Impact of motion on T1 mapping acquired with inversion recovery fast spin echo and rapid spoiled gradient recalled‐echo pulse sequences for delayed gadolinium‐enhanced MRI of cartilage (dGEMRIC) in volunteers

Purpose:

To evaluate the impact of motion on T1 values acquired by using either inversion‐recovery fast spin echo (IR‐FSE) or three‐dimensional (3D) spoiled gradient recalled‐echo (SPGR) sequences for delayed gadolinium‐enhanced magnetic resonance imaging of cartilage (dGEMRIC) in volunteers.

Materials and Methods:

Single‐slice IR‐FSE and 3D SPGR sequences were applied to perform dGEMRIC in five healthy volunteers. A mutual information‐based approach was used to correct for image misregistration. Displacements were expressed as averaged Euclidean distances and angles. Averages of differences in goodness of fit (Δχ²) tests and averages of relative differences in T1 values (ΔT1) before and after motion correction were computed.

Results:

Maximum Euclidean distance was 3.5 mm and 1.2 mm for IR‐FSE and SPGR respectively. Mean ± SD of Δχ² were 10.18 ± 8.4 for IR‐FSE and ?1.37 ± 5.5 for SPGR. Mean ± SD of ΔT1 were 0.008 ± 0.0048 for IR‐FSE and ?0.002 ± 0.019 for FSPGR. Pairwise comparison of Δχ² values showed a significant difference for IR‐FSE, but not for 3D‐SPGR. Significantly greater variability in T1 values was also noted for IR‐FSE than for 3D‐SPGR.

Conclusion:

Involuntary motion has a significant influence on T1 values acquired with IR‐FSE, but not with 3D‐SPGR in healthy volunteers. J. Magn. Reson. Imaging 2010;32:394–398. © 2010 Wiley‐Liss, Inc.

     

Local flip angle correction for improved volume T1‐quantification in three‐dimensional dGEMRIC using the look‐locker technique

Purpose

To present an evaluation method for three‐dimensional Look‐Locker (3D‐LL) based T1 quantification, calculating correct T1 values independent of local flip angle (FA) variations. The method was evaluated both in phantoms and in vivo in a delayed Gadolinium Enhanced MRI of Cartilage (dGEMRIC) study with 33 subjects.

Materials and Methods

T1 was measured with 3D‐LL, using both local FA correction and a precalculated FA slice profile, and compared with standard constant FA correction, for all slices in phantoms and in both femur condyles in vivo. T1 measured using two‐dimensional Inversion Recovery (2D‐IR) was used as gold standard.

Results

Due to the FA being slice dependent, the standard constant FA correction results in erroneous T1 (systematic error = 109.1 ms in vivo), especially in the outer slices. With local FA correction, the calculated T1 is excellent for all slices in phantoms (<5% deviation from 2D‐IR). In vivo the performance is lower (systematic error = ?57.5 ms), probably due to imperfect inversion. With precalculated FA correction the performance is very good also in vivo (systematic error = 13.3 ms).

Conclusion

With the precalculated FA correction method, the 3D‐LL sequence is robust enough for in vivo dGEMRIC, even outside the centermost slices. J. Magn. Reson. Imaging 2009;30:834–841. © 2009 Wiley‐Liss, Inc.

     

Repeatability of T1‐quantification in dGEMRIC for three different acquisition techniques: Two‐dimensional inversion recovery,three‐dimensional look locker,and three‐dimensional variable flip angle

Purpose:

To evaluate the repeatability of the dGEMRIC (delayed gadolinium enhanced MRI of cartilage) method in osteoarthritis‐prone knee joints for three different T1 quantification techniques: two‐dimensional inversion recovery (2D‐IR), three‐dimensional Look‐Locker (3D‐LL), and three‐dimensional variable flip angle (3D‐VFA).

Materials and Methods:

Nine subjects were examined twice, with a 2‐week interval, using all three measurement techniques. Four regions of interest were defined in the central medial and lateral femoral cartilage. The repeatability was evaluated for each measurement technique. For the 3D techniques, the variation between different slices was also evaluated.

Results:

Repeatability expressed by root‐mean‐square coefficient of variation (CV_RMS) showed similar results for 2D‐IR and 3D‐LL (5.4–8.4%). For 3D‐VFA CV_RMS was higher (9.3–15.2%). Intraclass correlation coefficient showed both 2D‐IR and 3D‐LL reliability to be moderate, while 3D‐VFA reliability was low. Inter‐slice CV_RMS and ICC was of the same magnitude as the repeatability. No clear differences could be interpreted between the condyles.

