Localized Proton Spectroscopy without Water Suppression: Removal of Gradient Induced Frequency Modulations by Modulus Signal Selection

Serrai, Haçène; Clayton, David; Senhadji, Lotfi; Chen, Zuo; Lenkinski, Robert E.

doi:10.1006/jmre.2001.2462

Cited by 37 publications

(69 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The NWS spectral lines restored after motion correction exhibit narrower line width (full width at half maximum ϳ10 Hz) than the WS spectral lines (full width at half maximum ϳ15 Hz). As a side note, some NWS sidebands arising from gradient coil oscillations (10,21) were visible in the spectra (arrows in Fig. 7).…”

Section: Effectiveness Of Motion Correction Using Nws Scansmentioning

confidence: 92%

See 1 more Smart Citation

Quantification of non–water‐suppressed MR spectra with correction for motion‐induced signal reduction

Lin

Tsai

Liu

et al. 2009

Magnetic Resonance in Med

View full text Add to dashboard Cite

Intrascan subject movement in clinical MR spectroscopic examinations may result in inconsistent water suppression that distorts the metabolite signals, frame-to-frame variations in spectral phase and frequency, and consequent reductions in the signal-to-noise ratio due to destructive averaging. Frameto-frame phase/frequency corrections, although reported to be successful in achieving constructive averaging, rely on consistent water suppression, which may be difficult in the presence of intrascan motion. In this study, motion correction using nonwater-suppressed data acquisition is proposed to overcome the above difficulties. The time-domain matrix-pencil postprocessing method was used to extract water signals from the non-water-suppressed spectroscopic data, followed by phase and frequency Inevitable subject motions during successive data acquisition in magnetic resonance spectroscopy (MRS) may cause signal loss because of two major mechanisms (1-4). First, motion-induced magnetic field drifts may lead to frequency shift over multiple MRS acquisition frames. Second, subject movements in the presence of the spoiler gradients may result in inconsistent phase variations among acquisition frames. In conventional MRS studies, data from all acquisition frames are simply averaged, and therefore the destructively averaged spectrum would be affected by signal-to-noise ratio (SNR) attenuation and spectral shape distortion because of frame-to-frame phase/ frequency variations. It has been shown that, by performing frame-by-frame corrections for the intrascan phase/ frequency variations, the constructively averaged MRS data exhibit significantly improved SNR and spectral quality (1-8). The search for an effective intrascan phase/frequency correction method is thus an active field of research for in vivo MRS.Over the past decades, several methods have been proposed to measure the intrascan phase/frequency variations in MRS scans in order to perform constructive averaging (1,2,4-6). In one of these methods, the non-water-suppressed (NWS) free induction decay and water-suppressed (WS) MRS data were acquired in an interleaved manner (2). Intrascan phase/frequency variations estimated from the NWS free induction decay were used to correct the WS MRS data. In this approach, however, the phase variations in WS MRS data are corrected by values estimated at different time points. Therefore, the effectiveness of the phase correction might be suboptimal, particularly in the presence of abrupt intrascan movements.Alternatively, the phase variations induced by intrascan motion could be measured on a frame-by-frame basis directly from the residual water signals of WS MRS data (1,4). However, even though the information estimated directly from the WS MRS data better reflects the instant phase variation in comparison to the interleaved free induction decay-based measurements, this approach has two main limitations: First, the residual water signals in WS MRS data have low SNR that limits the accuracy of frameby-frame phase estimation (1). ...

show abstract

Section: Effectiveness Of Motion Correction Using Nws Scansmentioning

confidence: 92%

“…The NWS MRS is potentially superior to WS MRS in several ways (9)(10)(11)(12). First, the metabolite signals in NWS MRS are not distorted by the water suppression pulses (13).…”

mentioning

confidence: 99%

Quantification of non–water‐suppressed MR spectra with correction for motion‐induced signal reduction

Lin

Tsai

Liu

et al. 2009

Magnetic Resonance in Med

View full text Add to dashboard Cite

show abstract

“…One disadvantage of using 1 H MRSI without WS is that audio vibrations from the gradient coils induce frequency modulations of the water signal that then produce several sidebands in the MR spectra. These sidebands increase noise in metabolite signals [10,19]. Although several methods have been proposed to suppress these sidebands [8,10,19], at present we suggest that our method for signal combination across coil elements should be applied only with data acquired using a long TE, thereby minimizing the presence of sidebands.…”

Section: Discussionmentioning

confidence: 93%

“…These sidebands increase noise in metabolite signals [10,19]. Although several methods have been proposed to suppress these sidebands [8,10,19], at present we suggest that our method for signal combination across coil elements should be applied only with data acquired using a long TE, thereby minimizing the presence of sidebands. In our experiment at TE=288 ms, the noise levels in individual coil elements for MRSI without WS were <3% greater than noise levels in MRSI with WS.…”

Section: Discussionmentioning

confidence: 93%

“…Although measuring water and metabolite signals in separate scans increases only marginally the total measurement time for single-voxel 1 H MRS, use of this same strategy would increase substantially the measurement time for 1 H MRSI. Other recent studies have demonstrated the feasibility and advantages of in vivo 1 H MRS and 1 H MRSI without WS while measuring metabolite and water signals simultaneously [8][9][10][11]; these studies used standard volume coils, however, not multi-channel coils. Finally, two recent conference abstracts have reported use of the unsuppressed water signal to generate the sensitivity maps used to unwrap the folded images in sensitivity-encoded spectroscopic imaging (SENSE-SI), images produced by under-sampling k-space data during signal acquisition with parallel imaging [12,13].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The rapid and automatic combination of proton MRSI data using multi-channel coils without water suppression

Dong

Peterson

2007

Magnetic Resonance Imaging

View full text Add to dashboard Cite

The use of multi-channel coils can efficiently increase the signal-to-noise ratio (SNR) of magnetic resonance spectroscopy data if the signals from multiple channels are optimally combined. Combining multi-channel signals requires proper alignment of the phases of the signals from each of the elements of the coil and then accurately weighting the summation of those signals. We present a procedure for acquiring proton magnetic resonance spectroscopic imaging (MRSI) data using an eight-channel coil without water suppression and a rapid and robust method that uses unsuppressed water signal as a reference both for aligning the phases and for weighting the summation of signals that originate in the multiple coil elements. We use both computer simulation and in vivo proton MRSI data to demonstrate the advantages of our method for optimizing the SNR of the combined signal compared with the SNRs of signals that were acquired either using a standard volume head coil or using an eight-channel coil with a metabolite signal as the reference for combination.

show abstract

Single Volume Localization and Water Suppression

Graaf

Robin²

2007

In Vivo NMR Spectroscopy

View full text Add to dashboard Cite

Localized Proton Spectroscopy without Water Suppression: Removal of Gradient Induced Frequency Modulations by Modulus Signal Selection

Cited by 37 publications

References 13 publications

Quantification of non–water‐suppressed MR spectra with correction for motion‐induced signal reduction

Quantification of non–water‐suppressed MR spectra with correction for motion‐induced signal reduction

The rapid and automatic combination of proton MRSI data using multi-channel coils without water suppression

Single Volume Localization and Water Suppression

Contact Info

Product

Resources

About