Ventral anterior temporal lobe and signal loss

Hello,

What is the optimal way to minimize the signal loss due to air-tissue interfaces in the Ventral anterior temporal lobe? We are interested in studying this and surrounding areas. However, what I understand is regular sequences such as the one we are using (TR=2,3x3x3mm voxels, 32 slices, TE=30ms, FA=78, FOV=192x192) is not very good in eliminating these artifacts?

Are there sequence parameters (printouts) or imaging methods (parallel, multiband) people would recommend using for this purpose?

I have heard that MB sequences may improve this signal loss, but I can not see how and why that would be the case. I am assuming using a MB sequence by on itself won’t change much unless the protocol parameters are modified accordingly as well. In other words, just putting a MB sequence with the same parameters as I mentioned above wouldn’t improve these artifacts, would they?

Thanks.

Hi,

The air tissue interface is creating two type of artefacts in that area for 2D GRE-EPI sequences used in BOLD imaging

  • susceptibility induced distorsions
  • signal dropout due to intravoxel dephasing

One strategy that can be advantageous for you would be to acquire BOLD images with a multi-echo GRE-EPI sequences with two echoes or more and combine those echoes according to method derived from the paper below and implemented in tools such as FMRIPREP and TEDANA

Kundu, P.; Voon, V.; Balchandani, P.; Lombardo, M. V.; Poser, B. A.; Bandettini, P. A. Multi-Echo FMRI: A Review of Applications in FMRI Denoising and Analysis of BOLD Signals. NeuroImage 2017, 154, 59–80. https://doi.org/10.1016/j.neuroimage.2017.03.033.

Other general approaches to improve the signal loss in this area could also use these strategies:

  • decrease the slice thickness to limit the intravoxel dephasing (but this will decrease your SNR)
  • change the slice orientation
  • reduce TE (knowing the best TE for BOLD sensitivity is for TE=T2*, one idea idea would be to measure the T2* in this area and optimize the TE with this knowledge).
1 Like

Thank you so much for your answer. I will look into these.