Conclusion:

Both 2D‐IR and 3D‐LL perform well in generating repeatable dGEMRIC results, while 3D‐VFA results are somewhat inferior. Furthermore, repeatability results in this study are similar to previously published results for healthy subjects. Finally, the positioning of the analyzed images is crucial to generate reliable repeatability results. J. Magn. Reson. Imaging 2010;31:1203–1209. © 2010 Wiley‐Liss, Inc.     

Using the dGEMRIC technique to evaluate cartilage health in the presence of surgical hardware at 3T: comparison of inversion recovery and saturation recovery approaches

Objective

To evaluate the effect of metal artifact reduction techniques on dGEMRIC T₁ calculation with surgical hardware present.

Materials and methods

We examined the effect of stainless-steel and titanium hardware on dGEMRIC T₁ maps. We tested two strategies to reduce metal artifact in dGEMRIC: (1) saturation recovery (SR) instead of inversion recovery (IR) and (2) applying the metal artifact reduction sequence (MARS), in a gadolinium-doped agarose gel phantom and in vivo with titanium hardware. T₁ maps were obtained using custom curve-fitting software and phantom ROIs were defined to compare conditions (metal, MARS, IR, SR).

Results

A large area of artifact appeared in phantom IR images with metal when TI?≤?700 ms. IR maps with metal had additional artifact both in vivo and in the phantom (shifted null points, increased mean T₁ (+151 % IR ROI_artifact) and decreased mean inversion efficiency (f; 0.45 ROI_artifact, versus 2 for perfect inversion)) compared to the SR maps (ROI_artifact: +13 % T₁ SR, 0.95 versus 1 for perfect excitation), however, SR produced noisier T₁ maps than IR (phantom SNR: 118 SR, 212 IR). MARS subtly reduced the extent of artifact in the phantom (IR and SR).

Conclusions

dGEMRIC measurement in the presence of surgical hardware at 3T is possible with appropriately applied strategies. Measurements may work best in the presence of titanium and are severely limited with stainless steel. For regions near hardware where IR produces large artifacts making dGEMRIC analysis impossible, SR-MARS may allow dGEMRIC measurements. The position and size of the IR artifact is variable, and must be assessed for each implant/imaging set-up.     

7 Tesla MR imaging of the human eye in vivo

Purpose:

To develop a protocol which optimizes contrast, resolution and scan time for three‐dimensional (3D) imaging of the human eye in vivo using a 7 Tesla (T) scanner and custom radio frequency (RF) coil.

Materials and Methods:

Initial testing was conducted to reduce motion and susceptibility artifacts. Three‐dimensional FFE and IR‐TFE images were obtained with variable flip angles and TI times. T₁ measurements were made and numerical simulations were performed to determine the ideal contrast of certain ocular structures. Studies were performed to optimize resolution and signal‐to‐noise ratio (SNR) with scan times from 20 s to 5 min.

Results:

Motion and susceptibility artifacts were reduced through careful subject preparation. T₁ values of the ocular structures are in line with previous work at 1.5T. A voxel size of 0.15 × 0.25 × 1.0 mm³ was obtained with a scan time of approximately 35 s for both 3D FFE and IR‐TFE sequences. Multiple images were registered in 3D to produce final SNRs over 40.

Conclusion:

Optimization of pulse sequences and avoidance of susceptibility and motion artifacts led to high quality images with spatial resolution and SNR exceeding prior work. Ocular imaging at 7T with a dedicated coil improves the ability to make measurements of the fine structures of the eye. J. Magn. Reson. Imaging 2009;30:924–932. © 2009 Wiley‐Liss, Inc.     

High-resolution 7T MRI of the human hippocampus in vivo

Purpose

To describe an initial experience imaging the human hippocampus in vivo using a 7T magnetic resonance (MR) scanner and a protocol developed for very high field neuroimaging.

Materials and Methods

Six normal subjects were scanned on a 7T whole body MR scanner equipped with a 16‐channel head coil. Sequences included a full field of view T1‐weighted 3D turbo field echo (T1W 3D TFE: time of acquisition (TA) = 08:58), T2*‐weighted 2D fast field echo (T2*W 2D FFE: TA = 05:20), and susceptibility‐weighted imaging (SWI: TA = 04:20). SWI data were postprocessed using a minimum intensity projection (minIP) algorithm. Total imaging time was 23 minutes.

