Scan Parameters for the Spin-Echo Imaging Sequence

2008 ◽  
pp. 193-230
Keyword(s):  
Spin Echo ◽  
Imaging Sequence

Highly Resolved MR Imaging of Arbitrary Subregions in Large Objects by a Whole-Body Imager

1993 ◽  
Vol 48 (7) ◽  
pp. 753-758
Author(s):  
Karin Pfeffer ◽  
Markus Pfeffer ◽  
Wulf-Ingo Jung ◽  
Otto Lutz ◽  
Fritz Schick
Keyword(s):  
High Resolution ◽  
Mr Imaging ◽  
Spin Echo ◽  
Regions Of Interest ◽  
Whole Body ◽  
Biological Objects ◽  
Imaging Sequence ◽  
Phantom Measurements

Abstract Highly resolved images of defined regions of interest within extended objects were obtaind with a 1.5 T whole-bode imager and standard hardware. The high-resolution spin echo imaging sequence avoids aliasing and allows pixel resolutions down to 39 µm which are confirmed by phantom measurements. The application of the sequence to large biological objects such as, for example, an amaryllis bulb results in images which provide much detail which could not be resolved with standard sequences.

Free-breathing BLADE acquisition method improves T2-weighted cardiac MR image quality compared with conventional breath-hold turbo spin-echo cartesian acquisition

2020 ◽  
pp. 028418512092456
Author(s):  
Jingjing Liu ◽  
Hang Jin ◽  
Yinyin Chen ◽  
Caixia Fu ◽  
Caizhong Chen ◽  
...  
Keyword(s):  
Image Quality ◽  
Spin Echo ◽  
Free Breathing ◽  
Fat Suppression ◽  
Breath Hold ◽  
Signal Loss ◽  
Turbo Spin Echo ◽  
Turbo Spin ◽  
Imaging Sequence ◽  
Ghosting Artifacts

Background Cardiac magnetic resonance (MR) has become an essential diagnostic imaging modality in cardiovascular disease. However, the insufficient image quality of traditional breath-hold (BH) T2-weighted (T2W) imaging may compromise its diagnostic accuracy. Purpose To assess the efficacy of the BLADE technique to reduce motion artifacts and improve the image quality. Material and Methods Free-breathing TSE-T2W imaging sequence with cartesian and BLADE k-space trajectory were acquired in 20 patients. Thirty patients underwent conventional BH turbo spin-echo (TSE) T2W imaging and free-breathing BLADE T2W (FB BLADE-T2W) imaging. Twenty-one patients who had a signal loss of myocardium in BH short-axis T2W turbo inversion recovery (TSE-T2W-TIR) were scanned using free-breathing BLADE T2W turbo inversion recovery (BLADE TSE-T2W-TIR). The overall image quality, blood nulling, and visualization of the heart were scored on a 5-point Likert scale. The signal loss of myocardium, incomplete fat suppression near the myocardium, and the streaking or ghosting artifacts were noted in T2W-TIR sequences additionally. Results The overall imaging quality, blood nulling, and the visualization of heart structure of FB BLADE-T2W imaging sequence were significantly better than those of FB T2W imaging with Cartesian k-space trajectory and BH TSE-T2W imaging sequence ( P<0.01). The FB BLADE TSE-T2W-TIR reduces the myocardium signal dropout ( P<0.05), incomplete fat suppression near myocardium ( P<0.05), and the streaking and ghosting artifacts ( P<0.05) in comparison with the BH TSE-T2W-TIR. Conclusions FB BLADE T2W imaging provides improved myocardial visibility, less motion sensitivity, and better image quality. It may be applied in patients who have poor breath-holding capability.

scholarly journals Acromegaly without Imaging Evidence of Pituitary Adenoma

2010 ◽  
Vol 95 (9) ◽  
pp. 4192-4196 ◽  
Author(s):  
Russell R. Lonser ◽  
Bogdan A. Kindzelski ◽  
Gautam U. Mehta ◽  
John A. Jane ◽  
Edward H. Oldfield
Keyword(s):  
Pituitary Adenoma ◽  
Mr Imaging ◽  
Pituitary Adenomas ◽  
Spin Echo ◽  
Tertiary Care ◽  
Breath Hold ◽  
Slice Thickness ◽  
Surgical Exploration ◽  
Imaging Sequence ◽  
Tertiary Care Centers

