Spatially selective T2 and T2∗ measurement with line-scan echo-planar spectroscopic imaging

Chen, Nan‐kuei; Oshio, Koichi; Panych, Lawrence P.; Rybicki, Frank J.; Mulkern, Robert V.

doi:10.1016/j.jmr.2004.08.004

Cited by 11 publications

(8 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The sensitivity-encoded (SENSE) MRSI phantom-replacement technique was able to provide reasonable N-acetyl aspartate (NAA), Choline and Creatine concentrations [30]. Long acquisition time (about tens of seconds) for MRSI [25,26,30] unfortunately cannot be appropriate for real-time studies where 1–2 sec feedback is required.…”

Section: Introductionmentioning

confidence: 99%

Single Voxel Proton Spectroscopy for Neurofeedback at 7 Tesla

2011

View full text Add to dashboard Cite

Echo-planar imaging (EPI) in fMRI is regularly used to reveal BOLD activation in presubscribed regions of interest (ROI). The response is mediated by relative changes in T2* which appear as changes in the image pixel intensities. We have proposed an application of functional single-voxel proton spectroscopy (fSVPS) for real-time studies at ultra-high MR field which can be comparable to the EPI BOLD fMRI technique. A spin-echo SVPS protocol without water suppression was acquired with 310 repetitions on a 7T Siemens MR scanner (TE/TR = 20/1000 ms, flip angle α = 90°, voxel size 10 × 10 × 10 mm3). Transmitter reference voltage was optimized for the voxel location. Spectral processing of the water signal free induction decay (FID) using log-linear regression was used to estimate the T2* change between rest and activation of a functional task. The FID spectrum was filtered with a Gaussian window around the water peak, and log-linear regression was optimized for the particular ROI by adoption of the linearization length. The spectroscopic voxel was positioned on an ROI defined from a real-time fMRI EPI BOLD localizer. Additional online signal processing algorithms performed signal drift removal (exponential moving average), despiking and low-pass filtering (modified Kalman filter) and, finally, the dynamic feedback signal normalization. Two functional tasks were used to estimate the sensitivity of the SVPS method compared to BOLD signal changes, namely the primary motor cortex (PMC, left hand finger tapping) and visual cortex (VC, blinking checkerboard). Four healthy volunteers performed these tasks and an additional session using real-time signal feedback modulating their activation level of the PMC. Results show that single voxel spectroscopy is able to provide a good and reliable estimation of the BOLD signal changes. Small data size and FID signal processing instead of processing entire brain volumes as well as more information revealed from the acquired total water spectrum, i.e., direct estimation of the T2* values and B0 changes, make SVPS proton spectroscopy suitable and advantageous for real-time neurofeedback studies. Particular challenges of ultra-high field spectroscopy due to the non-linearity in the spectral information, e.g., poor main magnetic field homogeneity and the absence of motion correction for the SVPS sequence may lead to the special artifacts in the control signal which still need to be addressed. The contrast to noise ratio (CNR), experimental statistic (t-values) and percent signal change were used as quality parameters to estimate the method performance. The potential and challenges of the spectroscopic approach for fMRI studies needs to be further investigated.

show abstract

Section: Introductionmentioning

confidence: 99%

Single Voxel Proton Spectroscopy for Neurofeedback at 7 Tesla

2011

View full text Add to dashboard Cite

show abstract

“…In the past, studies have explored spectroscopic, T 2 , and T 2 * measurements from a column of voxels (13)(14)(15)(16). The most pertinent (14) describes a method for multiecho T 2 *-weighted measurements of the primary motor cortex.…”