Results

T1W 3D TFE images with 700 μm isotropic voxels provided excellent anatomic depiction of macroscopic hippocampal structures. T2*W 2D FFE images with 0.5 mm in‐plane resolution and 2.5 mm slice thickness provided clear discrimination of the Cornu Ammonis and the compilation of adjacent sublayers of the hippocampus. SWI images (0.5 mm in‐plane resolution, 1.0 mm slice thickness) delineated microvenous anatomy of the hippocampus.

Conclusion

In vivo 7T MR imaging can take advantage of higher signal‐to‐noise and novel contrast mechanisms to provide increased conspicuity of hippocampal anatomy. J. Magn. Reson. Imaging 2008;28:1266–1272. © 2008 Wiley‐Liss, Inc.     

Improved fat water separation with water selective inversion pulse for inversion recovery imaging in cardiac MRI

Purpose:

To develop an improved chemical shift‐based water‐fat separation sequence using a water‐selective inversion pulse for inversion recovery 3D contrast‐enhanced cardiac magnetic resonance imaging (MRI).

Materials and Methods:

In inversion recovery sequences the fat signal is substantially reduced due to the application of a nonselective inversion pulse. Therefore, for simultaneous visualization of water, fat, and myocardial enhancement in inversion recovery‐based sequences such as late gadolinium enhancement imaging, two separate scans are used. To overcome this, the nonselective inversion pulse is replaced with a water‐selective inversion pulse. Imaging was performed in phantoms, nine healthy subjects, and nine patients with suspected arrhythmogenic right ventricular cardiomyopathy plus one patient for tumor/mass imaging. In patients, images with conventional turbo‐spin echo (TSE) with and without fat saturation were acquired prior to contrast injection for fat assessment. Subjective image scores (1 = poor, 4 = excellent) were used for image assessment.

Results:

Phantom experiments showed a fat signal‐to‐noise ratio (SNR) increase between 1.7 to 5.9 times for inversion times of 150 and 300 msec, respectively. The water‐selective inversion pulse retains the fat signal in contrast‐enhanced cardiac MR, allowing improved visualization of fat in the water‐fat separated images of healthy subjects with a score of 3.7 ± 0.6. Patient images acquired with the proposed sequence were scored higher when compared with a TSE sequence (3.5 ± 0.7 vs. 2.2 ± 0.5, P < 0.05).

Conclusion:

The water‐selective inversion pulse retains the fat signal in inversion recovery‐based contrast‐enhanced cardiac MR, allowing simultaneous visualization of water and fat. J. Magn. Reson. Imaging 2013;37:484–490. © 2012 Wiley Periodicals, Inc.     

Fluid and white matter suppression with the MP2RAGE sequence

Purpose:

To develop a magnetic resonance imaging (MRI) sequence (fluid and white matter suppression, FLAWS) for generating two sets of images from a single acquisition: one with contrast similar to a T1‐weighted magnetization‐prepared rapid gradient‐echo sequence (MPRAGE) for structural definition; the other with nulled white matter (WM) signal intensity, similar to the fast gray matter T1 inversion recovery (FGATIR) sequence, for improved delineation of subcortical brain structures.

Materials and Methods:

The recently proposed MP2RAGE, which is a modification of the MPRAGE and generates two image sets at different inversion times, was employed to generate the FGATIR‐like contrast (FLAWS1) and MPRAGE‐like contrast (FLAWS2). Five healthy volunteers were scanned at 3T and brain tissue contrast and contrast‐to‐noise were compared.

Results:

FLAWS1 and FLAWS2 exhibited similar tissue contrast and contrast‐to‐noise as the “reference” sequences, FGATIR and MPRAGE, respectively. Synthetic minimum value images generated from FLAWS1 and FLAWS2 provided a gray matter‐dominant image.

Conclusion:

FLAWS provides two coregistered 3D volumes, one with nulled WM signal intensity and another with nulled cerebrospinal fluid. The coregistered nature of the two datasets allows for generating images that might be helpful in segmentation algorithms and clinical diagnosis. J. Magn. Reson. Imaging 2012;35:1063‐1070. © 2011 Wiley Periodicals, 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.     

