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.

     

Signal polarity restoration in a 3D inversion recovery sequence used with delayed gadolinium‐enhanced magnetic resonance imaging of cartilage (dGEMRIC)

Purpose:

To develop an image reconstruction algorithm that restores the signal polarity in a three‐dimensional inversion‐recovery (3D‐IR) sequence used in delayed gadolinium‐enhanced MRI of cartilage (dGEMRIC). This approach effectively doubles the dynamic range of data used for T1 curve fitting.

Materials and Methods:

We applied this reconstruction algorithm to a 3D‐IR TFE sequence used for T1 mapping, validated the technique in a phantom study, and performed T1‐map calculations in postosteochondral allograft transplant (OAT) patients. In addition, we performed a signal simulation study to assess the algorithm's capability to reduce the number of inversion times used in the 3D‐IR TFE sequence.

Results:

In comparison to a standard T1‐mapping algorithm that uses the magnitude of the MRI signal, the proposed algorithm improves the reliability of T1 relaxation fits to the inversion‐recovery three‐parameter function. The signal simulation study shows that the number of TI inversion times can be reduced to as few as four, without compromising the accuracy of T1 calculations.

Conclusion:

This algorithm can be applied to any 2D‐ or 3D‐IR acquisition sequence used in conjunction with dGEMRIC. Application of the algorithm improves the reliability of T1 calculations and allows the number of TIs to be reduced, leading to shorter scan times in dGEMRIC. J. Magn. Reson. Imaging 2012;36:1248–1255. © 2012 Wiley Periodicals, Inc.     

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.

     

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.     

Variable velocity encoding in a three‐dimensional,three‐directional phase contrast sequence: Evaluation in phantom and volunteers

Purpose:

To evaluate accuracy and noise properties of a novel time‐resolved, three‐dimensional, three‐directional phase contrast sequence with variable velocity encoding (denoted 4D‐vPC) on a 3 Tesla MR system, and to investigate potential benefits and limitations of variable velocity encoding with respect to depicting blood flow patterns.

Materials and Methods:

A 4D PC‐MRI sequence was modified to allow variable velocity encoding (VENC) over the cardiac cycle in all three velocity directions independently. 4D‐PC sequences with constant and variable VENC were compared in a rotating phantom with respect to measured velocities and noise levels. Additionally, comparison of flow patterns in the ascending aorta was performed in six healthy volunteers.

Results:

Phantom measurements showed a linear relationship between velocity noise and velocity encoding. 4D‐vPC MRI presented lower noise levels than 4D‐PC both in phantom and in volunteer measurements, in agreement with theory. Volunteer comparisons revealed more consistent and detailed flow patterns in early diastole for the variable VENC sequences.

Conclusion:

Variable velocity encoding offers reduced noise levels compared with sequences with constant velocity encoding by optimizing the velocity‐to‐noise ratio (VNR) to the hemodynamic properties of the imaged area. Increased VNR ratios could be beneficial for blood flow visualizations of pathology in the cardiac cycle. J. Magn. Reson. Imaging 2012; 36:1450–1459. © 2012 Wiley Periodicals, Inc.     

Free‐breathing high‐spatial‐resolution delayed contrast‐enhanced three‐dimensional viability MR imaging of the myocardium at 3.0T: A feasibility study

Purpose

To assess the feasibility of free‐breathing high‐spatial‐resolution delayed contrast‐enhanced three‐dimensional (3D) viability magnetic resonance imaging (MRI) at 3.0T for the detection of myocardial damages.

Materials and Methods

Twenty‐five patients with myocardial diseases, including myocardial infarction and cardiomyopathies, were enrolled after informed consent was given. Free‐breathing 3D viability MRI with high spatial resolution (1.5 × 1.25 × 2.5 mm) at 3.0T, for which cardiac and navigator gating techniques were employed, was compared with breath‐hold two‐dimensional (2D) viability imaging (1.77 × 1.18 × 10 mm) for assessment of contrast‐to‐noise ratio (CNR) and myocardial damage.