Section: Discussionmentioning

confidence: 99%

“…Such methods were used to probe BOLD signal biophysics in the early development of fMRI (11), although their time efficiency for real-time fMRI NF has not been explored. Intermediate between single voxel and whole-brain coverage, methods have been developed that spatially resolve multiple compartments by limited phase encoding (12), as well as various ''line-scan'' methods that involve one-dimensional frequency encoding readouts or spatial localization provided by isolating a column of voxels in space (13)(14)(15)(16). In particular, line-scan methods provide the sensitivity benefits of single voxel approaches, with improved volume of coverage and computationally efficient spatial reconstruction.…”

mentioning

confidence: 99%

Multiecho coarse voxel acquisition for neurofeedback fMRI

Kuo

Chiew

Tam

et al. 2010

Magnetic Resonance in Med

View full text Add to dashboard Cite

''Real-time'' functional magnetic resonance imaging is starting to be used in neurofeedback applications, enabling individuals to regulate their brain activity for therapeutic purposes. These applications use two-dimensional multislice echo planar or spiral readouts to image the entire brain volume, often with a much smaller region of interest within the brain monitored for feedback purposes. Given that such brain activity should be sampled rapidly, it is worthwhile considering alternative functional magnetic resonance imaging pulse sequences that trade spatial resolution for temporal resolution. We developed a prototype sequence localizing a column of magnetization by outer volume saturation, from which densely sampled transverse relaxation time decays are obtained at coarse voxel locations using an asymmetric gradient echo train. For 5 3 20 3 20 mm 3 voxels, 256 echoes are sampled at~1 msec and then combined in weighted summation to increase functional magnetic resonance imaging signal contrast. This multiecho coarse voxel pulse sequence is shown experimentally at 1.5 T to provide the same signal contrast to noise ratio as obtained by spiral imaging for a primary motor cortex region of interest, but with potential for enhanced temporal resolution. A neurofeedback experiment also illustrates measurement and calculation of functional magnetic resonance imaging signals within 1 sec, emphasizing the future potential of the approach. Magn Reson Med 65:715-724,

show abstract

“…In comparison with many R2 (or T2) and R2’ measurement methods [13–23], SE-SS-PARSE has several potential basic advantages. In conventional methods, R2’ values are measured by subtracting R2 from R2* values.…”

Section: Discussionmentioning

confidence: 99%

“…However, EPI based imaging is vulnerable to geometric distortion artifacts [18–22]. Chen et al [23] have recently proposed a less field inhomogeneity sensitive method, Line-Scan Echo Planar Spectroscopic Imaging (LSEPSI). However, the 30 sec data acquisition time for a 2-dimensional slice image is too long to monitor rapidly changing signals, such as the BOLD fMRI responses.…”

Section: Introductionmentioning

confidence: 99%

Spin-echo SS-PARSE: a PARSE MRI method to estimate frequency, R2 and R2′ in a single shot

Bolding

Twieg

2010

Magnetic Resonance Imaging

View full text Add to dashboard Cite

Spin echo signals allow separate measurements of irreversible and reversible relaxation rates in MRI. A spin echo version of Single-shot Parameter Assessment by Retrieval from Signal Encoding (SE-SS-PARSE) method has been developed to quantitatively and accurately map transverse magnetization magnitude, frequency, irreversible and reversible relaxation rates in a single shot. These image parameters can be applied to fMRI research as well as a number of neuroimaging applications. Following a description of the signal model, this paper demonstrates the performance of SE-SS-PARSE in simulations with different noise levels and in phantom experiments. By solving an inverse problem, the estimated irreversible and reversible relaxation rates in SE-SS-PARSE are highly correlated with the reference relaxation rates from a standard technique (correlation coefficients r1=0.9636 for reversible relaxation rate, r2= 0.9788 for irreversible relaxation rate). The rapid SE-SS-PARSE technique has the potential to monitor transient changes in R2 and R2’ while minimizing motion artifacts, and also is free of geometric and ghosting errors. It is expected that this fast scan technique will find applications in both scientific research and clinical diagnosis.

show abstract

Spatially selective T2 and T2∗ measurement with line-scan echo-planar spectroscopic imaging

Cited by 11 publications

References 35 publications

Single Voxel Proton Spectroscopy for Neurofeedback at 7 Tesla

Single Voxel Proton Spectroscopy for Neurofeedback at 7 Tesla

Multiecho coarse voxel acquisition for neurofeedback fMRI

Spin-echo SS-PARSE: a PARSE MRI method to estimate frequency, R2 and R2′ in a single shot

Contact Info

Product

Resources

About