What is it about?

Since transverse (T2) and longitudinal (T1) relaxation times play an important role in optimizing MRI parameters [e.g., contrast level, signal-to-noise ratio], we measured these values for the first time in awake pigeons and rats. In addition, anesthesia drugs strongly confound MRI results. To overcome this effect, we optimized the habituation protocol which successfully limited movement of the awake animals to a negligible minimum, allowing reliable measurement of T1 and T2 values within all regions of interest.

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Why is it important?

The obtained T1 and T2 values for awake pigeons and rats and the optimized habituation protocol will help to optimize future MRI studies with awake animals. The differences in relaxation times observed between species underline the importance of the acquisition of T1/T2 values as reference points for specific experiments.

Perspectives

this study is reporting T1 and T2 values for the first time on awake pigeons and rats brain. We need this values to optimize fMRI sequence to measure BOLD signal variations. Apart from differences in structural brain organization, acquisition of reliable MR data in different species is further complicated by differences in skull structure. Pigeons, for example, possess air cavities in their skulls. These cavities cause very strong local magnetic field inhomogeneities resulting in severe signal loss. As a consequence, gradient echo-planar imaging (EPI) sequences, which are commonly used in fMRI in humans and rodents, cannot be used in pigeons. Instead, fast multiple spin echo sequences (RARE) in which SNR and signal contrast rely on longitudinal (T1) and transverse (T2) relaxation times have been proposed for fMRI in birds

Mehdi Behroozi
Ruhr-Universitat Bochum

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This page is a summary of: In vivo measurement of T1 and T2 relaxation times in awake pigeon and rat brains at 7T, Magnetic Resonance in Medicine, May 2017, Wiley,
DOI: 10.1002/mrm.26722.
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