Three‐dimensional (3D) visualization of endolymphatic hydrops after intratympanic injection of Gd‐DTPA: Optimization of a 3D‐real inversion‐recovery turbo spin‐echo (TSE) sequence and application of a 32‐channel head coil at 3T

Purpose:

To enable volume visualization of endolymphatic hydrops of Ménière's disease via a volume rendering (VR) technique, a three‐dimensional (3D) inversion‐recovery (IR) sequence with real reconstruction (3D‐real IR) sequence after intratympanic injection of Gd‐DTPA was optimized for higher spatial resolution using a 32‐channel head coil at 3T.

Materials and Methods:

Pulse sequence parameters were optimized using a diluted Gd‐DTPA phantom. Then, 11 patients who had been clinically diagnosed with Ménière's disease and a patient with sudden hearing loss were scanned. Images were processed using commercially available 3D‐VR software. 3D‐real IR data was processed to produce endolymph and perilymph fluid volume images in different colors. 3D‐CISS data was processed to generate total fluid volume images.

Results:

While maintaining a comparable signal‐to‐noise ratio (SNR) and scan time, the voxel volume could be reduced from 0.4 × 0.4 × 2 mm³ with a 12‐channel coil to 0.4 × 0.4 × 0.8 mm³ with a 32‐channel coil. A newly‐optimized protocol allowed the smooth, three‐dimensional visualization of endolymphatic hydrops in all patients with Ménière's disease.

Conclusion:

Volumetrically separate visualization of endo‐/perilymphatic space is now feasible in patients with Ménière's disease using an optimized 3D‐real IR sequence, a 32‐channel head coil, at 3T, after intratympanic administration of Gd‐DTPA. This will aid the understanding of the pathophysiology of Ménière's disease. J. Magn. Reson. Imaging 2010;31:210–214. © 2009 Wiley‐Liss, Inc.     

Delayed gadolinium‐enhanced MRI of cartilage in the ankle at 3 T: Feasibility and preliminary results after matrix‐associated autologous chondrocyte implantation

Purpose:

To demonstrate the feasibility of delayed gadolinium‐enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC) in the ankle at 3 T and to obtain preliminary data on matrix associated autologous chondrocyte (MACI) repair tissue.

Materials and Methods:

A 3D dual flip angle sequence was used with an eight‐channel multipurpose coil at 3 T to obtain T1 maps both pre‐ and postintravenous contrast agent (Magnevist, 0.2 mM/kg). Postcontrast T1 over time was evaluated in three volunteers; a modified dGEMRIC protocol was then used to assess 10 cases after MACI in the ankle.

Results:

Forty‐five minutes were found sufficient for maximum T1 decrease. MACI cases had a precontrast mean T1 of 1050 ± 148.4 msec in reference cartilage (RC) and 1080 ± 165.6 msec in repair tissue (RT). Postcontrast T1 decreased to 590 ± 134.0 msec in RC and 554 ± 133.0 msec in RT. There was no significant difference between the delta relaxation rates in RT (9.44 × 10^?4 s^?1) and RC (8.04 × 10^?4 s^?1, P = 0.487). The mean relative delta relaxation rate was 1.34 ± 0.83.

Conclusion:

It is feasible to assess the thin cartilage layers of the ankle with dGEMRIC at 3 T; MACI can yield RT with properties similar to articular cartilage. J. Magn. Reson. Imaging 2010;31:732–739. © 2010 Wiley‐Liss, Inc.

     

Head-to-head comparison of eight late gadolinium-enhanced cardiac MR (LGE CMR) sequences at 1.5 tesla: from bench to bedside

Purpose:

To compare—theoretically and experimentally—clinically available two‐dimensional/three‐dimensional (2D/3D), breathhold and non‐breathhold, inversion‐recovery (IR) gradient‐echo (GRE) sequences used to differentiate between nonviable injured and normal myocardium with late gadolinium‐enhanced techniques (IR‐GRE2D sequence is used as a reference), and to evaluate their respective clinical benefit.

