Quantitative T2 in the occipital lobe: the role of the CPMG refocusing rate

J Magn Reson Imaging. 2003 Sep;18(3):302-9. doi: 10.1002/jmri.10360.


Purpose: To investigate the dependence of occipital gray and white matter T(2) on the Carr-Purcell-Meiboom-Gill (CPMG) refocusing interval, thereby testing the basis of a novel functional magnetic resonance imaging (fMRI) method for blood volume quantification, and addressing recent questions surrounding T(2) contrast in the occipital lobe.

Materials and methods: A CPMG sequence with 1 x 1 x 5 mm(3) resolution was used to quantify T(2) in a single axial slice at the midlevel of the occipital lobe in 23 healthy adult volunteers. Refocusing intervals of 8, 11, and 22 msec were compared. A Bayesian classifier was used to classify a 1 x 1 x 1 mm(3) T(1)-weighted three-dimensional data set into gray matter, white matter, and cerebrospinal fluid, with an average 95% a posteriori probability used as the threshold for inclusion into a tissue-specific region of interest (ROI).

Results: The usual T(2) contrast between the gray and white matter (i.e., T(2GM) > T(2WM)) was observed, with a highly significant effect of tissue type on the estimated T(2) (P < 10(-5)). The observed T(2) gradually decreased with increasing refocusing interval, for a decrease of 3.3 +/- 1.5 msec in gray matter and 3.0 +/- 1.5 msec in white matter between the 8 and 22 msec refocusing interval acquisitions.

Conclusion: The observed T(2) shortening is consistent with the effect of the dramatic decrease in T(2) of partly deoxygenated blood on this range of refocusing rates.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Blood Volume Determination / methods
  • Humans
  • Magnetic Resonance Imaging / methods*
  • Occipital Lobe / anatomy & histology*