Abstract #0221

Investigating the impact of temporal signal fluctuations and local effective echo times on indices of BOLD sensitivity in healthy subjects and tumor patients at 7T.

Barbara Dymerska¹, Pedro Cardoso¹, Nina Mahr², Eva Matt², Florian Fischmeister², Roland Beisteiner², Siegfried Trattnig¹, and Simon Daniel Robinson¹

¹High Field MR Centre, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria, ²High Field MR Centre, Department of Neurology, Medical University of Vienna, Vienna, Austria

Temporal signal fluctuations (tSNR) and local effective echo time (TE_local) are explored and their influence on BOLD sensitivity is investigated at 7T for healthy subjects and tumor patients, where prominent spatial variations in those two measures are expected. We show that tSNR may indicate sufficient sensitivity to detect activation but that BOLD sensitivity may be dramatically reduced by changes in TE_local close to pathologies and vital brain functions (motor, speech, auditory). Neglecting local TE variations can thus lead to false negative results in clinical fMRI. We thus suggest a new BOLD sensitivity metric based on TE_local∙tSNR.

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