Materials and Methods:

Six breathhold (2D‐IR‐GRE, 3D‐IR‐GRE, balanced steady‐state free precession 2D‐IR‐bSSFP and 3D‐IR‐bSSFP, phase‐sensitive 2D‐PSIR‐GRE, and 2D‐PSIR‐bSSFP) and two non‐breathhold late gadolinium‐enhanced techniques (single‐shot 2D‐ssbSSFP and 2D‐PSIR‐ssbSSFP) were consecutively performed in 32 coronary artery disease patients with chronic myocardial infarction. Qualitative assessment and manual planimetry were performed by two independent observers. Quantitative assessment was based on percentage signal intensity elevation between injured and normal myocardium and contrast‐to‐noise ratio. Theoretical simulations were compared with experimental measurements performed on phantoms with various concentrations of gadolinium.

Results:

The 3D‐IR‐GRE image quality appeared better than the other 2D and 3D sequences, showing better delineation of complex nontransmural lesions, with significantly higher percentage signal intensity and contrast‐to‐noise ratio. PSIR techniques appeared more limited in differentiating sub‐endocardial lesions and intracavity blood pool, but in all other cases were comparable to the other techniques. Single‐shot PSIR‐ssbSSFP appeared to be a valuable alternative technique when breathhold cannot be achieved.

Conclusion:

We recommend 3D‐IR‐GRE as the method of choice for late gadolinium‐enhanced cardiac magnetic resonance imaging in clinical practice. J. Magn. Reson. Imaging 2011;. © 2011 Wiley Periodicals, Inc.     

A comparative analysis of double inversion recovery TFE and TSE sequences on carotid artery wall imaging

Objective

To analyze the characteristics of double inversion recovery (DIR) turbo field echo (TFE) and turbo spin echo (TSE) sequences and explore the value of double inversion recovery TFE sequence on carotid artery wall imaging.

Patients and methods

56 patients (32 males and 24 females, aged 31–76 years with a mean age of 53 years) were performed with DIR TFE and DIR TSE T1 weighted imaging (T1WI) sequences on carotid artery bifurcations. Image quality acquired by different techniques were evaluated and scored by two physicians. Whether there is significant difference is determined by SPSS 11.0 software. Paired-samples t test was used for statistics.

Results

There was no significant difference in the image quality scores between two sequences (t = 0.880, P = 0.383 > 0.05).

Conclusions

DIR TFE sequence has short scanning time and high spatial resolution. DIR TFE sequence can be used as the preferred sequence for screening carotid atherosclerotic plaque compared with DIR TSE sequence.     

Three-dimensional delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) for in vivo evaluation of reparative cartilage after matrix-associated autologous chondrocyte transplantation at 3.0T: Preliminary results

PURPOSE: To use a 3D gradient-echo (GRE) sequence with two flip angles for delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) to evaluate relative glycosaminoglycan content of repair tissue after matrix-associated autologous chondrocyte transplantation (MACT). MATERIALS AND METHODS: In a phantom study, T1-mapping based on a 3D-GRE sequence with different flip angle combinations was compared with a standard inversion recovery (IR) sequence at 3.0T. Fifteen patients were examined after MACT in the knee at "3-13 months" (group I) and "19-42 months" (group II). The delta relaxation rate (deltaR1) calculated for repair tissue and normal hyaline cartilage was measured and mean values were compared in different postoperative intervals using analysis of variance. RESULTS: The flip angle combination 35/10 degrees provided the best agreement with IR sequence for short and long T1 values. The mean deltaR1 for repair tissue was 2.49 versus 1.04 at the intact control site in group I and 1.90 compared with 0.81 in group II. Differences from repair tissue to control sites showed statistically significance for both groups; no significant difference was found between groups. CONCLUSION: The 3D dual flip angle dGEMRIC technique optimized for cartilage imaging is comparable to standard T1 IR technique for T1 mapping. Furthermore, the preliminary in vivo study demonstrates the feasibility of the technique in the evaluation of MACT patients.     

Optimized inversion-prepared gradient echo imaging

Purpose:

To implement a method using an extended phase graph (EPG)‐based simulation to optimize inversion‐prepared gradient echo sequences with respect to signal and contrast within the shortest acquisition time.

Materials and Methods:

A critical issue in rapid gradient‐echo imaging is the effect of residual transverse magnetization between consecutive data acquisition windows. Various spoiling schemes have been proposed to mitigate this problem, and while spoiling is often considered to be perfect, imaging can be more truthfully described using the EPG. An EPG‐based simulation is used to analyze and predict the image signal and contrast to serve as a basis for sequence optimization.

Results:

Fourteen biological phantom experiments and five brain imaging experiments on each of five healthy volunteers was performed to validate and verify the accuracy of the EPG‐based simulation. In addition, two experiments on an in‐cranial cadaver brain were performed to show the ability of the proposed method for improving overall image quality.

