Seyed Ali Nabavizadeh1, Sanjeev Chawla1, Pei-Hsin Wu1, Ana Rodriguez-Soto2, Erin Englund2, Michael C Langham1, Farzana Sayani1, Eric Russell1, and Felix W Wehrli1
1University of Pennsylvania, Philadelphia, PA, United States, 2University of California San Diego, La Jolla, CA, United States
Synopsis
Silent cerebral infarcts are the most common
neurologic injury in patients with sickle cell disease (SCD). In this study, we
compared T2 -relaxation under spin tagging (TRUST) and susceptibility-based
oximetry (SBO) techniques in a cohort of SCD patients compared to healthy control
subjects. We observed opposite trends in oxygen extraction fraction (OEF) and cerebral
metabolic rate of oxygen (CMRO2) in SCD patients compared to controls using
TRUST and SBO methods. High OEF measured by TRUST technique lead to very high supraphysiologic
CMRO2 values. We conclude that SBO method is more reliable in measuring OEF and
CMRO2 in patients with SCD.
Introduction:
Quantitative MRI based methods have been employed to study oxygen metabolism in
sickle cell disease (SCD) patients. T2 -relaxation under spin tagging (TRUST)
sequence uses spin labeling to isolate pure venous blood signals and measures
its T2 value, which is converted to venous oxygenation (Yv)
with a calibration plot1. However, there exists some
controversy on the impact of HbS on the calibration curve and oxygen extraction
fraction (OEF) parameters from TRUST MRI method2. The purpose of the present study
was to compute the values of OEF and cerebral metabolic rate of oxygen (CMRO2)
from SCD patients using both TRUST and susceptibility-based oximetry (SBO)
methods3 and to compare those with that of healthy
controls.
Methods:
A
cohort of 18 patients with SCD [males/females: 8/10; mean age: 28.52 ± 5.24 years;
mean hematocrit:30.92 ± 6.73%] and 12 age-matched healthy control subjects
underwent MR imaging on a 3T MR system equipped with 64 channel head phased
array coil. The imaging protocol included T1-weighted 3D magnetization-prepared
rapid gradient-echo (MPRAGE) sequence, SBO sequence comprising of an
interleaved, high temporal resolution 2D-gradient-recalled echo images and
TRUST MRI with a single slice EPI intersecting the lower superior sagittal
sinus region4. All data were processed using
in-house developed MATLAB scripts. Using Non-parametric Mann-Whitney U tests, OEF=
(Ya-Yv)/Ya) and CMRO2 were compared between healthy control and SCD patients as
obtained from TRUST and SBO methods. Additionally, CBF values as obtained from the
SBO sequence were also compared between the two groups.
Results:
Higher
global CBF was observed in SCD patients compared to control (84.8 ± 16.1 vs 46.0
± 5.6 ml/min/100g; p< 0.001). Using TRUST, higher OEF (52.7 ± 15.3 vs 35.5 ±
4.1; p< 0.001) were observed in SCD patients compared to the healthy control
group. On the other hand, lower OEF (26.4 ± 7.1 vs. 32.7 ± 3.3, p= 0.007) were
observed in SCD patients compared to healthy controls using SBO method. CMRO2
was significantly lower in SCD patients when measured by SBO technique compared
to TRUST (127.2 ± 41.6 vs. 251.8±75.4 µmol/100 g/min, p<0.000).
Conclusion:
We observed opposite trends in OEF and CMRO2 in SCD patients compared to controls
using TRUST and SBO methods. High OEF measured by TRUST technique lead to very
high supraphysiologic CMRO2 values. SBO method that does not depend upon the
morphologic and hematologic changes of sickle cell is more reliable in
measuring OEF and CMRO2 in patients with SCD.Acknowledgements
No acknowledgement found.References
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