Context: GH-secreting pituitary adenomas are nearly always visible on conventional magnetic resonance (MR) imaging. However, management and outcome of acromegalic patients lacking imaging evidence of GH-secreting pituitary adenomas are undefined. Objective: The aim was to evaluate surgical exploration for MR-invisible GH-secreting pituitary adenomas. Design and Setting: We conducted a retrospective review at two tertiary care centers. Patients or Other Participants: Consecutive acromegalic patients without imaging evidence of a pituitary adenoma on pre- and postcontrast, spin echo T1-weighted MR imaging and who lacked evidence of an ectopic (nonpituitary) source causing GH excess were included. Interventions: Surgical exploration with identification and resection of a pituitary adenoma was performed. Main Outcome Measures: Laboratory values (GH, IGF-I), surgical findings, and clinical outcome were analyzed. Results: Six patients (three males, three females; 3% of all patients) with suspected GH-secreting adenomas did not demonstrate imaging evidence of pituitary adenoma on conventional MR imaging. Three patients underwent a postcontrast, volumetric interpolated breath-hold examination MR-imaging sequence (1.2-mm slice thickness), which revealed a 4-mm pituitary adenoma not seen on the spin echo T1-weighted MR imaging in one patient. A pituitary adenoma was identified and removed in all patients (mean diameter, 5.6 mm; range, 5 to 6.7 mm). Histological analysis confirmed that the lesions were GH-secreting adenomas. All patients achieved biochemical remission after surgical resection. Conclusion: Acromegaly can be caused by GH-secreting pituitary adenomas that are not evident on conventional MR imaging. Adenomas in some of these patients become evident using volumetric interpolated breath-hold examination MR imaging. Surgical exploration of the pituitary gland in acromegalic patients with endocrine findings consistent with a GH-secreting adenoma but negative MR imaging can lead to identification and removal of an adenoma.

scholarly journals Simultaneous Perfusion and Permeability Measurements Using Combined Spin- and Gradient-Echo MRI

2013 ◽  
Vol 33 (5) ◽  
pp. 732-743 ◽  
Author(s):  
Heiko Schmiedeskamp ◽  
Jalal B Andre ◽  
Matus Straka ◽  
Thomas Christen ◽  
Seema Nagpal ◽  
...  
Keyword(s):  
Cerebral Blood Volume ◽  
Spin Echo ◽  
Mean Transit Time ◽  
Brain Perfusion ◽  
Gradient Echo ◽  
Planar Imaging ◽  
Imaging Sequence ◽  
Tissue Characteristics ◽  
Echo Planar ◽  
Good Agreement

The purpose of this study was to estimate magnetic resonance imaging-based brain perfusion parameters from combined multiecho spin-echo and gradient-echo acquisitions, to correct them for T1-, T2-, and T∗2-related contrast agent (CA) extravasation effects, and to simultaneously determine vascular permeability. Perfusion data were acquired using a combined multiecho spin- and gradient-echo (SAGE) echo-planar imaging sequence, which was corrected for CA extravasation effects using pharmacokinetic modeling. The presented method was validated in simulations and brain tumor patients, and compared with uncorrected single-echo and multiecho data. In the presence of CA extravasation, uncorrected single-echo data resulted in underestimated CA concentrations, leading to underestimated single-echo cerebral blood volume ( CBV) and mean transit time ( MTT). In contrast, uncorrected multiecho data resulted in overestimations of CA concentrations, CBV, and MTT. The correction of CA extravasation effects resulted in CBV and MTT estimates that were more consistent with the underlying tissue characteristics. Spin-echo perfusion data showed reduced large-vessel blooming effects, facilitating better distinction between increased CBV due to active tumor progression and elevated CBV due to the presence of cortical vessels in tumor proximity. Furthermore, extracted permeability parameters were in good agreement with elevated T1-weighted postcontrast signal values.

scholarly journals Diffusion in Sephadex Gel Structures: Time Dependency Revealed by Multi-Sequence Acquisition over a Broad Diffusion Time Range

Mathematics ◽  
2021 ◽  
Vol 9 (14) ◽  
pp. 1688
Author(s):  
Guangyu Dan ◽  
Weiguo Li ◽  
Zheng Zhong ◽  
Kaibao Sun ◽  
Qingfei Luo ◽  
...  
Keyword(s):  
Fractional Order ◽  
Spin Echo ◽  
Time Derivative ◽  
Biological Tissues ◽  
Diffusion Time ◽  
Time Range ◽  
Time Dependency ◽  
Planar Imaging ◽  
Imaging Sequence ◽  
Non Gaussian

It has been increasingly reported that in biological tissues diffusion-weighted MRI signal attenuation deviates from mono-exponential decay, especially at high b-values. A number of diffusion models have been proposed to characterize this non-Gaussian diffusion behavior. One of these models is the continuous-time random-walk (CTRW) model, which introduces two new parameters: a fractional order time derivative α and a fractional order spatial derivative β. These new parameters have been linked to intravoxel diffusion heterogeneities in time and space, respectively, and are believed to depend on diffusion times. Studies on this time dependency are limited, largely because the diffusion time cannot vary over a board range in a conventional spin-echo echo-planar imaging sequence due to the accompanying T2 decays. In this study, we investigated the time-dependency of the CTRW model in Sephadex gel phantoms across a broad diffusion time range by employing oscillating-gradient spin-echo, pulsed-gradient spin-echo, and pulsed-gradient stimulated echo sequences. We also performed Monte Carlo simulations to help understand our experimental results. It was observed that the diffusion process fell into the Gaussian regime at extremely short diffusion times whereas it exhibited a strong time dependency in the CTRW parameters at longer diffusion times.

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