Measurement of transit time and arterial blood volumes using EPISTAR

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Measurement of transit time and arterial blood
volumes using EPISTAR

• A. Sleigh, S. Francis, R. Bowtell, P. Gowland

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EPISTAR
180o
180o
TAG
90o
CONTROL
T A G
C O N T R O L
TI
TI
TR
-

CONTROL - TAG
?M
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ASL used to measure CBF changes on brain
activation
Transit time, ?
Passage time, ?
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Method

• 6 subjects, under rest conditions.
• 3.0 T scanner
• Transverse imaging, with 128 x 128 matrix size.
• 3 x 4 mm in-plane resolution, 8 mm slice
  thickness.
• EPI, 1.5kHz switching frequency.

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bw 2980 Hz
bw 2980 Hz
5 1
10 3 3
10 cm
TIs 0.3 0.5 1.4 1.8 s
(20 avs) TIs 0.7 0.9 1.1
s (40 avs)
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Analysis and results

• Control (C) images registered, applied to the
  tagged (T) images.
• C - T ?M images.
• C M

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Perfusion, f map Transit time, ? map ?M
image, TI1.1 s
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Noisy ? - Improve the model.

• Usually attenuate arterial blood signal.
• We do not
• - so modelling both arterial and capillary
  components
• will yield an improved model.
• Added advantage - can calculate arterial blood
  volume fraction in a pixel,
• along with transit time, ?A and passage
  time, ?A for
• the arterial compartment.

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Conclusion

• Produced transit maps - could be important in
  interpreting changes
• in the timing of the haemodynamic response.
• Extended model appears to fit the experimental
  data well
• - hoped that inserting this into the mapping
  program will
• yield improved transit and passage maps.
• Importance in activation studies
• - simple method of measuring changes in arterial
  blood
• volumes, as well as perfusion rate and transit
  time changes
• on brain activation.

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Acknowledgements
Sue Francis Penny Gowland Richard Bowtell
We thank EPSRC and MRC for funding this work