Effects of refocusing flip angle modulation and view ordering in 3D fast spin echo

Busse, Reed F.; Brau, Anja C. S.; Vu, Anthony T.; Michelich, Charles R.; Bayram, Ersin; Kijowski, Richard; Reeder, Scott B.; Rowley, Howard A.

doi:10.1002/mrm.21680

Cited by 236 publications

(314 citation statements)

References 17 publications

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“…[15][16][17][18] In our study, the total scan time of DE-VISTA at closed-and opened-mouth positions was 13 min 30 s. Diagnosis of disk dislocation cannot be established solely on the basis of oblique sagittal MR imagingˆndings. An oblique coronal section was also necessary to diagnose TMD.…”

Section: Discussionmentioning

confidence: 73%

“…Recently, use of the volumetric isotropic TSE acquisition (VISTA) sequence at clinical sites has enabled high speed imaging, even for spin echo 3D imaging. [15][16][17][18] We hypothesized that the dual echo VISTA (DE-VISTA) method could be used to overcome the issues of prolonged scan duration and susceptibility eŠects at the TMJ. In addition, because DE-VISTA-PDWI and DE-VISTA-T 2 WI have identical positional information, their data can be precisely added and calculated per voxel.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Usefulness of Dual Echo Volumetric Isotropic Turbo Spin Echo Acquisition (VISTA) in MR Imaging of the Temporomandibular Joint

Sugimori¹,

Tanaka²,

Nishimura³

et al. 2013

magn reson med sci

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Purpose: We investigated the ability to detect the articular disk and joint eŠusion of the temporomandibular joint (TMJ) of a method of dual echo volumetric isotropic turbo spin echo acquisition (DE-VISTA) additional fusion images (AFI).Methods: DE-VISTA was performed in the 26 TMJ of 13 volunteers and 26 TMJ of 13 patients. Two-dimensional (2D) dual echo turbo spin echo was performed in the 26 TMJ of 13 volunteers. On a workstation, we added proton density-weighted images (PDWI) and T 2 weighted images (T 2 WI) of the DE-VISTA per voxel to reconstruct DE-VISTA-AFI. Two radiologists reviewed these images visually and quantitatively.Results: Visual evaluation of the articular disk was equivalent between DE-VISTA-AFI and 2D-PDWI. The sliding thin-slab multiplanar reformation (MPR) method of DE-VISTA-AFI could detect all articular disks. The ratio of contrast (CR) of adipose tissue by the articular disk to that of the articular disk itself was signiˆcantly higher in DE-VISTA-AFI than DE-VISTA-PDWI (Pº0.05) in patients and volunteers with closed or open mouth. In volunteers, the CR between adipose tissue and the disk on DE-VISTA-AFI was marginally signiˆcant to that on 2D-PDWI at opened mouth (P＝0.071) and not signiˆcantly diŠerent (P＝0.18) from that at closed mouth. Joint eŠusion could be identiˆed in DE-VISTA-AFI in all 8 joints that had joint eŠusion in DE-VISTA-T 2 WI but in only 3 of those joints in 2D-T 2 WI. The CR of joint eŠusion to adipose tissue on DE-VISTA-AFI did not diŠer signiˆcantly from that on DE-VISTA-PDWI. However, using DE-VISTA-T 2 WI in addition to DE-VISTA-PDWI, we could visually identify joint eŠusion on DE-VISTA-AFI that could not be identiˆed on DE-VISTA-PDWI alone.Conclusion: DE-VISTA-AFI can depict the articular disk and a small amount of joint eŠusion by the required plane of MPR using the sliding thin-slab MPR method.

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Section: Discussionmentioning

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Usefulness of Dual Echo Volumetric Isotropic Turbo Spin Echo Acquisition (VISTA) in MR Imaging of the Temporomandibular Joint

Sugimori¹,

Tanaka²,

Nishimura³

et al. 2013

magn reson med sci

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“…3D variants with low refocusing angles (29,30) are also very promising at high field and warrant further investigation.…”

