Dataset Information

Fat suppression for ultrashort echo time imaging using a single-point Dixon method.

ABSTRACT:

Purpose

In ultrashort echo time (UTE) imaging, fat suppression can improve short T₂ * contrast but can also reduce short T₂ * signals. The conventional two-point Dixon (2p-Dixon) method does not perform well due to short T₂ * decay. In this study, we propose a new method to suppress fat for high contrast UTE imaging of short T₂ tissues, utilizing a single-point Dixon (1p-Dixon) method.

Methods

The proposed method utilizes dual-echo UTE imaging, where UTE is followed by the second TE, chosen flexibly. Fat is estimated by applying a 1p-Dixon method to the non-UTE image after correction of phase errors, which is used to suppress fat in the UTE image. In vivo ankle and knee imaging were performed at 3 T to evaluate the proposed method.

Result

It was observed that fat and water signals in tendons were misestimated by the 2p-Dixon method due to signal decay, while the 1p-Dixon method showed reliable fat and water separation not affected by the short T₂ * signal decay. Compared with the conventional chemical shift based fat saturation technique, the 1p-Dixon based approach showed much stronger signal intensities in the Achilles, quadriceps, and patellar tendons, with significantly improved contrast to noise ratios (CNRs) of 11.8 ± 2.2, 16.0 ± 1.6, and 26.8 ± 1.3 with the 1p-Dixon method and 0.6 ± 0.2, 4.6 ± 1.0, and 17.5 ± 1.4 with regular fat saturation, respectively.

Conclusion

The proposed 1p-Dixon based fat suppression allows more flexible selection of imaging parameters and more accurate fat and water separation over the conventional 2p-Dixon in UTE imaging. Moreover, the proposed method provides much improved CNR for short T₂ tissues over the conventional fat saturation method.

SUBMITTER: Jang H

PROVIDER: S-EPMC6476675 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature

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Publications

Fat suppression for ultrashort echo time imaging using a single-point Dixon method.

Jang Hyungseok H Carl Michael M Ma Yajun Y Jerban Saeed S Guo Tan T Zhao Wei W Chang Eric Y EY Du Jiang J

NMR in biomedicine 20190215 5

<h4>Purpose</h4>In ultrashort echo time (UTE) imaging, fat suppression can improve short T<sub>2</sub> * contrast but can also reduce short T<sub>2</sub> * signals. The conventional two-point Dixon (2p-Dixon) method does not perform well due to short T<sub>2</sub> * decay. In this study, we propose a new method to suppress fat for high contrast UTE imaging of short T<sub>2</sub> tissues, utilizing a single-point Dixon (1p-Dixon) method.<h4>Methods</h4>The proposed method utilizes dual-echo UTE i ...[more]

PMID: 30768813

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Project description:Background Signal contamination from long T2 water is a major challenge in direct imaging of myelin with MRI. Nulling of the unwanted long T2 signals can be achieved with an inversion recovery (IR) preparation pulse to null long T2 white matter within the brain. The remaining ultrashort T2 signal from myelin can be detected with an ultrashort echo time (UTE) sequence. Purpose To develop patient-specific whole-brain myelin imaging with a three-dimensional double-echo sliding inversion recovery (DESIRE) UTE sequence. Materials and Methods The DESIRE UTE sequence generates a series of IR images with different inversion times during a single scan. The optimal inversion time for nulling long T2 signal is determined by finding minimal signal on the second echo. Myelin images are generated by subtracting the second echo image from the first UTE image. To validate this method, a prospective study was performed in phantoms, cadaveric brain specimens, healthy volunteers, and patients with multiple sclerosis (MS). A total of 20 healthy volunteers (mean age, 40 years ± 13 [standard deviation], 10 women) and 20 patients with MS (mean age, 58 years ± 8; 15 women) who underwent MRI between November 2017 and February 2019 were prospectively included. Analysis of variance was performed to evaluate the signal difference between MS lesions and normal-appearing white matter in patients with MS. Results High signal intensity and corresponding T2* and T1 of the extracted myelin vesicles provided evidence for direct imaging of ultrashort-T2 myelin protons using the UTE sequence. Gadobenate dimeglumine phantoms with a wide range of T1 values were selectively suppressed with DESIRE UTE. In the ex vivo brain study of MS lesions, signal loss was observed in MS lesions and was conformed with histologic analysis. In the human study, there was a significant reduction in normalized signal intensity in MS lesions compared with that in normal-appearing white matter (0.19 ± 0.10 vs 0.76 ± 0.11, respectively; P < .001). Conclusion The double-echo sliding inversion recovery ultrashort echo time sequence can generate whole-brain myelin images specifically with a clinical 3-T scanner. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Port in this issue.

Dataset Information

Fat suppression for ultrashort echo time imaging using a single-point Dixon method.

Purpose

Methods

Result

Conclusion

Publications

Fat suppression for ultrashort echo time imaging using a single-point Dixon method.

Similar Datasets

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