the neointima/media and adventitia. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Submillimeter isotropic resolution carotid wall MRI with swallowing compensation: imaging results and semiautomated wall morphometry

PURPOSE: To assess a swallowing-compensated, three-dimensional (3D) diffusion-prepared segmented steady-state free precession (3D Nav-D-SSFP) technique for carotid wall MRI with 0.6-mm isotropic spatial resolution, and its utility for semiautomated carotid wall morphometry. MATERIALS AND METHODS: The carotid arteries of seven healthy volunteers (N=14) were imaged with 3D Nav-D-SSFP and black-blood T2-weighted (T2w) two-dimensional (2D) fast spin-echo (FSE). Carotid wall-lumen contrast-to-noise ratio (CNR) was measured with both sequences. Measurement of carotid wall area (WA) and lumen area (LA) made in a semiautomated manner off of the 3D Nav-D-SSFP images were compared to those made manually. RESULTS: Adjusted for voxel volume and number of slices, a near six-fold improvement in CNR per unit time was achieved with 3D Nav-D-SSFP relative to 2D T2w FSE (P<0.001). Manual and semiautomated measurements of carotid WA and LA on the 3D Nav-D-SSFP images were highly correlated (intraclass correlation coefficient (ICC)=0.961 and 0.996, respectively; P<0.001). CONCLUSION: 3D Nav-D-SSFP is a time-efficient, swallowing-compensated, black-blood technique that lends itself for semiautomated measurements of carotid WA and LA that are in good agreement with manual measurements.     

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.     

Multicompartmental analysis of late contrast enhancement in areas of myocardial infarction supplied by chronically occluded coronary arteries

Purpose

To analyze the relationship between late contrast enhancement (LCE) and the interstitial distribution volume (V_In) of gadolinium (Gd) tracers in the myocardial infarction (MI) areas supplied by chronically occluded arteries from patients. In animal experimental models, LCE has already been shown to correspond to an enhanced V_In of Gd tracers and thus, to a decrease in the amount of intact cells.

Materials and Methods

A multicompartmental analysis was applied to serial MRI images encompassing both infarct and remote areas and recorded with a conventional two‐dimensional (2D) segmented inversion‐recovery gradient‐echo (IR‐GRE) sequence during a 15‐minute period following Gd‐diethylenetriamine pentaacetic acid (Gd‐DTPA) injection in 12 patients with Q‐wave MI supplied by chronically occluded coronary arteries.

Results

V_In from infarct tissue was: 1) higher than V_In from remote areas (in % of myocardial volume: 74 ± 16% vs. 20 ± 7%, P < 0.001); and 2) correlated with the quantification of LCE between infarct and noninfarct areas at the 15th minute (R² = 0.63, P = 0.002). However, the difference in V_In between infarct and remote myocardium was a much better correlate of this quantified LCE (R² = 0.85, P < 0.001).

Conclusion

Detection of LCE in the MI territories supplied by chronically occluded arteries relates to the difference in the V_In of tracers between the infarct and the noninfarct areas. J. Magn. Reson. Imaging 2009;29:78–85. © 2008 Wiley‐Liss, Inc.     

High-resolution proton density weighted three-dimensional fast spin echo (3D-FSE) of the knee with IDEAL at 1.5 Tesla: comparison with 3D-FSE and 2D-FSE--initial experience

Purpose:

To assess the feasibility of combining three‐dimensional fast spin echo (3D‐FSE) and Iterative‐decomposition‐of water‐and‐fat‐with‐echo asymmetry‐and‐least‐squares‐estimation (IDEAL) at 1.5 Tesla (T), generating a high‐resolution 3D isotropic proton density‐weighted image set with and without “fat‐suppression” (FS) in a single acquisition, and to compare with 2D‐FSE and 3D‐FSE (without IDEAL).

Materials and Methods:

Ten asymptomatic volunteers prospectively underwent sagittal 3D‐FSE‐IDEAL, 3D‐FSE, and 2D‐FSE sequences at 1.5T (slice thickness [ST]: 0.8 mm, 0.8 mm, and 3.5 mm, respectively). 3D‐FSE and 2D‐FSE were repeated with frequency‐selective FS. Fluid, cartilage, and muscle signal‐to‐noise ratio (SNR) and fluid‐cartilage contrast‐to‐noise ratio (CNR) were compared among sequences. Three blinded reviewers independently scored quality of menisci/cartilage depiction for all sequences. “Fat‐suppression” was qualitatively scored and compared among sequences.

Results:

3D‐FSE‐IDEAL fluid‐cartilage CNR was higher than in 2D‐FSE (P < 0.05), not different from 3D‐FSE (P = 0.31). There was no significant difference in fluid SNR among sequences. 2D‐FSE cartilage SNR was higher than in 3D FSE‐IDEAL (P < 0.05), not different to 3D‐FSE (P = 0.059). 2D‐FSE muscle SNR was higher than in 3D‐FSE‐IDEAL (P < 0.05) and 3D‐FSE (P < 0.05). Good or excellent depiction of menisci/cartilage was achieved using 3D‐FSE‐IDEAL in the acquired sagittal and reformatted planes. Excellent, homogeneous “fat‐suppression” was achieved using 3D‐FSE‐IDEAL, superior to FS‐3D‐FSE and FS‐2D‐FSE (P < 0.05).