Results

Free‐breathing 3D viability imaging was achieved successfully in 21 of the 25 patients. This imaging technique depicted 84.6% of hyperenhancing myocardium with a higher CNR between hyperenhancing myocardium and blood and with excellent agreement for the transmural extension of myocardial damage (k = 0.91). In particular, the 3D viability images delineated the myocardial infarction and linear hyperenhancing myocardium, comparable to the 2D viability images.

Conclusion

Free‐breathing high‐spatial‐resolution delayed contrast‐enhanced 3D viability MRI using 3.0T was feasible for the evaluation of hyperenhancing myocardium, as seen with myocardial infarction and cardiomyopathies. J. Magn. Reson. Imaging 2008;28:1361–1367. © 2008 Wiley‐Liss, Inc.     

DC‐gated high resolution three‐dimensional lung imaging during free‐breathing

Purpose:

To use the acquisition of the k‐space center signal (DC signal) implemented into a Cartesian three‐dimensional (3D) FLASH sequence for retrospective respiratory self‐gating and, thus, for the examination of the whole human lung in high spatial resolution during free breathing.

Materials and Methods:

Volunteer as well as patient measurements were performed under free breathing conditions. The DC signal is acquired after the actual image data acquisition within each excitation of a 3D FLASH sequence. The DC signal is then used to track respiratory motion for retrospective respiratory gating.

Results:

It is shown that the acquisition of the DC signal after the imaging module can be used in a 3D FLASH sequence to extract respiratory motion information for retrospective respiratory self‐gating and allows for shorter echo times (TE) and therefore increased lung parenchyma SNR.

Conclusion:

The acquisition of the DC signal after image signal acquisition allows successful retrospective gating, enabling the reconstruction of high resolution images of the whole human lung under free breathing conditions. J. Magn. Reson. Imaging 2013;37:727–732. © 2012 Wiley Periodicals, Inc.     

Time‐resolved three‐dimensional magnetic resonance digital subtraction angiography without contrast material in the brain: Initial investigation

Purpose

To evaluate a novel magnetic resonance (MR) angiography (MRA) of three‐dimensional (3D) MR digital subtraction angiography (MRDSA) without contrast material, which is essentially 3D true steady‐state free precession (SSFP) with selected inversion recovery (IR) pulse using multiple cardiac phase acquisitions with a short increment delay in the assessment of normal cranial arteries, as a feasibility study before clinical use.

Materials and Methods

Serial MRA images using 3D MRDSA without contrast material were acquired from 10 healthy volunteers. Visualization of normal cranial arteries with time‐spatial labeling inversion pulse (Time‐SLIP) MRDSA was qualitatively compared with the conventional MRA method, 3D time‐of‐flight (TOF)‐MRA.

Results

In all volunteers, serial 3D MRDSAs containing hemodynamic information were successfully imaged. The results of visualization of the branches of the cranial arteries with Time‐SLIP MRDSA were comparable to those of 3D TOF‐MRA. The mean scores ± standard deviations for normal cerebral arteries (internal carotid arteries, middle cerebral arteries, anterior cerebral arteries, posterior cerebral arteries, and basilar arteries) were 2.4 ± 0.5, 2.3 ± 0.5, 2.0 ± 0.7, 2.3 ± 0.7, and 2.5 ± 0.7, respectively.

Conclusion

Time‐SLIP 3D MRDSA is a simple method for obtaining hemodynamic information. Although more MR sequence improvement is needed, it can play an important role in assessing cranial arteries without contrast material. J. Magn. Reson. Imaging 2009;30:214–218. © 2009 Wiley‐Liss, Inc.     

Computer‐aided detection of metastatic brain tumors using automated three‐dimensional template matching

Purpose:

To demonstrate the efficacy of an automated three‐dimensional (3D) template matching‐based algorithm in detecting brain metastases on conventional MR scans and the potential of our algorithm to be developed into a computer‐aided detection tool that will allow radiologists to maintain a high level of detection sensitivity while reducing image reading time.