Conclusion:

From the experiment results, it is demonstrated that optimization of 3D magnetization‐prepared rapid gradient‐echo imaging sequences can be performed with an EPG‐based simulation to manipulate the sequence parameters for generating images with highly specific signal and contrast characteristics for quantitative T1‐weighted human brain imaging. J. Magn. Reson. Imaging 2012;36:748–755. © 2012 Wiley Periodicals, Inc.     

High resolution fast T1 mapping technique for dGEMRIC

Purpose

To determine the feasibility of using a high resolution isotropic three‐dimensional (3D) fast T1 mapping sequence for delayed gadolinium‐enhanced MRI of cartilage (dGEMRIC) to assess osteoarthritis in the hip.

Materials and Methods

T1 maps of the hip were acquired using both low and high resolution techniques following the administration of 0.2 mmol/kg Gd‐DTPA^2‐ in 35 patients. Both T1 maps were generated from two separate spoiled GRE images. The high resolution T1 map was reconstructed in the anatomically equivalent plane as the low resolution map. T1 values from the equivalent anatomic regions containing femoral and acetabular cartilages were measured on the low and high resolution maps and compared using regression analysis.

Results

In vivo T1 measurements showed a statistically significant correlation between the low and high resolution acquisitions at 1.5 Tesla (R² = 0.958, P < 0.001). These results demonstrate the feasibility of using a fast two‐angle T1 mapping (F2T1) sequence with isotropic spatial resolution (0.8 × 0.8 × 0.8 mm) for quantitative assessment of biochemical status in articular cartilage of the hip.

Conclusion

The high resolution 3D F2T1 sequence provides accurate T1 measurements in femoral and acetabular cartilages of the hip, which enables the biochemical assessment of articular cartilage in any plane through the joint. It is a powerful tool for researchers and clinicians to acquire high resolution data in a reasonable scan time (< 30 min). J. Magn. Reson. Imaging 2009;30:896–900. © 2009 Wiley‐Liss, Inc.     

Visualization of deep veins and detection of deep vein thrombosis (DVT) with balanced turbo field echo (b‐TFE) and contrast‐enhanced T1 fast field echo (CE‐FFE) using a blood pool agent (BPA)

Purpose:

To assess image quality, vessel visualization, preliminary diagnostic properties, and interobserver variability of a novel balanced turbo field echo (b‐TFE) sequence and contrast‐enhanced T1 fast field echo (CE‐FFE) sequence with blood pool agent (BPA).

Materials and Methods:

A total of 15 healthy volunteers and six patients with ultrasound‐verified proximal deep vein thrombosis (DVT) were examined from the inferior vena cava (IVC) to the proximal calf veins.

Results:

The great majority of deep veins were completely visualized on both sequences. In healthy volunteers the IVC was completely visualized in five b‐TFE and 11 CE‐FFE scans, and partially in seven b‐TFE and four CE‐FFE scans (P = 0.008). Poorest image quality was in the pelvis. Contrast‐to‐noise ratio (CNR) was higher on b‐TFE compared to CE‐FFE, with significant difference in calf images (P = 0.036). Sensitivity was 100% for proximal DVT with both methods. Specificity was 70% (CE‐FFE) and 80% (b‐TFE) for proximal femoral DVT; 100% in distal femoral. Interobserver reliability was kappa 1.0 (b‐TFE), 0.9 (CE‐FFE) for proximal, and overall poor for distal DVT.

Conclusion:

Contrast‐enhancement did not add valuable information in visualizing deep veins of the lower limbs compared to b‐TFE, though the IVC was slightly better visualized. Diagnostic properties and interobserver reliability of both sequences were good for proximal DVT and poor for distal DVT. J. Magn. Reson. Imaging 2010; 31: 416–424. © 2010 Wiley‐Liss, Inc.     

Noncontrast MR angiography for comprehensive assessment of abdominopelvic arteries using quadruple inversion-recovery preconditioning and 3D balanced steady-state free precession imaging

Purpose:

To develop a noncontrast magnetic resonance angiography (MRA) method for comprehensive evaluation of abdominopelvic arteries in a single 3D acquisition.