Conclusion:

3D FSE‐IDEAL is a feasible approach to acquire multiplanar images of diagnostic quality, both with and without homogeneous “fat‐suppression” from a single acquisition. J. Magn. Reson. Imaging 2012;361‐369. © 2011 Wiley Periodicals, 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.     

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.     

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.     

Cartilage morphology at 3.0T: Assessment of three‐dimensional magnetic resonance imaging techniques

Purpose:

To compare six new three‐dimensional (3D) magnetic resonance (MR) methods for evaluating knee cartilage at 3.0T.

Materials and Methods:

We compared: fast‐spin‐echo cube (FSE‐Cube), vastly undersampled isotropic projection reconstruction balanced steady‐state free precession (VIPR‐bSSFP), iterative decomposition of water and fat with echo asymmetry and least‐squares estimation combined with spoiled gradient echo (IDEAL‐SPGR) and gradient echo (IDEAL‐GRASS), multiecho in steady‐state acquisition (MENSA), and coherent oscillatory state acquisition for manipulation of image contrast (COSMIC). Five‐minute sequences were performed twice on 10 healthy volunteers and once on five osteoarthritis (OA) patients. Signal‐to‐noise ratio (SNR) and contrast‐to‐noise ratio (CNR) were measured from the volunteers. Images of the five volunteers and the five OA patients were ranked on tissue contrast, articular surface clarity, reformat quality, and lesion conspicuity. FSE‐Cube and VIPR‐bSSFP were compared to IDEAL‐SPGR for cartilage volume measurements.

Results:

FSE‐Cube had top rankings for lesion conspicuity, overall SNR, and CNR (P < 0.02). VIPR‐bSSFP had top rankings in tissue contrast and articular surface clarity. VIPR and FSE‐Cube tied for best in reformatting ability. FSE‐Cube and VIPR‐bSSFP compared favorably to IDEAL‐SPGR in accuracy and precision of cartilage volume measurements.

Conclusion:

FSE‐Cube and VIPR‐bSSFP produce high image quality with accurate volume measurement of knee cartilage. J. Magn. Reson. Imaging 2010;32:173–183. © 2010 Wiley‐Liss, Inc.     

Automatic lumen and outer wall segmentation of the carotid artery using deformable three-dimensional models in MR angiography and vessel wall images

Purpose:

To develop and validate an automated segmentation technique for the detection of the lumen and outer wall boundaries in MR vessel wall studies of the common carotid artery.

Materials and Methods:

A new segmentation method was developed using a three‐dimensional (3D) deformable vessel model requiring only one single user interaction by combining 3D MR angiography (MRA) and 2D vessel wall images. This vessel model is a 3D cylindrical Non‐Uniform Rational B‐Spline (NURBS) surface which can be deformed to fit the underlying image data. Image data of 45 subjects was used to validate the method by comparing manual and automatic segmentations. Vessel wall thickness and volume measurements obtained by both methods were compared.

Results:

Substantial agreement was observed between manual and automatic segmentation; over 85% of the vessel wall contours were segmented successfully. The interclass correlation was 0.690 for the vessel wall thickness and 0.793 for the vessel wall volume. Compared with manual image analysis, the automated method demonstrated improved interobserver agreement and inter‐scan reproducibility. Additionally, the proposed automated image analysis approach was substantially faster.

Conclusion:

This new automated method can reduce analysis time and enhance reproducibility of the quantification of vessel wall dimensions in clinical studies. J. Magn. Reson. Imaging 2012;35:156‐165. © 2011 Wiley Periodicals, Inc.     

Estimation and visualization of regional and global pulmonary perfusion with 3D magnetic resonance angiography

The purposes of this work were to estimate regional and global pulmonary perfusion and display pulmonary vasculature in 10 postoperative lung transplant patients using breath‐hold, contrast‐enhanced (0.2 mmol/kg, Gd DTPA‐BMA, Omniscan, Nycomed, Inc., Princeton, NJ), three‐dimensional (3D) magnetic resonance angiography (MRA) with specially designed double‐variable‐angle uniform signal excitation (VUSE) radio frequency (RF) pulses. Double‐VUSE scans imaged both lungs simultaneously during contrast agent injection and provided both qualitative and quantitative information about pulmonary perfusion. Double‐VUSE pulses clearly displayed healthy and diseased vessels. There was a strong correlation between contrast‐enhanced double‐VUSE MRA flow estimates and those measured from nuclear scans for global or whole lung (R² = 0.95; P = 0.000002) and upper, central, and lower thirds of the lung (R² = 0.89, 0.92, and 0.86, respectively; P < 0.001 for each region). In conclusion, 3D MRA using VUSE pulses in combination with a contrast agent is a valuable tool for the assessment of pulmonary perfusion that simultaneously acquires data for both the qualitative display of pulmonary vessels and the quantification of regional and global differential pulmonary blood flow. J. Magn. Reson. Imaging 2001;14:734–740. © 2001 Wiley‐Liss, Inc.     