Materials and Methods:

Spherical tumor appearance models were created to match the expected geometry of brain metastases while accounting for partial volume effects and offsets due to the cut of MRI sampling planes. A 3D normalized cross‐correlation coefficient was calculated between the brain volume and spherical templates of varying radii using a fast frequency domain algorithm to identify likely positions of brain metastases.

Results:

Algorithm parameters were optimized on training datasets, and then data were collected on 22 patient datasets containing 79 total brain metastases producing a sensitivity of 89.9% with a false positive rate of 0.22 per image slice when restricted to the brain mass.

Conclusion:

Study results demonstrate that the 3D template matching‐based method can be an effective, fast, and accurate approach that could serve as a useful tool for assisting radiologists in providing earlier and more definitive diagnoses of metastases within the brain. J. Magn. Reson. Imaging 2010;31:85–93. © 2009 Wiley‐Liss, Inc.     

Measuring aortic diameter with different MR techniques: Comparison of three‐dimensional (3D) navigated steady‐state free‐precession (SSFP), 3D contrast‐enhanced magnetic resonance angiography (CE‐MRA), 2D T2 black blood,and 2D cine SSFP

Purpose:

To compare nongated three‐dimensional (3D) contrast‐enhanced magnetic resonance angiography (CE‐MRA) with 3D‐navigated cardiac‐gated steady‐state free‐precession bright blood (3D‐nav SSFP) and noncontrast 2D techniques for ascending aorta dimension measurements.

Materials and Methods:

Twenty‐five clinical exams were reviewed to evaluate the ascending aorta at 1.5T using: breathhold cine bright blood (SSFP), cardiac‐triggered T2 black blood (T2 BB), axial 3D‐nav SSFP, and nongated 3D CE‐MRA. Three radiologists independently measured aortic size at three specified locations for each sequence. Means, SDs, interobserver correlation, and vessel edge sharpness were statistically evaluated.

Results:

Measurements were greatest for 3D‐nav SSFP and 3D CE‐MRA and smallest for T2 BB. There was no significant difference between 3D‐nav SSFP and 3D CE‐MRA (P = 0.43–0.86), but significance was observed comparing T2 BB to all sequences. Interobserver agreement was uniformly >0.9, with T2 BB best, followed closely by 3D‐nav SSFP and 2D cine SSFP, and 3D CE‐MRA being the worst. Edge sharpness was significantly poorer for 3D CE‐MRA compared to the other sequences (P < 0.001).

Conclusion:

If diameter measurements are the main clinical concern, 3D‐nav SSFP appears to be the best choice, as it has a sharp edge profile, is easy to acquire and postprocess, and shows very good interobserver correlation. J. Magn. Reson. Imaging 2010;31:177–184. © 2009 Wiley‐Liss, Inc.     

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.     

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.     

Single breathhold cardiac CINE imaging with multi‐echo three‐dimensional hybrid radial SSFP acquisition

Purpose:

To achieve single breathhold whole heart cardiac CINE imaging with improved spatial resolution and temporal resolution by using a multi‐echo three‐dimensional (3D) hybrid radial SSFP acquisition.

Materials and Methods:

Multi‐echo 3D hybrid radial SSFP acquisitions were used to acquire cardiac CINE imaging within a single breathhold. An optimized interleaving scheme was developed for view ordering throughout the cardiac cycle.

Results:

Whole heart short axis views were acquired with a spatial resolution of 1.3 × 1.3 × 8.0 mm³ and temporal resolution of 45 ms, within a single 17 s breathhold. The technique was validated on eight healthy volunteers by measuring the left ventricular volume throughout the cardiac cycle and comparing with the conventional 2D multiple breathhold technique. The left ventricle functional measurement bias of our proposed 3D technique from the conventional 2D technique: end diastolic volume ?3.3 mL ± 13.7 mL, end systolic volume 1.4 mL ± 6.1 mL, and ejection fraction ?1.7% ± 4.3%, with high correlations 0.94, 0.97, and 0.91, accordingly.