Materials and Methods:

A noncontrast MRA (NC MRA) pulse sequence was developed using four inversion‐recovery (IR) pulses and 3D balanced steady‐state free precession (b‐SSFP) readout to provide arterial imaging from renal to external iliac arteries. Respiratory triggered, high spatial resolution (1.3 × 1.3 × 1.7 mm³) noncontrast angiograms were obtained in seven volunteers and ten patients referred for gadolinium‐enhanced MRA (CE MRA). Images were assessed for diagnostic quality by two radiologists. Quantitative measurements of arterial signal contrast were also performed.

Results:

NC MRA imaging was successfully completed in all subjects in 7.0 ± 2.3 minutes. In controls, image quality of NC MRA averaged 2.79 ± 0.39 on a scale of 0–3, where 3 is maximum. Image quality of NC MRA (2.65 ± 0.41) was comparable to that of CE MRA (2.9 ± 0.32) in all patients. Contrast ratio measurements in patients demonstrated that NC MRA provides arterial contrast comparable to source CE MRA images with adequate venous and excellent background tissue suppression.

Conclusion:

The proposed noncontrast MRA pulse sequence provides high‐quality visualization of abdominopelvic arteries within clinically feasible scan times. J. Magn. Reson. Imaging 2011;33:1430–1439. © 2011 Wiley‐Liss, Inc.     

dGEMRIC and subsequent T1 mapping of the hip at 1.5 Tesla: normative data on zonal and radial distribution in asymptomatic volunteers

Purpose:

To characterize the zonal distribution of three‐dimensional (3D) T1 mapping in the hip joint of asymptomatic adult volunteers.

Materials and Methods:

This study included 10 volunteers (3 males and 7 females with a mean age of 26.5 years; range, 24–31 years). MRI protocol included standard sequences for hip imaging and a dual‐flip‐angle 3D gradient‐echo (GRE) sequence with volumetric interpolated breathhold examination (VIBE) postcontrast administration. Seven radial cuts were created clockwise around the femoral neck by using multi‐planar reconstruction.

Results:

Analysis of the radial distribution revealed an increase of T1‐values toward the superior regions. T1‐values differed between the peripheral and central portions. The standard deviation (SD) ranged from 76.2 ms to 124.1 ms in the peripheral zone, and from 69.1 ms to 112.9 ms in the central zone. In both zones, SD was low in the superior regions compared with the anterior and posterior regions of the joint. Based on the high intra‐ (0.95) and interobserver (0.87) agreement, normative data from this study will prepare the foundation for further studies of dGEMRIC and T1 in the hip.

Conclusion:

We noted a radial T1 mapping pattern with higher values in the superior zone that was not statistically significant and a notable trend in zonal distribution between peripheral and central zones. These findings are critical while outlining future studies for detailed objective evaluation of zonal cartilage lesions due to varying pathologies. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.     

Aortic vessel wall magnetic resonance imaging at 3.0 Tesla: A reproducibility study of respiratory navigator gated free‐breathing 3D black blood magnetic resonance imaging

The purpose of this study was to evaluate a free‐breathing three‐dimensional (3D) dual inversion‐recovery (DIR) segmented k‐space gradient‐echo (turbo field echo [TFE]) imaging sequence at 3T for the quantification of aortic vessel wall dimensions. The effect of respiratory motion suppression on image quality was tested. Furthermore, the reproducibility of the aortic vessel wall measurements was investigated. Seven healthy subjects underwent 3D DIR TFE imaging of the aortic vessel wall with and without respiratory navigator. Subsequently, this sequence with respiratory navigator was performed twice in 10 healthy subjects to test its reproducibility. The signal‐to‐noise (SNR), contrast‐to‐noise ratio (CNR), vessel wall sharpness, and vessel wall volume (VWV) were assessed. Data were compared using the paired t‐test, and the reproducibility of VWV measurements was evaluated using intraclass correlation coefficients (ICCs). SNR, CNR, and vessel wall sharpness were superior in scans performed with respiratory navigator compared to scans performed without. The ICCs concerning intraobserver, interobserver, and interscan reproducibility were excellent (0.99, 0.94, and 0.95, respectively). In conclusion, respiratory motion suppression substantially improves image quality of 3D DIR TFE imaging of the aortic vessel wall at 3T. Furthermore, this optimized technique with respiratory motion suppression enables assessment of aortic vessel wall dimensions with high reproducibility. Magn Reson Med 61:35–44, 2009. © 2008 Wiley‐Liss, Inc.