Biliary anatomy on 3D MRCP: Comparison of volume‐rendering and maximum‐intensity‐projection algorithms

Purpose

To compare volume‐rendering (VR) and maximum‐intensity‐projection (MIP) of three‐dimensional T2‐weighted turbo spin‐echo magnetic resonance cholangiopancreatography using a free‐breathing navigator‐triggered prospective acquisition correction (3D‐TSE‐PACE‐MRCP) to define biliary anatomies.

Materials and Methods

VR and MIP images of 3D‐TSE‐PACE‐MRCP for 102 patients were retrospectively evaluated. Interpretation of cystic duct variation and biliary branching patterns of each image were recorded independently by two radiologists in a blinded fashion. Interpretation confidence on a five‐point scale was compared using the Wilcoxon signed‐rank test. The McNemar test was used to compare the accuracies of each reformation with the reference standard obtained by consensus interpretation of both the images and source images.

Results

The reference standard identified all biliary bifurcations and 95 of 102 cystic duct confluences (93.1%). VR findings agreed with the reference standard findings more often than MIP with regard to cystic duct variation (94 [92.2%] vs. 76 [74.5%], P < 0.01) while there was no significant difference for biliary branching patterns (99 [97.1%] vs. 92 [90.2%], P = 0.092). The mean confidence score was significantly higher with VR than MIP with regard to both cystic duct variation and biliary branching patterns (3.7 vs. 2.4; P < 0.01; 4.1 vs. 3.3; P < 0.01).

Conclusion

VR reformation of 3D‐TSE‐PACE‐MRCP defines biliary anatomies more accurately than MIP. J. Magn. Reson. Imaging 2009;29:601–606. © 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.     

Left ventricular infarct size,peri‐infarct zone,and papillary scar measurements: A comparison of high‐resolution 3D and conventional 2D late gadolinium enhancement cardiac MR

Purpose

To compare higher spatial resolution 3D late gadolinium enhancement (LGE) cardiovascular magnetic resonance (Cardiac MR) with 2D LGE in patients with prior myocardial infarction.

Materials and Methods

Fourteen patients were studied using high spatial resolution 3D LGE (1.3 × 1.3 × 5.0 mm³) and conventional 2D LGE (2 × 2 × 8 mm³) scans. The signal‐to‐noise ratio (SNR) and contrast‐to‐noise ratio (CNR) were measured. Total infarct volume, peri‐infarct volume measured in a limited slab, and papillary muscle scar volume were compared using Bland–Altman analysis. Image quality was graded.

Results

3D LGE had higher scar SNR (P < 0.001), higher myocardial SNR (P = 0.001), higher papillary scar‐blood CNR (P = 0.01), and greater sharpness (P = 0.01). The scar volumes agreed (14.5 ± 8.2 for 2D, vs. 13.2 ± 8.8 for 3D), with bias ± 2 standard deviations (SDs) of 0.5 ± 6.8 mL, P = 0.59 R = 0.91. The peri‐infarct volumes correlated but less strongly than scar (P = 0.40, R = 0.77). For patients with more heterogeneous scar, larger peri‐infarct volumes were measured by 3D (1.9 ± 1.1 mL for 2D vs. 2.4 ± 1.6 mL for 3D, P = 0.15, in the matched region). Papillary scar, present in 6/14 (42%) patients, was more confidently identified on 3D LGE.

Conclusion

Higher spatial resolution 3D LGE provides sharper images and higher SNR, but less myocardial nulling. Scar volumes agree well, with peri‐infarct volumes correlating less well. 3D LGE may be superior in visualization of papillary muscle scar. J. Magn. Reson. Imaging 2009;30:794–800. © 2009 Wiley‐Liss, Inc.     

The detection of coronary stiffness in cardiac allografts using MR imaging

Objective

To test the hypothesis that biomechanical changes are quantitatively related to morphological features of coronary arteries in heart transplant (HTx) recipients.

Materials and methods

With IRB approval, three-dimensional (3D) magnetic resonance (MR) angiography and two-dimensional (2D) black-blood stead-state free precession (SSFP) MR imaging were performed to image coronary arteries of 36 HTx patients. Contours of coronary wall were manually drawn. For each coronary segment, coronary wall thickness, wall area, lumen area (in systole and diastole) were acquired. Coronary distensibility index (CDI) and the percent of the coronary wall occupying the vessel area (PWOV) were calculated.

Results

There are totally 98 coronary segments eligible for quantitative analysis from 27 HTx patients. The CDI is 4.90 ± 2.44 mmHg⁻¹. The mean wall thickness is 1.49 ± 0.24 mm and the PWOV is 74.6% ± 7.5%. CDI has moderate correlations with wall thickness (r = −0.531, P < 0.001) and with PWOV (R = −0.435, P < 0.001).

Conclusions

Detected with coronary MR imaging, CDI is quantitatively correlated with the morphological features of the coronary artery in HTx patients. Coronary stiffness has the potential to become an alternative imaging biomarker for the quantitative assessment of the status of cardiac allografts.