Conclusion:

A multi‐echo 3D hybrid radial SSFP acquisition was developed to allow for a whole heart cardiac CINE exam in a single breathhold. Cardiac function measurements in volunteers compared favorably with the standard multiple breathhold exams. J. Magn. Reson. Imaging 2010;32:434–440. © 2010 Wiley‐Liss, Inc.

     

Accelerating three‐dimensional molecular cardiovascular MR imaging using compressed sensing

Purpose:

To accelerate the acquisition of three‐dimensional (3D) high‐resolution cardiovascular molecular MRI by using Compressed Sensing (CS) reconstruction.

Materials and Methods:

Molecular MRI is an emerging technique for the early assessment of cardiovascular disease. This technique provides excellent soft tissue differentiation at a molecular and cellular level using target‐specific contrast agents (CAs). However, long scan times are required for 3D molecular MRI. Parallel imaging can be used to speed‐up these acquisitions, but hardware considerations limit the maximum acceleration factor. This limitation is important in small‐animal studies, where single‐coils are commonly used. Here we exploit the sparse nature of molecular MR images, which are characterized by localized and high‐contrast biological target‐enhancement, to accelerate data acquisition. CS was applied to detect: (a) venous thromboembolism and (b) coronary injury and aortic vessel wall in single‐ and multiple‐coils acquisitions, respectively.

Results:

Retrospective undersampling showed good overall image quality with accelerations up to four for thrombus and aortic images, and up to three for coronary artery images. For higher acceleration factors, features with high CA uptake were still well recovered while low affinity targets were less preserved with increased CS undersampling artifacts. Prospective undersampling was performed in an aortic image with acceleration of two, showing good contrast and well‐defined tissue boundaries in the contrast‐enhanced regions.

Conclusion:

We demonstrate the successful application of CS to preclinical molecular MR with target specific gadolinium‐based CAs using retrospective (accelerations up to four) and prospective (acceleration of two) undersampling. J. Magn. Reson. Imaging 2012; 36:1362–1371. © 2012 Wiley Periodicals, Inc.     

Modulated repetition time look‐locker (MORTLL): A method for rapid high resolution three‐dimensional T1 mapping

Purpose

To demonstrate a modification of the Look‐Locker (LL) technique that enables rapid high resolution T1 mapping over the physiologic range of intracranial T1 values, ranging from white matter to cerebrospinal fluid (CSF). This is achieved by use of a three‐dimensional (3D) balanced steady‐state free precession (b‐SSFP) acquisition (for high signal‐to‐noise and resolution) along with variable repetition time to allow effective full recovery of longitudinal magnetization.

Materials and Methods

Two modifications to the Look‐Locker technique were made to realize high resolution imaging in a clinically reasonable scan time. The 3D b‐SSFP acquisition after an initial inversion pulse was followed by a variable repetition time. This technique makes it possible to image a volume of thin contiguous slices with high resolution and accuracy using a simple fitting procedure and is particularly useful for imaging long T1 species such as CSF. The total scan time is directly proportional to the number of slices to be acquired. The scan time was reduced by almost half when the repetition time was modified using a predesigned smooth function. Phantoms and volunteers were imaged at different resolutions on a 3 Tesla scanner. Results were compared with other accepted techniques.

Results

T1 values in the brain corresponded well with full repetition time imaging as well as inversion recovery spin echo imaging. T1 values for white matter, gray matter, and CSF were measured to be 755 ± 10 ms, 1202 ± 9 ms, and 4482 ± 71 ms, respectively. Scan times were reduced by approximately half over full repetition time measurements.

Conclusion

High resolution T1 maps can be obtained rapidly and with a relatively simple postprocessing method. The technique is particularly well suited for long T1 species. For example, changes in the composition of proteins in CSF are linked to various pathologies. The T1 values showed excellent agreement with values obtained from inversion recovery spin‐echo imaging. J. Magn. Reson. Imaging 2009. © 2009 Wiley‐Liss, Inc.     

