Effect of temporal resolution and serial autocorrelations in event‐related functional MRI

Sahib, Ashish; Mathiak, Klaus; Erb, Michael; Elshahabi, Adham; Klamer, Silke; Scheffler, Klaus; Focke, Niels K.; Ethofer, Thomas

doi:10.1002/mrm.26073

Cited by 39 publications

(47 citation statements)

References 49 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Therefore, it might be expected that imaging with a shorter TR has a punitive effect on image signal levels that in turn, will reduce fMRI sensitivity, which is consistent with our findings. Our findings demonstrate a more moderate reduction in TR is optimal compared with some previous studies even when a similar autoregressive model was used . This might be due to differences in the event‐related design, although we found that similar results at different PRs.…”

Section: Discussionsupporting

confidence: 51%

“…A second level analysis using a 2‐way repeated measures analysis of variance with factors TR and frequency was used to evaluate their effect on the t‐values using SPSS version 24 (https://www.ibm.com/pk-en/marketplace/spss-statistics). To test the effect of TR reduction with conservative control of potential t‐value inflation at shorter TRs, the 2‐way analysis of variance compared t‐values obtained with the standard SPM AR1 model for the standard TR value (2550 ms) and t‐values obtained using the fMRIstat AR(5) model at shorter TRs (412, 842, and 1250 ms). Significance for a factor or interaction was taken to be P < 0.05.…”

Section: Methodsmentioning

confidence: 99%

“…It is, therefore, imperative to control for this autocorrelation in the data which will increase as the TR is reduced. A recent study by Sahib et al found that stable statistics were dependent on the TR and AR model order. However, this study focused on sensitivity by means of t‐values for a single event‐related design based on a single patient with epilepsy and did not evaluate false positives.…”

Section: Introductionmentioning

confidence: 98%

See 2 more Smart Citations

Optimal repetition time reduction for single subject event‐related functional magnetic resonance imaging

McDowell¹,

Carmichael

2018

Magnetic Resonance in Med

View full text Add to dashboard Cite

show abstract

Section: Discussionsupporting

confidence: 51%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

See 1 more Smart Citation

Optimal repetition time reduction for single subject event‐related functional magnetic resonance imaging

McDowell¹,

Carmichael

2018

Magnetic Resonance in Med

View full text Add to dashboard Cite

show abstract

“…Here, we have shown that a more comprehensive model can improve the efficiency of prewhitening for TR ≤ 1.4s. However, like the AR(1) + white noise model, the FAST approach still uses a global correlation matrix V. There may be additional benefit to be gained from using spatially varying model coefficients (Eklund et al, 2012; Penny, Kiebel, & Friston, 2003; Sahib et al, 2016). However, regionally specific estimates of serial correlations are necessarily less efficient and might introduce unwanted variability in the estimates of nonsphericity.…”

Section: Discussionmentioning

confidence: 99%

Accurate modeling of temporal correlations in rapidly sampled fMRI time series

Corbin

Todd

Friston

et al. 2018

Human Brain Mapping

View full text Add to dashboard Cite

Rapid imaging techniques are increasingly used in functional MRI studies because they allow a greater number of samples to be acquired per unit time, thereby increasing statistical power. However, temporal correlations limit the increase in functional sensitivity and must be accurately accounted for to control the false‐positive rate. A common approach to accounting for temporal correlations is to whiten the data prior to estimating fMRI model parameters. Models of white noise plus a first‐order autoregressive process have proven sufficient for conventional imaging studies, but more elaborate models are required for rapidly sampled data. Here we show that when the “FAST” model implemented in SPM is used with a well‐controlled number of parameters, it can successfully prewhiten 80% of grey matter voxels even with volume repetition times as short as 0.35 s. We further show that the temporal signal‐to‐noise ratio (tSNR), which has conventionally been used to assess the relative functional sensitivity of competing imaging approaches, can be augmented to account for the temporal correlations in the time series. This amounts to computing the t‐score testing for the mean signal. We show in a visual perception task that unlike the tSNR weighted by the number of samples, the t‐score measure is directly related to the t‐score testing for activation when the temporal correlations are correctly modeled. This score affords a more accurate means of evaluating the functional sensitivity of different data acquisition options.

show abstract

“…Improved spatial resolution is useful for better identification of activation as well as reduced signal dropout in regions with large magnetic susceptibility induced distortion and signal loss . Increased temporal resolution has received particular interest in fMRI for enhanced statistical power, better resolution of the hemodynamic response function (HRF), and better identification of nuisance physiological components . A common method for increasing speed in MRI is to acquire reduced datasets with receiver coil arrays using parallel imaging .…”

Section: Introductionmentioning

confidence: 99%

A circular echo planar sequence for fast volumetric fMRI

Rettenmeier

Maziero

Qian

et al. 2018

Magnetic Resonance in Med

View full text Add to dashboard Cite

Purpose To demonstrate a circular EPI (CEPI) sequence as well as a generalized EPI reconstruction for fast fMRI with parallel imaging acceleration. Methods The CEPI acquisition was constructed using variable readout lengths and maximum ramp sampling as well as blipped‐CAIPI z‐gradient encoding for simultaneous multislice (SMS) and 3D volumetric imaging. A signal equation model with constant and linear phase terms was used to iteratively reconstruct images with low ghosting. Simulation, phantom, and human imaging experiments including audio/visual fMRI were performed at 3T using a 52‐channel coil. Results Application of CEPI gradients with duration of 27 ms covering a 22‐cm FOV at a 64 × 64 pixel resolution in SMS and 3D acquisitions resulted in images with comparable quality to those of standard Cartesian EPI. With parallel imaging techniques robust detection of BOLD fMRI activation with temporal sampling down to 275 ms was possible. The high temporal resolution enabled higher activation statistics at a penalty in increased noise and residual aliasing. The un‐accelerated 3D acquisition showed large temporal instability compared with a standard 2D acquisition. Conclusion Nonuniform sampling and generalized image reconstructions can be applied to EPI acquisitions including those with blipped‐CAIPI z gradients. The same gradients can be used for either SMS or 3D acquisitions providing identical coverage.

show abstract

Effect of temporal resolution and serial autocorrelations in event‐related functional MRI

Cited by 39 publications

References 49 publications

Optimal repetition time reduction for single subject event‐related functional magnetic resonance imaging

Optimal repetition time reduction for single subject event‐related functional magnetic resonance imaging

Accurate modeling of temporal correlations in rapidly sampled fMRI time series

A circular echo planar sequence for fast volumetric fMRI

Contact Info

Product

Resources

About