Section: Contrast and Intensity Variationsmentioning

confidence: 99%

Time‐efficient fast spin echo imaging at 4.7 T with low refocusing angles

Wilman

2009

Magnetic Resonance in Med

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An implementation of fast spin echo at 4.7 T designed for versatile and time-efficient T 2 -weighted imaging of the human brain is presented. Reduced refocusing angles (␣ < 180°) were employed to overcome specific absorption rate (SAR) constraints and their effects on image quality assessed. Image intensity and tissue contrast variations from heterogeneous RF transmit fields and incidental magnetization transfer effects were investigated at reduced refocusing angles. We found that intraslice signal variations are minimized with refocusing angles near 180°, but apparent gray/white matter contrast is independent of refocusing angle. Incidental magnetization transfer effects from multislice acquisitions were shown to attenuate white matter intensity by 25% and gray matter intensity by 15% at 180°; less than 5% attenuation was seen in all tissues at flip angles below 60°. We present multislice images acquired without excess delay time for SAR mitigation using a variety of protocols. Fast spin echo (FSE) imaging, also known as RARE (1) and TSE, is a robust imaging sequence with numerous clinical and research applications. Prototypical FSE uses a 90°e xcitation pulse and a train of 180°refocusing pulses repeated every TR to form a single image. These refocusing pulses render FSE largely insensitive to static field inhomogeneities. High-field imaging systems-loosely defined here as those exceeding 3 T-promise exceptional capabilities including faster or higher-resolution imaging with altered, and possibly enhanced, tissue contrast mechanisms. Unfortunately, there are impediments to high-field imaging (2): First, static magnetic field heterogeneities scale linearly with main field strength and exacerbate signal losses and geometric distortions. Second, short RF wavelengths cause nonuniform sensitivity profiles for excitation and reception (3). Third, RF power deposition scales approximately quadratically with static field strength (4); patient safety requirements can limit successive high flip angle pulses, as required by FSE.Nevertheless, high-resolution FSE images of the human brain have previously been obtained at 4.7 T (5,6) using long interecho spacings (22 ms) to reduce the temporal density of RF pulses, short echo trains (eight refocusing pulses), slightly reduced refocusing flip angles (162°), and likely also long RF pulses, to constrain specific absorption rate (SAR) within safety regulations (4 W/kg for short exposure times). These works demonstrate that FSE and high field are not mutually exclusive; however, this implementation is ill-suited for variants, such as half Fourier acquisition single-shot turbo spin echo (HASTE), where short echo spacings and long echo trains are required and would produce extreme SAR levels due to a large number of brief, high-angle pulses per unit time. SAR mitigation strategies such as RF pulse elongation and bandwidth reduction provide modest power savings and can be applied to high-resolution imaging, but are, in general, of limited versatility and are insufficient to compensa...

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“…Both minimum echo time (TE ¼ 30.4 ms) as well as repetition time (TR ¼ 800 ms) were used in a multi-slice sequence with slice interleaving using a skip factor of 4 (i.e., in a 12 slice sequence, slice were acquired with the order of [1,5,9,2,6,10,3,7,11,4,8,12]). Images were acquired by doubling the field-of-view to better visualize the intermediate aliasing caused by any instability in the nCPMG echotrain that arises for low refocusing flip angles.…”

Section: Phantom Scanningmentioning

confidence: 99%

Slice profile effects on nCPMG SS‐FSE

Gibbons

Roux²,

Pauly

et al. 2017

Magnetic Resonance in Med

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Purpose To determine the effects of the RF refocusing pulse profile on the magnitude of the transverse signal smoothness throughout the echo train in non‐Carr‐Purcell‐Meiboom‐Gill (nCPMG) single‐shot fast spin echo (SS‐FSE) imaging and to design an RF refocusing pulse that provides improved signal stability. Theory and Methods nCPMG SS‐FSE quadratic phase modulation requires sufficiently high and uniform refocusing flip angle to achieve a stable signal. Typically, refocusing pulses used in SS‐FSE sequences are designed for minimum duration to minimize echo spacing and as a consequence have poor selectivity. However, delay‐insensitive variable rate excitation Shinnar‐Le Roux (DV‐SLR) refocusing pulses can achieve both improved selectivity as well as a short duration. This class of RF pulse is compared against a traditional low time‐bandwidth refocusing pulse in a nCPMG SS‐FSE in simulation, phantom, and in vivo. Results DV‐SLR pulses achieve a more stable signal in simulation, phantom, and in vivo cases while maintaining an appropriately short duration as well as not dramatically increasing specific absorption rate (SAR) accumulation. Conclusion The nCPMG SS‐FSE method demonstrates improved robustness when a more selective refocusing pulse is used. Refocusing pulses that use a time‐varying excitation gradient can achieve this selectivity while maintaining short echo spacing. Magn Reson Med 79:430–438, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

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Effects of refocusing flip angle modulation and view ordering in 3D fast spin echo

Cited by 236 publications

References 17 publications

Usefulness of Dual Echo Volumetric Isotropic Turbo Spin Echo Acquisition (VISTA) in MR Imaging of the Temporomandibular Joint

Usefulness of Dual Echo Volumetric Isotropic Turbo Spin Echo Acquisition (VISTA) in MR Imaging of the Temporomandibular Joint

Time‐efficient fast spin echo imaging at 4.7 T with low refocusing angles

Slice profile effects on nCPMG SS‐FSE

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