Accuracy and repeatability of fourier velocity encoded M‐mode and two‐dimensional cine phase contrast for pulse wave velocity measurement in the descending aorta

Purpose:

To assess the accuracy and repeatability of Fourier velocity encoded (FVE) M‐mode and two‐dimensional (2D) phase contrast with through‐plane velocity encoding (2D‐PC) for pulse wave velocity (PWV) evaluation in the descending aorta using five different analysis techniques.

Materials and Methods:

Accuracy experiments were conducted on a tubular human‐tissue‐mimicking phantom integrated into a flow simulator. The theoretical PWV value was derived from the Moens‐Korteweg equation after measurement of the tube elastic modulus by uniaxial tensile testing (PWV = 6.6 ± 0.7 m/s). Repeatability was assessed on 20 healthy volunteers undergoing three consecutive MR examinations.

Results:

FVE M‐mode PWV was more repeatable than 2D‐PC PWV independently of the analysis technique used. The early systolic fit (ESF) method, followed by the maximum of the first derivative (1st der.) method, was the most accurate (PWV = 6.8 ± 0.4 m/s and PWV = 7.0 ± 0.6 m/s, respectively) and repeatable (inter‐scan within‐subject variation δ = 0.096 and δ = 0.107, respectively) for FVE M‐mode. For 2D‐PC, the 1st der. method performed best in terms of accuracy (PWV = 6.8 ± 1.1 m/s), whereas the ESF algorithm was the most repeatable (δ = 0.386).

Conclusion:

FVE M‐mode allows rapid, accurate and repeatable central PWV evaluation when the ESF algorithm is used. 2D‐PC requires long scan times and can provide accurate although much less repeatable PWV measurements when the 1st der. method is used. J. Magn. Reson. Imaging 2010;31:1185–1194. © 2010 Wiley‐Liss, Inc.     

Fast three‐dimensional dual echo dixon technique improves fat suppression in breast MRI

Purpose:

To compare qualitative and quantitative measures of the contrast‐enhanced dual‐echo Dixon technique with the commonly used standard three‐dimensional (3D) gradient echo (spectrally selective fat suppression) technique (SS‐FS) in breast MRI exams (bMRI).

Materials and Methods:

A total of 19 women, with prescheduled bMRI exam, were recruited to our study between 2006 and 2008. Dixon and standard SS‐SF techniques were used on both breasts of each patient. Image quality was rated in five categories: fat suppression quality, fat suppression uniformity, lesion margin clarity, lesion visibility, and axillary visibility. For quantitative assessment, we calculated the signal‐to‐noise ratio (SNR) and contrast‐to‐noise ratio (CNR) of lesion to breast, SNR efficiency, and CNR efficiency.

Results:

Of 19 patients evaluated, 13 had a primary breast malignancy and 6 had benign lesions or negative exams. Dixon images were rated higher in four of five qualitative categories (P < 0.0001) and required a shorter scan time. Dixon images yielded significantly higher SNR (43.8) and CNR (40.1) values than did 3DGRE images (SNR = 34.8, CNR = 25.3; P < 0.05). SNR efficiency (36.30) and CNR efficiency (33.79) values for Dixon images were also higher than were 3DGRE images (SNR efficiency =25.7, CNR efficiency = 19.1; P < 0.05).

Conclusion:

Dixon images were superior to the standard SS‐SF images in both qualitative and quantitative assessment of 19 bMRI exams. The Dixon technique could replace standard SS‐SF technique in bMRI exam, after our findings have been confirmed in future studies with a larger sample size. J. Magn. Reson. Imaging 2010;31:889–894. ©2010 Wiley‐Liss, Inc.     

Evaluation of intraneural ganglion cysts using three‐dimensional fast spin echo‐cube

Purpose:

To compare conventional two‐dimensional fast spin echo (FSE) MRI sequences with a three‐dimensional FSE extended echo train acquisition method, known as Cube, in the evaluation of intraneural ganglion cysts. Also, to demonstrate that Cube enables the consistent identification and thorough characterization of the cystic joint connection, and therefore improves patient care by superior preoperative planning.

