Iron-Induced Susceptibility Effect at the Globus Pallidus Causes Underestimation of Flow and Volume on Dynamic Susceptibility Contrast-Enhanced MR Perfusion Images
Kei Yamadaa,
R. Gilberto Gonzalezb,
Leif Østergaardc,
Suzanne Komilib,
Robert M. Weisskoffb,
Bruce R. Rosenb,
Walter J. Koroshetzb,
Tsunehiko Nishimuraa and
A. Gregory Sorensenb
a Department of Radiology, Kyoto Prefectural University of Medicine, Kyoto City, Japan
b Massachusetts General Hospital NMR-Center, Harvard Medical School, Boston MA
c Department of Neuroradiology, Århus University Hospital, Århus, Denmark
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FIG 1. Representative case with region of interest on globus pallidus (arrow).
A, Conventional T2-weighted image (T2-WI).
B, Source image obtained by gradient-echo echo-planar imaging sequence. Note the hypointensity at the globus pallidus and putamen. Also note the susceptibility effect at the frontal skull base near the air-tissue interface.
C, Source image shows region of interest (ROI) (arrow). Anatomic boundary of the region of interest was determined based on the imaging findings.
D, Perfusion map shows rCBF.
E, Perfusion map shows rCBV.
F, Perfusion map shows MTT.
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FIG 2. Graphs show measured values of rCBF, rCBV, and MTT at each region of interest. Error bars indicate SD ± 1. Measured values were normalized with the temporal white matter (WM), and values on the y axis thus represent gray matter-white matter ratios. Dashed horizontal lines intersect at a gray matter-white matter ratio of 1. Statistically significant differences in the mean values between various locations are indicated (*, P < .05; **, P < .005; ***, P < .0005; unpaired t test). Columns with statistically significant differences between gradient-echo (GRE) and spin-echo (SE) sequences are marked ( , statistically significant difference between gradient-echo and spin-echo with P < .05;  , statistically significant difference between gradient-echo and spin-echo with P < .005). Columns marked by these symbols represent those with higher values.
A, Measurements of the rCBF by gradient-echo echo-planar imaging.
B, Measurements of the rCBF by spin-echo echo-planar imaging.
C, Measurements of the rCBV by gradient-echo echo-planar imaging.
D, Measurements of the rCBV by spin-echo echo-planar imaging.
E, Measurements of the MTT by gradient-echo echo-planar imaging.
F, Measurements of the MTT by spin-echo echo-planar imaging.
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FIG 3. Signal intensity time curves of gradient-echo (GRE) and spin-echo (SE) echo-planar imaging sequences. Region of interest measurements were obtained from three representative locations: globus pallidus, caudate head, and thalamus. The y axes for both gradient-echo and spin-echo sequences are scaled to the same range of signal intensity (400–1600 A.U.). Note that the signal change is more prominent on the gradient-echo sequence than on the spin-echo sequence. The signal intensity difference between the thalamus and globus pallidus is also more prominent for the gradient-echo sequence.
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FIG 4. Trend of lower baseline signal intensity was more prominent for gradient-echo (GRE) sequence. Error bars indicate SD ± 1. Measured values were normalized with temporal white matter (WM), and y axis thus represents gray matter:white matter ratio (*, P < .05; **, P < .005; unpaired t test). Columns with statistically significant differences between gradient-echo and spin-echo (SE) sequences are marked (, statistically significant difference between gradient-echo and spin-echo sequences with P < .05). Columns marked by these symbols represent those with higher values.
A, Measurements of the baseline signal intensity by gradient-echo echo-planar imaging.
B, Measurements of the baseline signal intensity by spin-echo echo-planar imaging.
C, Measurements of maximum magnitude of signal change by gradient-echo echo-planar imaging.
D, Measurements of maximum magnitude of signal change by spin-echo echo-planar imaging.
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