Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

PURPOSE: The calculation of the calibration parameter M, which represents the maximum theoretically possible blood oxygen level dependent (BOLD) signal increase, is an essential intermediate step in any calibrated fMRI experiment. To better compare M values obtained across different studies, it is common to scale M values from their original BOLD echo time (TE) to a different echo time according to the theory that M is directly proportional to TE. To the best of our knowledge, this relationship has never been directly tested. THEORY AND METHODS: A pseudocontinuous arterial spin labeling sequence with five readouts (TE ranging from 20 to 78 ms) was implemented to test the relationship between M and TE, both with and without the application of flow crushing gradients. RESULTS: Both M and the BOLD signal were found to be linear functions of TE, but with a nonzero intercept. This intercept was reduced when crusher gradients were added, suggesting that the deviation from theory is a result of nonnegligible intravascular signal. CONCLUSION: The linear scaling method introduces some error when comparing M values acquired with different BOLD echo times. However, this error is small compared with other considerations, and would generally not preclude the continued use of this scaling method.

Original publication

DOI

10.1002/mrm.25603

Type

Journal article

Journal

Magn Reson Med

Publication Date

02/2016

Volume

75

Pages

556 - 561

Keywords

BOLD, MRI, calibration, echo time, hypercapnia, Brain, Calibration, Cerebrovascular Circulation, Female, Healthy Volunteers, Humans, Hypercapnia, Image Processing, Computer-Assisted, Magnetic Resonance Imaging, Male, Oxygen, Spin Labels, Young Adult