Materials and Methods:

Six patients with intraneural ganglia in the knee region (five involving the peroneal and one the tibial nerve) were evaluated using both conventional FSE MR sequences and the Cube sequence. Studies were interpreted by the consensus of three board certified musculoskeletal radiologists and one peripheral nerve neurosurgeon. Surgical correlation was available in five of the six cases.

Results:

Both imaging methods demonstrated the cysts and at least part of their joint connections after variable amount of postprocessing. Cube proved superior to conventional imaging in its ability to acquire isotropic data that could easily be reconstructed in any plane and its ability to resolve fine anatomical details.

Conclusion:

Cube is a new MR pulse sequence that enables the consistent identification of the intraneural ganglion cyst joint connection. We believe that improved visualization and characterization of the entire cyst will improve patient outcomes by facilitating more accurate surgical intervention. J. Magn. Reson. Imaging 2010;32:714–718. © 2010 Wiley‐Liss, Inc.     

Four‐dimensional velocity‐encoded magnetic resonance imaging improves blood flow quantification in patients with complex accelerated flow

Purpose:

To evaluate the use of four‐dimensional (4D) velocity‐encoded magnetic resonance imaging (VEC MRI) for blood flow quantification in patients with semilunar valve stenosis and complex accelerated flow.

Materials and Methods:

Peak velocities (Vmax) and stroke volumes (SV) were quantified by 2D and 4D VEC MRI in volunteers (n = 7) and patients with semilunar valve stenosis (n = 18). Measurements were performed above the aortic and pulmonary valve with both techniques and, additionally, at multiple predefined planes in the ascending aorta and in the pulmonary trunk within the 4D dataset. In patients, 4D VEC MRI streamline analysis identified flow patterns and regions of highest flow velocity (4D_{max‐targeted}) for further measurements and Vmax was also measured by Doppler‐echocardiography.

Results:

In patients, 4D VEC MRI showed higher Vmax than 2D VEC MRI (2.7 ± 0.6 m/s vs. 2.4 ± 0.5 m/s, P < 0.03) and was more comparable to Doppler‐echocardiography (2.8 ± 0.7 m/s). 4D_{max‐targeted} revealed highest Vmax values (3.1 ± 0.6 m/s). SV measurements showed significant differences between different anatomical levels in the ascending aorta in patients with complex accelerated flow, whereas differences in volunteers with laminar flow patterns were negligible (P = 0.004).

Conclusion:

4D VEC MRI improves MRI‐derived blood flow quantification in patients with semilunar valve stenosis and complex accelerated flow. J. Magn. Reson. Imaging 2013;37:208–216. © 2012 Wiley Periodicals, Inc.     

Three‐dimensional plus time biventricular strain from tagged MR images by phase‐unwrapped harmonic phase

Purpose:

To validate a method called bi‐ventricular strain unwrapped phase (BiSUP) for reconstructing three‐dimensional plus time (3D+t) biventricular strain maps from phase‐unwrapped harmonic phase (HARP) images derived from tagged cardiac magnetic resonance imaging (MRI).

Materials and Methods:

A set of 30 human subjects were imaged with tagged MRI. In each study, HARP phase was computed and unwrapped in each short‐axis and long‐axis image. Inconsistencies in unwrapped phase were resolved using branch cuts manually placed with a graphical user interface. The 3D strain maps were computed independently in each imaged time frame through systole and mid diastole in each study. The BiSUP strain and displacements were compared with those estimated by a 3D feature‐based (FB) technique and a 2D+t HARP technique.

Results:

The standard deviation of the difference between strains measured by the FB and the BiSUP methods was less than 4% of the average of the strains from the two methods. The correlation between peak minimum principal strain measured using the BiSUP and HARP techniques was over 83%.

Conclusion:

The BiSUP technique can reconstruct full 3D+t strain maps from tagged MR images through the cardiac cycle in a reasonable amount of time and user interaction compared with other 3D analysis methods. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.